NewR

I am not sure whether I should be happy or I am in for a major headache. I got this car free from a co-worker who does not want to spend anymore money on this car.

It is a 1991 420SEL with 171K miles. To date, he'd replaced the computer (4yrs ago) , rebuilt transmission (6 months ago), AC (2yrs), Radiator (2mo), Tires (3mos), sunroof, o2 sensor, battery last month and ect. Also the car was repainted a little more than a year ago. He gets so sick of the car that he does not want to deal with it anymore after recent incident.

Here is the damage. From looking at the pictures, I guess the rail or the tensioner failed and cause the timing chain to get loose and broke a piece off the valve cover. I do not think the chain is broken because I tried to get it out but I could not. I have removed the engine but have not had the time to open it up to see the extent of the damage.

What can you tell just from looking at the pictures? Any educated guess is much appreciated. Am I better off rebuilding this engine? or just buy a used engine?

Thanks in advance.

golfboy

Mine did that a year ago... sorry man.

The plastic rails didn't get replaced on schedule (100,000) and failed, letting the timing chain jump off track and break through the left valve colver.

Your valves are shot. If you have a good/honest mercedes mechanic nearby, he can put new heads on it and you'll be good for another 250,000 as long as the oil is/has been changed regularly. The bottom end does NOT need to be rebuilt.
It ended up costing me about $3,500 total.

Sorry for the bad news.

braverichard

Actually the plastic rails have no scheduled replacement. In fact, the M-B manual says ABSOLUTELY NOTHING about timing chain / rails replacement. The reason for this? Well, if oil changes had been performed religiously on schedule, the timing chain shouldn't break before the top end of the engine would require work.

Finding a used engine would obviously be the best for you, not to mention, cheaper than rebuilding that one. You can get a used engine with relatively low miles, change the timing chain and be set to go. However such an engine could be difficult to find.

SL BRABUS

Now here come the hard part. ....Try to find someone who can fix it for FREE...... :p ..

waybomb

Solution: Give it to me for free! My 16 year old would love to fix this one. He helps out on my Benzes. How 'bout it?

golfboy

hmmm... then 3 Mercedes mechanics lied to me!
And actually, the chain will have to be replaced but it's not broken.
These are lessons learned the hard way.

NewR

Believe or not. There is someone who is fixing it for me for almost free.. I just have to provide the beers and help him with the repair. Problem is, he can only work on it whenever he is not working on customer's cars. It's probably going to take a long time to finish this car... but hey.... it's FREE..

golfboy

Wow, I would have jumped on that deal myself. Congratulations! It's a great opportunity to learn too... you should work on it yourself, ask him "what comes off next" and get it all disassembled so that you can get the valves and everything redone.

By the way, I purchased a used valve cover for an excellent price at Potomac - IIRC it was about $40.

NewR

Actually, I am doing all the work (disassemble) myself and asking him when I need to. Like you said, it's a great opportunity to learn. I will probably ask him to involve more when assembling the engine back together.

I will post more pic when I get the heads and the timing chain cover off and hopefully not too much damage is done. I have already seen pieces of the guide rails.

modem

Please, please document everything and take photos. I will be doing the chain replacement, guide rails, tensioner, etc on my 380 sometime soon. The car has 135000 kilometers and I Know it should be done before 160000k's. This is going to be a challange but I know many have done the job themselves.

Messerchmidt

Sell that thing to the bone yard

old mercedes when they give problems becomes black holes eating your money

NewR

Thanks to sites like this one, some holes are not as black as you think they are.

braverichard

While you are correct on that, to some extent, even all the advice you can get on this website won't necessarily save you on expensive to replace parts and labor-intensive operations that even the most hardcore DIYer would rather not do.

However I am not recommending you sell the car to the junk yard as of yet. It is up to you to determine how much money + time you have and are willing to dig into that beast.

Good luck,

Richard

braverichard

Actually, I don't believe they are all liars. I just believe they all have information that is misleading and don't know it is untrue. Check out the M-B recommended service manuals, owner's manual and service bulletins. M-B puts out no recommended date for timing chain work at all. Gas engines put more stress on the chain than do diesels, and that's why the gas engines have a double row which is stronger than the single row in the diesels. I know a guy who owns an '81 240D (original owner) with 310K miles and he has never replaced the timing chain. All he does is check it for stretch every 15K miles when he has to open the valve cover gasket to perform a valve adjustment. He still doesn't even have sufficient stretch that requires replacement. I also know an original 560SEL owner who has 243K miles on his engine -- his timing chain has never been replaced. In fact, his car is currently in the shop for a new headgasket and a valve job and so he's having them replace the chains while they are in there. The fact is, if oil changes are performed religiously, the chain will never need replacement until the engine gets overhauled. If somewhere during the life of the car oil changes weren't quite performed as they should, dirt accumulates on the timing chain rails, the oil's TBN number (a chemical analysis measure of how well it can do its job as a lubricant) decreases sharply and next thing you know, the chains jump their rails, break and in the case of M-B engines which are all of interference type, cause expensive engine damage.

Here's a better one: my friend's family has an '81 Toyota Diesel pickup truck. It currently has over 600K miles on it (odometer rolled over more times than they can remember and now doesn't work). Truck has rust all over it. Its timing chain has never been replaced. My friend's dad is strict about oil changes though: he performs his every 2,000 miles no matter what!!

Hey, those mechanics have surely made a lot of money by convincing the ignorant that timing chains should be changed every 100,000 miles. Just like they did with promoting 3,000 mile oil changes. Actually, I even had a mechanic tell me that my diesel's fuel injectors need replacement every 100,000 miles. Well, I know of a diesel with 322K miles running on the original injectors. And when tested, they came out almost as good as new, without sufficient deterioration to warrant replacements. You have to do your own research as those mechanics are all in it for money!!

NewR

Thanks Richard
The heads and timing chain cover should be out of the way by Sunday for me to assess the extent of the damage. By then I should know whether to junk it or fix it. Crossing my fingers