190 2.3-16v timing chain question - PeachParts Mercedes-Benz Forum

reinier · #1 05-20-2006, 02:19 PM

Ok, how stupid is it to only put a new timing chain and rails/tensioner on a 190 2.3 16v which has done 200.000 km/ 120.000 miles, and leave the sprockets of the cams an crankshaft where they are?

Because the chain is not very expensive, en sometimes breaks (read somewhere also about failing tensioners (are they also relatively cheap?), but the sprockets/gears (what is the exact word?) are expensive (2-300 euros a piece)

Its for a car that wont be running much, but dont want to take the risk of a breaking chain.

Maddog · #2 05-20-2006, 10:09 PM

i wouldnt worry about the gears. They arn't normal maintenance items.

#3 05-20-2006, 11:06 PM

I had my TC done at ~90k, it was very noisey in comparison to the new one. My mechanic recomended I do the sprockets (cams and i think one more) as well because of the labor involved in removing the front timing chain cover to get at all the guides. The sprockets _were_ worn, and they would have added slop and accelerated wear in the new chain unless they were replaced. This job is such a pita that you don't want to do it EVER again-money for the sprockets would be well-spent i think.

Get the updated tensioner from MB as well. Are you doing the job yourself?

cheers,
dan r.

ps. Maddog! Are you dong the 2006 challenge? Good luck!

t walgamuth · #4 05-21-2006, 09:29 AM

i have no specific 16v experience but if the sprokets are not worn i wouldnt see a problem with reusing them. if they are worn they will stretch the chain and reduce the life of it drastically.

tom w

Maddog · #5 05-23-2006, 09:17 PM

Wreck Racing will be back at the 2006 challenge with our BMW from last year. We are turbocharging it this summer and hope to make a good showing.

yhliem · #6 05-25-2006, 06:35 PM

Quote:

Originally Posted by reinier

Ok, how stupid is it to only put a new timing chain and rails/tensioner on a 190 2.3 16v which has done 200.000 km/ 120.000 miles, and leave the sprockets of the cams an crankshaft where they are?

Unless they are worn, not very stupid at all.

Quote:

Originally Posted by reinier

Because the chain is not very expensive, en sometimes breaks (read somewhere also about failing tensioners (are they also relatively cheap?), but the sprockets/gears (what is the exact word?) are expensive (2-300 euros a piece)

Ok...a little clarification. The EXACT nature of the 2.3-16 timing chain/tensioner is as follows:

Timing Chain

As a result of the twincam head, the 16v timing chain is longer and has a longer distance to travel than the 8v timing chain. As a result of THAT, lubrication of the chain at the exhaust cam sprocket (or gear, if you prefer) is less than ideal resulting in accellerated wear and/or chain stretch. (As an aside, This is why the 2.5-16 had duplex timing chains and why frequent and religious oil changes are necessary on the 2.3-16.)

Two options exist to rectify this issue:

1) convert your 2.3-16 to a duplex timing chain. This is an expensive conversion as I was quoted $2000+ CDN for parts alone. To put this into perspective, however, a new cylinder head from MB is $9700 CDN.

2) drill an oil journal into the #1 exhaust cam bearing cap such that it directs a jet of oil onto the exhaust cam sprocket.

Timing Chain Tensioner

The original tensioner does not fail in the sense that it breaks. To properly explain the issue, you need to first understand how the tensioner works.

The tensioner is, in essence, a 3-piece assembly comprised of a hollow tensioner body, a plunger, and, a cap. (There are a couple of other bits, but they're not important to understanding the basic operation of the tensioner.) The plunger fits in the tensioner body and the cap retains the plunger at one end. The other end is left open for the plunger to protrude out of. Oil pressure is introduced into the tensioner and forces the plunger out of the open end. The plunger, in turn, pushes against the tensioning rail and the rail puts tension on the chain.

The issue with the original tensioner is that when oil pressure is cut off (ie. when the engine has been shut off) oil can drain out of the tensioner allowing the plunger to retract. This becomes very apparent after the chain has already stretched and is symptomized by timing chain rattle on cold starts.

The danger here is that during the initial period before sufficient oil pressure in the block (and tensioner) has built to the point of taking up the slack there is the chance that the chain break off bits of the plastic chain guides which could get stuck in places we don't want them to. Or worse yet, the chain could jump timing which is not desireable. On an interference engine like the M102.983, incorrect timing is even less desireable.

The updated tensioner works in the same way as the original one with one important design change: the plunger has been modified to accept a spring clip and the barrel of the body has rings machined out for the spring clip to seat in. This creates a ratcheting tensioner that does not back out and solves the initial slack problem. The only downsside is that with THIS tensioner, if you hear chain rattle on startup, change the timing chain RIGHT AWAY.

Also, when you change the tensioner, you'd be well advised to change the plastic chain guides as well since they tend to get hard and brittle after spending 90,000 miles or more in the HOT M102.983.

t walgamuth · #7 05-26-2006, 12:27 AM

what size hole to drill in the cam bearing?

tom w

yhliem · #8 05-26-2006, 08:04 PM

1/16" should be fine

ATATEXAN · #9 06-17-2006, 03:22 PM

Unfortunately I've had personal experience with a new-but-"superceded" chain tensioner failing and trashing my 16V valves and pistons (back in 1997). Make sure that you are gertting the latest p/n from M-B.Don't skrimp on properly repairing this system. The advice on chain rail replacement is also right on the money. Also check your oil pump. A stretched chain can wear it down. Finally, the 2.3-16V has no key-way locking the lower gear, etc. to the crankshaft. You have to lock the crank down at the back of the engine and tighten the bolt to 240 ft/lbs. Yes, 240. Otherwise it comes loose.

There are lots of things to get wrong on this engine. Be careful and good luck!

reinier · #10 10-08-2006, 07:36 PM

Quote:

Originally Posted by yhliem

As a result of the twincam head, the 16v timing chain is longer and has a longer distance to travel than the 8v timing chain. As a result of THAT, lubrication of the chain at the exhaust cam sprocket (or gear, if you prefer) is less than ideal resulting in accellerated wear and/or chain stretch.

2) drill an oil journal into the #1 exhaust cam bearing cap such that it directs a jet of oil onto the exhaust cam sprocket.

.

Took the complete engine out for new timing chain, guides, and tierod bearings.
Sprocket of the intake canmshaft is worn, and also the small sprocket that comes after the intake cam is worn very bad.

Other sprockets are ok.

Why??

Maybe because these mentioned sprockets are 'last in line' when it comes to lubricating? And 'high' in the engine, and not in a oil bath?

When thats so, it would seem drilling a hole in the bearing of the INLET cam is smarter.

Anyway, the inlet sprocket is 350 euro's, and the small one also 140 or something like that. Bought the whole running car for 275, so no way.
D@mn it.
Put the m102 in a corner of my garage, waiting for a nice, secondhand, cheap sprocket to come by.
And there was this om603T right next to the car....doning nothing at the moment.

So i am putting that one in.