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

 

Could be a vacuum leak, listen under the hood at idle.

Glenn Beasley
Chrysler Tech

 

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

 

Check the PCV valve by temporarily removing/bypassing it. Some
aftermarket valves will whistle like a train.

 

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

 

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

 

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

 

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')

 

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.

 

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

 

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.

 

Please stop crying

 

Whatever.

 

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

 

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

 

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

 

This could very well be the problem because after having spent another hour
or so today, it doesn seem
like it is coming from somewhere obvious and outside around the engine.
Looks like it won't be easy to get to it though.
I will read up on it.

BTW, does it invlove getting to the bloody timing belt ?

-Paul

 

I replaced the PCV valve with another chrysler made but not a new one. The
bloddy whistle is still there.

-Paul

 

Few other things I tried today. In short no success yet.

a) Replaced the PCV valve with another chrysler made I acquired but it is
used.
b) Stethoscope method to find the source.
c) Adjusted tension on the compressor belt while it was running. Heck
nothing changed while it was whistling.
d) Before starting the engine, tried clockwise rotation on the auto
tensioner. It feels alright to me. It had enough tension and free movement
without making any squealing sound.

Another thing to note:
When the whistle kicks in, it does so abruptly that the surpentine belt
or something of that sort does not feel like the cause of it. If the belt is
the cause it will have some constant slow to becoming loud sound. When the
fan comes on, it goes away slowly but not abruptly. If the engine was hot,
it was whistling and I turn the darn thing off and start again, it takes few
minutes before the whistle comes back and then the whole thing repeats.

Thanks again guys!. You have given me a lot to think about. My caravan is
our spare vehical but my wife keeps complaining because she has to park her
Honda outside while my old caravan comfortably sits in the garage and
protected from acid rain.

-Paul

 

That sounds more and more like a cooling system problem (whistle goes
along with gradual pressurization/de-pressurization) - maybe the water
pump thing that was discussed earlier?

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')