Defective Chain Tensioner?

[Ottawa911]

Hi all,
I'm new to this forum and I must say that this is probably one of the best, most informative newsgroups I've ever visited.

Anyways, on to my problem.....
I'm a proud new owner of a '70 911T and according to the logs, the mechanical tensioners were replaced about 5000 mi ago (about 1997). Recently, I heard a horrible noise coming from the engine compartment. It sounded like a loud rattling noise, (like someone dropping marbles into a garbage can) but it only occurred at low idle. At higher RPM, it seemed to go away. Before I got a chance to check it out, the noise went away and hasn't come back since.
Is this a sign of a failing chain tensioner? Is it common for a tensioner to fail and then recover?
Thanks.

[rstoll]

Might be a broken chain ramp. Same noise on mine, drivers side lower chain ramp was in oil sump. Updated to pressure fed tensioners and replaced ramps. I would pull the covers and have a look.

[Raynald]

Hello,
my name is Raynald, i am from Québec, i wish you: Bienvenue
i don't know your problem but if you need tensioners i have a pair of good one, i rebult my engine and upgrade to carrera...

welcome again!

[jbirkett]

I experienced a similar problem with my '72. After removing the chain covers I found that the previous owner had installed the tensioner collars, which by the way saved a complete failure. The noise would come and go but was enough for me to park the Pcar for a while until I could upgrade to pressure fed tensioners.

[Wayne 962]

I would indeed tear in there, and see what you have. The instructions for the upgrade / disassembly can be found in 101 Projects...

-Wayne

[Doug Zielke]

Originally posted by Wayne at Pelican Parts
I would indeed tear in there, and see what you have. The instructions for the upgrade / disassembly can be found in 101 Projects...

-Wayne

Yet another disgusting shill for this eminently useful and essential book

[Ottawa911]

That's ok.....I've already purchased the book!

[Wayne 962]

Everyone should have two copies - one for the office/can and one for the garage!

-Wayne

[CamB]

I very recently dealt with this.

The chain was rattling only when the engine was cold and only at lower revs (I guess since I don't rev beyond 3-4k while it is cold then I have no idea if it rattled at higher revs...).

I removed the chain covers to have a look after chasing down a set of known to be good tensioners (it wasn't quite that simple, but in the end Matt Smith has lent me his ones left over after he upgraded to pressure fed).

The tensioners looked fine, but one was a little spongy. I replaced them with Matt's ones. The chain and ramps looked newish (as if they were already replaced).

The noise had now gone away. It may be worth following up the offer for the working tensioners above, or upgrading to pressure fed ones as per Wayne's book.

Matt had chain rattle as one of his ramps was broken - either way you would need to take the covers off to have a look (and will need new gaskets when you put them back on).

Cam

[WJG2]

I have, as usual, no helpful information, other than to welcome you as another Porscher in the Great White North -- may you never have to buy parts south of the border with the current exchange rate!

[JMPRO]

I HAVE A 78 911 SC . IS THERE ANY WAY TO TELL IF YOUR TENSIONERS HAVE ALREADY BEEN UP GRADED. I HAVE HAD THE CAR SINCE 83 BUT HAD NO CONTACT W/ THE PREVIOUS OWNER .
JERRY

[CamB]

It is very easy to tell if you have the upgrade to Carrera pressure-fed tensioners. If they are there, your chain covers will look like this:



Ok, so maybe it won't be so clean, but the important thing to check for are the oil lines running down to feed the tensioner in the middle of the cover.

If you don't have the oil line, you don't have pressure fed tensioners but there is not way of telling if they are the ones which came with the engine or if they have been replaced in the last 20 years.

[Pillow]

Now for the unpopular opinion on this board

Keep the regular tensioners from the factory and put in "collars" just-in-case. Save a few bucks and not have to worry about more ding dang oil lines.

My mechanic initially put me onto keeping the stock tensioners and I did. Now the more I learn/know the more I like to keep the stock tensioners.

I think a good paralell can be drawn from the debate over hydraulic lifters versus solid lifters in the 914 forum. I could see issues when the car sits and the hydrualic tensioners pumping up and of course if there are oil pressure issues the chain will get slack and may junp the sprockets, meaning killed valves.

You are right on track with listening for the dragging chains, when this happens stop immediately listen at low RPM (less chance of jumping a sprocket) and see what is going on. Possibly a tow ride home if it is bad and you are not sure that you have "collars". I have heard the best way to test the tensioners is to rev the motor to 2000-2500RPM and listen for the tell tale dragging clatter.

I am sure there is a quite bunch of stock tensioners out there to agree with this.... Right...?

[Matt Smith]

Actually, the clean engine pic raises an interesting point.
Perhaps you shouldn't do the tensioner upgrade unless your insides are as clean as those externals. Roland posted an interesting saga on Renlist a while back stating how putting the new pressure fed tensioners into 'dirty' engines (ie, not freshly rebuilt ones) is a primary cause of failure. It sounds reasonable- perhaps Roland could weigh in here for the benefit of Pelicanheads?

Hydraulic tensioner pro's: Engine 'whirrr' sounds so good you could eat it; uses nice new attractive clean parts; immediately obvious to the casual observer, and supposedly increases resale value; reckoned to be a fool-proof fix for the 911's archilles heel.

Cons: I'm not so sure about the-fool proof fix bit.

[Doug Zielke]

Originally posted by Pillow

I am sure there is a quite bunch of stock tensioners out there to agree with this.... Right...?

And more than a few valves that don't....

[Ottawa911]

Looks like we have a difference in opinion! What about it guys/gals? Anybody out there have a bad experience with the hydraulic tensioners?

I'm thinking that if I'm going to go to the trouble of opening up the timing chain covers to inspect the tensioners and ramps, I might as well go ahead and replace them if I suspect them as being bad. I was going to install the hydraulic tensioner upgrade but what do you think?
Thanks

[rstoll]

I avoided a bad experience. Upon hearing the "death rattle" I installed pressure fed tensioners before driving the car again. Whether pressure fed, or hydraulic, do something. I talked to Charlie Jones at "Foreign and Classic Motors" after installing my pressure fed tensioners. He was kinda neutral on them. Said in 30 years he had few hydraulics fail. Didn't really have a problem with them. I jumped in and bought pressure fed mainly on hype I had read in ads. Glad I have them now, but probably would have gone with a rebuild on my old ones in hindsight.

[jstobo]

I have a 69E. My tensioners went(for the second time) but the second time a piece of a chain guide broke off and fell into the crankcase. The dirty little bugger got between the gears and womp! four rocker arms broken and numerous bent valves. So if the tensioners are gon. Replace them. Make sure the guides are the new type not the old rubber. The oil makes the rubber hard and brittle. Your 70T may have had the chain guides changed previously but you should make sure. Good luck.

[Pillow]

Doug, was that valve bent with the "collars" on the tensioners? Or just regular stock with no "collars"?

From what I have heard "collars" will prevent that from happening...

Matt Smith also brought up a great point of the internal cleanliness of the motor. Your oil needs to be very clean for anything hydraulic to work properly. On the 914 board you will hear that most hydraulic lifters fail because the oil is not changed regularly.

Also I have heard that there have been a few bad batches of hydraulic chain tensioner kits... Not sure what would fail, but there is a risk of getting a bad kit.

I prefer the stock setup with "collars", but I think there is no right or wrong option here... Given proper maintenance both should work well.

[83SC in PA]

I recently bought a set of new PF tensioners and one of them failed immediately after the engine was buttoned up and started. Didn't give me a warm and fuzzy feeling.