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Discussion Starter · #1 ·
Hi all,

2002 Grand Caravan Sport 3.3 (118k miles)

Been experiencing a problem with the engine running cold. This doesn't happen all the time, but it is becoming increasingly frequent.

Normally, when the engine has reached its normal operating temp, the temp gauge on the dash reads just below the half mark and the heater blows extremely hot. When this problem happens the temp gauge stays just over the "C" mark and there is very little heat from the heater.

The fact that both the gauge and heater match makes me believe this is truly a problem of the engine running too cold sometimes and not a gauge failure nor a heater failure.

There is no check engine light and it runs perfectly with no driveability problems at any time.

Possible causes?

Thermostat sticking open sometimes?
Temp sensor or other computer problem?
 

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I'd start by total flushing / back flush the radiator and put a new t-stat in

if the hoses are old IMO go ahead and eplace those as well

then with totally fresh antifreze and t-stat - let us know if the problem disappears


don't just drain out the old stuff - tell a shop you want it completely back flushed out
 

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Discussion Starter · #3 ·
OK, thanks. I'll ask my mechanic to do that. Can you please explain what "back" flushing is as opposed to just "flushing"? Or is that the same?
 

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when some places flush the radiator, its no more than draining out the fluid and running water from a hose thru the radiator with the drain **** open

back flushing also flushes out anything that is in the block / intake and heater core

To picture it in your mind, the flush kit goes kind of in a reverse direction that your vehicle normally runs antifreeze thru, and any loose sludge, deposits and gunk that would not normally be cleaned away by just running water thru a hose.

It gets thoroughly cleaned, and really, its the only way to do it
 

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thermostat. I just changed mine. same issues. turns out it was staying open. easy to change. takes 20 minutes on a 2000 3.3. p.s. my motor only has 67k.
 

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Discussion Starter · #6 · (Edited)
Thanks! It's probably due for a cooling flush anyway. I just checked my records and the last (and only) time it was done was at 70k miles.

BTW, how often should you flush the cooling system on this engine?
 

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Book says to drain and replace every 30,000 or 24 months. I would flush it every second drain. You can never over maintain a vehicle especially with fluids and filters.
 

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cold

If its truly running cold it should throw a error code . Do the keydance to get the code , ignition on,off,on off, then on and watch the odometer readout for an error code , if none has been thrown it will read done . I think a cold error is code 16 . There is not really anything that would govern a cold engine other than the thermostat .
 

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Discussion Starter · #9 ·
Book says to drain and replace every 30,000 or 24 months.
What book is that? The maintenance schedule in the owner's manual says to flush and replace coolant at 100,000 miles or 60 months. My mechanic did it at 70k without my asking.

I used to do the coolant every 30k with my 1989 Caravan. I don't know why it doesn't say to do that every 30k in the manuals anymore.
 

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It all depends on what coolant you use. As many of us PO'd GM owners can attest, GM's version of extended life coolant, Dex Cool, attached the intake manifold gaskets long before it was time to replace the coolant.
After what I've been through with my Bonneville, I would never go 100,000 miles without changing the coolant, regardless of the car or coolant.
 

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Discussion Starter · #11 ·
If its truly running cold it should throw a error code . Do the keydance to get the code , ignition on,off,on off, then on and watch the odometer readout for an error code , if none has been thrown it will read done . I think a cold error is code 16 . There is not really anything that would govern a cold engine other than the thermostat .
Yeah, there's no CE light and keydance reports "done". I'm inclined to believe this is a thermostat sticking open to varying degrees (no pun), which is why this is an intermittent problem.

Car goes to my mechanic next Monday. I'll report back with results. Thanks all!
 

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Haynes manual. They shorten the intervals to ensure,for example,that such items as lubricants and fluids are checked/changed at intervals that promote maximum engine/driveline service life.
 

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Discussion Starter · #13 ·
Got a new thermostat and coolant flush yesterday. My mechanic showed me the old thermostat - it was in pretty sad shape. Runs perfect now.

But... after I left the shop, I began to hear a sound of water running/trickling coming from behind the dash on the driver's side. The sound would come and go with throttle input and would happen either parked or moving. I let it run for a while and the sound went away. It came back a little today so, I took the car back to my mechanic, but it had already gone away again by the time I got to his shop and he didn't get to hear it.

If the sound persists, I will leave it with him overnight so he can experience it.

What do you guys think I'm hearing?
 

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possibly heater core

but maybe after a complete flush, its just the fluid going back into place

did it only do it that one time or does it do it everytime you go somewhere or ?
 

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Discussion Starter · #15 ·
possibly heater core

but maybe after a complete flush, its just the fluid going back into place

did it only do it that one time or does it do it everytime you go somewhere or ?
It did it right after the flush but went away after letting it run for 15-20 minutes. Then it came back again a little bit the next day when I first started it, but went away completely within 5 minutes and never came back. It hasn't made that sound again since.

What do you think it could have been?
 
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