98 Caravan Overheating, Whining, and more

My 98 Grand Caravan 3.3L (130K miles) is giving me problems again.
First problem began a couple weeks ago when I noticed a whine that
appeared to be coming from the back of the engine (possibly on the
driver's side, but I'm not certain). It only seems noticable when
idling, coasting, or driving at low speeds (maybe under 25mph). It
sounds like when you blow up a balloon, then pinch the opening and
slowly release the air - that kind of high pitch sound. And when I
accelerate, it seems to go up in pitch and then disappear. About a week
ago, I noticed the Service Engine Soon lamp came on, with no noticable
variation in performance. A couple days later, the car overheated. It
has since had overheating problems. And when I sit at a light, the AC
starts to blow warm air.

In April I had the water pump replaced after it seized up, and new
coolant was put in at that time. I replaced the thermostat, air filter,
and PCV valve last week. The head gasket is less than 2 years old. The
fan relay switch and O2 sensors have also been replaced in the last
year. Serpentine belt seems to be in pretty good shape. I believe it's
maybe a year or two old, tops.

The AC problem, I am assuming is happeneing because the fans aren't
kicking on. Last time that was the case, the fan relay was replaced and
solved the problem. I need to double check that the next time it
overheats.

The crossover pipe has been an issue for quite a long time (maybe 5
years), but I have not been able to find the part as it's apparently
not made or always on back order. I realize this could be part of the
whine problem.

I was thinking a vaccuum leak or the existing crossover leak could be
the causes of the whine. The fans not kicking on could be a problem for
the AC. I have no idea about the overheating, unless maybe it's plugged
up. Radiator hasn't been flushed in at least 5 years. I am guessing the
AC and overheating ARE possibly related, and the whine is possibly
unrelated. But I am certainly no expert. Just wondering if anyone has
any ideas to throw at me.

Was thinking about taking it to a dealer to at least see if they can
give me a diagnosis.

Thanks in advance.

 

I also wanted to add that I replaced the radiator cap, and the
overheating seems to occur more when I drive around the city and goes
away if I drive at highway speeds.

Thanks again

 

Have you at least tried to spin the fan blades?? (key off) Possibly related
to everything

Glenn Beasley
Chrysler Tech

 

Spun the blades by hand and they did move. I ran a couple of short
errands and let the car run in my driveway as I watched the fans. Never
saw them kick on, so that could be the reason for the overheating.
Again, the AC was blowing cold while moving and started to blow
"outside air" when not moving. I also noticed the serpentine belt is
about 1/8" off track. I had checked that a few days back, thinking it
could be a tensioner or other problem, and didn't notice it being off
at that time. I'm thinking that's related to the whine, but am not
sure.

 

You have replaced the fan relay. It is unlikely both fan motors would
burn out at the same time. There is a Coolant Temperature Sensor that
one manufacturer describes as "for AC". My guess is that this sensor
is supposed to turn the radiator cooling fans on when the coolant
reaches a certain temperature and / or if the AC is turned on.
Here is a photo of the sensor:
http://www.rockauto.com/ref/SMP/SMPDetail2.html?TX81.jpg

 

Didn't know of that one but I'll definitely check it out. Thanks!