Pulsating noise from left rear ....

Hodgey · Hodgey's Garage

Hello all........
I have a strange pulsating noise coming from the rear left ( I think!!) it appears: it does not change with road speed so I do not think it is a wheel bearing, and it does not get louder or go away when I go around a corner in either direction.

It almost sounds like resonance due to harmonics or maybe in the engine tin perhaps, but it's difficult to describe...it sounds like a dry bearing but because it does'nt change with road speed I have discounted it.

Any pointers would be greatly appreciated.

Neil

Oh Haha · 02-10-2010, 05:34 PM

Tough one.

Does it occur at a specific RPM range? On a specific road?(don't laugh, a road in my area has a funny texture which makes my tires "buzz" like mudders.)

Can you hear/feel it if you rev the engine in neutral?

How old are your tires? Wear pattern good?

James Brown · James Brown's Garage

so we can exclude anything that turns when the car is in motion (engine, trans, bearings, brakes, tires, ect). hummm could it be in the stereo system? or an aerodynamic cause? not much help, sorry.

Sean A · Sean A's Garage

Fuel pump/accumulator are both located in the right rear area of the car. Your fuel pump may be causing the noise if its loose in its cradle or the bearings are starting to go bad. You can find it mounted below the left rear torsion tube.

EDIT: Sorry, didnt read you had an 87 carrera, disregard the fuel pump being in the rear of the car. My 74 has the pump in the rear, but yours does not.

carrera turbo · 02-10-2010, 09:34 PM

hello

well try a little diagnostic, while driving the speed you here the noise try applying the breaks and see if the sound diminishes , if that doesn't work with your thumb on the button apply the e-brake a little and see if it lessons at all. another thing to try is switch tires from left to right and see if noise moves. also check for loose lug nuts as any of the one things i mentioned could be heard as a strange sound.

a broken belt in a tire makes strange sounds as well.

good luck

cheers ed

Oh Haha · 02-11-2010, 01:24 AM

Quote:

Originally Posted by Sean A

Fuel pump/accumulator are both located in the right rear area of the car. Your fuel pump may be causing the noise if its loose in its cradle or the bearings are starting to go bad. You can find it mounted below the left rear torsion tube.

Sorry but the fuel pump is NOT located in the rear. It is located in the front, mounted by the steering rack.

The fuel accumulator is in the engine compartment but I highly doubt this is the cause of the noise.

DanielDudley · 02-11-2010, 02:22 AM

It only happens when you are rolling ? What happens if you push the clutch in at speed ?

twistoffat · 02-11-2010, 03:05 AM

Could it be a small hole in your exhaust? Just a hunch as that usually causes an acoustic blowing noise

Hodgey · Hodgey's Garage

Thanks for the replies....
I am heading out of town for the weekend so I will be back on this next week...I know it isn't the stereo as the first time I heard it the stereo was not on.

It doesn't happen at any specific range in RPM and does not increase or decrease in frequency which is what leads me to side with the opinion of James other than the tyres which I could swap over.

I will try the thumb on the e brake for sure today and see how that goes and will report back.

It is irritating more than potentially catastrophic I think..but you never know. I want to enjoy the sound of the engine more and less of 'white noise"....lol

I will report back.

thanks again gents and keep the ideas rolling in please.

Neil

Hodgey · Hodgey's Garage

what about the cruise control vacuum unit? Could that be leaking? How would I check?