Strange sounds

s_wilwerding · s_wilwerding's Garage

Lately, my car has been making a knocking/rattling sound under power from about 2000 RPM on up - it does not make the sound at idle. Could this be valves? I'm planning on checking them soon, so if that's the problem, it will be fixed soon. If not the valves, what would it be? Could it be detonation?

surflvr911sc · surflvr911sc's Garage

Don’t hate me for the suggestion, broken head stud maybe? It can sound just like that. I’d check out the exhaust side studs when you check exhaust valves. Maybe one will fall into your hand when you remove the valve cover. Mine did.

Sorry to jump to this conclusion. I hope it’s much more minor than that but it would still not have to be the end of the world.

Jdub · 10-17-2002, 06:49 AM

Boy that does not sound good to me. I would drop those lower valve covers and see what's up.

John

s_wilwerding · s_wilwerding's Garage

Well, I don't think (and hope) that it is not a head stud. The PO just had them all changed about 30K ago, so I would think that they would still be fine.

Perhaps I should clarify the noise. It is not loud and sometimes barely perceptible and it may just be the sound the engine makes. Also, the sound tends to go away after the car warms up in 10 - 15 minutes. That's why I was thinking it may be the valves. Do you still think it is the head studs?

If so, what kind of repair bill am I looking at?

surflvr911sc · surflvr911sc's Garage

Steve, that sounds hopeful that it's not a head stud. Mine gets more pronounced as the car warms up. Almost never hear it for the first 30 min of driving. Hopefully the PO had steel studs installed not OE exhaust studs.

Anyway, Quick check under the valve covers would tell the story. Valves tend to be noisier when the engine is cold so maybe it's just trying to tell you it's time for an adjustment. I’ll keep my fingers crossed for you.

s_wilwerding · s_wilwerding's Garage

I plan on checking this weekend - if indeed it is a head stud, I should only have to replace that, not everything else, since the PO did a complete top end only a few years ago. I'm pretty confident it's not the head stud, though, after reading through other head stud posts in the archives.

Thanks to everyone for their help.

rstoll · 10-17-2002, 10:02 AM

Yes it can be detonation. Check your timing and run a bottle of Techron thru your next tank of gas.

surflvr911sc · surflvr911sc's Garage

Robert,

Educate me here on detonation. I thought that this usually occurred at full operating temp not when cold. Can it happen at any temp? Is there a way to clean the injectors other than fuel additives like Techron and not pull the injectors?

rstoll · 10-17-2002, 10:24 AM

I suppose it can happen at any temp if your engine is carboned up enough or your timing is advanced too far. I would try the techron treatment before pulling the valve covers. If that doesnt do it then pull the covers and change the oil. When I first bought my 83 it hammered under load. Ran a couple bottles of techron thru it and cured most of the problem. Reset timing and cured the rest.