Ticking Sound

[okc-esprit]

I've got a strange sound in either the engine or exhaust. If the car had hydraulic lifters, I would say I have a sticky lifter but since it doesn't I'm stumped. So far, I've wired open the EBPV without any impact on the sound. The sound is speed dependent but can't tell if it is RPM dependent. Also, if I let the car sit for three days or so, I can get the sound by blipping the throttle from idle to 3000 rpms. Any guesses? Could this be related to the IAC popping out?
Thanks

>>> Edited by okc-esprit on Friday 28th May 14:48

[Dr.Hess]

It does it while stopped? If so, it is an engine noise. If it will do it while idling, get a long extension and stick it on your ear, then stick the other end on various (non-moving) engine parts like the cam tower, turbo, bell housing, engine block, etc. and see where you can hear it. This is sort of a "poor man's" mechanic's stethoscope. Or buy a real mechanic's stethoscope, they aren't that expensive.

I had a lifter go bad on a 72 Caddie CDV (472 motor.) It made one hell of a racket. Hope your noise isn't like that.

Dr.Hess

[okc-esprit]

Dr. thanks for the response. I had been over the top of the engine once with my trusty copper tube and couldn't find anything. This time I put my wife in the trunk with a hose while I blipped the throttle. She found nothing up top but located the noise coming out the driver's side rear wheel well. Low and behold, we are missing two exhaust manifold studs on the number 4(?) (rearmost) cylinder. Unfortunately, the gasket has shifted which means loosening the entire manifold in order to put things straight. Hopefully, the gasket has survived in useable condition.

This raises two questions: 1. Is it possible that the studs backed themselves out? 2. Based on the nut and depth to the bottom of the hole the studs appear to be M8 1.25 x 30 or M8 1.25 x 38 is that correct?
Thanks again

[danny tattersall]

The ticking sound that exhaust manifolds make is quite distinctive. You are right about the studs being M8 x 1.25 mm. The shorter end goes into the head. If the threads in the aluminium look at all worn it may be worthwhile using the studs the other way round (ie long end into the head) and locking two nuts together to bottom it in the hole. I would have thought that it is unlikely that the manifold gasket would be damaged as they are fairly robust. They are also quite expensive. If you are going to the trouble of backing all the other studs off though you may as well replace it for peace of mind.

Danny.

[Dr.Hess]

Howdy, Neighbor.
Funny you should have those studs missing. When I did my timing belt adjustment (only took a week, another story), I found that my two bottom studs on #4 were missing too! Fortunately the gasket was still OK. Maybe the same Faries that struck me went west after you.
I put two new studs in with some red loctite (studlocker) and used stainless non-nylon locking nuts. with some Never-Seize.

Dr.Hess

[okc-esprit]

That is really strange. British gremlins running around Arkansas and Oklahoma. Watch out Dr. Ian they may be moving north.

Seriously, I appreciate the added knowledge that it unfortunately happened on your vehicle as well. I was somewhat concerned that they were left out when the vehicle was last serviced at the shop.

If you don't mind were your replacements about 2 inches in length?

[Dr.Hess]

I think they were a little shorter than 2". They were the only ones the nut and bolt shop I went to had in that thread pitch, and turned out to be just a tad shorter than the OEM ones, based on how much is sticking out of the header on the rest. I put them in with the two-nut method and had no trouble reaching them from under the car with suitable extensions.

Dr.Hess

[okc-esprit]

Thanks - my local Autozone had both lengths of both 30mm and 38mm. I bought both just in case. Looks like the 30's will be fine. Now to make time to do the job.
Thanks again everyone,
Bill