Noise at 4000 RPM after service

Hi guys. I was looking for a little help.
I recently performed a major service on my 1984 308 QV. Took my time and thought I did everything well.
Removed all belts, valve covers, removed cams and changed the seals and shimmed the valves as well as torqued the heads.Everything line up perfectly.
Reassembled and the car runs and idles great. and drives great too.

When accelerating quickly through 4000 RPM in 2nd and 3rd gear there is a metal on metal rubbing noise for 1 -2 secs then it's gone. Doesn't affect performance.

Went back and re-tensioned all belts and moved the coolant pipe to make sure nothing was rubbing…..still there,
Went back and removed the AC compressor and left it off the car. Still there. Nothing obvious I can see, sounds like it's outside the engine and coming from the Rear right.
It runs cool and cleaner than before the major, has lots of power and torque but this sound concerns me.
It does not make the sound when revving in neutral. Only makes it with a load on the engine.
There is some play in my rear engine sway bar. Not sure how much was normal.
Sound wasn't there before the service so I'm pretty confident it's something I did but cannot retrace it.
Any suggestions would be greatly appreciated.
Thanks. Brent.

 

Couple other quick notes~
Replaced the water pump with one from East Coast Jaguar.
Never had a problem with the belts prior to this.
Drained all brake fluid and replaced , just in case the noise is somehow coming from the brakes.
Thanks. Brent

 

How are your lower drive bearings?

 

Good question!
I was just reading a post on them. I never changed them but there is no oil seepage.
If they were bad, would it not make the sound all the time and not just while driving?

I did some searching and found some articles here that indicate because the sound doesn't change with the speed of the car, or gear it's in, means it cannot be on the engine or the accessories.
I'll double check them for oil leakage. Thanks for the post

 

Sounds like (no pun intended) a sympathetic vibration that occurs at or around 4k rpm. Check for loose heat shields, exhaust parts etc.


When all else fails read the damn manual. - wife

 

Thanks. I am hoping that's what it is.
I has the sound of something turning touching soft metal.
I'm going to have another look at the idle bearings. Maybe they should be changed anyway.
Thanks. Brent

 

In my case it has been loose bolts on heat shield, brake lines vibrating, a/c lines vibrating and hitting fender well. Around the 4k rpm harmonic range. I have a 1989 328 GTS. Good luck.

 

The seal sits behind the bearing so a leak may not be present. When mine went it started making noise at specific RPMs from the harmonics and quickly got worse.

Second you stated you did a a major but later said you didn't change the idler
Bearings? Do you mean the tensioners?

 

My '89 328 GTB has a buzzing beginning at exactly 2450 rpm which stops at 2550 pm; it comes from the heat shield above the front manifold. She has that buzzing since I got her six years ago; I managed to get rid of it, about five years ago, by gently tightening the nut & bolts...but it slowly crept back. Since I know from what it comes, I no longer worry and have accepted it as part of the car's character...

Rgds

 

Thanks for the replies. I replaced the tensioner bearings with new ferrari ones. Not Hill's.
I meant the third small pulley that the timing belt goes around at the bottom of the engine.
Thanks. I hope it's a vibration. Just sounds strange. Maybe I should just change those other bearings to be sure. Looks like a big job with special tools though.
Thanks. Brent.

 

Sorry. Just to be clear. I changed the tensioner bearings but not the lower drive bearings.
Thanks

 

Just thought of a questions. Did yours make noise at 4000rpm with the car parked or only when it was being driven?
Thanks.

 

The only thing that comes to mind is Alternator vibration... did you loosen and re tighten the mounting bracket?, also is the AC comressor is out of the car what about the hoses & connections? and or the ground wire to the dip stick ( for the AC?)

also could be the bolts holding the intake ductwork as well... rubbing vibrating? Normally there is no heat shield or anything like that in the way. check your hose clamps on the main coolant down pipe as well.

 

Thanks!
I have re-tightened everything I can Think of!
I'm going to keep plugging away!!

 

Because I already had the AC belt off, as well as the compressor I figured I would narrow it down slightly.
I took both the water pump belt and alternator belt off and took it for a short spin.

No noise!!

I therefore suspect that it is either something with the water pump shaft/impeller, or bearings, including the tensioning pulley and bearings
or something in the alternator.
I am going to fully charge the battery, let it cool down until tomorrow then take if for another spin with just one belt to narrow it down further…….then I'm going to develop something so that I don't need the accessory belts because you can really feel the difference without having to turn those 3 belts.

 

The only slight concern is in the past I have let it warm up 5 minutes before driving. This time because the water pump and alternator belts were not on I started it and took off right away. May still be something that has to warm up before it shows it's ugly head. I hope not.

 

Quick update
I took it for a ride with just the alternator belt on. No noise!
It is most likely in the water pump. Given the fact that I bought a rebuilt water pump with new bearings and East Coast Jaguar has a good reputation I will try replacing the water pump tensioner pulley and bearing.
I have one from Hill engineering and I ordered the bearings.
Hopefully it will be problem solved.
Brent