Porsche still run if CHAIN TENSIONERS fail?

Will my Porsche still run if chain tensioners fail and how can I tell they have? Stupid question but I'm not mechanically inclined

[Rot 911]

It sure will. Right up to the point that the cams jump timing and drop some valves into the pistons. Then the engine will stop running. A chain tensioner that has failed makes a sound like a heavy chain being dragged over a metal trash can.

Oh so I'd definetly notice that. I guess I'm not used to the sound of air cooled engines I'm beggining to think my car was purposly set at high idle because it would stall. Definetly the mixture settings. I gatta take it to that Porsche guy whos got the tools.. I was reading my manual, I need some kind of too to syncronize all the carburators?

[Early_S_Man]

It will let you know when it got too tired to go any further ... "WHUMP ... SCREECH!!! ... dead silence." Those being the sounds of intake valves hitting pistons and bending, followed by rocker arms breaking, and the engine locking up ,,, followed by screeching tires! If you push in the clutch ... a quiet coast-down follows while you decide where to park it ...

[cary]

Kurt's is the perfect explanation. I can remember that noise like its yesterday. 15 years ago.

[cegerer]

I've told this before, but I had a tensioner failure on my first 911, many moons ago (before the days of the internet and great resources like this BBS!!). I didn't even know what a chain tensioner was back then. It made one heck of a racket ( imagine a bag of assorted nuts and bolts banging around inside your motor - that's the noise!) and there was no doubt something was wrong. So I just drove it slowly, back to my house and then 10-15 miles to my mechanic the next day. Miraculously, there was no damage at all, other than the tensioner itself! -- Curt

[RazorRacer]

So how much time does it take between hearing the sound of chains dragging over metal trash cans or bags of metal shaking in your engine until the valves drop into the piston and the engine seezes?

Are we talking seconds, minutes, hours, days or are we talking feet, blocks, miles?

I'm driving a 78SC and get the feeling I'm driving a time bomb. But if I get a few miles notice, then I will have a fair chance to defuse it, right?

[Early_S_Man]

Raz,

Like Cary, I remember that sound ... and just thinking back to that day in April 1979 ... gives me chills up the spine!

Since my experience occured at startup ... it didn't take but about five seconds at high idle ... before I killed the engine, so I didm't get to find out how long before the engine would crater at speed.

If anecdotal evidence can be trusted, and I tend to think it can be in this particular scenario, most tensioner failures occur at startup, so you don't have much to worry about! So, I tend to believe that you will have the usual 'chain dragging' warning, and you can take the time to order parts, and decide when to do the repair.

[stevef]

So in some ways it would be best not to install those Hydrostop thingies. If the tensioners failed you would want to know about it wouldn't you. Is there a way to tell if the tensioners fail if you have the mechanical retainers installed. If they are set .125" off the tensioner body you might not know a tensioner has gone until it completely goes. Anybody know what happens?

[dhaines]

Yep, still makes a racket with the stops installed. I just had this happen to mine, I noticed it when the engine was deaccelerating, could hear the chain slapping around. It is something you should be aware of when you hear a new noise, but I could hear it clearly from the drivers seat. Probably saved my engine though...

[Sunroof]

I bought an aftermarket banana shape muffler from a parts house, and a few months later I heard this incredible rattle as you guys describe................it was the muffler!
A baffle broke off and was going for a wild ride inside that muffler. Finally, one day it lodged somewhere and the noise went away.

Needless to say, my heart was in my toes when I heard it at first.
I was lucky...................

Regards
Bob
73.5T

[James_TX]

My chain tnesioner went out about 2 weeks ago. HORRID sound!

When your at idle you will hear the noise. At higher RPM's the noise seems to fade away.

I got lucky, no damage. Just a hefty 500$ tow bill from a road trip.



Good luck!

[724doorE]

Think I got a bad tensioner. I was checking some stuff along with changing the oil. I thought I heard some funny noises back there, but not as loud as you all have described. Well, I refitted a bunch of loose engine tin and started it, after refilling with oil , and then I could clearly hear it, but still not so loud. Went back there and stuck a screw driver in my ear to listen with and finally found the noise on the passenger side chain housing. I had presumed it was the drivers side and even checked that side before hand. These are the old spring style. Me thinks me needs the pressure fed variety...

Should I replace any ramps or anything else while I'm in there. Chains and gears are about 5K miles from new as is the failed tensioner

[CamB]

It could just be the ramps... were they replaced?

[Bones]

Originally posted by RazorRacer
So how much time does it take between hearing the sound of chains dragging over metal trash cans or bags of metal shaking in your engine until the valves drop into the piston and the engine seezes?

Are we talking seconds, minutes, hours, days or are we talking feet, blocks, miles?

I'm driving a 78SC and get the feeling I'm driving a time bomb. But if I get a few miles notice, then I will have a fair chance to defuse it, right?

Razor stop worrying you are definately not driving a time bomb , if your engine is properly maintained the stock tensioners will do their job for miles . I have 144,00 on the clock and when I decide to rebuild I'm not sure that I will fit the later tensioners as thay are not without problems to . At least the non-hydraulic ones are a simple design and there is a lot to be said for that!

[724doorE]

Yea the ramps were new as well.

I pulled off the offending cover and could easily see where the chain was hitting the case, pass side top of chain housing where it meets the case. Fortunately at this point the rub marks are just that, shiney rub marks. The tensioner was failed. It was an aftermarket HP tensioner from the old performance products probably purchased in about 1992. I could fairly easily depress the shaft with a screw driver and even though it was still whole, the body and upper portion with the snap rings seemed to be separated and non concentric. The ramp under the rub marks looks good still, I need to check the ramps inside the case also. Oh well, I guess I have some work to do! Oh and there was no junk in the oil. Although, I have gassy oil (from the mfi pump) and a little bit of condensate(my daily commute is only five minutes so it never heats up. I probably need to change my oil more often, maybe 1K -1.5K.miles.

[RazorRacer]

Thanks Bones. Eventually I will rebuild my engine, too.

BTW, looks like we are driving the same car...guards red, whale tail, Targa, and 78SC. Sweet.

[724doorE]

I think, Razor, that in most cases you can tell when they/one starts to fail, like in my case. I probably could have gone on for a while. More likely that big damage is done when the early signals of failure are ignored or missed. In my case the signal was the raspy metallic chain on a trashcan noise, only it was not very loud. It was only audible at idle and coastdown when the slack was being tossed around. You should be able to notice it easily and carefully get to your destination and then make plans for the cure. My input is to NOT replace with the HP spring tensioners that I used. Don't know if they are available anyway.

Another thing to consider is the fact that the price for both is similar.

Although, if you had a big failure and valves hit pistons, you would have a great reason to invest in some high comp 3.0 pistons

[Bones]

Originally posted by RazorRacer
Thanks Bones. Eventually I will rebuild my engine, too.

BTW, looks like we are driving the same car...guards red, whale tail, Targa, and 78SC. Sweet.

Yeh love the whole Targa experience too. Send me your email and I'll send you a few pics . I have a 964 kit on there . Next year it's ssi's and suspension .

[viejopatron]

Razor, FWIW Chain tensioner failure and the aforementioned results is a “chain” [Har!] of related events. By design, chain drives have and need some slop for several reasons, so it’s always there.

Failure starts with the catastrophic failure of the tensioner spring. This spring spends most of it’s life stressed to a relatively high level and consequently is designed to use a high-strength, not-real-ductile material. So when it fails, under load, it snaps and that load, used to tension the chain, disappears. Now here’s where the variables come in. A new system, with no or little wear in chain, ramps, bearings, etc. will have minimal slop. In a used system as wear progresses [it always does], slop increases. If you’ve ever observed free slop in a high-speed chain drive, it looks like a “bump” in the chain line and will move back and forth between sprockets as load changes. In the cam chain drive, when that bump travels up to and on a sprocket… Well, let’s just say the rest can be spectacular.

Bottom line: Be aware of wear.