Understanding Cam tensioners

[mojoluthier]

I recently changed my IMS bearing/Clutch/seals in my newly acquired '02 S at 100k, right here in my dirt floored garage, but not before I built an inch and an eighth 8' x 16' wooden floor in it. The IMS bearing was in perfect condition as it turned out, but I will sleep better knowing.

When I backed out the two tensioners in my 5 chain engine, the right side one had to be removed as it held serious tension all the way out, the left hand side (IMS tensioner) had no tension on it at all and I backed it out perhaps 4 turns. Now I am losing sleep over the tensioners as it seems unlikely that no tension is right. I do hear a rhythmic (about a 1 second cycle with a definite peak in it) rattling at idle when the engine is hot only, and it doesn't seem to be loose external parts. Is a new tensioner liable to fix this? There is no oil leak at any tensioner, and though I read plenty about replacing them, there is little on why.

This car runs great, by the way. My only reference has been 101 tips and this forum.

Thank you in advance.

[BYprodriver]

Originally Posted by mojoluthier

I recently changed my IMS bearing/Clutch/seals in my newly acquired '02 S at 100k, right here in my dirt floored garage, but not before I built an inch and an eighth 8' x 16' wooden floor in it. The IMS bearing was in perfect condition as it turned out, but I will sleep better knowing.

When I backed out the two tensioners in my 5 chain engine, the right side one had to be removed as it held serious tension all the way out, the left hand side (IMS tensioner) had no tension on it at all and I backed it out perhaps 4 turns. Now I am losing sleep over the tensioners as it seems unlikely that no tension is right. I do hear a rhythmic (about a 1 second cycle with a definite peak in it) rattling at idle when the engine is hot only, and it doesn't seem to be loose external parts. Is a new tensioner liable to fix this? There is no oil leak at any tensioner, and though I read plenty about replacing them, there is little on why.

This car runs great, by the way. My only reference has been 101 tips and this forum.

Thank you in advance.

The hydraulic chain tensioners work similar to hydraulic valve lifters & have some of the tightest clearances in your engine (less than .001"). So they are a likely part to get clogged with debris carried in the oil. Replacing the tensioners 1 at a time often cures internal engine noises, but if I am understanding your description correctly it maybe valve lifter noise.

[JFP in PA]

I would tend to agree with the lifter diagnosis; that said, you can try replacing the tensioners (they are a lot easier to get at than the lifters) to see it it helps. If the car has a lot of miles on it, they could be varnished or full of crud.

[mojoluthier]

I would like to hear the difference in the spring load of the two tensioners addressed, please. I am trying to understand, not just get an end game analysis. Since they are hydraulic (news to me) it may be the tight one failing rather than the low tension one. (?)

[mojoluthier]

If it were lifters the cycle would be much faster, at least 400 times a minute. My sound is like a loose body part rattle, and I can imagine it is the timing chain dragging unevenly as it has perhaps 30 flutter twacks in it on a dynamic rhythmic repetition.
tttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt

[tomk]

hi mojo, guessing that you are a guitar guy, with a handle like that. I am new to the boxster forum but am not new to various engines and cam chain tensioners in general, including aircooled 911's and BMW V8's etc. Based onyour description and my own general background you should have tension on tensioner most if not all the way out of removing it. The tensioner works on spring force and the oil serves to dampen its response. I just bought my boxster as a project car and it rattles like hell for a second after startup so I have ordered all the tensioners, 3 of them, plus the cam locking tool to hold everything steady while i replace them. If this question is still open in a few days I can report my experience to you if you want.
Good Luck

[harryrcb]

as tomk said, the tensioner have tension to the last thread, which you will feel when you put them back on. Soooo, if you had no tension then the tensioner is hanging up. sometimes you can get lucky and soak them in degrease over night then clean them real good but if it were me or one of my customers cars I would replace it.

[mojoluthier]

This is the kind of info I seek! Thank you.

Yes, I am a luthier, a maker of guitars and violins, mostly. Put a .com on my handle and you can check my stuff out!

[tomk]

Once I get my tensioners and install them i will post an update on how much force they exerted on the way out. One question for you, you mentioned that you recently installed a new ISB, I am guessing you purchased the install kit? If so I am planning to do mine at some point for peace of mind and was wondering if you would like to sell your puller/install kit? LMK

[mojoluthier]

I have decided to replace the one tensioner, and it should arrive in a day or so. I plan to simply unscrew the old one and screw in the new one as I cannot see how the chain could possibly jump a tooth if the engine is not turned over. Unless someone saves me, but otherwise, let logic prevail: IF there is no tension on the chain now, as I believe, THEN it cannot matter if I pull the tensioner; that's my logic.

I am hanging onto my IMS tool set for the next time, or until I know there won't be one.

[mojoluthier]

OK. No one said anything, I have just finished putting in the new motor mount (the old one was completely separated!), the car is up on the stands, and the tensioner just arrived. I'll let you know if I ruin the engine. I always was a free thinker (troublemaker)!

[j911brick]

Originally Posted by mojoluthier

I have decided to replace the one tensioner, and it should arrive in a day or so. I plan to simply unscrew the old one and screw in the new one as I cannot see how the chain could possibly jump a tooth if the engine is not turned over. Unless someone saves me, but otherwise, let logic prevail: IF there is no tension on the chain now, as I believe, THEN it cannot matter if I pull the tensioner; that's my logic.

I am hanging onto my IMS tool set for the next time, or until I know there won't be one.

Doesn't matter is the motor is turned over. The valve springs put tension on the cam. Once the tensoner gets loose it could try to turn either way.

[mattatk]

Is it hard to get at the 4-6 tensioner? Can you remove it whilst engine is in the car?
Can you replace 1 tensioner at a time without locking the camshafts??

[j911brick]

Originally Posted by mattatk

Can you replace 1 tensioner at a time without locking the camshafts??

I wouldn't try it. There is only a very, very small possibility the cams won't turn.

[mattatk]

OK, I'll get the lock.....but is the 4-6 tensioner hard to get at?

[harryrcb]

Originally Posted by mattatk

OK, I'll get the lock.....but is the 4-6 tensioner hard to get at?

Somewhat, you have the power steering line running over top of it etc etc you will need to access it from behind the driver seat with the carpet and panel removed
(of course you knew that) It's been a while since I have had to access it so I don't remember everything but give it a shot.

[mattatk]

Thanks I'll post the results.....wasn't sure without looking if other items had to be removed first.

Cheers

[tomk]

hi a quick update since i just installed all three
-when i removed the tensioner for the IMS shaft it came out without resistance toward the end of the threads. after i got it out it was clearly stuck in its travel, after some exercise on the bench it came free but still had binding in its travel. the replacement unit had a change of design so dont be put off by that

- the 4-6 tensioner was not bad to remove, i used a 1 1/4 box end wrench to get it free and then it was easy from there, again they changed the design so you will need a 14mm allen wrench to secure the replacement

- when installing the holding fixture be careful to note that although the slot in the cam might appear to be in the right position, vertical, you might need to move the crank another 360 degrees since the slot in the cam is very slightly offset from center. the slot will be vertical in any case

[tomk]

i omitted the most impotant point , the rattle on startup is gone

[harryrcb]

Awsome, good job