Frightening squealing sound from the engine

[Helirich]

Hi there folks, this morning me and my friend sat and listened to the noise very carefully for about twenty minutes... We helped ourselves with a water hose, trying to locate the source of the noise!

The sound is definitely coming from the center / left rear side of the engine... We weren't able to perform the removal of the belt, we'll try that out another time. Regardless, our common opinion is that the noise is caused by a leak somewhere, specifically an air leak. The point is we can't locate it.

The noise occurs whenever the engine demands for air, whether at idle (the infamous hunting motion) or at low speed when the throttle is pressed. In fact it appears when the cars slows down, at turns or when it stops... At normal travelling speed the wail just isn't there. The noise is so loud that it freaks everybody out!

We plan to dedicate some more hours to search and analysis... Any further suggestions are appreciated!



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You really need to remove the belt before anything else. It can change because of alternator load at anytime. If you really don?t feel like removing it, just spray it with some belt dressing when it?s making the noise.

[dmcman73]

If you have a smoke machine, use that to track down any air leaks, an air leak that is substantial in size can cause a whistle noise as well. Since you believe it was coming from the idle speed motor and you changed it, check that the cup seal under the air intake has not come out. This cup seal is hard to see and it is where the pipe (the pipe if agony) that connects to the rear port of the idle speed motor slides into under the air intake on the drivers side. With the engine off, if you remove the air filter housing and press the air meter flap all the way down, using a flash light, look towards the left side towards the rear of the meter unit, you should see the pipe from the idle speed motor sticking into the air mixture unit, that should give you an idea where it is, the seal is installed from the outside.

Other things that could cause a screeching noise would be the throw out bearing (if you have a 5 speed manual transmission), alternator bearing or a water pump that is about to fail. Do as Bitsyncmaster suggested and pull the belt off the alternator and start the car and see if the noise is gone, don't leave the engine running too long as you won't have any cooling since the water pump will be inactive. If the noise still persists, then shut the engine down and re-install the belt.

[TheStoot]

Unplug idle speed motor power, that eliminates that if sound is still present. Remove belt, eliminates alternator or water pump. U could have had this done within the 20 minutes u spent listening to the engine make noise. Do these and get back to the group

[JohnZ]

Here I am! So: the noise went away for quite some time (months), and then it went back full force! The idle speed motor is brand new, and the replacement of that part did not solve the problem. Taking out the water pump / alternator belt did not solve the problem. Lately I've been experiencing temporary misfire and erratic behaviour of the engine (just once), then after a couple of minutes the engine was ok again, than the noise turns up at full volume... this screeching sound is located in the distributor / CSV zone. Gaskets, intake o-rings, distributor bearing... plenty of suggestions from many people and professionals, but no one is sure about it, and neither am I!

I took a video of the noise with out the air filter on, maybe we can track the sucker down all together:



I'm lost here... and mad. The noise is embarassing and keeps me from taking the car out, not to mention I don't want to ruin the engine in some ways!

Cheers!

[Michael]

Judging from the video and previous posts, sounds like air whistling around a foreign object somewhere in the intake tract.

Seems directly related to the metering plate position too.

[Bitsyncmaster]

Did you install the idle motor backwards. I've not seen any difference with mine backwards but it seem like your idle motor is binding.

[Ron]

Try using a short piece of garden hose as a stethoscope/probe to narrow down the location...

[JohnZ]

The idle speed motor is correctly installed, as per DeLoreanGo instructions (arrow on the casing pointing to the back of the car), also: the noise is still present even if I unplug the motor. Besides it was present with the previous idle motor and it's present with the new idle motor...

The news is that the noise is evolving, now it's there no matter the temperature and it has turned into a howling sound, much like a wolf howling madly... and ultimately dying of starvation and old age



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[Bitsyncmaster]

Well something is wrong with your idle with it dropping that low. It does sound around the idle motor. Make sure that pipe from the idle motor is seated in the intake fully. Look inside the air flap with a flash light pointing to where that pipe enters to see if you see any light.

[Helirich]

Judging from the video and previous posts, sounds like air whistling around a foreign object somewhere in the intake tract.

Seems directly related to the metering plate position too.

This is what I was thinking. How about spraying starting fluid around differnt spots? If the motor revs up, you found the leak.