Chain tensioner question

[JackS]

I have put my '74 911 away for the New England Winter, but have a nagging question. Prior to storing the car, I had my mechanic tune it up, change the oil and adjust the valves. He is a respected long time Porsche mechanic who is honest and thorough. The question is about a funny noise in the area of the right side chain tensioner. At first he thought it might be a vibration in the heat exchangers, but used a stethoscope to listen in the area of the right rear of the motor, and ruled out the exhaust noise.
It has been making this noise for a year, but only when the car is started from cold. The rumble/ rattle goes away with a minute or two, then there is no noise. The car runs fantastic, and I autcrossed it all Summer without incident.
My mechanic thinks that the chain maybe stretched, or the tensioner may be bad. BTW, they are oil fed tensioners with only about 10K on them. He also is not that concerned, and suggests we take the cover off and look when we have a chance. I completely trust my mechanic, but I am wondering if this sounds like a familliar symptom for something I need to worry about. Has anyone out there had this type of transient noise that goes away when the car is warmed up?
Thanks for the input. I'm anxious to hear what you all think.

[nick-moss]

The cam chain tensioner has a helper spring. Maybe this has broken and you are only getting proper tension on the chain when you have full oil pressure/temp. Does the noise occur at tick-over when the oil is warm?

[john walker's workshop]

i've noticed some whirring noise from the chain housings in really cold weather in some engines, as well as mine, that were equipped with the pressure fed setup. it goes away fairly soon, and nothing has ever come of it. who knows, cold oil makes them sluggish?

[Superman]

Perhaps there is a broken or missing rail. I deeply question whether this problem could be caused by a tensioner weakness and here's why. Within one second after startup, my oil pressure goes to about 4 bar, at idle. It would be hard to convince me that a tensioner, under 4+ bar of pressure, would fail to make that chain tight. And then, later, when pressure falls by 50% or more, things are okay. Doesn't make sense.

[tryan]

i though i read here, that the spring holds tension and the oil pressure dampens the oscillations ( sp ) on the newer/politicaly correct tensioners.

i would not think it would be oil pressure related since it occurs for a couple minutes.

rocker arm pivot getting loose/ dry? any ramp particles in your oil? i HATE abnormal noises. i would not be able to sleep all winter.

good luck.

[Superman]

Yes, I've heard that too, but I'm not sure I agree. We've also heard recently that empty pressure tensioners can be compressed by hand. That tells me that the spring is not the whole story as far as keeping tension against the chain.

[JackS]

Thank you all for those interesting answers. You're right...I can't sleep all Winter until I figure this out. My sense is to have my mechanic pull the cover off and advise. Why take a chance?
Funny that I drove all Summer with no problem.
The noise occurs after ignition. Not when turning the engine over. As the weather gets colder, the noise lasts longer. On restart, with a warmish engine there is no noise. It seems to be related to the oil temp and oil viscocity. More comments are welcome.
Thanks again.

[nick-moss]

I would but at least $.02 on a broken spring

[juanbenae]

i have the upgraded tensioners and i experience a great deal of the whirlling that mr. walker speaks of, is your noise a whirlling sort of sound? mine goes away upon warm up and i have been told that it is the tensioners, and not to worry.

[boyt911sc]

JW,
I recently installed the tensioner upgrade kit for my '78SC and performed valve adjustment too. What I noticed after the upgrade was the louder rocker noise for the 4-5-6 valves. The 1-2-3 cylinder sound great.

I am tempted to install back the old tensioners and see if they make the same loud noise which I never noticed before with the old tensioner. The car runs great but the loud noise coming from right side (cyl. 4-5-6) of the motor really bothers me. I would welcome any suggestion. Thanks.

[john walker's workshop]

if a tensioner fails, the noise is from the chain housing, not the rockers. maybe go over the right bank again.