M42 Tensioner Failure -- How bad?

[recall]

Found a 318is up for sale and I'm thinking about picking it up for a DD. The timing tensioner has failed and the owner apparently doesn't want to fix it, saying the timing is off and a special tool is needed to put everything back in time.

So my question is how bad could a failure of the tensioner be? And how tough of a job is it to fix it up? I'm somewhat familiar with the M20 and recently replaced a timing belt, but the M42 is an entirely different beast. Owner says that he lined the chain up (though a tooth off on the intake side?) and ran a compression test that indicated close compression across all 4, citing this to say that there's been no damage to the valves/head when the tensioner failed and the fact that the engine wasn't under a heavy load when it went kaput.

Since I'm new to things, I'm wondering what else I should check for as an indicator for potential problems coming from this failure?

[FredK]

Just replace the entire engine.

The hydraulic tensioner does not fail. The chain rails let go because they are made of plastic from recycled Legos and milk bottles, and when they do, pistons hit valves, unless the owner killed the engine in one engine revolution. Right.

Did you ask what the "close compression" was across cylinders? Maybe 50 psi?

[KenC]

The tensioner itself is like 50 bucks and takes ten minutes to change.

I'd put a new tensioner in, time it correctly, and do a compression test yourself. Look for 190+ in all four cylinders.

[xwill112x]

Just replace the entire engine.



The hydraulic tensioner does not fail. The chain rails let go because they are made of plastic from recycled Legos and milk bottles, and when they do, pistons hit valves, unless the owner killed the engine in one engine revolution. Right.



Did you ask what the "close compression" was across cylinders? Maybe 50 psi?

not exactly. i've personally seen a m42 with a "failed" tensioner. lots of rattle and knocking and clacking due to the chain just slapping around.

[FredK]

Yes. Then you put a new tensioner in, and in the interim, because you've run with low chain tension for such a long time, the cam gears are worn as hell, and the plastic guides are grooved.

M42 does well with preventative maintenance, not reactive maintenance.

Look at the cam gears. Touch the teeth. If they are sharp, plan on replacing a lot of parts.

[tjts1]

Who cares about the cam gears. Slap in a new tensioner and drive the snot out of it until it fails completely. Replace the engine whenever that happens.

http://www.m42club.com/forums/showthread.php?t=2925

[recall]

He said the compression was 180-185 across, which might be low. Maybe within the bounds of measurement error?

He did specifically say the cam gear teeth weren't sharp, so maybe that's a good sign. I'll definitely check that out for myself. How bad is timing the M42?

I'm curious if he's dumping the car for reasons beyond this, obviously harder to find when the car isn't drivable, but first I need to make sure this problem can be fixed without too many headaches.

[xwill112x]

if it runs, buy it.

[325ix]

whats he asking for it?

[recall]

A grand. He says the intake sprocket jumped a tooth when the tensioner failed, though I'm guessing a tooth on the M42 could be worse than a tooth on the M20 camshaft.

[tjts1]

Too much. Offer $500 depending on the condition of the rest of the car.

[10Toes]

Thats not too much if it is clean. If it is only off one tooth then the engine is probably fine. I would get it take the timing cover offf and see what it looks like and then go from there.