Loud knocking coming from rear of engine?

[Rennsport]

There is a loud knocking sound coming from the rear of the engine. its not the valves, or spark plugs.
sounds kind of like a desiel engine.

its only on throttle, sound goes away when engine is slowing down.

aslo my starter is going out, could this be contributing to this sound

any ideas?

[euroshark]

LOUD knocking? Is there a thumping that you can feel also? It could be the guibo or the driveshaft center support.

[Rennsport]

no, it also does it in neutral so it would have nothing to do with the tranny/driveshaft

[markseven]

Starter solenoid allowing the gear to randomly hit the flywheel?

[joshh]

It could be the start of the crank starting to destroy itself.

Does it do it when the motor is idle or just when the car is in motion??

[ivo316]

Hi, a friend of mine had a similar sound in his luv, when you pressed the clutch it went away, we all blamed it on the clutch, but when we dissasembled everything it was crankshaft end play.
Use a long rod, press it to the engine and press your ear to the other end, place the rod in different areas of the engine/tranny, that will tell you exactly where the noise is coming from (and make it clearer for you to identify the pitch and area).
I said a long rod because an automotive stethoscope is not easy to find.

good luck.

BTW if it's on top of the engine could be a piston pin, if it's on the bottom a rod or crankshaft bearing.

[Rennsport]

It could be the start of the crank starting to destroy itself.

Does it do it when the motor is idle or just when the car is in motion??

the sound starts when the r3v's are at approx 2500-3000 (my tach doesnt work, so im guessing)

Starter solenoid allowing the gear to randomly hit the flywheel?

i hope so, i have another starter that im going to put in today.

[Rennsport]

took it to my mechanic today. cylinder 3 has a broken rod bearing, possible damage to crank and rod.
both motor mounts are broken.

[Mike325]

took it to my mechanic today. cylinder 3 has a broken rod bearing, possible damage to crank and rod.
both motor mounts are broken.

That sucks. M50?:D

[joshh]

Good luck with the fix.

[Rennsport]

thx, this will be my first time tearing an engine down to this extent, but it will give me good experience for the future. ill take pictures!

unfortunatly my other engine (2.7 building for turbo) isnt anywhere close to being completed, otherwise now would be the perfect time to drop it in.