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1994 SL320 / 1987 300D / 2013 GL550
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Discussion Starter · #21 · (Edited)
Definitely been a while since I've shared an update!
  • got a new glove box (the eye glasses box) since the vinyl panel was loose (wouldn't always open)
  • repaired center AC vent (moving the middle piece didn't do anything before)
  • got some interior paint from SEM. Color is "Med Gray" 15393 (trying to match Alpaca gray). Having an older car (1994), it came with the split center with ashtray and cassette holders. Months ago (see above posts), I retrofit the cupholders from a wrecked 1999 but it was Orion gray (much lighter in color). After refinishing with the SEM paint, it's not an exact match... but it's close enough.
  • Put in a new 3rd brake light assembly. The tabs broke on the inner piece (the part that holds the bulbs) and it was flopping around

Not pictured here - but I did get a new LEFT (US drivers side) door panel because the flip up armrest on the door was broken (the springs were missing; plastic parts all broken). I had a super hard time finding a good shape one and ended up getting a passenger door from the UK in mint shape. Now that armrest / map storage stays up in place (after you lift it up) and all the plastic is perfect.

I did finally get the wheels squared away - huge thanks to WSI here locally for refinishing. Brand new Michelin Pilot Sport 4S tires too and a proper 17 inch spare wheel in the trunk (same wheel / tire setup as the sport model option). Didn't need to roll the fenders, it's a great fit
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Lastly - this is a good one; definitely wanted to share. The trunk latch assembly is pretty interesting. When you open it, it's supposed to turn the trunk light on. When you close it, it's supposed to turn the light off. While it is open, you are supposed to be able to operate it by hand by moving it (there's a notch for your finger to move it). If the spring breaks, the light won't turn off by itself and it'll drain your battery. If the yellow plastic breaks (what happened to me), then the light won't turn on.

I looked all over eBay; all of the units had a broken yellow piece (see picture). It's supposed to have a small pole that goes through the second plastic bit, keeping them in sync.
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After some searching, I found a place in Germany that makes a metal version of this! 馃槂

It's reasonably priced - but unfortunately they won't ship to the USA. I shipped to a friend and then he mailed to me (total cost was ~45 euros). But now it works perfectly and won't have to worry about it breaking again 馃檪
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Lots more to come. Need to do the motor mounts, replace the shocks, the strut mounts are cracked... After that need a proper alignment. The roof hydraulics are leaking. I still haven't even seen the soft top yet (no idea if it's in good shape or not). The wiring harness does look to be original - the wires are going to crack when it's time to do valve cover gaskets. I got an extra valve cover at the junk yard that I'm going to clean up and get powder coated for when that time comes. Not sure if I'll rebuild the harness myself or try to find a used repaired one (DM me if you know a source!).

Definitely got enough to stay busy for a while 馃檪 If that list above isn't enough, I've also been thinking about doing a transmission swap for a 5 speed manual down the road (once other items are sorted). Trying to find an R129 one is hard... but the R170 SLK offered an M104 with a 5 speed. There might be a bolt up option (clutch pedal, master cylinder, shifter, etc)
 

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
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1,689 Posts
Discussion Starter · #22 ·
Question for folks who have replaced the wiring harness in 1993 - 1995 cars. I am almost positive my car has an original harness. It's part number 140-540-69-32

I'm looking for rebuilt units (if you know where to find one, please DM me!). I noticed there is a similar part number 140-440-46-05 and I'm curious if this would work too? I haven't found any exact information - but I did see notes in this thread:

Here @Voyager1988 said the difference seems to be w/ thermostat plug (2 plugs in 1404404605 versus 1 in 1405406932).
 

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
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1,689 Posts
Discussion Starter · #24 · (Edited)
It's been a while - wanted to share an update. I've got a bunch of things in progress 馃檪

I got a replacement engine wiring harness (140-540-69-32) along with a rebuilt ETA (000-141-57-25, rebuilt by ProgRama), new hoses for all the cooling systems, new valve cover gaskets, new engine mounts (2x 129-240-08-17), transmission mount (124-240-06-18), new O2 sensors, new spark plugs (003-159-68-03), all kinds of stuff (and more still on order). Enough parts that I'm having a hard time trying to figure out what order to do them in 馃槀 Here's just a small sample (also got the paper M104 workshop manual).
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Along with those jobs - I found a 1998 SL600 at the junkyard and harvested all the wood bits (including the wooden center roll box; see pictures 1+2 below) from the car. I sent those over to Igor at restoredinusa.com and they're being refinished in bird's eye maple (kind of a dark gray with swirls; see picture 3 below). I included pieces for 1990 - 1995 (what I have) and 1996 - 2002 (the door wood is different; older style not pictured) so that the veneer will all match in case I ever decide to get another R129 and swap the wood out.
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It's been really hard to find time to set aside to do repairs - and it's hot outside here in Arizona (getting as hot as 115F recently). I did get one small job done recently. I replaced the small strut in the armrest. Now when you push the button, the armrest pops up nice and quickly. Super small and easy to do job - but worth it in my opinion. It was $70 USD for the part (part number 000-980-75-64) and took me about 20 mins to swap out. Be sure to take the armrest out and put it on a bench where you won't lose the e-clips that hold it in place.
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I sold my 2009 CL63 recently on bringatrailer.com so now the SL is finally in the garage. I've been driving it daily and really enjoying it 馃檪

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Premium Member
1994 SL320 / 1987 300D / 2013 GL550
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1,689 Posts
Discussion Starter · #25 ·
Got some really good wrenching done over the weekend! It's still really hot here - I tackled most of the work yesterday when it was 104F (40C)
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Replaced:
  • both engine mounts
  • transmission mount
  • front and rear O2 sensors
  • oil level sensor (along w/ oil change)

Both front engine mounts were collapsed... the drivers side was much worse (top in the picture). Here's a picture of a new mount (left) next to the drivers side mount (right)
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Before this, the steering wheel was shaking and idle felt a bit rough. It's much much better now 馃檪 Still have plans to do a "tune up" (new coil packs, spark plugs, wiring harness, spark plug wiring). Likely going to tackle the cooling system in total first (radiator, water pump, new hoses). I recorded some video of the work I did which includes specific tips on how I got to everything and how I broke things loose. By far, the two worst ones were the 19mm nut on top of the transmission mount and then the 17mm bolt on top of the driver's side engine mount

A few SLs appeared recently at the local junkyards, so I hit them pretty hard over the past few weekends. Using the great videos by Klaus from Top Hydraulics, I got all of the cylinders and the pump removed (not pictured: bow cylinders. I got those in a second trip).
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I cleaned these up and will be sending them over to Klaus in the near future. My hydraulics are visibly leaking in the front - likely others leaking too. I've avoided using the roof for that reason and (after almost a full year of ownership) I still don't actually know the condition of the soft top! That'll be fun to find out - hoping it's in good shape

I've also gotten spare parts for all of the original Becker / Bose components and have some rebuilt units (BE1692 head unit w/ bluetooth, Bose Amp, Hirschmann antenna) which have a 3 year warranty on the way over. I've pulled wiring harnesses from a few other cars so I can cleanly (soldering and shrinkwrap) repair the wiring harness back to the original when installing everything (later this year when it's good weather)
 

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1994 SL320 / 1987 300D / 2013 GL550
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Discussion Starter · #26 ·
Lots more great work done - I tried to capture as much as I could in video form which you can find here:

This of course is the M104 (SL320) so this may not be too helpful to folks with the V8s. But over a two day period I was able to tackle the following jobs:
  • Replace valve cover gaskets (oil was leaking into sparkplugs badly)
  • New spark plugs - as a bonus, one of the old ones broke as I was removing it 馃槶
  • Replace throttle body with a rebuilt one
  • Replace engine wiring harness with a rebuilt (2007) Delphi unit
  • New ignition coils

Compared to the mounts video, this shows more hands on work. Things like the throttle body can be tricky and I wanted to share good tips there. Shout out to Victor at RestoreYourMercedes.com for a great video on that (see here)

Everything worked out great! Car is idling nice and smooth, it's a pleasure to drive. I sent the hydraulic cylinders over to Klaus to be rebuilt. The wood I shared a few posts above was being restored by Igor at restoredinusa.com and it's finished! It should be on the way back soon - will be fun to share how that looks (especially being a non-standard color, Birds Eye Maple).
 

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1994 SL320 / 1987 300D / 2013 GL550
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Discussion Starter · #28 ·
@PalmBeach95 thanks for following along! Lots more to come. It's been a lot of fun getting super hands on with the car compared to my first SL. I got to know the features of the car back then (2008 - 2012) but never really turned a wrench, at least not for anything major.
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I did put together a decent compilation of information back then including a buyers guide which is on my website. At some point, I'm going to dig in again and give that page a major refresh with everything I've learned (which has been a lot!). The forums and YouTube have been great places to learn and share

For junkyards, you might try searching on row52.com. I have 5 local sites bookmarked in my browser and I'll refresh those occasionally. Guessing you're from West Palm Beach - here's a link to a yard that should be close to you. Doesn't look like any SL's there... but I have noticed folks messing up online and putting "S class" or putting "500" / "320" instead of SL. Whenever I see a new W126, W124, or R129 here in the Phoenix area I get the toolbox ready 馃槉
 

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1995 SL 320
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136 Posts
Noticed you replaced the valve cover gasket. It鈥檚 mainly those 9 bolts, correct? Torque them back at 9nm鈥 Any suggestions or thoughts when I do mine? I just replace my plugs but I plan on pulling them back out along with the coils when I remove the cover.

Any suggestions would be appreciated.
 

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1986 560SEC, 1989 560SL, 1994 SL500
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Noticed you replaced the valve cover gasket. It鈥檚 mainly those 9 bolts, correct? Torque them back at 9nm鈥 Any suggestions or thoughts when I do mine? I just replace my plugs but I plan on pulling them back out along with the coils when I remove the cover.

Any suggestions would be appreciated.
I found this guide (posts #1, #15) to be super helpful. The valve cover gaskets get replaced in the process so you can still follow along as a general guide. Same engine, different car so part numbers may be different but the general order of operations is the same.

HIGHLY recommend being ready to replace some of the breather hoses. Mine couldn't come off without breaking- specifically the driver side hose towards the front of the engine. Also get new copper crush washers for all the bolts!
 

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1994 SL320 / 1987 300D / 2013 GL550
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Discussion Starter · #33 · (Edited)
The M104.991 that I have has 12 bolts holding it down actually (not 9). You don't need crush washers for these - but you SHOULD get 12 of the rubber seals that go under the part which holds the bolt (104-016-03-64). They compress as you tighten up the bolt. In my case, I just got them tight since I don't have anything that goes as low as 9nm... but last time I overtightened, the bolt broke off in the head 馃槺 (was on a 300E). I captured some of that fun here (around 4:08):

The breather seals are tricky to remove. I didn't remove them in my case because I didn't want to reseal the plate holding down the baffling (will be powder coating the valve cover sometime). But I have removed them on another car before. I got it out with a chisel from underneath. Breather seals for 104.991 are part# 104-016-09-80 (valve cover has 2 of them). Just for reference, my valve cover has part# 104-016-07-05
 

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1995 SL 320
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The M104.991 that I have has 12 bolts holding it down actually (not 9). You don't need crush washers for these - but you SHOULD get 12 of the rubber seals that go under the part which holds the bolt (104-016-03-64). They compress as you tighten up the bolt. In my case, I just got them tight since I don't have anything that goes as low as 9nm... but last time I overtightened, the bolt broke off in the head 馃槺 (was on a 300E). I captured some of that fun here (around 4:08):

The breather seals are tricky to remove. I didn't remove them in my case because I didn't want to reseal the plate holding down the baffling (will be powder coating the valve cover sometime). But I have removed them on another car before. I got it out with a chisel from underneath. Breather seals for 104.991 are part# 104-016-09-80 (valve cover has 2 of them). Just for reference, my valve cover has part# 104-016-07-05
WOW!!!! Did you get it out? I was going to buy a 1/4 torque鈥 proba just do a 7 or so then go to 9 Nm a few hours later.. did you have a pattern on tightening the bolts?
 

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
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1,689 Posts
Discussion Starter · #35 ·
WOW!!!! Did you get it out? I was going to buy a 1/4 torque鈥 proba just do a 7 or so then go to 9 Nm a few hours later.. did you have a pattern on tightening the bolts?
I did! I made a follow up video (pinned in the comments for that video). I basically used a diamond tipped hole saw and got it out, finished the job. That was a PAIN in the ass.

As for tightening, I didn't find a bolt order sequence.
  • I started by hand (holding the socket and turning it) one at a time (crisscross pattern) until it started to get hard to turn
  • Now I used 1/4 inch ratchet to tighten, but not all the way. I did this one at a time with crisscross pattern also.
  • Finally, I tightened to the final spec (what felt like 9nm in my head)
 

Premium Member
1994 SL320 / 1987 300D / 2013 GL550
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Discussion Starter · #36 ·
Tackling another big job: I'm restoring all of the audio components back to stock (or close to it). I'm 2 days into the work so far, about 14 hours. Taking my time and doing it right

A while back, I had ordered a few refurbished parts from Becker Autosound:
  • Hirschmann antenna (129-820-16-75)
  • BOSE Amp (129-820-03-89)
  • Becker 1692 with Bluetooth mod (I think my car originally came with a 1492 which looks almost the same, but this is a better unit).

All of these parts come with a 3 year warranty 馃檪

At the time of writing this post , I basically have everything working and just need to do some final clean up (put paneling back in car, use the heat gun to shrink wrap the splices). I put on the radio and the quality is already LOADS better than it was before.

I have more details captured on video (will edit and upload once it's all wrapped up) for the whole process, but much of the wiring in my car was hacked up. You can see some of the hack job (and my temporary clean up) in earlier posts in this thread. Cheap speaker wire was ran to each of the speakers and an Alpine KTP-445U "Power Pack" amp was installed in the back (sub woofer was there, but had wires cut)

Getting super lucky at the local Pull N Save, I got all the parts needed (along with the Becker order) to finish the wiring:
  • Original door speakers (left and right; from a 1994 SL500) in great shape - including the pigtail that plugs into it. None of the plastic on this assembly was broken on this (where bolts hold it down or screws secure it) where mine was hanging on by 2 or 3 screws
  • Full pigtail from the rear wiring to the amp and subwoofer. I got this from a 1995 SL320 and most of it matched up perfect. I wanted to have way more than enough to do a really clean splice
  • Pigtail for the Hirschmann antenna (so I can splice this back in)
  • Replacement OEM wiring to both the rear speakers
  • Wiring harness pigtail for the head unit (so I could cleanly splice this in)

I did the antenna first. That was super easy and I even soldered / heat shrinked the wiring so you can barely tell.

After that, I put the door speakers in. The pigtail for those has 2 caps that you can heat with an iron, pull the wires out, and then put your wire through the cap. Way easier to do that than to splice.

The head unit wiring was straight forward. I used male/female disconnects for this because space is super limited and I am not good enough with a soldering iron to attempt to solder all the connections! It's easy enough to disconnect these too in case I die and the next person wants to put something else in 馃槀
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The amp wiring is what took a lot of time today. You have to take the back tray (with the two cubby doors) out. Since I had already removed the subwoofer and tucked it away, this was pretty easy. Then you can take the rear side paneling out (the carpeted panel that the rear speakers are mounted to). With that out, I hacked together a quick and dirty splice just to verify this even worked
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This worked great - so I could put things into the final position and mark where the cuts need to be for the splice. I went in thinking I'd solder these too - but some of the wire is larger... like 10 gauge... and I don't feel comfortable soldering that. I ended up using butt splices but I took a lot of time to do it right. The butt splices themselves have heat shrink on them and then I slipped some heat shrink around both sides that I'll slip over to completely cover the butt splices.
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So that's where I'm at so far - mostly there! Tomorrow will be when it's all finally finished. Mercedes-Benz did a really nice job with the sound in the R129, in my opinion. You can replace individual speakers of course (and you should as they age)- but I'm not sure why someone would ever hack the wiring like this and put worse components in. I didn't get a chance to test the Bluetooth on the Becker head unit yet... but I'll be selling the Continental TR7412UB-OR when this is all done if anyone is interested

Coming up next weekend - replacing all the wood with Birds Eye Maple. Igor at RestoredInUsa.com did this for me recently and I even had the SL600 wooden pieces (for the roll box and center console frame). Can't wait to see how this looks 馃檪 He just shipped back the refinished wood and it's due to arrive this week
 

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1994 SL320 / 1987 300D / 2013 GL550
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Discussion Starter · #39 ·
Finally got some time to do editing 馃檪 Here's a video capturing all the audio fixups I did for those interested

Today, I got one of the refinished wood pieces back from Igor and it looks AMAZING. It's a pretty close match to the special edition Birds Eye Maple that some R129s had (Silver arrow for example). I'll share some pics of this once the rest of the pieces arrive
 

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1995 SL 320
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Finally got some time to do editing 馃檪 Here's a video capturing all the audio fixups I did for those interested

Today, I got one of the refinished wood pieces back from Igor and it looks AMAZING. It's a pretty close match to the special edition Birds Eye Maple that some R129s had (Silver arrow for example). I'll share some pics of this once the rest of the pieces arrive
Nice viddo鈥 lot of work. I usually use a smaller diameter of solder to make it easier.
 
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