chain noise
 

Every time I cold start my car there is a strange noise for 5-10 secs, seems to be from the chains. It looks like as oil starts going up the noise dissapears.
Has anybody experienced this?

Marcello, That sounds like the dreaded 'chain dragged out of a bucket' sound to me ... only heard it once, in the spring of '79, but it is one of those things you NEVER forget! I would suggest NOT running the engine any more, until you can remove the muffler and chain gallery covers to see which tensioner has failed. It is usually just one side. Good luck!

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Warren Hall
1973 911S Targa

Warren,
actualy I had a chain tensioner failure two mths ago, and had it fixed..and the noise is terible, looks like your motor is falling apart, but it only hapens in low rpms. But this is more of a smoth sound like "rrrrrrrrr" and only 5-10 secs during cold start. Then I assume that when oil starts punping up, it stops and iddles perfect.
Remember, my ext. oil cooler has no thermostat! Could that be the lubrication problem I assume?

Could be related to your external cooler putting an 'extra' load on the scavenge pump when it is trying to empty those 3 to 5 qts/liters of 'cold' oil out of the crankcase, but I'm not so sure? If it does, indeed, sound like chain noise, as you said intitially, I wouldn't discount tensioner problems again, this soon! They can fail any time ... according to Bruce Anderson, so yours could be 'infant mortality' problems ... a term normally applied to early life component failures in the semiconductor industry, but it seems to be applicable to 911 chain tensioners, as well!!!

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Warren Hall
1973 911S Targa

I think my car does this as well (hard to be sure when the description is the phrase Rrrrr http://www.pelicanparts.com/ultimate/wink.gif). The only other characteristic I would note is that my car only tends to do it when I first start it from cold, and lasts for about 3-5 seconds. I too thought it was something to do with the chains (p.f tensioners) but after 12 months and about 2000 miles, have stopped being overly concerned.

Warren re: your second suggestion I don't have an external cooler.

I would be interested to know what it is, in case it is something potentially serious.
Regards,


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Paul
911T'69

[This message has been edited by Paul W (edited 03-13-2000).]

Paul, If your car does it only on startup, does the temp. of the oil have any effect on the noise, or the 'time' for the noise to go away? If the time is SLIGHTLY less for a 'warm' engine that was previously up to regular operating temp, but has sit up for, say two hours, the oil would still be rather 'warm' and should take less time for the scavenge pump to empty the sump. My only thoughts ... if it ISN'T the tensioners, would be the bearings, or gears, for the intermediate shaft, since that is what drives the oil pump, and the 'load' on that shaft and the pumps would logically be highest and 'worst case' at startup with a cold engine and oil supply! If it isn't tensioner failure, then maybe it is just the pressure-fed tensioners getting the chain 'aligned' properly and tensioned, ready for another day's hard work at the treadmill, so to speak!!! It doesn't sound too bad or threatening to me if it has been going on for 12 months and hasn't changed or gotten any worse.

One suggestion for troubleshooting: Get someone else to start the engine for you, and be back at the engine with hood up ... and Time the Rrrrrr 'noise' duration, to a tenth of a second resolution, if possible. After running for half an hour or more at full, normal engine temp, stop and let the engine sit for five minutes. With help of 'trusted' friend again, be ready back at the engine, hood up, again, for the restart ... retime the Rrrrrr 'noise' duration again ... and let us know if there is ANY significant difference in the 'hot' and 'cold' noise time duration, OK?

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Warren Hall
1973 911S Targa

Hi Warren
Without going to a documented experiment I can say that after an initial start and warm up, if I am to start the car again within a period of a couple of hours most of the time there is no noise (9/10 times). If there is any it is very light and goes quickly. I agree with where your line of reasoning is heading, it feels as if it has something to with oil. I can definitely say over the 12 month period I have owned the car the noise has not got worse, and maybe a touch better, but that might just be me getting use to it.

I’ll try your suggested experiment next weekend.

Marcello do you find your car starts without the noise when warm?

Regards,


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Paul
911T'69

[This message has been edited by Paul W (edited 03-13-2000).]

Yes the "Rrrr" noise is shorter if the motor is started warm. I haven´t timed it, but would say that cold 10-15 secs, and warm 2-5 secs.
What do u sugest Warren, check the bearings or gears?
Or something nothing to worry about?

If it is the scavenge pump emptying the crankcase of cold oil, I don't think it anything to worry about.

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Warren Hall
1973 911S Targa

I'd like to add one other note to Warren's suggestion. You can do a great job of determining where the noise is coming from with a dowel rod, broomstick, or large screwdriver (don't get your hair caught in the fan...OUCH!). hold the stick against the chain cover, put your ear DIRECTLY on the other end of the stick, have your freind start the car. You'll be supprised at how much better solid matter transfers sound than air. I've used this method to determine loose valves and even bad rod bearings. If you move the stick to defferent places, I'll bet you can pinpoint the noise to within 3-6 inches.
Good luck!!!!

NOW THIS MAY SEEM COUNTER TO THE CLAIMS OF RELIABILITY OF THE PRESSURE FED TENSIONERS BUT I'VE HAD EXPERIENCES WITH TWO OF MY CARS WITH THE 84 AND LATER TENSIONERS THAT WOULD ALLOW CHAIN RATTLE ON COLD START FOR ONE TO TWO SECONDS BEFORE THEY FILLED.
KNOWING FULL WELL WHAT THE DREADED RATTLE SOUNDS LIKE FROM A CHAIN FAILURE ON MY OLD 69 911, I KNOW THE FEAR THAT STRIKES WHEN THAT SOUND IS HEARD.
I ALSO HAD A TENSIONER ON A 84 CARRERA THAT WOULD FAIL INTERMITTENTLY, USUALLY AFTER THE ENGINE HAD COOLED DOWN FOR ABOUT TWENTY MINUTES AFTER A FULL WARMUP AND RUN. I KNOW IT SOUNDS WEIRD, BUT I'M CONVINCED THAT THERE WAS A METAL FATIGUE OR EXPANSION AT THAT ONE TEMPERATURE THAT CAUSED THE PARTIAL FAILURE.IT FELT AS IF THE PISTON WAS PARTIALLY COLLAPSED AND NOT FULLY OPERATIONAL AS THE RATTLE WAS NOT THE TERRIFYING CLATTER. IF LEFT AT IDLE, IT WOULD GRADUALLY CORRECT ITSELF, AS IF IT FILLED AND MAINTAINED PRESSURE AND REACHED AN OPERATING TEMPERATURE THAT IT LIKED. AND I HAD REMOVED AND BLOWN OUT THE FEEDER LINES AS A FIRST PRECAUTION.
THE TENSIONER DID EVENTUALLY FAIL COMPLETELY. IRONICALLY, JUST AFTER I HAD REINSTALLED THE ENGINE AFTER A CLUTCH REPLACEMENT.THE NOISE INDICATED A FULL BLOWN COLLAPSE AND I COULDN'T SHUT THE ENGINE OFF FAST ENOUGH!
ONE LESSON TO BE LEARNED IS THAT IT IS NOT WORTH WAITING TO REPLACE THE UNIT IF YOU HAVE ANY DOUBTS AND WANT TO BE SAFE.
THERE IS ALSO ANOTHER SYMPTOM THAT CAN REPLICATE THE CHAIN FAILURE NOISE. IF THE LEFT SIDE CHAIN STRETCHES WITH WEAR,IT CAN ALLOW THE SPROCKET ARM TO ACTUALLY MAKE CONTACT WITH THE UPPER INSIDE SURFACE OF THE CHAIN HOUSING AND AS IT FLEXES, IT MIMICS THE SAME RATTLE.
NOW JUST DON'T ASK ME IF I WAS DUMB ENOUGH TO COMPLETELY REMOVE THE OLD CHAIN AND NOT USE IT TO THREAD THE NEW ONE THROUGH THE CHAIN HOUSING AS IT WAS REMOVED.

Guys,I also suffer from the demon chain drag/rattle noise for a second or two on starting. It goes away at idle. I have an 87 and am familiar with the sound from a tensioner failure in my 77. Believe that i saw in some P site that it is a result of using thin --10-30 oil and is cured by using 15-50. Will let youall know what happens after I fill it up, after I fix the return tubes after the weather warms up. Ned

In the lattest issue of excellence there is an article on the different systems Porsche has used over the years. I know in there they discussed this phenomena. I will try to find it and post it latter.

Bruce

I just looked up that reference it doesn't really apply. It talked about a mechanical tensioner used to take up the chain slack when timing the cams. some people use these for operation. these mechanical units take time to warm up with everything else and until they do there is the noise.

Bruce

Valerie,
I actualy use 20-50.