HIGH PITCH NOISE when decelerating.

[Mr. Bone]

Hello All,

Recently I've noticed a high pitch noise coming from the vicinity of the vacuum pump. I hear the noise at low speeds 5 -10mph esp. when i am decelerating.

Is this a normal sound or is the vacuum pump dying?

Thank you.

[Robyn]

I would yank the pump out and check it over.
Also check it with a vacuum gauge. 26" and steady is normal if the gauge is wobbly or low its time to get a fresh one..

Good luck

Robyn

[Mr. Bone]

thank you. I'll give it a vacuum test tomorrow. I recently checked the pump out when i changed the water pump. . . it looked and sounded good then. Thanks again.

[john8662]

Is this only heard when you're running the engine with the doghouse removed?

They do make some noise tho.

J

[Mr. Bone]

Okay. I've finally gotten around to checking the hg's on my vac. pump and they are good (around 26). The noise is getting progressively worse. It only happens when i'm decelerating AND if i put it in nuetral when i'm slowing down then the noise goes away.

The noise is very audible with the dog house ON. The warmer the engine the louder the sound.

Thank you.

[Maxxman23]

Do you think it could be a throw-out bearing in the tranny? My Mercedes makes that same high pitched noise when decelerating. It almost sounds a little bit like an old police siren.

[Mr. Bone]

As the noise gets louder i'm able to do a little more of a diagnosis. What about the power steering pump OR the reservoir that circulates the fluid which is attached to the v belt? does the bearing on this circ. pump tend to go?

Thanks

[Robyn]

Can you get the rig to make the noise when its sitting still??

This almost sounds like it might be connected with the tranny.
A torque converter going south will make similar noises.

More info please

Robyn

[Mr. Bone]

No I cannot get it to make the noise when still. . .well sometimes it will last for a few seconds when stopped at a light. It goes away quickly when idling though. It does seem to be popping into gear differently - Esp. neutral to reverse. . .a pretty good "thunk" sound.

To get back to the question about the siren sound. . .it definitely does not sound like that and the noise is in the front of the van - v belt area.

Does this help?

Also i am getting a little more vibration btw 15 - 30 mph then i used to. . .i figured it was suspension related. The ride smooths out at 45+mph.

Thanks again.

[Robyn]

If the rig will do it cold, yank the belts off and try a quick run and see if the noise is gone.

If the noise is gone with the belts off then you know its an accessory issue and you can move your search up front.

I have seen water pumps make a lot of noise when the bearings are going out but that noise will stay as long as the engine is running.

[Mr. Bone]

Ahhh, very good. I love the little tricks that experienced people know. Life's all abou the little tricks.

What is a safe amount of time to run a cold engine without belts? My main concern is the electrical sys.

Thanks.

[Robyn]

Just watch the temp gauge and dont get it near the crispy zone.
You can run it long enough to do some diagnostics.