E420 M119 Timing Chain- Here's my story
 

I recently finished changing the timing chain in my 94 E420 and would like to share some of my experience and thoughts about this job. It's a long post!

First of all, my car has almost 150,000 miles on it, so I was beginning to worry about the possibility of the chain or guides failing, and the subsequent disastrous engine damage. I had no bad sounds on startup. I do maintain the car fairly meticulously, and change the oil at 1/2 the recommended change intervals (about every 3750 miles) with Mobil 1, and have done so since I purchased the car with 62,000 miles on it. The end result of all this work was that I was amazed that the guides were all in excellent shape, with only very shallow grooves- visible, but could only be felt with my fingernail. And, though I did not test the chain stretch with angle indicators, I had no difficulty slipping the camshaft locks in place, which says to me there couldn't have been too much stretch. I'm glad the job is done, but I'll bet it could have waited another 50,000 miles or more!

In my mind, there are 3 "stages" of this type of repair. One could change the timing chain, tensioner and top rails with very little engine disassembly. I believe, though, that three tools would be necessary- available from Sir Tools. One would be the clamp on guide to keep the chain on the camshaft gears as the new one is thread in, a timing chain press tool (I used one available for motorcycle chains,) and the holding pins for the camshafts (for installation of the tensioner.)

The disadvantage to this is that this leaves all the guides that might be prone to fail in place. From what I've read on this message board, failure of these guides is what frequently leads to failure of the chain, or the oil pump. (This is not unique to Mercedes engines- I've personally rebuilt an old buick engine that had plastic teeth on its timing gears that broke off and caused the oil pump to fail resulting in spun rod bearings- something else plastic in a Honda engine, too.)

The second "level" of this repair is to also replace the tensioner guide rail and the inner and outer guide rails in the heads. I would consider this the minimum level of this repair that I would feel okay about. It adds a significant amount of work, and the need for another tool- also available from Sir tools. This is a small pin extractor tool that allows the pins that hold the guides in place to be pulled out of the head though small holes on it's front side. I also was able to borrow from the local dealer a tool to help reassemble the camshaft adjusters which have to be put back together under spring pressure. You'll also need a very high quality torx driver in the T27 size to remove the camshaft gears.

This level of repair requires that the poly belt, its tensioner, power steering pump, distributor caps, rotors, front head covers, camshaft adjusters, maybe also the air pump be removed, roughly doubling the time involved.

The third level is to also include the final guide rail in the timing cover on the driver's side. This is what I did, and it involves an almost insane amount of work. This requires that the front timing cover be removed. I believe that I must have printed out about 20 separate repair operations from the CD repair manual (maybe more.) I'm sure that I put in about 40 hours of work over 6 days- not much sleep that week!

This level requires that the radiator, fan, fan clutch, alternator, air pump, power steering pump, air conditioner (these two can be unbolted, but their hoses still connected,) poly belt, its tensioner, water pump and it's reservoir (anybody know what that thing is for?,) fan bearing bracket, harmonic balancer, oil pan (which can just be lowered- be careful with the gasket,) and maybe something else that I've forgotten also be removed. I would hate to imagine what it would cost to pay someone to do this. To any of the techs reading this- is this ever done?

Here are some tips:

The rear bolts on the head valve covers are REALLY hard to get at. Find a friend with small hands and use a 1/4 inch universal joint socket (Sears has them in 1/4 inch drive) with an allen driver bit. This will bend in just the right place- use a little grease to hold the bit in the socket.

Might as well grab some new spark plugs, dist caps and rotors- might also consider new spark plug wires if it's been a while- definitely change the water pump and thermostat, and consider the poly belt tensioner- update it if necessary, poly belt and radiator hoses at the front, as well as the voltage regulator in the alternator. At this mileage, all this stuff should probably be replaced. It all has to come off, and the labor to do it later is significant for some of it. It does all add quite a bit to the cost of the parts. I replaced the chain, tensioner, all of the guides including the one on the oil pump, the oil filter housing check valve, the water pump, thermostat, hoses, poly belt tensioner, and pan gasket, but not the ignition stuff as it had been recently done. This amounted to almost $700 all at least 20% off list price. I spent another few hundred on tools.

The threaded (about $40) pin extractor works great- so I wouldn't bother with the slide hammer type that Mercedes shows in the manual.

I used a flywheel locking device purchased from Performance. It didn't fit quite right, and was expensive at $150, but did work when wired in place. My 1/2" impact wrench running at 140 psi removed the crank bolt on the harmonic balancer fairly easily. This bolt is usually a you know what to remove, so the tool was worth it to me. A loaner puller is available from Autozone to remove the hub after the bolt is out.

The locking pins for the camshaft gears are fairly cheap, and worth it. It would also be handy to have a fairly thin, but large (can't remember for sure, but I think about 24 or 26 mm) open ended wrench to twist the camshaft slightly to get the timing chain to fit exactly right on the gears.

Where any other manufacturer would use 2 bolts, Mercedes uses 6, and at different angles, lengths, head type, etc. They seem to take pride at engineering the crap out of every part. You'll find the most outboard timing chain cover bolt on the driver's side coming down on the outside of the head itself. There are two bolts holding the power steering pump that come in from behind it. Feel around up there from under the car up behind the air conditioner compressor, and over it. An allen headed 3/8 inch drive socket on a short extension with a ratchet will get them. MANY bolts on the air conditioner compressor and it's bracket. Just keep looking. And try to mark clearly where each bolt came from. I thought I could trust my memory- oh boy.

You might get a replacement water pump reservoir as it's plastic pipe snapped right off on me when I tried to remove it.

It is possible, but difficult to replace the oil pan gasket without lifting the engine, by removing all the bolts, and reaching your hand in from the front and sides to tease the old one out and slip the new one in- with the appropriate sealer in the rear (here I used the Mercedes recommended stuff.)

I really can't imagine trying to do this job without the CD manual, but don't use the sealer recommended there. Get the newer stuff recommended by the WIS- it's been posted on these boards by the techs- Loctite 5900, I believe, but Permatex Ultra Black is probably similar.

Enough for now, I'll add more if I remember. Feel free to ask questions.

Great info for the archives! Thanks for sharing.

Good job! I saved it ;)

Any pictures of your E420 with 225/50/16 tires on 16" wheels?

Look for the post entitled "E420 Euro Sport pics" for pictures of my car.

Very good write up Bob.
I have just gone through this same procedure on a 300SE with the addition of the valve guides/seals job too. That crank locking tool is worth every bit of the $$ isn't it:). The oil pump chain tensioning slide rail was the MOST worn one in the the car I did (155k miles).

Great posting, thanks!
Almost sounds like it would have been easier to pull the motor and put it on a stand where access would be easy...
Comments?

I have changed the timing chain, most rails (except the one low on the driver's side), and chain tensioner on my 119 5.0L V8. I have spoken to many techs about this and none of them really recommended removing the front cover. That lower rail doesn't have much tension on it and is mostly in oil. Also, the heads rest on the front cover per se and can cause future leaks unless properly sealed up in place. Quite frankly, for the amount of labor involved, there is very diminishing return for pulling the front cover, et al. I would ignore that lower rail.

That's good that even at 150k the guides still were in very good condition. I'm never going to change my timing chain and since my car is at 150k I don't think I'll be having any issues with that until 200k. When that breaks I'll buy a new car!

I recall a discussion on someone's thought process on the issue of running a 400E until the chain breaks. Are you the fellow in Thousand Oaks or thereabouts?

Sixto
95 S420
87 300SDL
83 300SD ... $950, see cars forum

Yes that is me. Don't get me wrong, I do take car of my car but by the time the chain breaks I will be due for a new car, so the timing will be perfect. LOL:D

That seems like a waste of a car. (IMHO) :(

It does seem like a waste of car but I get tried of cars rather quickly, I usually buy a car once a year on average. This car was also rear ended and has not been properly fixed. It will need about 4k in body work to fix it back to spec. Everything works fine and the damage is very minimal so it's not so bad. But if I was to do the body work and the timing chain that would be 6K right there which is a good chunk of change that can be saved for another car.

The prosecution grilled zeronero on this matter sometime back and the jury acquitted him. Case closed :)

Sixto
95 S420
87 300SDL
83 300SD

Sorry, I must have missed that case.

I pleaded insanity:eek:

zeronero thinks like a naive child!

What if the timing chain broke when he was driving in the middle of a night and on a long trip.

You may not need to care for your car, but your safety needs your attention my friend....

on the dangers of waiting for chain noise
 

We have my wife's 400E in the shop right now, in what has turned into a monster job, alleviated only by my mechanic's willingness to go easy on me (they service 3 MB's and more for us)

The car is at 180K, was starting to make noise at cold startup. I had bought the chain, guides, and gaskets last spring, and just hadn't gotten around to scheduling the job. Needed to take the car on a long trip, and decided to get the chain done.

Turns out the upper rails were grenaded. My mechanics can't believe the chain didn't slip a tooth: probably my wife's driving style. They couldn't find two of the rails at all, just a bunch of pieces down in the bottom, and the pins. SO, I dodged a bullet....

...except that the lower rails were broken, as a result of the lack of any other guides to stay that slapping chain. My guys say they have never seen lower rails that needed replacement, 12 years each in the MB repair business.

Front cover comes off, which means heads come off (they share the head gaskets), water pump, the ac compressor, ps pump, alternator has to float on its harness, oil pump and chain removed, etc, etc. When you're that deep in, you do the water pump, all the cooling hoses, the high pressure ps hose, the engine mounts, valve job, etc. Add a crack in the radiator neck, a harness on its way out, and you're having a real party!

We got the car at 150K, and it ran smoothly to date. The noise at start-up wasn't much worse than noisy lifters, and never got real bad. We found lots of sludge in the heads and carbonned piston heads, which we attributed to the previous owner, as it has only seen mobil 1 and premium gas during our ownership. My guess is also that the timing can't have been perfect, given the state of affairs above.

Do your chain at 150K, noise or no noise. I agree with Nguyen: whether you can afford a complete overhaul including rods, you don't want to grenade an engine 2 hours into a six hour road trip.

It's a lot of money for a 12 year old car, but ours is in nice shape, the interior is almost mint, nice paint with only a few imperfections, great stereo, we got it for a reasonable price, and the wife loves it, esp. the V8. And I will NEVER buy another MB V8 unless it's new (haha) or the chain has been done.

Maybe we paint it a new color, something lucky!

Re: on the dangers of waiting for chain noise
 

Peter,

So..... lots of sludge, carbon buildup, and atypical destruction of most rails. What kind of service did this beast get before you bought it? Sounds like it was neglected a wee bit...

Don't know for sure, Steve, we've had the car for a bit over a year now, synthetic all the way, so the sludge was a surprise. I would have thought the engine would have cleaned up. It seems to have been a timebomb!

We bought the car from a wholesaler who found out the car needed a blower motor and sold it to us cheap (I know, I know). The car was and is very clean, and seemed mechanically okay. My mechanic got the car for a diagnosis and called me.

I would have been totally devastated (and the recipient of some hard stares from my wife, who relies on my automotive judgment) if we had blown the chain while driving, a big sigh of relief there.

Like everyone here says, know the car you buy or don't buy. Or be prepared for lots of overdue maintenance and worse!

We wouldn't own the car if not for my mechanics. They do MB's. When they go out of business, I find another mechanic who I like, and I drive the car he/she specializes in. I love these cars, but they are out of my maintenance price range without friends in the business. MB's are not for the faint of heart! They do make the heart stir, though!

what am i saying, i might have to go back to doing the wrenching myself before I abandon the faith....

now that i think about it....
 

....my tech runs across a lot of cars that seem to result from owners who buy "the star", then gasp when some major ($$$) repair is called for, and promptly look to dump the car.

Which is why a used MB can be a good deal.

Valve job?!! You don't need a valve job. Period. You really don't have to remove the heads either...

Having more of the same kind of fun with my 16 valve. Started 10 days ago, and still in the proccess cleaning and preparing a parts list. This car was bought knowing it was rode hard and put away wet. Many of the known squaks are now revealing their origin.

Squak List;

Oil leaks
Timing Chain, Guides and Tensioner
A/C Clutch
Power Steering hoses
Cruise Control Actuator mounts and linkages
Starter rebuild
Heater Blower Motor
Heater core or valve leak
Climate Contol vacuum actuator rigging
Install Seater Heaters

This list keeps on growing, suspension and steering are for summer repairs. Still amazed at how many bolts have to be removed to get at any thing, of course you wouldn't if a bolt is missing either!

With all the pain involved, I still love the car! This restoration will just add to the miles of smiles that I get from driving down the road!

I give.
 

How do you guarantee not to damage the original head gasket without at least loosening the heads? I was there when we pulled the front cover without the heads on and it required a good bit of persuading.

With the sludge buildup in the heads, would you have told me to leave them be? What better time to do a valve job on a car with no history?

If you are worried I have gotten bilked out of additional $$, I am sure I have not. My tech tries to save me $$$, and I try not to ask him to kill a lot of time taking chancy shortcuts.

Some things are penny-wise and pound foolish. Pay for the labor once.

Just because you had sludge in the engine doesn't mean by far your valve guides are worn or even close to it. 119 valve guides rarely wear until they have well over 300000 miles on them. 50% of your project was to recondition the valvetrain.

Not pound foolish...just wise and pennysmart. A valvejob at your mileage is just flat out foolish. I'll bet your machinest will find nothing wrong or nothing wrong enough to even mess with the valvetrain.

Satish

true, if the heads don't have to come off...
 

Satish: you still didn't say how you get the front cover off cleanly, or is that a trade secret?

My techs indicated that they didn't expect the valve guides to be a problem, but since I had the heads off, might as well boil out the passages, inspect all the valves and re-cut the seats.

You are probably a better mechanic than I, but from what I know, most of the labor is disassembly and assembly of the engine, not the heads. 1/2 hour on the exhaust manifolds and camshafts, and hour for the valves themselves, my actual time (iwith a hand or two on the valves), to break the heads down.

These engines are bullet-proof except for the chain and rails, I agree, and if I were paying an MB dealership, I might do as you recommend. But...

Well, perhaps you didn't read Bob Johnson's post that actually started this thread! He removed the front timing cover without pulling the heads...no problem. You simply didn't need to do it. It would save you hundreds.

Most of the labor IS in pulling the heads, machining the valve seats, resetting all 32 valves, rocker arms, cam towers, camshafts, head gaskets, etc. 1/2 hour for valvetrain and a few hours for heads? Clearly you haven't taken apart one of these motors before...

Like I said, I just did.

What I said was once the heads were OFF, taking them apart is a few hours work.

didn't encounter any rocker arms, if I recall...but, like I said you are probably a better mechanic than I...

Where to purchase CD
 

I see a lot of post talking about a repair manual CD. Where do you purchase a CD,do they make one for a 1992 500SEL,what is the cost,Thanks Bill

Front cover removal
 

I have done 3 119 engine timing chains and lower rails without removing the heads or the oil pan. The trick is to get a thin piece of flashing like you would use on your roof. Take the flashing and bend it at a 90 degree angle and bolt it to the front of the heads. Oh buy the way this is a two person procedure. Trust me... I ruined a head gasket trying it by myself. The next step is to line the front cover up so that you can go straight in without wasting to much time. Next have the other guy guide the oil pump chain thru the slot at the bottom of the cover. Once this step is complete, use the mercedes loctite sealant and seal both sides of the cover. At this point the cover is ready to slide in. Now the most crucial part of this job is to use aircraft sealant on the top of the cover and on the bottom of the head gasket so that it will slip in easier. Take two bolts just as reference and put them in the cover at the half way point. Now you have about 25mm of distance between the go or no go portion of this program. Take somemore of the aviation sealant and layer the bottom of the cover as well as the top of the oil pan. Lightly tap on the cover with a rubber mallet while tightning up on your two bolts by (HAND). At this point you will notice some slight binding. This is caused by the other tech getting tired of holding the oil pump drive chain. Tell him to suck it up because you are almost there. You will have to do some manuvering of the oil pump drive chain to get it past or you can replace the chain and roll it in instead of fighting with it to get the cover to go past. Now you only have 15mm left and you are locked in!!. Check your head gaskets and the metal shims to make sure they are not binding and continue to walk it in untill it is flush. I cannot take the credit for this knowledge as MB DOC was the one that led me step by step thru the whole process on my first attempt.

Nothing beats a failure but a try!!!:cool:

Oh PS

You only have 15 minutes max to get that cover locked in as the loctite will harden up on you ;)

Got a product name and/or part number for that "aircraft sealant"? Is there any MB sealant recommended for the top & bottom gaskets (at oil pan & cylinder head) what will work, for sliding the timing cover back in with the bold pan+head gaskets?

:confused: