rfuerst

O.K. here is a theory-on the 16 valve cars one of the weak spots is the cam chain tensioner,and it is my understanding that 2 things can fail-the plastic or nylon ramp that the chain rides on and the tensioner itself failing.My theory is that a way of stopping the tensioner from collapsing when it fails is to put a split collar around the shaft of the tensioner.As an example if the shaft is 3/8 in diameter and 1/2 tall when under pressure,if you were to install a split collar with a 3/8 inside diameter and 1/2 inch tall then in theory if the tensioner were to fail you would not have a catastrophic failure!It seems to be a guessing game as to when to replace the tensioner and many of them are replaced before they need to be,if this would work it may save a bunch of engines including mine.Any comments?Thanks <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Melchior

That idea could work, but wouldn't you want to make the height a little shorter so that the tensioner could relax pressure when the engine was off?

rfuerst

David that is a good idea,I am posting this to see what others have to say.I am getting ready to replace the nylon pad on my tensioner and I was thinking of this collar idea.I do not know if the previous owner of my 1987-944S ever replaced the tensioner,but I do not want to spend $300.00 if not needed,thats why I posed the question.Thanks for the reply. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Tom Pultz

[quote]Originally posted by rfuerst944s:
<strong>I do not want to spend $300.00 if not needed</strong><hr></blockquote>As the Fram ads say, "You can pay me now or you can pay me later." Sure, nobody wants to spend $300 needlessly, but do you want to spend $3000 instead? Changing the whole tensioner seems like cheap insurance to me. I would not screw around with the design.

rfuerst

Tom thanks for the response,I do not believe I am screwing around the design,in fact if you look in various Porsche parts listings you will see some companies sell these collars I am talking about for Porsche 911s,the reason being that the tensioners are prone to breaking and the collar stops expensive damage!I am not trying to re-invent the wheel,just add a insurance policy if you will.There are some Porsche 911 and 944 owners that have maintained the tensioners and still had failures,that is what I want to prevent.Thanks <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Riff

This is a good idea, but I don't think that the tensioner collapsing is actually the failure mode. I think it is the pad disintegrating that is the true failure mode of the system; the tensioner collapsing would be the by product. The tensioner is supported by a spring and is fed oil and it collapsing might actually help you in the event that the nylon pad disintegrates. This assumes that the remnants of the pad do not gum up the works or your chain does not jump a few teeth once the tension has been relieved. You see beneath the pad, the upper tensioner plate edges that are perpendicular to the direction of movement of the chain ARE NOT FLAT! There is a cut out on both ends, just right for catching the chain and holding it tight while everything goes to pieces.

Please note that this is just my opinon based on looking at the system. I believe that the nylon pads are meant to be the sacrifical part of the system, helping to absord some of the lash of the chain. I have no experience with 911 or their problems with the chain tensioners, though I have heard of them. My best guess as to why a collar stay would aid them is that whatever is acting upon the chain does not have any type of void that would catch the chain and stop it's movement. Instead any slack in the chain would lead to damage. Unfortunately this is not the case with our cars. Best piece of mind would be regular inspection of the system. I will check mine at 45K intervals with changes at 90K. FYI I replaced my tensioner when my car had 99K, it now has 144K. I'll give it a look this winter during hibernation.


My $.02,

Wolf-Dietmar

Hi,

as fare as I have seen only the plastic ramp can get broken in the range of 80-100.000 km.

Are you aware that the plastic is available from Porsche for approx. 2 USD ?
(It's in the piece part listing of the 968 - model, NOT in the 944.)

For preventive action that would be the best compromise.

rfuerst

Thanks everyone for the input. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

P-on

I have a question regarding the cam chain tensioner, even though you're all sick of the topic. I've ordered the "stuff" to do my 75K S2. I'll follow the direction in the link given earlier. Do I need to worry about re-timing the cams or some such thing? One parts retailer said no, another said absolutely, and yet another said no "but it wouldn't hurt". I'm confused now. These are all well known aftermarket retailers.

Advice appreciated. Thanks.

Dal Heger

no, you do not need to retime the cams. You're not removing the cams. you only need to retime the cams if you remove them, or if you take the cam pulley off. You're not doing either.

Dal.

Dal Heger

I wouldn't worry about the split collar idea. The tensioner has a rather strong spring within it to keep it tensioned, even if the oil pressure falls (from a failed supply tube, etc.)
I have yet to see or hear of a tensioner failing on these engines. The common failure mode is the pad disintegrating and the cam chain getting caught on the metal lip of the tensioner, ripping the tensioner assembly off the head and causing all sorts of damage.

Replace the pad and the tensioner at regular intervals and you'll be fine.

Dal

Luis de Prat

Dal and others, I recently had an engine oil overfill situation in my 136K mile S2 (tensioner replaced at 124K) and since I was wondering whether the J-Tube had collapsed and was spilling oil, I opened the cam cover to replace the J-Tube, crush washers, cam cover gasket, O-Rings and bolt grommets, etc.

However, I noticed the tube in my car was brass, just like the part I replaced it with. Previously, I had heard about these J-Tubes being plastic and therefore disintegrating? Can you confirm/clarify this? Thanks.

Dal Heger

I don't know about the old versions, but the new version of the J tube is metal. You shouldn't have any problems with this part unless you end up ripping the tensioner off during a failure.

Dal.