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What is this?....


New Member
Nov 4, 2021
Country Flag
Hi all, I'm still learning way around my Colorado/ Prado 95 series 1KZTE 3.0L diesel truck (1999 with 252,000 miles) so forgive me for this question as a non qualified 'mechanic'!

I've just finished changing the water pump (including backing), timing belt (including tensioner & pulley) & air-con idler pulley in the hope of solving a whining noise coming from the engine bay. These things needed changing anyway, but the noise seems to still be there.

Maybe someone can advise of what else may be causing that? I'm pretty sure it's not the power steering as it only whines when I press the accelerator, not when I turn the steering wheel.

Anyway, I also came across this which sits just under the timing belt cover and wondered what it was (see photo). Can anyone advise on that also please do I can determine if that's involved in the whining?

Thanks in advance.

Have you tried runnng the cold engine without the aux belt for a few seconds and seeing if the noise is still there? It its not then its likely something attached to the aux belt which you havent changed yet.

Also you can (carefully) use long screwdriver or a stethoscope to try and narrow down where the noise is coming from
Is that the aircon pump/compressor whatever ?

WD-40 on all your belts just to see if the whine stops temporarily , sometimes they just wear in such a way that they aren't running true .

A split air pipe can make some odd noises , took me forever and sounded like screaming demons were eating my turbo before i finally worked out the noise was caused by a split at the bottom of crank breather pipe .

Hope your not hearing diff whine , something I have fortunately never experienced but its been talked about many a time on here .
Thanks for the ideas. I forgot to mention that the whining can be heard when I press the accelerator in low revs. It's a low pitch, soft whining sound that follows the revs of the engine.

I am planning to get a vehicle stethoscope or long screwdriver to detect where it might be coming from so I'll get back to you if I manage.

All the three belts were changed quite recently so I don't think it will be them. I've inspected them & they look great.

Regarding the part that I don't know what it is... It sits directly in front of the power steering pump and seems bolted to it. It's at the bottom of the timing belt cover.. I've added a few more pics. It isn't the AC compressor. That's situated at the top, above the alternator.

More thoughts appreciated!


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Power steering pump, never heard of anyone having a problem with that on the 90 but pretty much all of us changed the steering rack due to leaks years ago .

A new belt might try to follow wear made by the old belt , WD-40 just lets it slip a little before it dries out in minutes .

Loose exhaust manifold heat shield vibrating was another source of noise i couldn't decipher until it got loose enough to obviously make a vibration sound .
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Last year I removed the power steering pump and changed seals etc so it's not the pump I'm confused about but what's in front of it. Unless I'm mistaken and it's somehow related?
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That is the brake vacuum pump for your brake servo. It is linked to the power steering pump through the front casing. It is full of oil so put something under the engine if you take it off. You wont loose much oil but it does hold a fair bit.
Yes, you're right! Thank you Steve.
Do you know if these have seals inside which can cause a low whining noise that I'm hearing?
The whining sound may be the turbo - you have a relatively high mileage. It should be easy enough to check it.

I like to hear the turbo sing but on a standard truck i don't think you can hear it until you get a hole in the exhaust .