atari_st

Three months ago, I noticed a ticking sound under the hood while in the car. It sounded like a diesel engine. The sound was more noticeable if the car was in gear..slight tap to the gas peddle made it louder. After about 1500 rpm...engine drowned it out. Happened when engine is cold or hot. I was almost sure it was coming from the drivers side cam gear cover. Pulled the cover and the belt was ridding off the front edge just slightly. Spent two months on the TB/WP and complete top refresh. Got it back together...belt rides more toward the center...not dead center but pretty close. Well.....the sound it still there. Spent the evening trying to isolate the sound and I am 90% sure its coming from the driver side cam cover. Took the cover off...and all looks ok. When I put my stethoscope on the rear metal cover next to the head, I can hear it...but when I put in on the front side top of the black cover right where it meets the rear metal cover...its loud. Again, the sound is louder with the car in gear…not sure if this puts more tension on the belt, cam gears, etc compared to the car in park. So here is my question:

Could I possibly have a cracked/broken Spider or messed up woodruff key behind the cam gear that would make the clicking/tapping noise? I know the cam gear is tight...checked for movement and the paint spots I made never moved. I have read in some post that an over tensioned belt could wear on the spider and woodruff key behind the cam gear. Like I said, the sound appears to be coming from behind the cam gear. I can hear it with the stethoscope on my cam covers…but its slight…sounds more like the injectors firing. I assume the noise may be traveling across my cam into the cam cover.

Thoughts anyone?

Imo000

I think it's a valve lifter. There are several ways of fixing this problem. Some are with different oil additives. Seach the archives and you will find all the different methods.

SteveG

Mine tics continuously. At first I thought it was specific to one location, from under the left front valve cover, but as I have developed my "928 ear" I conclude it moves as I move around the bay. I am going to invest in a stethoscope, but for now I'm sure mine is the injectors.

WallyP

Make very sure that it isn't an exhaust leak...

atari_st

Checked for exhaust leak...nothing. Added oil treatment at last oil change..nothing. The noise is coming from behind the driver side cam gear. Passanger side does not make the sound. The click..tick..rattle... is a metal sound. What I struggle with is that it is louder with the car in gear versus in park...still cant figure that one out. Anybody else had this problem before?

Imo000

OK, here is one possibility. This happened to my bother's 83 928 last year. The driver side valve cover started to make a very loud and high pitched ticking whine. I looked for the problem and appear to be a bearing noise behind the cam sprocket. However there are no bearings located at this location. After a further investigation it started to look as if the noise was originating from one of the accessories (PS pump or alternator). I first cut the PS pump belt and the noise was still there, then the alternator belt was cut. At this moment the noise went away. The belts were old so there was no loss here. Turned out to be a failure of the rear alternator bearing. The cooling blades of the alternator were hitting the housing. Since the housing has opening in it the sound was a continuous tick.

I know this might or might not be your problem, but it’s worth at least take the belts off an see if the noise goes away.

I hope this helps!