Recent rebuild with new housings.
Car starts fine, when idle drops down you can hear this piston type sound.
Still there at higher idle, but not as noticeable.

I was hoping it was the Airpump, but seems like it's coming from the UIM area.

Hoping it's something simple. . .

Thanks for any ideas.

 

Check to see if the noise rate is 1/3 the rpm. If so it may be rotor slap.
What condition was the rotor bearings?
Did you install new bearings on the stat gears?

 

hard to tell if it is 1/3 the rpm. But a compression check should tell the story -- right?

 

If it turns out to be a bearing issue, what is the prognosis?
Really don't want to tear it down again, just spent big $$ on new housings and new engine wiring.

thanks for any input.

 

Take off the belt(s) and start the car and see if you still hear it. If not it's an accessory, if so then check the transmission area for the noise. Easier to isolate. Remember with the belt off you have no water pump so it will heat up quickly so be sure just to start it and run it for a very short time.

 

could it be clutch related or the throwout bearing?

 

Actuate the clutch and see if it changes the sound. If no change...move along.

 

Clutch doesn't seem to make any difference to the knocking noise, in or out.

What about this -- New housing but old rotors with new seals -- any "adjusting" during initial mileage that would cause this sound? I remember reading about seals forming to the housings or something similar?

thanks

 

Notice how the noise seems to be in time with the markings on the drive belt on the air pump...?

 

The air pump (from memory, I could be wrong) has rotor type vanes inside it, a bit like the insides of a pneumatic die grinder, etc. If the noise follows that mark on the air pump drive belt, could be one of the internal vanes in the air pump has an issue.

Is it possible to rotate the air pump by hand and feel if it has some sort of click/notchy feeling to it?

 

Does it still make the noise with the clutch engaged? My friend had a throw out bearing issue and it sounded like crap. Not like the noise you have but you never know. The only thing you can do it make sure the car is cold and take the belts off. turn it on and listen if it stops then you know it is something on the belt assembly. Air pump, air compressor or PS.

Good luck!

 

I vote pull belts and see what's up. I assume the sound increases with RPM?

Dale

 

Yes, the sound increases with RPM.
I'm travelling now, but will try the belts off test.

In the meantime, I've started using premix--just in case it has anything to do with the OMP.

thanks

 

If it is a problem with the OPM premix its probably too late. Like I and most other said, belts first and then go from there.

 

Another possibility is that the turbo control gate is flopping.
Either not connected to its actuator or the actuator is oscillating.

 

thanks.
Just drove it 200 miles (Dad went into hospital) -- oil pressure steady the whole way at 55, water temp never above 160F. Sound was still there at idle/low rpm. Still using premix until I can get closer to an answer. Vacuum at highway cruise steady at -16.

 

160F seems pretty low. My temps are 185-192F and I live in Canada.

 

Yes, it seems low -- but after all the time "in the red", we are so happy to Not have an overheat problem. Our gauge may not be super accurate either.

Thanks

 

What no answer yet to what you tested/tried or ruled out??????????????????

 

Noise is still there. I've been out of pocket, down in Ft Myers with my Dad who's been in the hospital and now into a rehab home.

Latest is now a Vibration through the cabin during any pulls. I'm not talking about hard driving, just normal 2nd and 3rd degree acceleration. The vibration sounds like it's rattling the bins or rear struts.

I am Hoping that this might be another clue and that the Clutch/throwout bearing become more of a suspect. Also noticed that the noise might NOT always be there at startup. Can't really figure out when it comes online, but it is Always there by the time I shut her down. I have the car with me, it is still a daily driver==but I'm away from the tools and comfort of a garage to do much.

Thanks for checking back, any new thoughts would be appreciated.

 

Some have given you some good test to perform, but until you actually start doing them nothing is known.

You can also remove the clutch slave, and disconnect the T.O. bearing from the clutch and prop it back. Check the clutch bolts torque settings, then rev the engine for noise and vibrations.

I do not think you ever answered the question about the stat gear bearings.