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Do It Yourself (DIY) repair thread and wheel and tyre thread

537K views 293 replies 103 participants last post by  ianrandom 
#1 ·
If you can link to or post repairs, please do so in this thread. I will be "polishing up" the thread later to make it easy to follow.
 
#2 ·
#6 ·
AC expansion valve W126

I did a writeup on this job. This is a true (not a cheapo) R134a conversion that has held and worked nicely in hot&humid Washington, D.C. for two full seasons now. I'm not talking about the conversion - all I am explaining is how to replace the expansion valve (which is the first thing to go after a doubtful conversion) yourself for about 90 bucks in parts in one afternoon. This is a job that was quoted to me at several places at over $1,250 (yes, with the r134a conversion already done, so the quote means the refrigerant for the entire system only cost me $15 at Target...).

http://www.funnyyouasked.com/Mercedes/W126/ExpValve/removal_and_replacement_of_expan.htm
 
#9 ·
How To : change wiper blades

having done a search here & looking at the owners manual i was none the wiser in changing the rubber wiper blades...

having bought the wrong set of blades, i then went to a mb spare parts & garage and bought the correct bosch 4224 22inch blades... (AUD$18.00 each - even though they came in a pair packet - maybe the garage priced them that way to make it easier for them when replacing only one on customer's cars)

i removed the old ones and correctly fitted the new ones, but realised they didn't look right - as in the manual... there were no 'metal' strips in the rubber blades... so, i took the metal strips out from the old blades and , , , voila, , , success!!!

so, just in case, another benzworld and car newbie doesn't know "how to" change things, i thought i'd post this as well as attach a pic of the correct bits :)

safe and happy motoring

kindest
~m
 

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#10 ·
Wheel fitment thread

Below is a list of links that will answer most questions about what rims will fit on a W126. the single most important thing to remember is that an offset (ET) of 25 or less is what the car calls for.


Anyone wishing to add to this thread please do.





Wheel fitment links

http://benzworld.org/forums/forums/thread-view.asp?tid=1253232&posts=7
http://benzworld.org/forums/forums/thread-view.asp?tid=1253713&posts=4
http://benzworld.org/forums/forums/thread-view.asp?tid=1249823&posts=2
http://benzworld.org/forums/forums/thread-view.asp?tid=1248573&posts=8
http://benzworld.org/forums/forums/thread-view.asp?tid=1247774&posts=3
http://benzworld.org/forums/forums/thread-view.asp?tid=1246617&posts=6
http://benzworld.org/forums/forums/thread-view.asp?tid=1245906&posts=2
http://benzworld.org/forums/forums/thread-view.asp?tid=1245593&posts=4
http://benzworld.org/forums/forums/thread-view.asp?tid=1244092&posts=2
http://benzworld.org/forums/forums/thread-view.asp?tid=1242571&posts=2
http://benzworld.org/forums/forums/thread-view.asp?tid=1242366&posts=15
http://benzworld.org/forums/forums/thread-view.asp?tid=1241700&posts=15
http://benzworld.org/forums/forums/thread-view.asp?tid=1240225&posts=25
http://benzworld.org/forums/forums/thread-view.asp?tid=1240055&posts=3
http://benzworld.org/forums/forums/thread-view.asp?tid=1239304&posts=16
 
#11 ·
RE: Wheel fitment thread

Here's a list of wheel widths and offsets that I wanted to add last night but couldn't get to format right. I think Talbir is the one to thank for the original list.
 

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#13 ·
RE: Do It Yourself (DIY) repair thread

POOR IDLE

quote:
48hp - 3/4/2006 1:33 PM

Per Factory Service manual V-8 Engine 116..96 & 117.96:

Checking electric activation of idle spead adjuster (ICV)

Engine - operating temperature.
Ignition switched on.
Pull coupling from idle speed adjuster and measure voltage.

Readout approx. 12v then

Checking regulation of control unit

Engine at idle at operating temp. Plug on couple at idle speed adjuster in a manner that voltage can be measured on plug.

Readout 5v +-1 then

Check idle speed adjuster

Engine at idle.
Simulate coolant temp <42 degree C, for this purpose pull coupling from temp switch and bridge. (located at rear passenger side on top of manifold)

Idle speed increases to approx. 750/min.

End of test

Any other values then those described above suggest a faulty control unit (located at firewall)

If a faulty control unit is found, nowhere within the Mercedes Manual does it suggest this method but others have suggested this and it worked for me. Remove the control unit cover and lightly twisting from side to side while engine is running. Idle should drop to normal speed once twisted in a manner that effects the potential poor solder union. Heat each and every connection, adding a bit of solder to each point. My idle is now on the money.

Hope that helps.
 
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#14 ·
RE: Wheel fitment thread

Here are a couple more:

http://www.mbnz.org/forums/forums/thread-view.asp?tid=1166576&posts=9
http://www.mbnz.org/forums/forums/thread-view.asp?tid=191006&posts=6
http://www.miata.net/garage/tirecalc.html

link didn't work for this page but here's the info..

Wheel Offsets

There are two basic offsets. The early cars had a small offset:
Pontons, Fintail, 108/109, 114/115, 116, 126, 123 and 107
More recent cars had the larger offset:
201, 124, 202, 140, 129, 210, etc, etc.
As offset change with rim width there are heaps of differant offsets.

The Late Ones The Early Ones

5.5 X 14 ET35 6.0 X 14 ET30
5.0 X 14 ET50 6.5 X 14 ET30
6.0 X 15 ET49 6.5 X 15 ET30
6.5 X 15 ET49 7.0 X 15 ET25
7.0 X 15 ET44 8.0 X 16 ET23

ET44 is the dimension in mm front centre of the rim to the face where the hub bolts to the rim.
So ET25 is quite small (25mm from the centre of a 7" rim). The later cars were something like ET44, that is a lot further from the centre. So if you put a W124 rim on a W126 the inside of the rim is in danger of fowling on the steering arm and maybe even the brake lines - this is known in the trade as "a real bad thing".

The stud pattern has remained the same over the years, just the offset changed. Regarding spacers: check with the local regulatory agencies first. They're illegal here in Australia.

John Greene

Some actual offsets of various Mercedes chassis
W126
6.5" - 21.5mm
7" 25mm
201 and 124 Mercedes offsets

The '84 201s came standard with a 14" 15 hole alloy 5" wheel (looked like the 15" wheels used on 124/126 from '86 on but was 14"). It had a unique lug bolt (not used on ANYTHING else that I know of). Part way into '85 they switched to a 6x15" wheel (changing to the same lug bolt used on the 124s). Except for not fitting on the 190E-16V sports cars, in '84-'86 you could swap these 14 and 15" wheels around. The introduction of the 190E 2.6 and 190D 2.5 turbo, both with vented front rotors and a larger caliper assembly (in MY '87 I think) the 15" wheels were redesigned and while none of the standard measurements changed listed in the specs changed, the newer wheels cleared the larger brake assemblies fitted to the more powerful of these newer cars where the older ones didn't clear! All of these wheels had 48-50 mm offset. The later wheels could be used on all of the earlier cars. All the US sold 124s thru the '80s used 6.5x15" wheels with ~49 mm offset (though the sportlines in the mid '90s MIGHT have used a 7 or 7.5" wide wheel - I have NO wheel listings for '90s 124s). None of these wheels should be fitted on any 123/126 even if they MIGHT physically fit! The '86+ 126s used either 6.5 or 7 x 15 wheels with 21.5 or 25 mm offset respectively. THEY can be fitted to older 126 and 123 cars but NOT to 124/201s

Marshall Booth
 
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#17 · (Edited by Moderator)
To replace the shifter bushings:


You will have to get under the car and disconnect the shifter lever at the trans. Put the shifter inside the car into position 2. There is a bolt holding the lever onto the shifter shaft. Once you slide the clip off the shifter rod, the lever will come off. The NSS has a moveable lever on it and it has to line up with the hold in the shift lever. The NSS is held onto the transmission with two 10 mm bolts. The electrical connector has a twisting locking ring so rotate it, can't remember which way, and pull it off. Replace the NSS with the new one, align the NSS lever with the shoft lever hole and put it back on. You may want to replace the shift bushing while you're in there. The rear bushing is a PITA but can be done from below but is best done from above by removing the center console and shifter mechanism.
 
#18 ·
Brake Pad Replacement

It’s best to put the front of the car on jack stands and remove both tires at once. That way you can turn the steering wheel and the calipers out for easier access. The procedure is the same for the rear brakes, simply delete the wear sensors.

Tools/supplies:

Textar pads
Bottle of DOT 3 brake fluid, do not open as it may not be needed.
MB anti-rattle paste
Anti-rattle spring a.k.a. cross spring
Four pad wear sensors
Channel lock pliers
Brake fluid bleed screw hose and fluid container
(a Mity-Vac is best)
3/8 in bleed screw wrench
Hammer and punch
Assortment of rags and large and small standard screw drivers

Using the hammer and punch remove the retaining pins. A small screwdriver will work as well. The pins are held fast by the cross spring. When enough of the pinhead on the inside of the caliper is exposed remove the pin with pliers.

The cross spring can be removed when the pins are out. Note that the pins pass through the corresponding loops on the top of the pad. Remove the bleed screw nipple cover and place the bleed screw wrench on the bleed screw and attach the hose over the bleed screw nipple. The connection needs to be air tight as to not get air in the system. The small container at the end on the hose will collect the excess brake fluid when the caliper pistons are retracted. Open the bleed screw. Remember you’re working backwards – as you’re facing the caliper you’ll turn clockwise to loosen, the screw opens with very little effort.

Resist the temptation to pull both pads at once! Do one pad at a time, do not have the caliper ‘padless.’

Using the channel lock pull the pad away from the rotor and against the caliper and piston. This should free the pad enough to remove. It is common for the pad to be hard to remove; being very gentle and careful use the large standard screwdriver to coax the pad out, gently moving it back and forth until it’s free. Pull it out with the pliers when you can.

Open the channel lock all the way, place one jaw on the outside of the caliper and the other on the solid metal part of the piston. Note the dust shield on the outside of the piston, make sure the plier's jaw is clear of the dust shield and very gently push the piston back into the caliper – DO NOT PUSH TOO FAR or you’ll damage the caliper. As you retract the piston you see a small amount of brake fluid drain into the hose and container.
Spread a thin amount of anti-rattle paste on the back of the pad where indicated in the image below. One packet can do an axle. Insert the wear sensor and install the pad.
Repeat the process for the other pad and again the other caliper.

Close the bleed screw and remove the hose, replace the cover over the bleed screw nipple. Place the cross spring in the caliper and insert the retaining pin through the brake pad loops. Using the punch drive the pin into the caliper so the pin is secure, you should see the point of the pin sticking out of the caliper pinhole just as it was before the job.

The brakes may feel a little light when you first step on them but they’ll firm back to normal on the second or third application. With new pads the pistons do not need to extend as far for the pads to contact the rotor, thus less fluid is needed. The amount of fluid bled will be equal to the greater thickness of the pads. If the low brake fluid light come on add some fluid to the reservoir

I recommend checking the pads once a year and replacing them when half worn, to wear to the brake pad sensor is too low in my opinion and forces the pistons to ‘hyper-extend’ to compensate. I believe this adds stress to the caliper and may cause leaking and a premature rebuild or replacement of the caliper.
 

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#19 ·
M103 Motor Mount Replacement

The mount replacement for the 300 SE/L is the same as the V8 cars, the mounts are chassis, not engine, specific using the same basic w123 part number with different p/n’s for the left and right mounts.

Left/LHD driver side: 1232415013
Right/LHD passenger side: 1232415213 (under protective shield)

As correctly noted in a recent thread get the mounts from the MB dealer only, do not use after market as they can fail too soon. In this case the extra expense of the dealer is worth it.

Engine prep: detach lower part of engine shocks, fan shroud, snorkel, and disconnect the battery.

Tools: 6 mm Allen key, 8 mm Allen/hex socket bit, 3/8 wrench with extension, bottle, floor, or engine jack, large block of wood for the oil pan (see bottle jack/wood block image below).

The mount is attached to the cross member by two 6 mm Allen bolts and to the engine by one 8 mm Allen bolt. Remove the 8 mm bolts first to free the mount from the engine and raise the engine enough to gain access to the 6 mm bolts. The 8 mm bolt is accessed via the cross member passthrough under each mount. Take care removing the 8 mm bolt: make very sure the hex bit is snug in the bolt hex recess otherwise it may get stripped. A breaker may be needed for your ratchet and an extra pair of hands is a good idea, one person to turn and the other to make sue the hex bit remains snug in the bolt recess. For the passenger side mount protective cover there is an arrow pointing forward for correct replacement. With the 8 mm bolts off the protective shield can be turned to access the 6 mm bolts.

Using the 6 mm Allen key remove the two bolts holding the mount to the cross member. You may raise the engine more for better access. When the mounts are out clean the cross member where the mounts rest of debris, it can be considerable over the years and will fall in your face when installing the new mounts. As you introduce the new mounts take care in raising the engine, raise the engine only enough to insert the mount and clear the engine foot. Attach the new mount to the cross member and slowly lower the engine on the mount. Secure the engine to the mount with the 8 mm bolt.

The two most difficult parts of mount replacement were breaking free the 8 mm bolts and aligning the mounts to the engine ‘s 8 mm bolt and cross member. This requires raising and lowering the engine to make sure the 8 mm bolt is connected correctly to the threads in the engine foot to avoid stripping the thread.

Below are pics of my old crushed mounts in the middle with new mounts on either side, as you can see there is a considerable difference in engine elevation. In my case the passenger’s side mount (second from left) was torn and the top part of the mount resting on the cross member. When I replaced the fan shroud I had to adjust it a little higher from the original placement with the engine at its proper height.
 

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#20 ·
Changing the ATF and Filter

Tools and Supplies:
8 quarts of Dexron III ATF
AT filter
Pan gasket
Ramps and chocks
Torque wrench
Funnel that fits the dipstick tube
27mm socket/wrench with extension
5mm Allen key
Phillips screw driver
8 quart (minimum) drain pan
Lots and lots of rags

Ramps are the safest way to work under the car if you don’t have a lift, imo. First, remove the axle cross member (6 16mm bolts) to access the torque converter drain plug vent. Attach the 27mm socket to the crankshaft bolt and turn the engine clockwise until the converter drain plug can be seen through the vent. Open the plug with the Allen key and let it drain.

Using the Allen key remove the drain plug on the AT pan and let the fluid drain. One option is to let it drain overnight. The lower part of the AT and filter are submerged in ATF in the pan sump and will drip forever when you drop the pan and the filter. Letting it drip will avoid much of the mess. If you elect to drop the pan and replace the filter right away make sure you’ve got lots of rags around. DO NOT WIPE ANY PART OF THE AT WITH RAGS. Even the smallest fiber can damage the system. There are three Phillips screws holding the filter to the bottom of the AT. Remove the old filter and replace with the new one. Clean the AT pan.

Remove the old pan gasket and replace with the new one, reattach the pan to the bottom of the AT.

Add four quarts of ATF to the transmission through the dipstick tube using a funnel. Start the car and run the gear selector through all gears. Add more ATF up to less then one quart of ATF to avoid overfilling. For example, if your AT takes 7.9 quarts of fluid add seven quarts. Drive the car and get the ATF hot. On level ground run the gear selector through all the gears again and check the ATF level. Add more fluid if needed.

Pan bolts torque to 8 Nm.

Pan drain plug and torque converter drain plug 14 Nm.
 
#22 ·
Timing chain and tensioner in M116/M117

The following two DIY reports come from Benzwag:thumbsup:

The new timing chain, upper chain rails and tensioner are finally in the 1989 420sel with 98Kmi. This report summarizes some thoughts that might be useful to a first-time DIY'er.
A. This job took at least twice as long as I thought it would, and that didn't include time studying the manual and other sources. If you are in a hurry or do not enjoy the work, this may not be a job for for a DIY'er.
B. Information--Search the List archives for useful information. Especially useful threads were "timing chain and rail replacement questions for a 117 engine" (Nov. 28-30, 2004) and "420sel timing chain" (October 29-30, 2003). I also bought an illustrated booklet ("preventing catastrophic V-8 engine failure") from Mercedessource.com (no connection) and this explained most of what the manual does not. There are photos of the "3 vice-grip method" of chain replacement at Mercedesshop.com ("M116/117 timing chain replacement"). Also, the recent book "Mercedes Benz Technical Companion" has several useful articles on timing chains and chain replacement.
C. The manual is essential reading of course, but I found several possible discrepancies. First, the camshaft sprockets should (must?) be removed to replace the upper chain rails. Second, it appears possible to wind in a new chain without removing the right side rockers. I did remove them, as recommended, to eliminate the problems of the right cam possibly jumping time. Third, I used a bit less than the manual's 25nm of torque on the 8mm bolts that attach various parts to the heads. The 1991 Technical Data Manual seems to indicate 21nm of torque for most of these. Also, I left the old tensioner partially inserted in the right head (held with a long 8mm bolt and nut arrangement) while winding in the new chain, so most of the slack on that side of the chain would be taken up.
D. Unanticipated problems--the 4 left-side chain rail pins were more or less rusted inside. A 6mm bottom tap cleaned them up. All 6 pins came out relatively easily after soaking in Kroil. I also "chilled" them with Radio Shack component cooler, and that might have helped. I bought 4 new pins. An old pin is the perfect drift for replacing the pins recessed in the heads. One of the cap screws holding the alternator mount on the right head was corroded and I bought a new one. The distributor retaining bolt was hard to get out. That bolt goes down through a 2-inch long spacer under the distributor and you need to get the Kroil down in there. Remember to counter-hold the fuel line fittings at the fuel distributor when disconnecting the fuel lines. Be prepared for a minor fuel spill. Relieving the gas tank pressure at the gas cap may alleviate this.
E. Other jobs--While the front of the engine is clear, it is easy to replace the thermostat, the radiator hoses and the voltage regulator. (Mine were original and due for replacement.) Also, with the top radiator hose off, the fan shroud can come out making it a little easier to work on the front of the engine.
F. Parts--I used genuine MB parts (chain, rails, tensioner, oil tube kits, valve cover gaskets and bolt washers). There are reports of aftermarket rails (and chains) failing relatively quickly. The new chain came with the "fish head" clip on the connecting link favored by Stu. (The clip must be installed so that the "head" points in the direction of chain travel.) I replaced the tension rail lining (available from MB as a separate part) and re-used the tension rail itself. I did not replace the cam sprockets, which looked fine.
G. Tools--Nothing truly exotic is required. A special valve spring compressor if the rockers are to be removed, a good 6mm hex bit socket, and a tool for pulling the chain rail pins. For the latter I ordered online a few long, fully-threaded 8.8 strength 6mm bolts, nuts and fender washers from the Bolt Depot (again, no connection), and used them with various sockets, large nuts, shim washers, etc. to replicate the official pin puller tool. The websites of Assenmacher, Zdmak, etc. illustrate the factory tools.
H. Although there may be some short-cuts, my order of battle was as follows (refer to the manual and/or the Mercedessource booklet for the job procedure details):
1. Disconnect battery. Remove air cleaner. Remove fan together with visco fan clutch (store in upright position), leaving 1 bolt in the fan pulley. I used a strap wrench on the pulley hub to keep it from turning. A long 10mm box wrench is helpful.
2. Unbolt the cruise control actuator and put to one side. Remove alternator and then alternator mount from right head.
3. Remove spark plug wires from plugs. Remove distributor cap together with plug wires. Set engine to TDC. On the engine, mark orientation of the distributor mark/rotor so the distributor can be replaced in the same position. Remove distributor.
4, Unbolt P/S pump and tie off to the side (the hoses remain connected). Unbolt P/S pump mounting plate from left head.
5. Disconnect fuel lines at fuel distributor and tie up out of the way. Remove valve covers. Gently pry off oil tubes and clean any plastic bits out of the cam bearing towers with picks and tweezers. If you are going to remove the right side rockers, now is a good time.
6. Check 3 upper chain rails for damage. Assuming no broken rails, pull all 6 chain rail pins 1/4 of the way out (about 3/8 of an inch). if you are going to have a problem with these, now is the time to know.
7. Slightly loosen both cam sprocket bolts. Reset engine to TDC and confirm/evaluate camshaft timing.
8. Mark and remove left camshaft sprocket, keeping tension on the chain (I used 2 bungee cords with hooks suspended from the garage overhead). Pull pins and fit new left side chain rails, one at a time. Refit left sprocket, observing marks, and the bolt.
9. Remove old chain tensioner. Mark and remove right camshaft sprocket, keeping tension on the chain. Pull the 2 rail pins and remove the old right side chain rail. Remove tension rail, replace lining, and refit the tension rail. Fit new right side chain rail. Replace right side cam sprocket, observing marks, and the bolt. (I deferred retorquing the cam sprocket bolts in case the timing needed to be adjusted after the new chain is in.) Reconfirm camshaft timing.
10. Wind in the new chain using the 3 vice-grip method or, with an assistant, using the method in the manual. It is easier if the spark plugs are out, but I would remove them only if new plugs are going in.
11. Fit new chain tensioner. Double check camshaft timing. Torque cam sprocket bolts to 100nm.
12. Put everything back together in reverse order. Use new oil tube kits and valve cover gaskets. Remember to set the distributor timing precisely according to the manual (before installing valve covers to make TDC identification easy). Do oil and filter change.
The main thing is to work patiently and carefully, and always use shop rags, etc. to prevent anything from falling into the engine. Be especially careful with the timing chains, as it would be a disaster if a chain fell into the engine.
All in all, the job was challenging and fun (and successful), but time-consuming as constant vigilance is necessary to avoid an expensive mistake.
At 98Kmi and 15 years, the old chain and rails were in OK shape (right cam retarded about 5 degrees), and didn't yet make noise on start-up. They probably would have gone a few more years. The plastic oiler tube clips were very brittle and definitely needed to be renewed.
I hope this report is of some help to other W126 DIY'ers. Thanks to Stu, Bob and others for their helpful advice. Charlie Wagner, 1989 420sel 98Kmi.
 
#23 ·
continued

continued...
New valve stem seals are (finally) in the 1991 420sel at 120Kmi. Many thanks to Stu and others for their help on the project. This report summarizes information that may be useful to a first-time DIY'er.
Reading: Search the archives for postings on the subject. Particularly useful were "Valve Stem Seals" (March 4, 2001). The manual sections on the valve train are essential reading of course. If you have no experience under the valve covers, I would recommend a Mercedessource.com (no connection) publication "Preventing Catastrophic V-8 Engine Failure", which is directed to changing timing chains and rails, but also addresses oil tube clips and other points.
Tools: For this job you need (i) the factory valve spring compressor or equivalent from SIR Tools, Assenmacher, etc, and (ii) the genuine MB "magnetic finger" tool. Also very helpful are (i) valve seal pliers to remove the old seals and (ii) the valve seal mandrel tool (for 9mm stems) to press on the new seals. The "magnetic finger" tool makes it easy to get the valve cone halves (keepers) out, and I can't see how you can do the job without this inexpensive tool. Long needlenose pliers (or hemostats from your fishing vest) are needed to replace the keepers. You will also need a pair of curved, pointed tweezers to manipulate and position the keepers as you replace them. Also needed is an air compressor and a way to pressurize the cylinders. I used the inexpensive KD Tools version (# 901 Air Hold Fitting Set). It has a spark plug thread on one end and a female thread in the other end. Screw in a male quick-release air fitting and voila! Also, this rig is about the same size as a spark plug, so you can use your spark plug replacement technique to install it. (I use a 3-inch long piece of 8mm ID rubber hose to screw plugs in by hand several turns.)
Parts: I used genuine MB valve seals (and they are not expensive compared to aftermarket). I also replaced the oil tube clips, as it is easier to work with the oil tubes out and you could break the clips during the job. New valve cover gaskets too.
Procedure: The procedure is fairly straightforward and is described accurately in the manual, with the warning noted below. Note the following points:
1. Disconnect battery; remove air cleaner; remove fan and visco clutch, leaving 1 or 2 bolts in the pulley hub (and store fan/clutch in vertical position); remove cruise control servo, plug wires and valve covers.
2. Relieve gas tank pressure at the gas cap before removing gas line connections. Counterhold fittings with a thin 17mm wrench.
3. The manual has a page (in section 05-250) which shows the amount of crankshaft rotation after #1 TDC for each piston to be located at the top. This can be double-checked with the position of the rotor under the distributor cap. The harmonic balancer is marked every 90 degrees. See manual section 15-535 if you are unsure of cylinder location or firing order.
4. Prevent the possibility of rotation of the crankshaft while a cylinder is under air pressure with a 22mm socket/ratchet rig on the right camshaft nut and the 26mm socket/ratchet rig on the crankshaft nut. Brace each with the ratchets set to prevent rotation in opposite directions. I experienced no crank rotation when the timing marks were used precisely to set each cylinder to TDC.
5. The springs have a top and bottom and must be replaced as they were. On my engine, all the large/outer springs were marked with red paint on the bottom. Some inner springs were not marked.
6. Of course use shop rags to prevent anything from falling into the engine near the cam sprockets. I used a large cloth to cover the intake manifold and the side of the engine not being worked on, and this provided a place to put tools and parts.
7. On my engine both intake and exhaust valve stems are 9mm diameter. So only one size mandrel is needed to press the valve seals home. Also, the valve springs can be depressed as far as necessary to remove the keepers. On some engines, one valve stem is 11mm diameter, which makes for 2 sizes of valve seals and mandrels, and makes it much harder to remove the keepers from the larger stem.
8. I used a 20 gallon air compressor generating about 5 scfm at 90psi with a standard quick-release fitting on the hose. It wanted to operate at its set pressure of 100-125 psi,and this worked fine. It generated much more air than I needed, and most of the air was lost to a slight leak at the quick-release connection to the air hold fitting. A smaller compressor probably would have worked.
9. WARNING--While replacing the rockers after installing all of the valve seals, I had one valve stick in the closed position while depressing the valve spring retainer with the compressor tool. I saw the "thrust piece" rise a bit, and was able to stop before the valve keepers fell out of place. This would have been a disaster, as the valve would then have been free to drop into the engine. The problem is that the valve keepers are set gently into the spring retainer when the springs are replaced after the new valve seal is installed. To make sure that there is enough friction between the keepers and the spring retainer, just before you replace a rocker (i.e., while the related cam lobe is pointed straight up) and before putting the thrust piece in place, either (i) give the valve stem tip a gentle whack with a drift/hammer, or (ii) use the valve spring compressor to check the friction between the valve keepers and the spring retainer, and let the valve close smartly. Then go ahead and replace the thrust piece and the rocker. Turn engine and repeat for the next valve.

As usual for me, the job took much longer than I anticipated. And I replaced a number of things (chain rails, tension rail lining, P/S pump seal, radiator hoses, thermostat) whose time was up. But it was fun and with the right tools fairly easy.
Charlie Wagner, 1991 420sel
 
#24 ·
The W126 needs an offset of 25 or lower with a 5 x 112 bolt pattern correct?
 
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