M117 V8 Timing Chain Tensioner - PeachParts Mercedes-Benz Forum

Carlo(s) · #1 07-04-2009, 10:56 PM

1986 420SE V8 full emissions gear now 124K miles. Just read 500 posts on "Timing Chain Tensioner" but did not find a clear answer to my timing chain clacking noise. Clacking Noise goes away when car is idling; goes away when engine is revved. Clacking noise been there since I bought car at 93K miles and had just had right side cam replaced by a German indie. Clacking noise is getting louder now. Engine has factory compression, does not burn oil; very strong acceleration, smooth idle; no metal shavings in oil pan. Up front: new timing chain and rails; new timing chain tensioner installed about 10K miles ago to solve clacking noise with no success neither has the new timing chain and rails made the clacking noise go away. Air pump is disconnected. Cruise control unit is disconnected. I know there has to be a solution to this problem that does not require an engine tear down as some less than reputable Mercedes shops in my area have suggested (they can hear those $5,000 dollars ringing!).

E150GT · #2 07-04-2009, 11:09 PM

I do not know the answer to your question but your engine should be an M116 , not an M117.

Chadahar · #3 07-05-2009, 12:09 PM

Yep 116 engine.
Are you sure it isn't lifter noise?
New oilers might fix that. lso use 15-45 Chevron Delo LE Oil it has higher Zinc content that our engines like.

How about engine mounts, the clacking could be the fan hitting the shroud. Look at the lower passenger side of the shroud to see if there are scrape marks. Engine fan would hit at idle and then go away upon higher RPM due to engine lift.

porkface · #4 07-05-2009, 02:23 PM

i would not start the car again until this is fixed. sounds like the chain and tensioner need replacing. the tensioner works on oil pressure and when weak will loose the spring tension needed for when oil pressure is not present. the noise at idle sounds like the tensioner is bleeding pressure off internally-really weak. if the chain slips, you can bend valves and that means pulling the heads-very exspensive.

pull both valve covers and look at the plastic chain guides. the inner 1 on the lh head is the most fragile of the bunch. because of the way the chain runs, it's the 1st to break. any broken bits must be fished out of the engine. pull the lower oil pan and get the pieces. they can get into the oil pump from there or the new chain can jump if apiece falls out of the timing cover. seen it twice.

while the covers are off, turn the engine by hand to tdc on the crank pulley. there are marks on the cams and heads to line up. keep turning the motor until the marks on the lh cam line up. then, look at the crank pulley. if the pulley is PAST tdc 7 degrees or more, you need a chain and tensioner.
good luck, chuck.

Carlo(s) · #5 07-05-2009, 10:29 PM

Thanks for all the good suggestions! To restate: (1) car has a brand new timing chain and upper guides; (2) New timing chain tensioner put on 10K miles ago; (3) new motor mounts just installed (found one broken mount but new motor mounts made no difference); all lifters tested good; since noise comes from passenger side front of engine by cylinder No. 1; new lifters for cylinder 1 installed that made NO difference. Using Castrol GTX 20-50 now upon suggestion of indie mechanic; used to run diesel Rotella 10-40 and seemed to quiet it down a little. How do I test for camshaft play? maybe there is some camshaft "float"? some bushing somewhere? all cam towers torqued to specs with NO difference. Car has been running with this clacking noise since I acquired at 93K miles; now shows 125K with no ill effects other than it is bothersome to hear the noise and I want to solve the problem.!

TOPGUN · #6 07-05-2009, 11:08 PM

I replaced the chain, guides, and tensioner. The engine started up with a rattle on the passenger side valve cover. I imediately shut the engine off. I checked with the local indy shop. He advised me to send the tensioner back and get a MB tesioner. He said he has had the same problem with after market tensioners. I reinstalled the old tesioner until Phil sent a new MB tensioner. All is fine. As previosly stated I would check oil pressure to the tensioner. Are the holes in the gasket lined up and clear to allow oil to reach tensioner? I got lucky and did not damage the valves. Good luck.

Chadahar · #7 07-05-2009, 11:17 PM

Is it possible that you have an exhaust leak on #1 cylinder. They clack and go away when heated up.

Have you listened via a dowel rod to the engine. Dowel against the Valve cover and other end at your ear.Place the dowel on the VC at each cylinder. Put it on the alternator, air pump, etc you'll likely find where it is really coming from. An Auto stethoscope will work too.