Exhaust camshaft broke again!!!

[team45]

Why, why, why ...
I have N reg (1996) c180 with 93k miles. When i bought the car it was making some kind of rattling noise and overheating. I asked a friend for advise he advise me to changed the chain tensioner and i bought haynes manual and as it describes i changed the tensioner. When i started the engine after 5 min. engine cut off and didn't start again. I decided to open the engine cover and i found out exhaust camshaft was broken. After that i decided to change camshaft and i bought a camshaft and i replaced it the way it describes in haynes manual. When i started the engine it run smoothly about ten minutes and started overheating and after 15 minutes cut off again and didn't start. I opened the engine cover and found out exhaust camshaft was broken again. Camshaft is very strong build part of the engine what can brake that i don't really know but only idea i have in my head is that must be something to do with overheating because when the car overheats around 100c it breaks. It is very difficult to test now i am planning to buy another camshaft and replace it again but i would like to seek for some advice if this happened to anyone before. I am sure it will brake third camshaft. Some people may think why i don't take it to the garage. I spend some money already but when i asked them they are talking about £500 - £600 minimum and i don't have that kind of money at the moment. I am confident if i get the right advice i can fix this problem.

Many thanks.

 

[BlackC55]

I would suggest that the oil galleries are blocked and dry causing the cam to lock and shear or the hydralic tappets are seizing up not allowing the lobes to push them down. The cam is not very strong in a shearing action and will break easily.

 

[lexuscol]

Are you sure you are getting the cam timing right?

 

[grober]

Forgive me for saying this but you need another pair of (experienced ) eyes to look at your problem. You have tried your best but you may be overlooking some fundamental problem which is causing this. Atho getting some professional help is expensive just how many exhaust cams can you afford to break? The other possibility is to get an entire engine from a vehicle breaker?

 

[kth286]

Merc cams of that era are hollow and considered to be very fragile and need to be tightened down in a strict order.

BUT the main thing that breaks cams is the inexperienced person not fitting the chain tensioner correctly.

I guess your new tensioner was assembled when you bought it ????????

Did you taking it apart before you fitted it ???????????

If not you should do.

The internal needs to be pushed through the rear of the main body and fed into the front again when fitting.

So; the empty body needs to be fitted into the engine, and then the internal needs to be pushed into the body.

Otherwise there is too much tension on the chain, and the fragile cam just breaks, as you have found out to your cost.

 

[Glenn Smith]

Merc cams of that era are hollow and considered to be very fragile and need to be tightened down in a strict order.

BUT the main thing that breaks cams is the inexperienced person not fitting the chain tensioner correctly.

I guess your new tensioner was assembled when you bought it ????????

Did you taking it apart before you fitted it ???????????

If not you should do.

The internal needs to be pushed through the rear of the main body and fed into the front again when fitting.

So; the empty body needs to be fitted into the engine, and then the internal needs to be pushed into the body.

Otherwise there is too much tension on the chain, and the fragile cam just breaks, as you have found out to your cost.

I would agree

 

[team45]

I would suggest that the oil galleries are blocked and dry causing the cam to lock and shear or the hydralic tappets are seizing up not allowing the lobes to push them down. The cam is not very strong in a shearing action and will break easily.

Thank you for your reply;
when i opened the cover second time camshaft and all around was very oily. I am convinced that i don't think this is an oil problem because first time when i had the car engine was running long time but it didn't brake the camshaft it start the broke when i put a brand new chain tensioner. But still i will keep in mind. Thank you for your advice.

 

[team45]

Are you sure you are getting the cam timing right?

Thank you for your reply;
I think timing is ok because it looks very simple to to the timing. First of all you turn the crankshaft pulley at 20 degree ATDC after that align the inlet and exhaust camshaft with the holes on the each brace, lock it with drill bits and connect the chain. The reason i am saying timing was fine because after the job i drove the car for short time sound and power of the engine was fine. I thing if you miss the the timing even by one tooth on the chain you will feel loose of power and maybe some noise on the engine.

 

[team45]

Forgive me for saying this but you need another pair of (experienced ) eyes to look at your problem. You have tried your best but you may be overlooking some fundamental problem which is causing this. Atho getting some professional help is expensive just how many exhaust cams can you afford to break? The other possibility is to get an entire engine from a vehicle breaker?

Thank you for your reply;
I live in central London which is now in congestion zone, i am not driving the car at the moment and once i fix this problem i am planing to sell it. The reason i am not taking to the garage i had really bad experiences before. When i took my previous car to the garage there was lots of work done and money spend on it but some of the problems was still coming up again on later stages. This time i spend some money and i bought some pro tools like Britool set and some more stuff i am really keen to learn some of the things about engine. May be some of you thinking i am playing some dangerous games to go advance repair steps, i agree with you i know if i do the wrong thing i can brake the valves or piston heads but i guess this is the hard way to learn.
Thank you very much for your advice and giving me your honest opinion.

 

[team45]

Merc cams of that era are hollow and considered to be very fragile and need to be tightened down in a strict order.

BUT the main thing that breaks cams is the inexperienced person not fitting the chain tensioner correctly.

I guess your new tensioner was assembled when you bought it ????????

Did you taking it apart before you fitted it ???????????

If not you should do.

The internal needs to be pushed through the rear of the main body and fed into the front again when fitting.

So; the empty body needs to be fitted into the engine, and then the internal needs to be pushed into the body.

Otherwise there is too much tension on the chain, and the fragile cam just breaks, as you have found out to your cost.

Thank you for your reply;
I was thinking the whole thing all over again like i was remembering a movie i watched before. I think you are right because when i had the car first time car was making some kind of rattling noise and overheating but it was running long period of time witout brakeing the camshaft. For the noise i had some advise from friend of mine and decided to change the chain tensioner. I bought brand new tensioner from mercedes and changed the way explains in haynes manual. When i started the car engine ran about 5 min and broke the camshaft. Changing the tensioner on haynes manual looks very easy but i learn in very expensive way that it is not that simple. Chain tensioner has four internal pieces. those are sliding portion, spring, some kind of composit and end screw piece. In haynes manual says first turn the crankshaft to the 20 ATDC to release the chain to not jump a tooth when you take out the old tensioner. Take out the old tensioner, Put the sliding portion in to the empty body and install in to the block and torque to specified value which is 59 lbft, Install chain tensioner central spring composit part and end screw and torque to specified value which is 29 lbft. But some people says install the empty body of the tensioner first which is i can't see the the difference, because sliding portion is a loose part in the tensioner until you install the spring and end screw piece it can't give any pressure to the chain. What difference it makes if you put the sliding portion into the tensioner body before you install the empty body in to the block or after? Because before you install spring and end screw piece sliding portion can't give any pressure to the chain because it is loose inside the tensioner body. I guess this is something where the experience is important and experience can be very expensive. Now i am planning to try one more time i hope tensioner is the problem. Because i am thinking how this camshaft can brake and i come up with two fundamental ideas those are first as you say i over tension the chain and when i run the car at the beginning it was ok but when the car overheats because of the heat camshaft becomes weak for the tension of the chain and broke. Second idea is something stopping the camshaft to turn and braking, but the problem with the second idea why it started the braking the camshaft after i change the tensioner if something was stopping the camshaft why not before?
Many thanks for your advice.

 

[kth286]

The reason for putting the body of the tensioner into engine first, before the internal into the body, is that there is a ratchet effect built into the tensioner design.

That means the internal can go one way forward but it will never come backwards from that point.

So, until the internal is actually against the chain you do not know how much to push the internal into the body.

If you insert the internal into the body whilst it is not against the chain you may have pushed it too far inside from where it will never be able to move back again.

The above is how it is on my car. I do not know if the design was changed for your car.

 

[team45]

The reason for putting the body of the tensioner into engine first, before the internal into the body, is that there is a ratchet effect built into the tensioner design.

That means the internal can go one way forward but it will never come backwards from that point.

So, until the internal is actually against the chain you do not know how much to push the internal into the body.

If you insert the internal into the body whilst it is not against the chain you may have pushed it too far inside from where it will never be able to move back again.

The above is how it is on my car. I do not know if the design was changed for your car.

Hi kth286,
I am sorry for late reply, i was a bit busy. I read your advise and i think what you say is right because i install the tensioner two times and both times i install the tensioner with the sliding part together but as you say it was going to far and not be able to come back again so thats why it was braking the camshaft. I order another used camshaft i am planning to try one more time the way you explained and i am hoping to succeed, i will be more careful this time. I would like ask you one more thing i just remembered, when i fit the camshaft last time i run the engine but battery war weak and i had to jump start and when i was running the engine before the camshaft broke i notice something strange. First thing was while the engine was running internal lights in the car was vibrating which means they weren't stable and second thing was when you switch on the long beam lights or heating engine was cutting off. Is this do you thing because of the engine under pressure or something else?
Many many thanks for your useful advices.

 

[television]

The chain problem has nothing to do with the electrics, it sounds to me as though you have a wire off the alternator.

 

[kth286]

The battery is very low and it needs to be charged with it disconnected from the car.

You are trying to use the electrics before it has had a chance to charge up, and I wonder if your charging system is working properly anyway and/or your battery is any good or needs to be replaced.

Give the battery a good charge for a day and night at low current and see if it holds it's charge .

Best wishes this time on the camshaft.

 

[big x]

Hi kth286,
I am sorry for late reply, i was a bit busy. I read your advise and i think what you say is right because i install the tensioner two times and both times i install the tensioner with the sliding part together but as you say it was going to far and not be able to come back again so thats why it was braking the camshaft. I order another used camshaft i am planning to try one more time the way you explained and i am hoping to succeed, i will be more careful this time. I would like ask you one more thing i just remembered, when i fit the camshaft last time i run the engine but battery war weak and i had to jump start and when i was running the engine before the camshaft broke i notice something strange. First thing was while the engine was running internal lights in the car was vibrating which means they weren't stable and second thing was when you switch on the long beam lights or heating engine was cutting off. Is this do you thing because of the engine under pressure or something else?
Many many thanks for your useful advices.

The Haynes manual does say quite clearly don't install the tensioner complete or it will be to tight !

adam

 

[Ian B Walker]

The Haynes manual does say quite clearly don't install the tensioner complete or it will be to tight !

adam

I made that mistake on a E220 once, only the once, as I was taught an expensive lesson.

 

[team45]

Thank you for your reply,

I have the haynes manual for c class it doesn' t say that maybe later editions had correction about it.