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Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #1 ·
Hi folks,

I used to spend a LOT of time here when I had a 2001 SL500 (bought in 2008; sold in 2012). I miss the car sometimes - but don't regret selling it. We needed more space as the family grew and home depot runs became more of a thing 馃檪

Last Friday, I bought a 1994 SL320. This is my first real "hands on" experience with an earlier model R129 and I'm liking it so far. The engine isn't a V8, but it's also fairly easy to work on. I got extremely hands on with the M104 when I was fixing up a 1993 300E 2.8 earlier this year (bought for $1k; fixed up; sold on Bring a Trailer). I definitely feel confident pulling any of the accessories, doing valve cover gaskets, replacing wiring harness, etc

I just got the car smogged - going to get it titled and officially registered soon. I've already started some small repairs - replacing burnt out light bulbs, fixing the center console wood / sunken buttons, etc. Going to replace a lot of small things on the car as time allows on the weekend 馃檪

I put together a YouTube video for the first pieces of work I did and wanted to share

This was a fun format for the W124 I had fixed up; you can see those on my channel too

Will likely have a bunch of questions and will be on here more. It's got a check engine light on... and even though this car is a 1994, it does have the OBD II port. I got it scanned at Advance Auto Parts last night and it had the following codes:
  • P1700 (Transmission upshift delay switchover valve (Y3/3) without function (Logic chain))
  • P1342 (Electrical activation of adjustable camshaft timing solenoid (Y49))

The switchover valve is likely a vacuum leak; should be easy to troubleshoot/fix (ex: cut some new vacuum line). The timing issue - a little concerned about that. If it really is the cam position sensor, I'll have to pull the valve cover and timing cover off to replace. I found lots on search here

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #3 ·
Car passed emissions without any issues - got the car registered now and title transfer in progress.

I just got back inside after driving up on some rhino ramps and spend an hour going over everything. I wanted to share some pictures - I could definitely use help if anyone is familiar with the issues I'm working through! 馃檪

For a 1994, I was surprised to see this does have two oxygen sensors (pre and post cat). Some parts sites showed one, some showed two. The rear O2 sensor is a piece of cake to reach (you can just slide under the passenger side, right in front of the rear wheel) but the front one is a PITA. I know it'll be a 22mm socket (need to get a crows foot) but just on ramps it's nearly impossible to slide under and reach. I do have a replacement part for the front so it would be good to swap it out. Might have to look at jacking the car up and putting it on stands all around to get enough clearance
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As shared above, there was a code being thrown:
P1700 (Transmission upshift delay switchover valve (Y3/3) without function (Logic chain))
Everything I could find pointed at this assembly and the green vacuum line attached to it. For reference, this is on the passenger side attached to the firewall (pretty close to the plastic veneer that houses the 38 pin SDS port). There's also a black vacuum line attached - I have no idea where this is going. The vacuum pump in the trunk makes all kinds of groaning noises after starting the car - I'm guessing it's related to this leak

I followed the green wire down and and it's going to the PASSENGER side of the transmission. It looks to be attached to an actuator. I found a picture of the 722.5 transmission and drew (in red) where the line goes

It's basically impossible to reach though. When you're under the car, I think you'd need to jack up the transmission and then remove the transmission mount / support bar to have enough room to get your hand in there. Here's the best possible picture I could snap while under there - it's tight

Looking on the other side of the transmission (DRIVERS side), I did see a black vacuum line going to a 2 pin connector. Is this the same black wire that's connected to the upshift delay switchover valve? I have no idea what this part is but it's in rough shape. Since this attaches to a vacuum line, I can definitely see this causing a problem. I'm going to try and find the part number so I can swap it out. It's basically screwed on. Worth a shot replacing

What are some good ways to test vacuum lines? I thought about getting a smoke machine which would make it easy to ID but they're way too expensive

The last thing I was looking at was the engine wiring harness (since this should have had a biodegradable one). It looks to be in good shape - the fabric tape is still around most of the loom and I didn't see any exposed wires. When I was fixing up a 1993 W124 which had the original bio harness, there was a tag right in the passenger side where the 38 pin SDS connector is (that's there the battery is on the W124). It had the wiring harness date on it. I couldn't find this on the SL. I did find a part number on the harness though. It would be amazing if a previous owner had replaced this already. The last number is cut off in the picture - but it's a 2 (and then there's a symbol next to that). Full part number is 140-540-6932

Is this the updated harness? I really hope so. Parts catalogs (like show this replaces 140-540-07-32 and 140-540-69-32-05

94 SL320 98 SL500 99 SL600 07 SL55
1,343 Posts
Check Ebay for cheap smoke machine they work as good as the expensive ones. If you peel back a little bit of the loom covering the the connectors in the front of the engine and check for crumbling insulation

1992 CE 300-24
891 Posts
Are you getting all 5 speeds in that 722.5?

Check the 'StarTekInfo' sticky thread in
the W140 section of this forum, it covers
your issue, inc' (from memory) the need
to clear the code with the engine running
at ^1,000 rpm if that solenoid switch has
been disturbed/re-connected.

There is a 4-5-4th selector switch in the shift
console that might also respond to a clean,
if its been collecting detritus for decades.

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #6 ·
Will check out the wiring harness in more detail tomorrow - but I remember the front connectors being in pretty good shape. The harness for my old W124 was falling apart bigtime before I replaced - all the plastic fittings were broken on the front. I hope this means this one was replaced! If not, it's all good. At some point, I'm going to do the spark plugs / ignition coils / valve cover gaskets - that's where the harness broke last time (moving it out of the way when removing valve cover). I'll leave it alone for now

The other day, I got a box of goodies from Autohaus AZ. Replaced the gas cap, radiator expansion tank cap, thermostat, air intake filter, replaced the oil dip stick O-ring and put a nice and new front engine cover on. Also went through the car and replaced all the dead light bulbs - like in the AC unit, the shifter, the light switch / rear fog light, inside the armrest storage, etc. The trunk light seems to have a wiring issue - not getting any power there

For the broken rubber boot part (attaches to drivers side of transmission), I was able to find out more info 馃檪 Well, first I electrical taped it up really good. This seems to have fixed the shifting problems I was experiencing (it was getting super high RPM and then violently shifting). For a long term proper fix, the folks at 500eboard helped me find a replacement part for that (had to be ordered from a reproduction parts company in Germany). When I do that, I'll likely replace the entire overflow protection switch. More info at HOW-TO: Transmission Overload Protection Switch Removal | "HOW-TO" Tutorial Articles

There are some intermittent electrical problems with the drivers side door. I checked the fuses and they're all original aluminum ones, definitely suspect 馃槺 (they're heavily oxidized). I'll go and swap those out tomorrow with copper ones. If that doesn't work, the door panel needs to come off for some cosmetic fixes anyways (need to epoxy some loose panels)

This week, I should get some more parts in and will do some more small projects:
  • AMG pedals (parking, brake, accelerator)
  • New W140 style headlamp wipers. Much cleaner looking - got new plastic caps ordered and will refinish them
  • An entire center console assembly from a later model car (has the cupholders, etc). Will need to clean and repair a bit. The one currently in the car has the ashtray and cassette tape holders in the center, which is ugly and useless IMO

- Need to fix the horn. Not sure if the clock spring has an issue? but I have extras. It's just not beeping when you push it. Should be easy enough to fix

Keeping an eye out for 18 inch monoblock wheels. Definitely not in a hurry - but those will take the car to the next level 馃檪 Overall, good steady progress

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #7 ·
Made some really great progress - I'll definitely have to capture an update video and share here

I took out and repaired the mirror assembly. I got some videos on this - just need to edit and upload. Luckily, all the broken plastic parts were still inside the mirror housing itself. It just took a whole lot of JB Weld - but that assembly is as good as new 馃檪 Really cool that the older ones allow you to move the mirror via button and even save the position

Replaced the worn out stock pedals with AMG pedals. Super easy upgrade, pretty cheap too ($73 for genuine MB parts). Here are the part numbers I ordered:
170-290-01-82 Brake; $26.99
203-430-00-84 Parking Brake; $14.47
170-300-00-04 Accelerator; $31.58

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One of the previous owners had put replacement speaker grills in the back - they stick out, so you can't properly open and close the two rear compartments. Their "solution" for being able to open those compartments was to remove the bolts on the hinge and velcro the lid in place. I took the speaker grill off (trash!) and put the proper hardware back on (bolts are M5). I ordered the Bose part from eBay. The speakers themselves don't stick out and putting the right speaker grill (flush with the carpeting) will be a nice touch - even if it's not actually "Bose".

The cupholder assembly (screenshot in the post above this one)- I was able to repair that completely (fixed the springs, etc) and after a good cleaning, I installed in the car 馃檪 Also replaced the broken button on the sliding armrest and lubricated it with some of the MB Gleitpaste, it's smooth as butter. If anyone is interested in the older two compartment (ashtray + cassette tapes) assembly, shoot me a DM. The new unit has a vacuum line also - so when you lock the car it'll lock the compartment too which is nice.

Definitely need to replace the gas spring inside the armrest storage compartment, mine is shot. A company called You.S has one on eBay for ~$16 (versus the $72.73 price from my usual MB parts source, Part number 000-980-75-64. Will be ordering this soon

I got a cheap $50 aftermarket antenna (manufacturer is "Ser A") to replace the broken Hirschmann one. I replaced the rubber seals too - anything rubber gets shot here in Arizona (part# 129-827-02-98-7C45 for outer and 129-827-03-98-7C45 for inner). I was able to reuse the Hirschmann chrome circle hardware and make it look "pretty good". Cut the wires nice and clean, butt spliced it into the stock radio harness. The aftermarket antenna has Red and Green and MB harness has Red/Green, Blue, and Brown. Red on antenna goes to Red/Green on harness and Green on antenna goes to Blue on harness. Brown is ground and isn't needed (antenna itself already has a ground). While I was in there, I took out the original Alpine CD changer and threw it in the trash 馃檪
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I replaced the two blown gas springs in the trunk (part# 129-980-06-64)- this is lifting great now. On eBay you can get them for $54.88 for two shipped which is a great deal (arrived in 2 days). They're the same as the MB part (Stabilis) which cost about $51 each- just without the MB stamp.

The trunk latch assembly isn't turning on the trunk light automatically. I checked this out and the spring was missing. I cut a spring and fit it, now it "kind of" works. You can manually enable the light in the trunk using your finger and pushing the yellow switch. If it's on, closing the trunk will properly turn it off now. But opening doesn't turn it on. There must be a broken plastic bit in there.

Will be looking at buying Euro spec glass lenses. I've got the euro style wipers ready to go (taken from a W140; thanks to @duh_vinci for the tip)

95 SL500, 07 E350, 89 944 S2, 04 XC70
1,322 Posts
...Will be looking at buying Euro spec glass lenses. I've got the euro style wipers ready to go (taken from a W140; thanks to @duh_vinci for the tip)

Be ready to do small modifications to make those work, you will find details here Album unsorted, exterior but basically W140 shaft diameter is larger, I had to make a bushing to make these work with smaller R129 shaft. Also, small hole needs to be drilled into the arm for the washer hose to go inside the arm


P.S. And when you get the Euro glass, do yourself a favor, use Laminx to protect them, these are getting more and more expensive every year!

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #10 · (Edited)
Lots of small updates! Small, but rewarding

Got the proper euro headlamps on here. These are the Automotive Lighting (basically same as Bosch; just post Bosch/Magneti Marelli merger) brand. I sold the dark amber corners on eBay to someone who ended up being a BenzWorld member. I couldn't get them to give a deep "CLICK" like the US ones do when you push them into place. I think the plastic bracket on my car that the signal clicks against is bent or something

Also pictured - got the deleted wiper panels (left: 129-826-05-77, right: 129-826-06-77) and the seals for them (left: 129-826-098064, right: 129-826-10-80). $183 in parts - not too bad. I took the headlamp wiper motors out, took the pump for the headlamp wiper out and all the washer tubing. I plugged the hole for the pump with a grommet (000-997-33-20) and then replaced the regular windshield wiper grommet with a new one (123-997-36-81). I had to paint the valence panels myself and I'm surprised they were plastic. I went to Space Age Auto in Mesa, AZ and got some adhesion promoter and had them make me a rattle can of 199 metallic. The paint came out great!

One thing to note: the seals need to be pushed in place using a very small punch. It's easy to do this for the panel itself, but the bumper will need to come off to properly access the ones that go under the front quarter panel. There's a hole in the seal itself that you insert the punch into so that you can push it in place. Removing the old seal, you will likely break those black rubber plugs off in there.
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As mentioned above, I did a small job on the 722.5 transmission that I have. The boot around the overload protection switch was ripped and so I replaced the entire switch and all O-rings/seals/etc. It was REALLY stuck on there and I had to use an impact wrench to get it off. Tons of details documented here (the folks on 500eboard are awesome):

I replaced the vacuum distribution block under the hood - I was having all kinds of weird vacuum noises. This fixed several issues - the center vents are blowing again like they should and this should help with the Y11 code I had gotten. I captured more notes about that job here:

I also figured out the horn issue. I replaced the horn relay (001-542-99-19) and that didn't do anything. I went down to physically inspect the horn itself and saw someone cut the wires. I got this back together - took the time to solder it and use heat shrink-wrap so it's nice and clean. Back in business again 馃檪 But now my SRS is on from removing the airbag (was checking to see if wires were connected to contact ring / clock spring)

Interior-wise, got a few small things done. I swapped out the cassette tape roll box for the cup holder assembly. I had to repair the springs on the cupholder themself - just hold in position and break out the torch to get it to keep the original shape again. They're working great now! I took the armrest assembly apart completely and got all the broken plastic bits for the button out of there and lubricated the moving parts really well with the MB Gleitpaste (love this stuff; originally for sunroof but good all over). New button in place, it's working great

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Not pictured - I fixed problems with the drivers side door panel. Someone had clearly taken it off before and didn't put the screws back in. I have a huge collection of nuts/bolts/screws/etc from cars I've taken apart and I found the ones that should be there. I also took apart the seat adjustment switch, cleaned it really good, and repaired the buttons so they click when you press them (there's a small tab under the button on both sides of the button; had to JB weld that back in place). Had to plug in the vacuum line for the door also - so that it locks the storage compartment again. The wood for the seat adjustment area was bigtime warped. I used a heat gun to get it back into the shape and a mixture of wood glue and super glue to get it adhering to the aluminum behind it again. I'm waiting for one plastic trim piece so that this will snap into place - I'll take a picture when I get that in.

I'm trying to put together a full set of 18" AMG monoblock style I wheels - basically what was on the sport package in 1999 - 2002. I've got 3 of the wheels in (two rear: 129-401-18-02, one front: 129-401-17-02)... trying to find another front wheel. I replaced the spare with the version of the wheel that comes in the sport package too (17" compact spare: 129-401-13-02). This thing will look great once I get these refinished in the stock gray color and get new tires. If anyone has an extra FRONT wheel, let me know! 馃檪
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Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #11 · (Edited)
Finished the seals that go to the valence (under the headlamps). The bumper you can loosen with one 13mm bolt (on each side) near the fog light. When that is loose (don鈥檛 remove), the bumper will loosen up just enough that you can move it and use an angled pick tool to get the rubber 鈥渂umpers鈥 on the seal seated up into the holes under the quarter panel (in the pictures for the last update, you can see that part dangling)

I got a Continental TR7412UB-OR open box on eBay for $123 shipped last week and went to attempt the install. If you have a stock head unit, I think the Continental would just be plug and play 馃檪 But in my case, the previous owner had installed an aftermarket setup (running an amp, splicing the harness, running new wiring). There are only RCA connectors behind the head unit- so I鈥檒l have to redo with proper +/- speaker connections. Definitely a mess. Today, I took most of the back compartments apart so I can check out the wiring. It will take some time and careful thought to sort this out- but should be rewarding 馃檪 After I figure out the wiring, I鈥檒l look at replacing the individual speakers
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1996 SL500, 2000 E430, 2011 E350
5,418 Posts
A great feature of the 94 SL320 is the mirror adjustment and OBDII all the other cars had to wait till 97
OBD ll came out for model year 1996. It鈥檚 helped me several times.

It鈥檚 interesting that was in your model year 1994.

Which means for planning purposes it was planned at least a year earlier.

Which meant the codes must鈥檝e been distributed to carmakers years before.

I found it to be a great enhancing feature. Twice it has save me from angst and long-distance car trips.

One time it was a coil igniter going out and I went the last 600 miles on seven cylinders. I figured the computer was smart enough to shut off the fuel for that cylinder

The second time it was a loose gas cap on my 2000 W210.

What first got me interested in R129鈥榮 was a friend letting me drive his SL 320. I thought it very well balanced and certainly adequate power. It felt better balanced than the V-8鈥檚

I miss my 300 E, too.

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #13 · (Edited)
Had some time last night and this afternoon and tackled most of the stereo cleanup / install 馃檪

Here's the (almost) finished product - listening to Latino Mix 100.3 (local station)
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I need to get the "Illumination" wire figured out. I connected the one from the stock harness, but it doesn't seem to matter (always powers the screen on - versus only power the screen when the lights are on). Someone mentioned using the line going to the light from the ashtray - I did find an extra line (I think it was a leftover from where the ashtray WAS, over the transmission tunnel... before I replaced with a cupholder). I'll check that out next, tie the wiring up a bit, and then clean the car while it's still all disassembled.

Everything else was easy to figure out. With the TR7412UB-OR wiring harness, the A4 goes to ignition and the A7 goes to battery (the wires themselves on the harness have small writing which is confusing; red "Power" goes to battery and yellow "Memory" is going to ignition). Besides that, the only weird thing was that the RF input for radio antenna had some kind of weird conversion plug that you need to pull out (newer cars must have a new type of connection).

Here are all the old wiring and the old head unit that I pulled. I printed all the wiring harness diagrams out and used a continuity tester to make sure everything was wired where it needed to be.
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I basically kept the aftermarket Alpine Head Unit Power Pack KTP-445U amp and ran 14 gauge speaker wire from the head unit to the amp as input. It's all ran nice and neatly through the tray under the door sill and cable tied up every 1 foot or so. The amp output already had wiring to the front speakers (only the doors) so I left that as-is. I did replace the ghetto wiring to the rear speaker also using the 14 gauge speaker wire. I took the time to solder the connection to the rear speakers and use heat shrink tubing so it looks nice and neat

Overall, super happy to have all the electrical taped things out of here. I'd like to have soldered everything, but it would have taken forever. The butt splices work just fine and weren't too bad
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Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #14 · (Edited)
Quick follow up to the above! I've got the wiring finalized for the head unit. It took some trial and error; wanted to share some tips. This might be common sense for a lot of folks - but wanted to share since I had to do a lot of searching 馃檪

1. If you are attempting to install the Continental head unit using the stock wiring harness (unmodified) for the R129, it will fit but you need to swap pins A4 and A7. You can use the guide (attached to this post as Connections for radio, testing electrical system, radio (RD).pdf) to ID the pins if you're not sure of the pin numbers. You can use a paperclip to poke the pins out from the front.
2. If your wires are already spliced up like mine were (see picture below), match the RED (with white stripe) wire to the supplied Continental harness RED wire and the BLACK (with blue stripe) wire to the supplied Continental harness YELLOW wire.

If you want to verify your work, you can grab a multimeter. Unplug the connector from the back of the Continental head unit and put one end of the multimeter on ground (black) pin (pin A8) and the other on red pin (pin A7). Per instructions, this should be BATTERY - so you should read ~12 volts. Keep the one end on ground (pin A8) and move the other one over to the yellow (pin A4). With the car off, you should read 0 volts. When you turn ignition to position 2, you should get ~12 volts.

If it's wired backwards (like mine was in the previous post above this one), the head unit will still work just fine. But you'll have to turn it on every time you get into the car. When it's wired correctly, the head unit will automatically turn on and extend your antenna when the key is moved into position 2 (like you would expect).

Regarding illumination: you can test this wire using a multimeter also. It'll read 0 volts when lights are off and ~12 when lights are on. This is the Continental orange wire (on Mercedes wiring harness it's the WHITE wire with blue strip). The illumination wiring ONLY seems to affect the lights behind the buttons (ex: src, band, sel, <<, >>, 1 - 6, etc), NOT the actual display screen. It seems like the display screen is always on 馃し鈥嶁檧锔

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Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #15 ·
I got an Autel MaxiDAS DS808 code reader recently and it came with the 38-pin connector adapter for older Mercedes. I plugged it into both the 38-pin port and also the ODB port under the dash and there's almost nothing available for the SL, unfortunately. The 38-pin offers more options for sure, but it's still limited. For older cars, I think you have to use a real Startek SDS unit in order to do things like clear the SRS light. When I plugged in, it would show Airbag under Systems but then say Unknown version or something like this. I'll have to get someone with a real system to reset my SRS light- accidentally tripped it when I removed the airbag with the car on.

I tried this code reader on my newer cars (2009 CL63, 2013 GL550) and it works amazing. With my CL63 which has ABC suspension, you can even do a Rodeo test. The newer cars just have the standard ODB2 port and with that can access and test basically everything with it. On our GL550 (X166), one of the distance sensors (used for Parktronic) went bad. When it fails, it won't say which one - it just turns off Parktronic. Using the reader, I was able to find out which one was bad and replaced it myself. Since you have to take the bumper off to replace the sensors, DIY definitely helped save some money!
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With the SL320, I did some deep cleaning tonight 馃檪 While everything is mostly apart for the stereo wiring, I gave the car a really good vacuum and then broke out the Folex

If you've never used it before, it's pretty good at cleaning - both with removing stains and for removing smells. I took the seat bottoms out, soaked everything, and scrubbed like crazy
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The parts which were already removed for the stereo install - I hit those really good too 馃檪
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Once everything dries, I'll see if it needs another round. Just waiting on a new convertible top button to come in (the red pull switch; 129-820-16-10) and then I can start putting it all back together! 馃檪

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #16 ·
I got a 36 sq ft "Super Bulk" kit of HushMat Ultra 10801 and have been installing this recently. It's a sound dampening insulation (a lot of people call this insulation by the company name "Dynamat" that popularized the product). Should help get rid of road noise and might even help with the heat (being in Arizona every bit helps).

The main areas I'm going to hit are:
  • Under the center console (over the transmission / drive shaft tunnel)
  • Both doors
  • The rear area (what would be the back seats if there were back seats)
  • The removable hard top

I took apart the center console and rolled the first piece on over the transmission / driveshaft. The previous owner had removed the cassette tape holder that typically goes here and when it was exposed, I found it was giving off a lot of heat. Really helps making a cardboard template first so you can avoid wasting material and you can pre-cut the areas with screws. Before you apply, you'll want to scrub really well first with soapy water and then with rubbing alcohol. I used a small handheld wooden roller to press it on good.
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Next up was the drivers door. This took a lot longer to do than I thought it would. There are so many small things you have to account for, even if you think your template is perfect. The door takes more than one full sheet of material- so you need to plan where to do the division. Another thing to watch out for: you want to go under parts like the metal hook (for mechanically locking the door). Other parts I felt OK about going over (some parts of the wiring harness). Also there were a lot of "while you're in there" types of projects.

I took this chance to fully clean and lubricate the window parts. For the gliders (the two rails, one on each side) I slathered on a bunch of Mercedes-Benz "Gleitpaste" (001-989-46-51). It's like $70 for a 1.1 pound can, but I've had it for years and I'm barely making a dent. It's amazing for sunroofs and for any areas where there's sliding parts. I greased up the teeth on the window regulator too and the window is moving nice and smoothly.
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One of the previous owners had put aftermarket speakers in, so I cleaned things up a bit. I put proper ring connectors on all the wiring and JB welded broken parts of the plastic speaker assembly (what holds the speaker) that someone had broken along the way. Everything went back on perfectly!
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After having this all back together, I took the car for a spin. I don't have any way to properly measure decibels, so my experience is subjective. But it seems like there is less road noise coming in. The passenger side is up next - I'll have to fix the IR sensor on that side while it's apart. The rear of the car (where you would lean your back if you sat in the "back seat") is letting a TON of noise through. Besides the road noise, you can hear everything the vacuum pump is doing (which is super noisy; might need to get a rebuilt unit). I still have 7 full sheets (32 inch x 18 inch) of this HushMat material left so hitting that area shouldn't be a problem.

Besides all this audio fun, I have a full set now of the AMG monoblock style 1 wheels (some of them pictured in a previous post). Working with a local place called WSI in Tempe to get them refinished and get some tires put on. That's going to be a really fun update to share when everything is finished 馃檪

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #18 · (Edited)
Nice and small - but rewarding - update here 馃檪 Since I've had the car, the passenger side IR (infrared) sensor hasn't worked. Turning the key inside the lock works fine, just not the one button FOB. Drivers side and trunk IR sensors both work great.

I had the door panel off as I'm doing the HushMat install, but turns out that's not needed at all. I followed the steps here from this video:

Basic steps:
  • Put key into lock
  • Pull weather stripping down door (carefully!) until you see a small hole
  • Use a 4mm long allen key and turn counter clockwise
  • Use the allen key to "push" the lock out
  • It may take some jiggling, but the IR sensor and lock come out as one piece
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Here's how things looked when I removed it:
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The electrical connectors (easy to spot with the two red o-rings) weren't plugged in. If you look closely, there's a lip around the edges (to the left of the two connectors). You can pull the connector FORWARD and there's a notch in it which lets you slide the connector into place on the left of the door. You can push as hard as you want then, it won't move. When you go to put the door lock back in, it'll line up and connect perfectly

After doing this, the lock behavior was a bit weird. The remote didn't work immediately. I unplugged the negative from the battery for 10 seconds, reconnected it, and then tried each of the IR sensors (drivers door, trunk, passengers door). They all worked great! 馃檪
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UPDATE: seems there's an official synchronizing procedure. Here's what the manual has for my model year (1994)
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Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #19 ·
Just about finished with the HushMat install. I made an update video here if you wanted to see where it's installed:

Will be putting this all back together soon - really hope it's worth it! The goal in my case was to eliminate as much road noise as possible... but it might work well as heat insulation. I have 3 left over sheets which should be more than enough to do the hard top. I'll have to take that apart at some point to fix the broken trim panels and to get it painted (car is 199 blue/black; roof is 040 black but faded... matches when dusty or at 20+ ft)

Wheel-wise, I got an appointment in 3 weeks to get the AMG wheels refinished. I just need to work with someone local to strip the chrome off one of the wheels first. I contacted a media blasting place and they wouldn't do it; following up with a second place tomorrow which advertises chrome stripping.

I've been watching all of the Top Hydraulics videos (which are amazing) and will definitely be taking out all of the pistons/cylinders out sometime in 2022 to get rebuilt 馃檪

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
1,689 Posts
Discussion Starter · #20 ·
Right after the holidays, I got Covid-19 馃檨 Got nailed hard for one day and then took it easy for two more days. After that, everything's been fine. I'm still testing positive, but it's been 10 days since the first positive test. After I felt better, I finished up the HushMat install above. Will capture a follow up video on YouTube soon. Everything went back together great and I believe it does make a difference! Might have to get a decibel measurement tool to see where things register

Lining the roof with HushMat will be a great one too. When that time comes, I have to repair some interior panels on the roof that are damaged and I also noticed the top hydraulics are leaking for the front two above the visor 馃槺 Going to leave the roof alone until all the other stuff is sorted out

I got the single chromed AMG wheel over to folks that will get it chemically stripped. That should be ready sometime this upcoming week and then finally it'll be time to refinish all four of the AMG wheels I've had taking up space in the stock Silver color and get some proper tires on them 馃檪

In the meantime, I've been tackling some smaller projects. I replaced the cabin filter (129-835-00-47), it was filthy. Vacuumed out everything and hit with some soapy water. With your hood 90 degrees, it's just two simple screws and the three retaining clips on the bottom loosen up with a flathead screwdriver
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The hood pad has been disintegrating since I bought the car so I finally removed most of it. This is a job I did with my old 560SEC and it's definitely not difficult, just time consuming. The more time you put into prep, the better the job will turn out. I used a putty knife gently at first - but it was leaving minor scratches. Ended up removing most of it by hand (just pulling it off). Hit it with multiple rags with hot soapy water and it's looking good! Still some adhesive to remove, but this was a great start. Hood pad is 129-680-20-25 and I got 16 clips total (14x 230-990-00-92 and 2x 230-990-01-92). Will be shooting to wrap this up before the end of the month
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The last noteworthy thing I did was replace the windshield wipers (129-820-08-45). I went with a Bosch part instead of the Mercedes-Benz part. It worked, but next time I'll definitely be ordering the MB part number (which is slightly different, but is also by Bosch). I had to use my tin snips to shorten the wiper blade a bit - but it fit great after that.
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