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Ryan7361 · 09-20-2015, 03:54 PM

OK
1987 Establishment P30 454 engine
I get a high-pitched squealing sound ONLY between 45 and 55 miles per hour.
I cannot duplicate it by "gassing it" in park! Because it only happens driving down the road it's nearly impossible to pinpoint a location.(i might end up getting a neighbor to ride along and poke their head in the doghouse as we roll) What would cause such an RPM specific noise?? worn-out pulley? failing water pump? serpentine too tight or too loose? I'm grateful for any ideas!

jacwjames · 09-20-2015, 04:44 PM

Sounds like a turbo problem, higher rpm's means 10X times that at the turbo.

I would check the connections from the exhaust to the turbo.

I would also check the connections to the CAC (charge air cooler) as the turbo pulls air through the CAC and pushed it to the intake side of the engine. The CAC could have failed and what you hear is the whistling of air being sucked in.

CJ7365 · 09-20-2015, 04:56 PM

Quote:

Originally Posted by jacwjames

Sounds like a turbo problem, higher rpm's means 10X times that at the turbo.

I would check the connections from the exhaust to the turbo.

I would also check the connections to the CAC (charge air cooler) as the turbo pulls air through the CAC and pushed it to the intake side of the engine. The CAC could have failed and what you hear is the whistling of air being sucked in.

I would guess he does not have a turbo on a 454 gas motor

but OP your are in the right direction in checking pulleys and belt, my 454 does not have a belt tensioner, so I would just change out the belt, then go from there, usually if the water pump is going it will leak a little coolant out of the weep hole, this is on the bottom of the water pump, get a flash light and take a look, after vehicle has been running.

mfire1339 · 09-20-2015, 05:11 PM

On my 1986 p-30 the alt belt had to be (REAL) tight!

Mike

530ktm · 09-21-2015, 09:06 AM

Are you running the A/C unit when this is happening? May be causing addition drag on belt and I agree with CJ7. If belt is old it may be glazed and squeal at times.

I can assure you that you do not have a turbo to be concerned about.

Ryan7361 · 09-21-2015, 10:03 AM

Dash AC compressor has been totally bypassed. I have a v-belt on power steering pump. Serpentine belt covers alternator, smog pump, and water pump.

jacwjames · 09-21-2015, 10:18 AM

CJ7635 is correct probably not turbo with 454 gas.

I tried to delete my response twice after posting and finally gave up. Good lesson on reading and understanding OP's question before responding, I HATE making mistakes or providing bad advice.

I agree that it could be a belt issue, after the vehicle gets warm the belt may expand/slip.

DonDee · 09-21-2015, 10:24 AM

Quote:

Originally Posted by mfire1339

On my 1986 p-30 the alt belt had to be (REAL) tight!

Mike

Same here.

slickest1 · 09-21-2015, 08:21 PM

Also could be a vacuum leak. Check hoses from intake manifold.

TQ60 · 09-22-2015, 07:45 AM

Try forced downshift at speed to confirm which side of tranny making noise.

If changes then engine if no change running gear.

A friend recently had to change front rotor and brakes due to clogged brake line that would not allow caliber to fully rest. ..made same noise.

Murf2u · 09-23-2015, 06:25 AM

If you have a clutch fan check it. They are notorious for howling or screeching at a certain speed as they're failing.

TeJay · 09-23-2015, 06:59 AM

Putting anything on the back of a belt like: spray belt dressing, bees wax, candle wax, will for a short time change the coefficient of friction and the belt will usually stop squeaking if it's a belt. Very simple diagnostic practice. I do not recommend any of those as a FIX just a diagnostic technique to narrow down the problem.

JFYI, The tension on belts should not be REAL tight. REAL tight means some of the bearings in the devices being spun by the belt may have to much excessive side forces placed on them and may fail earlier than designed.

There is a specific way of determining the correct belt tension. They do make belt tension gauges but i never owned one. You just know from experience how tight to make them. Some would say 1/2" deflection in the center of the belt. That's not always easy because most belts have various distances between pulleys. I'm a fan of the serpentine belt and the the automation belt tension pulley. That does take the guess work out of the equation and the tension is good for as long as it and the belt hold up.

A serpentine belt can't be to tight only to loose if the spring in the tension assembly is weak. There is a bearing in that tension pulley that might be the cause of the noise. The dynamics of the belt and the tension-er do change based on current (alternator) demand, speed, load, centrifugal forces on the belt etc. That may be why the noise is speed (RPM's) specific.

TeJay