What does a broken head stud sound like?
 

Does a broken head stud bouncing around in the valve cover sound like an engine knocking?

I have a rattle from my engine when it's hot and under load - for all practical purposes it sounds like the engines knocking from detonation...

However, I've increased the fuel and decreased the ignition timing and even run 104 octane fuel but still it rattles. Runs great, but it knocks under load.

I've noticed that my B&B headers and exhaust both rattle if I tap on them with a rubber mallet - I'm currently re-installing my original exhaust to see if they are the source.

I guess I'll pull off the lower valve covers and test torque all the studs to see if they're all intact.

tia,
Chuck.H
'89 TurboLookTarga, 200k miles

Chuck,
Depending where the stud is broken, the head (barrell) nut may be rattling around the cam tower. But I doubt you would hear that.

The sound of broken head stud so accurately mimics detontation, it is spooky. When one stud on my motor broke and I heard the noise, I immediately suspected the timing, distributor, the CIS, fuel, etc.
But the minute my pro-wrench took the car for a drive, there was no doubt. He said: " Go home and pull the lower right valve cover, and you will find the broken stud." That's exactly what it was.

I know you don’t want to hear this but a rod bearing going bad also rattles under load. I chased a rattle for 2 months until the bearing totally failed then there is no mistaking the sound.

Good luck

Tim

Tim, was that on a Porsche motor? You don't hear of that very often.

Loud exhaust leak flap-flap-flap when accelerating...

You can hear it most when driving next to a wall.

-Wayne

It sounds like a cash register! Chu-ching!;) Hope it turns out OK. Keep us abreast of the condition.

Yes,

It was on a 84 911 with 120,000mi (with a lot of track mi) I have been keeping track since mine went and it happens more than you think. Its sounds like a rattle most noticeable under hard acceleration 3000 4500 rpm maybe a little like an exhaust leek but you don’t hear it if you rev the motor with no load.

Tim

Well, I didn't get a chance to pull the lower valve covers (read: lazy) but I did re-install the original exhaust and it still rattles.

I only hear it once the engine gets warm, and it's most noticable at 3000 - 4000 rpm, in 3rd gear under medium load (no full throttle until I figure this out).

Thanks for all the responses - I promise I'll pull the valve covers today and report back.

Chuck.H
'89 TurboLookTarga, 200k miles

My stud that broke sounded like a playing card stuck in the spokes of a bicycle.

By the time it sounds like that, you probably have more than just 1 broken stud per cylinder, and the heads are seriously loose....and damaged.

Many of us are familiar with the Rabbit/Cabrio 4-cylinder and the way the manifold would inevitably warp. The sound is much like what you hear when that happens, a popping that becomes more like a knock.

Did you change your oil recently? Are you using a synthetic?

John

I started using the castrol high-mileage oil about a year ago in an attempt to control some oil seepage. 10w40 weight. hopefully that didn't seal up an oil passage on me.

I tried mobil-1 years ago but like many others saw my oil seepage increase so I switch back to regular oil.

Chuck.H
'89 TurboLookTarga, 200k miles

Remeber Ross Perot describing the effects of NAFTA "a great sucking noise" talking about jobs leaving the country.

Same sound but coming from your bank account.