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fredrikl · Joined: 03 Nov 2002 Posts: 73

Hello,

Some questions about valve noises:

1) When it's cold outisde (below 0 deg C, 32 deg F) the engine sounds very much like a diesel when started (especially under load). This noise disappears completely after 2-3 minutes of warming up.

2) When the "dieseling" stops, the engine sounds fine until throroughly hot after about 15 minutes. Then, the valves instead get a rough ticking, somehow slightly grinding noise. Very unsmooth and does not sound like incorrect valve clearances. I may be wrong, but I have a feeling that the arrival of this noise is accompanied by a certain loss of engine power.

Oil pressure is fine, engine does not overheat, engine oil level OK (10W40, semi-synthetic). Oil consumption has been increasing a bit lately. The car has done 100K miles.

What is causing these noises and how can they be cured? All hints are appreciated.

Greetings,
Fredrik

Paul · Posted: Sun Nov 03, 2002 6:37 am Post subject:

Do you have a 924 or 924S?
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

fredrikl · Joined: 03 Nov 2002 Posts: 73

Sorry, I forgot to mention that. It's a 1982 924 NA, Euro spec.

Paul · Posted: Mon Nov 04, 2002 1:03 am Post subject:

I'd adjust the valves just to rule them out and while you're in there, check the plastic elbow on the oiling tube, plus check the tube to make sure all holes are open. Inspect the cam lobes and buckets for wear.

This may not be a valve related noise. Drain your oil and look for metal, cut the oil filter open and look for metal.

Try to isolate the noise using your favorite method (hose, screwdriver, stethoscope, etc).

Good luck!

fredrikl · Joined: 03 Nov 2002 Posts: 73

I adjusted the valves fairly recently and I am quite sure the clearances are OK. At that time, I also had a look at the plastic elbow, which looked OK. However, I guess it could be broken anyway or has broken since. I did not examine the tube any further at that time. I'll have a look at it.

How can you tell if the cam lobes are too worn? Can the camshaft be repaired in that case or does it have to be replaced?

What surprises me the most is that the noise does not appear until the engine is thoroughly hot.

Greetings,
Fredrik

Joes924Racer · Posted: Mon Nov 04, 2002 11:14 am Post subject:

and this just started out as a noise and power loss.
question..is the timing set correctly?
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Richard · Joined: 04 Nov 2002 Posts: 617 Location: Pacific N.W.

What weight oil are using? The plastic elbow may not be cracked, but the oil tube holes may be blocked. What do the top of the followers look like (pitted, grooved, x patteren)?. Cam lobe wear is measured with a dial indicator and compared with stock figures. Remove the valve cover and turn the engine over by hand and observe the operation. Do you get the same valve clearances on each valve the same time after time or do they change. Build a splash guard out of sheet metal and start the engine with the valve cover off and watch for anything abnormal. Just some ideas, thinking aloud as it were.

fredrikl · Joined: 03 Nov 2002 Posts: 73

I am using 10W40 semi-synthetic oil. Ignition timing is correctly set at 10 degrees BTDC (Euro spec. car).

I really must remove the camshaft cover to inspect the camshaft, elbow and oil tube. I am fairly sure the noise is coming from that area and that it's not incorrect clearances.

By the way, what is the problem if the clearances vary each time I measure? How does that relate to the noise?

Thanks for all the advice so far.

Fredrik

Lizard · Posted: Tue Nov 05, 2002 5:28 am Post subject:

it could mean the tappets are sitting correctly causing them to jump around abit causing the noise
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3 928s,

Paul · Posted: Tue Nov 05, 2002 9:28 am Post subject:

Or it could be tensioner noise. as posted before try to locate the noise.

numbbers · Posted: Tue Nov 05, 2002 10:12 am Post subject:

And, how cold is it Sweden when you are starting the car?

Richard · Joined: 04 Nov 2002 Posts: 617 Location: Pacific N.W.

The oil sounds real good. I was thinking worn valve guides, weak or broken spring, valve seat recession or mushroomed valve stem tip. If a valve cocks a little in its seat, it could give different clearances. I'm still trying to fiqure out why the sound comes and goes and comes again.

Porschephile · Joined: 04 Nov 2002 Posts: 825 Location: Denver, Colorado

heh...valve noise...that's what I thought...then the main bearing spun...imagine the look on my face...damn I was pissed.
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Paul · Posted: Wed Nov 06, 2002 10:11 am Post subject:

fredrikl · Joined: 03 Nov 2002 Posts: 73

Thanks for all the input.

Just to clarify, the noise doesn't come and go while driving. It just isn't there during the warm-up period, arrives after about 10-15 minutes and then stays once it has started.

Also, the noise does not seem to be related to just one or two valves, since it is very frequent and there seems to be a grinding "click" every time a valve is opened or closed.

At start-up (about 0 deg C or colder) the engine has a diesel-like sound, which is not similar to the noise that arrives when it is warmed up.

As I wrote earlier, the oil consumption has been rising a bit lately. However, oil pressure is fine and there is no blue smoke.

Bye for now,
Fredrik