Dodge Caravan 93 3.0l Engine whistles at idle

When the engine is cold it is OK but at normal temperature if I let the engine idle it starts giving a loud whistle. If I rev it high it goes away.
The idle RPM is between 750-800. I am pretty sure it does not come from the belts or pulleys. Any ideas what could be the problem ?
TIA Paul
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Could be a vacuum leak, listen under the hood at idle.
Glenn Beasley Chrysler Tech

away.
the
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Thanks for the reply. While the engine is running I have tried to unplug and plug the vacuum pipes back. The darn thing does not seem to make any difference. I just can;t seem to locate the source. I will keep trying.
-Paul

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Check the PCV valve by temporarily removing/bypassing it. Some aftermarket valves will whistle like a train.
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I replaced the PCV valve with another chrysler made but not a new one. The bloddy whistle is still there. :)
-Paul

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it could be a broken intake gasket, if it is a vacuum leak, take a runner hose to your ear and use it as a stethoscope to locate the leak, or at lease eliminate that possibility

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In between I have cleaned the throttle body, air plennum and fuel injectors( new O rings). All the gaskets were replaced with the new and the bolts were tightened to the FRM specified torques. Lot of black stuff I removed. The whistle was there before and still is. I cleaned the intake area because I have never cleaned it in over 12 years. So I suspect that is not the cause. Last night I looked at it again but nothing positive to report about. I think it may help if I explain the symptoms a little more.
a) The whistle only comes when the Engine is at operating temps. b) If I come home and sit there for couple of minutes without turning the engine off, no whistle. c) If I let it idle for few more minutes, whistle yes. If I rev it, it goes away. Let it idle, it will come back. d) Driving normally, no whistle. e) While idling if the radiator fan comes on, whistle goes away. It comes back as soon as the fan stops. f) I removed the PCV valve suction pipe and put my finger on the PCV valve to seal the suction. Nope it didn;t help. I can remove the PCV valve completely and then see if the whistle goes away.
Lately I also replaced the thermostat because of the engine code. The thermostat I bought is not made by chrysler but got it from Schucks which I think is made by prestone. Come to think of it, the whistle was there prior to replacing the thermostat.
I tried to locate the vacuum leak. No luck yet. While the engine is running I tried removing one vacuum pipe at a time to see if that makes any difference. No luck. Well, I haven't tried all of them yet.
The fan belts seem to have proper tension, auto tensioner is free to move and has good tension to keep the belt tight. The compressor belt has enough tension. I have tried different levels of tension on the compressor belt. I would suspect the pulleys if the whistle is there all the time. If I start the engine cold, no whistle. It starts suddenly when the temp is about to reach the operating level.
Can it be ignition timing related at all ?
Bloody hell, I can't even pin point where the whistle is coming from. I asked my wife to help me locate the area it may be coming from. She seems to think it is from the left side of the engine i.e. the surpentine belt area. It is getting to be a challenge now. :)
I will try your runner hose method and will report.
-Paul
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runner
over
explain
goes
I
prior
running
enough
I
to
area.
Sounds like it changes when the load changes (vacuum) I would suspect a piece of old gasket left when reassembled. but without hearing it, it is hard to tell. get out that heater hose and use it as a stethoscope and you will pin point the noise
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Paul Singh wrote:

The noise coming on just as it reaches operating temp, and the fans being on or not affecting it - what shape is the coolant pressure cap in (i.e., does it need replacing?)? Also, the fans coming on could simply be changing engine operation enough to cause the noise to stop by loading the alternator.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')
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seems to

area.
Some FEAD tensioners use a damping shoe arrangment to tame wierd belt dynamics at idle or with varying loads . I have an older minivan (with most likely a worn out damper) that will get into belt squeal at the alternator at idle, but the squeal goes away with any amount of increased throttle.....just a small shot of spray-on belt dressing will quiet it for days at a time.
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I
most
idle,
shot
Be careful with that belt dressing, allot of times the belt squeals because of alignment problems, and putting that stuff on my make the belt slide off the tensioner, Not saying that is why yours is squealing
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from.
belt
in
simply
because
off
As I said, "a small shot". If I had ever had a belt jump in this manner, do you really believe I would have even mentioned it?
We were trying to help the OP find his :"whistle"...not give me a lesson in belt alignment or other FEAD design issues.
Thanks anyway.
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She
cap
(with
small
do
in
Please stop crying
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fans
belt
at
slide
manner,
Whatever.
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I can try to spray some lubricant around the tensioner pulley and the other end connected to the block. Let's see if that helps.
Thanks. -Paul
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I
in
other
Well, take it easy with the lube (I hope you mean belt dressing)..just a little bit on the drive side of the belt is plenty..(see maxpower's caution about belt jumping). Frankly, now that Denny has surfaced the water pump seal possibility, that sounds more likely.....
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I
in
other
can drive someone nuts. If you had a long piece of heater hose you could slip it down the front by the timing cover just over the water pump and pick it up that way with your ear, anyway, good luck
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Thanks a lot guys!. Seems like the water pump work is quite involving. I am going to defer it till summer.
Once again, all of you guys who tried to help, you guys ROCK!!!!
-Paul

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The cap looks alright. Even though it is the original. But the sound does not seem to be coming from there or around it.
-Paul
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This sounds so familiar I could cry.. It is coming from the seal in the water pump. And don't ask me how long it took me to find it the first time I ran into it. <G> I've ran into this whistle noise exactly as you have described it two times and the pump has fixed it both times.
Denny
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