NOISE: ONLY @top/TB end of engine, ONLY at start up, 3.8 '97 LeSabre

[97BuickLL]

Limited, 150k Miles, Automatic.

Recent repairs:
1- Upper and lower Intake Gaskets replaced, Dex-kool flushed and replaced with Green glycol coolant.
2- Plenum replaced with Dorman brand , (classic EGR melt/leak),
New gaskets at Plenum to TB , Plenum to Intake .

Noise only at first few minutes , is more of a mild roar than a mechanical grinding
( broom handle to ear can not locate a exact spot on the TB end of engine ( driver's side ).

Neither is it a noise from a big air leak:
Removed and hand cleaned the IAC valve/port and TB insides and butterfly valve edges and TB contact area.

Unplugged cable to EGR valve.

None EFFECTED the noise.

Scan tool: no codes or abnormal data...just NOISE !

Found another owner of same model and claims he also has same noise and just ignores it. (I haven't seen/heard it in person .)

Called Buick dealer : says that noise is normal on that car.

Grandaughter can't say if it had a noise before under the hood as she was always inside with windows up and radio on.

??
Anyone know what is really causing the noise?
And how serious is it?
Start up Oil supply to lifters at just that end of engine ?

We also did a (health) compression check and all cylinders are good and very close.
(nothing to do with noise).

THANKS !

[BNaylor]

Welcome to AF.

It sounds like a problem related to the UIM/LIM job. The noise is not normal. If it sounds like rushing air or a motor boating sound it is most likely a vacuum leak. One thing you can check is make sure the PCV valve located at the right hand side of plenum under the MAP sensor has the black o-ring seal. Also, the big orange o-ring seal. Last person I worked with on a similar problem left the PCV valve out after replacing the UIM. Link below should help.

Click here

Also, there is a tube related to PCV inside the UIM that may have popped off.

[jconatser]

Don't know if this applys, but check this out:

A/T - 4T60E Cold Start Rattle Noise
File In Section: 7 - Transmission
Bulletin No.: 57-71-06A
Date: December, 1996
Subject:
Cold Start Rattle Noise
(Diagnosis/Service Procedure) Models:
1991 Buick Reatta
1991-96 Buick Riviera
1991-96 Buick Park Avenue, Ultra
1991-97 Buick Regal
1992-97 Buick LeSabre
1994-96 Buick Century
1994-97 Buick Skylark
1991-93 Cadillac Eldorado, Seville, Sixty Special and Fleetwood (FWD)
1991-95 Cadillac DeVille
1991-97 Chevrolet Lumina
1992-96 Chevrolet Lumina APV
1997 Chevrolet Venture
1994-95 Chevrolet Beretta, Corsica
1995-97 Chevrolet Monte Carlo
1991-92 Oldsmobile Toronado, Trofeo
1991-95 Oldsmobile Ninety Eight
1991-97 Oldsmobile Cutlass Supreme
1992-97 Oldsmobile Eighty Eight, Silhouette
1994-96 Oldsmobile Cutlass Ciera
1994-97 Oldsmobile Achieva
1991-97 Pontiac Grand Prix
1992-97 Pontiac Bonneville, Trans Sport
1994-97 Pontiac Grand Am
with HYDRA-MATIC 4T60-E (RPO M13) This bulletin is being revised to add models and 1996-97 model years. Please discard Corporate Bulletin Number 57-71-06 (Section 7 - Transmission).
Condition
Some owners may notice a rattle noise from the engine compartment after a cold start that lasts for less than one minute. This condition will usually only occur once per day after the vehicle is started after sitting overnight or an extended period of time.
Cause
This rattle noise may be assumed to be an engine related noise (piston slap, bearing knock, lifter rattle, etc.) but may actually be a 4T60-E transaxle noise caused by a combination of oil pump starvation/cavitation and pressure regulator valve instability. This transaxle noise condition DOES NOT DAMAGE THE TRANSAXLE AND DOES NOT CAUSE A DURABILITY CONCERN. This transaxle noise condition is more noticeable with engines that exhibit a "fast" start (short crank times and immediate engine RPM increase after start). The 3.1L engine (VIN M - RPO L82) is a good example of a "fast" starting engine, though other 4T60-E/engine combinations may exhibit this noise also.
Correction
If the diagnostic steps listed under SERVICE PROCEDURE lead to the 4T60-E transaxle as the cause of the cold start rattle noise, NO REPAIRS SHOULD BE ATTEMPTED. There is no repair for this noise condition at this time. This bulletin will be updated when a repair becomes available. Refer to the WARRANTY INFORMATION for diagnosis allowance.
Service Procedure
1. Check for a disconnected transaxle modulator vacuum line (this could cause excessive transaxle oil pump noise). 2. Raise the vehicle on a hoist. 3. Remove the flywheel dust shield(s) and remove the torque converter flywheel bolts. 4. Position the torque converter as far away from the flywheel as possible (usually no more than 7 mm (1/4 in)). It may be helpful to use a piece of wire looped around a torque converter lug and a loosened bottom pan bolt. This will hold the torque converter away from the flywheel. 5. Lower the hoist and allow the vehicle to sit a minimum of six hours (preferably overnight). 6. Start the vehicle and listen for the cold start rattle noise. This could be performed with the owner, if possible. ^ If the cold start rattle noise IS STILL PRESENT, the condition IS CAUSED BY THE ENGINE AND THIS BULLETIN NO LONGER APPLIES. Refer to Section 6 of the Service Manual for engine noise symptom diagnosis. ^ If the cold start rattle noise IS NOT PRESENT, the condition is CAUSED BY THE TRANSAXLE AND NO REPAIRS SHOULD BE ATTEMPTED. Refer to the WARRANTY INFORMATION for diagnosis allowance.