I have a 99 GS with a 420a short block and new internals. When i start the car up it has a knocking from the engine bay and then stops when it warms up. Anybody know what could be causing this

Is it a knocking, or a grinding? Is it a pronounced knock, or is it somewhat subtle?

It's more of a grinding, it sounds like it's coming from the transmission side.

Just TOB noise, don't worry about it. They all do that at some point.

Did you replace any clutch components?

yes i put a whole new tranmission in about 6000 miles ago

What about the Clutch and Throw Out Bearing?? TOB will definately make some noise when cold, if it's bad that is.

-Kevin

IF it is the TOB, it will likely not make the noise when you press the clutch pedal. Try that. Did you rebuild with OEM pistons or forged pistons? Forged pistons will make a knocking sound until the car is warmed up also. Just a story... One time I cracked a piston and simply replaced it with a stocker, and it turned out my block had been previously bored to .020" over and it was slapping like mad, it was less audible after the car warmed up.... obviously I replaced it and it didn't slap anymore. :D

Yes i did rebuild it with forged pistons. but it sounds more like a grinding then a knock

Does the sound change when you put the clutch in?

Forged pistons WILL knock. Perhaps it sounds grindish due to imperfections on the cylinder walls, but I think that is a little far fetched. Did you have the cylinders honed?

I left the car in the garage were it's warmer last night and then started it in the this morning to see if the noise continued. Well it has stopped so i guess that would just be the TOB disagreeing with the cold weather right?

Come to think of it, TOB noise is more of a grindish/rattle sound. When you start it cold, press the clutch pedal in and if it doesn't make the sound, that is your problem, no biggie.

so this TOB .... mine does the same shit. Should i worry about it? Will it blow goin down the highway when i drive 1.5 hours to UTI every day?

Originally posted by Resol
so this TOB .... mine does the same shit. Should i worry about it? Will it blow goin down the highway when i drive 1.5 hours to UTI every day?

mine rattles, always has... I've gone a few years with it rattling... it rattled before I had the trans rebuilt, and started after it was rebuilt because the trans shop guys are retarded.

If I can go that long like that and make 7 hour drives, you'll be fine.

Thank you