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Strange noise when warming up

scam75

scam75

Well-known member
Hi Chaps

Had this problem since I got the car (about a year ago), doesn't seem to cause any problems but a bit concerning never the less. If I start my car from cold and let it idle you can hear an intermittent knock coming from near the distributor cap (could be inside the engine but definitely right at the dizzy end). It sounds like the arm clunking off the cap and if you play about with the cap whilst running the noise can come and go. There are no obvious signs of trauma to cap or arm however. Noise will go away when car heats up to first line on temp gauge or after a few revs. If you get in the car and drive it from cold you tend not to hear anything at all.

I have tried a different cap and arm and also replaced the gasket the cap sits on. All made no difference.

Has anybody experienced this before?

Stuart
 
Hi Stuart sorry you haven't had a response yet.
Its difficult to diagnose a noise without hearing it. Any chance you could record it and shove it on youtube ?

Have you tried to pinpoint the noise precisly using a wooden dowel or long screwdriver held to your ear ?

Is the noise in sync with your engine speed ? ie it increases uniformly with revs ?

Is it possible that there is some float in the camshaft ? and the roter is striking anything in the cap?

Have you tried removing a plug lead one by one to see if the noise goes away when any of the pistons arn't firing ?






 
Hi Peanut.

The noise goes away when you rev and comes back at idle. It is in sync with engine speed. I suspect float in the camshaft. I have not tried taking of the leads one by one. Can try that later. If I get time I will record it and post on youtube.

Cheers

Stuart
 
If the noise dies away with an increase in revs then it is likely to be something loose rather than worn. I'd check around for something loose. The HT rotars on these cars apparently can come loose when the grub screws back out
 
Try this from 944online http://www.944online.com/cgi-bin/forum/forum.cgi?board=944-1;action=display;num=1268871523
I have a similar rattle from mine, but having taken the cam sprocket housing off I can't understand where the bolt they are referring to is hiding - might need to take the sprocket off to find it ? What I did find was play in the cam belt idler roller which is probably sufficient to cause a little rattle, but am still suspicious...... When she actually stays running will investigate again and let you know.
 
Alan, will try re-torquing the cam bolt tomorrow and see if it makes any differnce on Stuarts car. It does sound like a bit of end float, the cam box oil O ring is leaking too so the whole lot will be coming off at the next belt change. The power steering pump bracket has also been welded in the past on Stuarts car so a that will be getting changed as well.
Alasdair

 
Interesting, I would hazard a guess that I may be suffering from an early onslaught of this problem. Another guys says his goes away when his car heats up.

Will check this tomorrow with Alasdair and report back.

Stuart
 
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