OT-Funny car noise

[Dan-IA]

Got a noise I can't identify. Engine in 1990 Buick Skylark, 4-tech 2.5L 4cyl engine. Over 200,000 miles. Just developed a hammering noise we can't identify. Doesn't do it when it's stone cold, terrible rattle rest of the time. Developed it on a trip, limped it home 260 miles that way. Suspected the tranny, changed ATF and filter. Can feel the vibration in the two bolts sticking up through the air cleaner. I've sorta guessed it's not a valve spring or lifter or piston broken because it doesn't do it cold and those should rattle all the time. Family mechanic said he's never heard a rattle like that before. I'd post it on youtube or something but our digital cameras don't do sound.

 

[Anonymous-0]

Could be vibration damper rubber is shot and the rattle may be the metal stops hitting in the damper. The damper would be located at the water pump end of the engine attached to the crankshaft and probably has the pulley attached to it. Some front pulleys bolt to the damper and may also become loose and also cause the rattle.

 

[Anonymous-0]

The flywheel to converter bolts may also have worked loose and can cause that noise.

 

[Allan in NE]

Dan,

Does it sound like a diesel engine running?

Allan

 

[Allan in NE]

They had two bad habits.

If it has the "diesel" sound, problem is the timing gear.

If it is just "rapping", singular noise then it's more than likely a wrist pin on #2 or #3 cylinder.

Allan

 

[Anonymous-0]

All funny cars are noisy, ever been to the races? Just kiddind. Most 2.5 noises are from the timing gear.

 

[Allan in NE]

Yep,

You can tell what's wrong with 'em from a block away depending on the noise.

Also, that darned broken head bolt back in the corner is another little item that followed that engine around all over the country. :>)

Allan

 

[Dan-IA]

Maybe a worn out and abused Cummins. Lot louder and worse than a diesel sound. Neighbor said it made her pictures on the walls shake when I parked outside her house.

 

[Allan in NE]

If it is a definite "diesel" sound, then the timing gear has to be replaced at the camshaft. It will sound just as though the engine were a diesel setting there idleing.

If it is a repetetive slap/rap, slap/rap, slap/rap sound then it is the wrist pin issue. If it is WAY, WAY loud, the piston is probably hitting the head or broken.

Both noises were very, very common on that engine.

If the converter bolts are loose, the noise will stop when you drop it in gear (loading the torque).

However, either way, it is a pretty simple fix all said and done.

Allan

 

[Anonymous-0]

Check your belt for chunks missing.

 

[Duner Wi]

Had the front crank pulley retaining bolt come loose on a 2.5 once. Made a bit of a racket.

 

[CaseChev]

Besides torque convertor/flexplate bolts being loose, much more common is a cracked flexplate which should change in noise level when car goes from neutral to drive.

 

[6U684]

'60 Ford 6 cyl sure made a racket when the little screw in the choke flap got sucked into #1 cylinder! Leonard

 

[Jim.UT]

I've had both a Ford Tempo and a Pontiac Bonneville that had the harmonic balancer come apart. Made quite a racket both times.

 

[bradk]

Dan

Unlike most of the General's 2.5(R) engines, the Skyhawk has a 2.5(U) engine and uses a timing chain instead of gears.

I've replaced a few broken auto tensioners inside the timing cover.When they go,it hurts your ears listening to it.A very sharp rattle noise.

Also,pull the air cleaner cover off and see if the noise is coming from the throttle-body or throttle bore.

A cheap stethoscope can help find the noise.Take a long(1 1/2-2 foot) screw driver or prybar and put the handle to your ear and the business end at suspect locations on the engine including the timing cover.You'll hear it. ~brad

 

[npuller]

Dan them 2.5 chevys oil pump is mounted to the bottom of the engine and have two balance shafts in the oil pump assemly.At over 200000 miles the bearings on the balance shafts are most likey gone.And like the others have said timeing gears flex plate and conveter bolts could allso be a problem.HTH Ross

 

[Larry59]

First question.

Dose the sound go... chitty chitty bang bang?
If so.. watch out for low flying planes. lol

 

[Anonymous-0]

Give it a compression test, I would suspect the top of a piston has departed,would get blown down on power stroke, crank would be out of balance hence vibration.
Keep us posted...........

If there is no plane, it could be "Mary Poppins."