328i E36: whining noise when decelerating

[B234R]

Hi everybody, let´s see if you could help me with this issue.

My car is a 328i E36, manual, 130,000 miles. I´ve bought it one and a half years ago, it drank a lot of oil so last summer my mechanic put a second hand engine from a 1998 528i E39 auto, and a new Sachs clutch kit. This engine doesn´t use a drop of oil.

Problem is, since the "new" engine (and clutch) was installed, there is a whinning noise when I lift off the throttle. I know that trying to diagnose a noise it´s diffcult, but...

-It happens in every gear
-Always with the car in motion
-Only sounds when decelerating; if i´m accelerating it doesn´t sound at all
-The noise sounds louder depending on the engine RPMs
-If I push the clutch the RPMs fall and the noise is very low, although I swear it still sounds a little bit. If I put neutral it doesn´t sounds at all.
-When putting the engine and the new clutch my mechanic said the old dual mass flywheel was in good condition, so he didn´t replaced it. He changed the gearbox oil
-Gearbox works fine, clutch too

With the old engine (and clutch) there wasn´t any whinning noise. If there is a problem with the gearbox, I suppose the noise would increase when accelerating, wouldn´t it?

The noise is a bit annoying, not more. It isn´t worse now than a few months.

Any suggestions and experiences would be great...

Thanks!

[Ahbefive]

Does the noise sound like its coming from the front or rear of the car?

[B234R]

I´m not very sure, but I believe it´s from the front of the car.

[SebringMan]

Do you have a video at all?

[roofer]

I'd be going for layshaft bearing.

[S1_RS]

Possibly worn engine mount allowing engine to move into a position that something is touching where it shouldn't.

[B234R]

I don´t have a video but I´ll make one.

Engine mounts were replaced while the engine swap. I don´t see the engine moving too much with the open bonnet.

I´ve seen videos of layshaft bearing failure on youtube and the sound is different, and it sounds when accelerating. Mine only sounds when lifting off the throttle...

Thanks a lot!

[BGarside]

Alternator/water pump/tensioner bearing, the belt driven ancillaries at the front of the engine? Does switching the AC on and off make any difference?

Did the engine need to be altered to work with a manual gearbox? Maybe the garage screwed up something there?

[B234R]

With the A/C on the noise is the same.

When they changed the engine, the workshop told me that the swap was very straightforward despite being a M52 unit from an auto...

The fact that the noise is only present when lifting off the throttle makes me suppose that it´s not a problem from the gearbox, differential, etc...it could be an air leak somewhere. I´m going to tell the mechanic to remove the inlet manifold, and take a look for vaccum hoses. I´ll keep you informed.

Thanks!

[B234R]

Well, after removing the intake manifold it seems everything is right, so I suppose we´ll have to take out the gearbox and see what´s going on.

The car goes perfectly and the sound isn´t loud, but I´m very picky with car noises..

[BGarside]

I know you said the noise seems to be from the front of the car but sometimes it's difficult to tell due to the sound reverberating around the interior.

Just wondering if it could be the rear diff? I've noticed a fairly noticeable whine from the diffs of both my E36s on deceleration.

[LiamB]

S1_RS said:

Possibly worn engine mount allowing engine to move into a position that something is touching where it shouldn't.

Possibly this, I had a dodgy engine mount which ended up rubbing against my timing belt and breaking it. I had the exact same symptoms as you, a sort of whine as I came off the throttle. Probably isn't that but worth checking!

[B234R]

I don´t think it could be the engine mounts, they are new, and the whine doesn´t sound at idle, only in deceleration...
Before the engine swap the differential was silent.

I suspect of something screwed up in the engine/gearbox installation, I´ve just read some posts in a US Subaru forum where people complain about a whining noise when decelerating right after a clutch replacement in their Impreza WRX, the problem is a slight drivetrain alignment. I´m going to try pumping up the tyres in one axe and letting out air in the other and see if there is a difference.

[TonyW1967]

B234R said:

I don´t think it could be the engine mounts, they are new, and the whine doesn´t sound at idle, only in deceleration...
Before the engine swap the differential was silent.

I suspect of something screwed up in the engine/gearbox installation, I´ve just read some posts in a US Subaru forum where people complain about a whining noise when decelerating right after a clutch replacement in their Impreza WRX, the problem is a slight drivetrain alignment. I´m going to try pumping up the tyres in one axe and letting out air in the other and see if there is a difference.

Hi B234R,

Did you find out the cause of the issue?

[steve_bmw]

I would guess worn diff bearings.

[naturalaspiration]

Try adding LM Ceratec into both the gearbox and the diff (assume not limited slip) - 6% of the filling capacity. If there is any bearing noise it should all but disappear unless terminal.