intermittent cooling


Old 05-25-03, 04:50 AM
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intermittent cooling

Hello, Have a 93 Dakota, 2.5 with 170K. During intial warm up temp gauge rises to normally(10 min or so) and will sit at normal for a short while then rise to about a needle width less than Hot.
Then drop to normal and go back and forth.

When I bought the truck I replaced radiator(damage) Since than 2 thernostats. Thought I had a defective one. Lower Rad hose water pump. Belt looks new. added flush, drained(did not back flush. No coolant lost or over-boil.

Circutation is poor. Will run about 2/3 gauge at idle and only gets hot in 4th, 5th gear(low RPM) if I sit and run about 3000 rpm temp gauge will drop back to normal. Also top hose is full of water and hot, while the lower hose is ice cold when hot.

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Old 05-25-03, 05:07 AM
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Location: Kansas City, Missouri.
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I don't want to state the obvious, but here goes anyway. Are you certain you have the thermostat installed right side up?
Old 05-25-03, 06:41 AM
darrell McCoy
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Are you buying quality thermostats? Sure sounds like thats what it is, yet. Also is fan operating properly? Maybe an air lock. Many years ago, I replaced a water pump for a guy, S-10 P/U. Noticed the replacement was not like the OEM, that thing ran "Warmer" than it did with original pump. I have seen pump impellers slip on the shaft also. Rare but it does happen.
Old 05-25-03, 09:24 AM
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Don't trust the dash gauge, it's optimistic at best. Use a temperature probe or scanner to determine actual coolant temperature.

I believe this vehicle has a fan clutch. At that age, I'd replace it with a new OEM one. Chances are it's wasted. That will contribute to your problem here.
Old 05-25-03, 10:02 AM
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If it has a clutched fan (not direct driven) could be a bad fan clutch.
Old 05-26-03, 07:52 AM
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Thanks guys. Yes does seem to act like a bad thermostat. Is installed right. All cant be bad? Has electric fan. I wired direct to eliminate that posible cause. Ran with cap loose a couple days, same thing but doesnt get hearly as hot.

I was going to try to roughing up the water pump pully with sand paper so the belt has more bite. It runs of the back of the belt(flat pully). think its worth it?
Old 05-26-03, 08:33 AM
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No, that's a waste of time... won't do anything.

Run it without the thermostat and if it doesn't run as hot, you have a defective stat. Get an OEM stat from the dealer and the problem should be solved.

Again, Chrysler temp gauges stink, are known to fluctuate and should not be assessed as accurate. Only a scan tool reading or reliable temperature probe should be used.

You could also have a bad sending unit for the gauge which will MAKE you think it's overheating, but there is no problem .

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