How does a 603 chain tensioner work? - PeachParts Mercedes-Benz Forum

New2MB · #1 11-13-2010, 01:37 PM

I recently installed a new chain tensioner only to realize that I didn't know what I was doing.

First I didn't fill it with oil, then I filled it with the wrong oil and didn't do the procedure properly.

After reading the FSM I see that I should have used SAE 10 but I used 10w-30.

I thought that I was simply priming the tensioner and that engine oil (15w-40) would be flowing through it while the engine was running, it seems that is incorrect?

The FSM also states that it should be relatively easy to push the tensioner in. However, due to my incorrect filling method or maybe the incorrect oil, mine is very hard to push in.

This seems to have created a sort of hollow metallic scraping noise coming from possibly the lower end of my timing cover. When I backed the tensioner out of the block a thread it quieted the noise down so it seems I have too much tension on the timing chain.

On my tensioner there is the hexagon for tightening the tensioner into the block and there is also a hexagon at the end of the tensioner that sticks out of the block, what is that other hexagon for? Is there some tensioner adjustment?

Thanks!

duxthe1 · #2 11-13-2010, 09:53 PM

There is a spring in the tensioner that pushes the plunger out. Given that once the plunger moves out there is a stepped ratchet that prevents it from retracting, you can not simply screw it in. You have to disassemble it, install the housing, then the plunger and spring and finally the cap. If you just screwed in the new tensioner you put WAY too much pressure on the chain and other timing components, that's why you heard a noise. Depending on how long it ran in this condition, damage may already be done.

Carpenterman · #3 11-13-2010, 10:54 PM

I made the same mistake on my 617. I just about ruined the tensioner rail until I figured out the problem.

That was the last time I used the Haines repair manual for anything important on my car.

New2MB · #4 11-13-2010, 11:58 PM

Excellent, thank you!

It has not run at all, just cranked over a bit.

I will reassemble correctly and hope for the best.

Quote:

Originally Posted by duxthe1

There is a spring in the tensioner that pushes the plunger out. Given that once the plunger moves out there is a stepped ratchet that prevents it from retracting, you can not simply screw it in. You have to disassemble it, install the housing, then the plunger and spring and finally the cap. If you just screwed in the new tensioner you put WAY too much pressure on the chain and other timing components, that's why you heard a noise. Depending on how long it ran in this condition, damage may already be done.

jt20 · #5 11-14-2010, 12:44 AM

Quote:

Originally Posted by duxthe1

There is a spring in the tensioner that pushes the plunger out. Given that once the plunger moves out there is a stepped ratchet that prevents it from retracting, you can not simply screw it in. You have to disassemble it, install the housing, then the plunger and spring and finally the cap. If you just screwed in the new tensioner you put WAY too much pressure on the chain and other timing components, that's why you heard a noise. Depending on how long it ran in this condition, damage may already be done.

are you certain of this?

617s had a ratcheting tensioner, but not any 60x engine that I am aware of.

jt20 · #6 11-14-2010, 12:53 AM

Quote:

Originally Posted by New2MB

First I didn't fill it with oil, then I filled it with the wrong oil and didn't do the procedure properly.

After reading the FSM I see that I should have used SAE 10 but I used 10w-30.

I thought that I was simply priming the tensioner and that engine oil (15w-40) would be flowing through it while the engine was running, it seems that is incorrect?

The FSM also states that it should be relatively easy to push the tensioner in. However, due to my incorrect filling method or maybe the incorrect oil, mine is very hard to push in.

The oil type is not a big deal.

It is only for damping effects before oil pressure is sufficient and reaches the tensioner.

It is easy to push in when its not primed, otherwise, it is difficult.

The metallic sound concerns me, try to make sure it is not just the chain on the rail.

With the tensioner out, try to wiggle the tensioning rail side to side.

If the noise continues, you may want to take off the valve cover to get a look at things.

New2MB · #7 11-14-2010, 11:52 AM

It sounds a little metallic but honestly it's hard to tell for sure.

When I release the tension in the chain the noise goes away.

I've got the valve cover off and I don't see anything out of the ordinary.

If I don't have a ratcheting type do I need to install it any differently?

Do I just screw the plunger in all the way?

Interesting that the FSM does not mention the installation process.

compu_85 · #8 11-14-2010, 01:43 PM

I've had the tensioner out of my car a couple of times. After filling it with oil outside the motor I simply screwed it into the block slowly. Did not have any issues.

-Jason

jt20 · #9 11-14-2010, 03:54 PM

Quote:

Originally Posted by compu_85

I've had the tensioner out of my car a couple of times. After filling it with oil outside the motor I simply screwed it into the block slowly. Did not have any issues.

-Jason

ditto.

I don't even prime it anymore unless the engine has been apart.

jt20 · #10 11-14-2010, 03:59 PM

Quote:

Originally Posted by compu_85

I've had the tensioner out of my car a couple of times. After filling it with oil outside the motor I simply screwed it into the block slowly. Did not have any issues.

-Jason

there's rally nothing special about the installation.

its a hydraulic ram that pushes on a fulcrum... it either provides pressure, or does not.

the one thing I was concerned about was the side to side movement of the rail that it pushes on. If it is worn enough to mis-align with the tensioner pin, the chain could be hanging off of it.

If you dont see anything wrong by looking down into the cavity with the tensioner in, you're probably OK.

New2MB · #11 11-14-2010, 05:42 PM

So you don't even take the plunger out and re-install it seperately when putting the tensioner back in?

All of my chain guides are brand new and none of them (the two that I can see) show any signs of misalignment or any other issue.

jt20 · #12 11-14-2010, 05:51 PM

I have never opened it.

Bill Ladd · #13 11-14-2010, 09:03 PM

Quote:

Originally Posted by New2MB

So you don't even take the plunger out and re-install it seperately when putting the tensioner back in?

No.

New2MB · #14 11-15-2010, 10:38 AM

Looking at the schematic of the tensioner it looks like there is no reason to remove the sealing plug to install the tensioner.

I don't see how it would make any difference.

And the directions don't mention it either.

Is there any way to tell if my tensioner is applying too much tension to the chain?

compu_85 · #15 11-15-2010, 10:41 AM

If the tensioner is in question why not replace it? A new one is just $50. Heck, you can have my (good) old one. Where in MI are you?

-Jason