overheating

[BRAIN]

my chrokee has a 401 engine with a new 190 deg
thermostat. when i am driving sometimes it will
heat up into the red. other times it runs cool
any ideas?

[illegalFSJ]

water pump
low coolant level
internal coolant leak
external coolant leak
leaking head gasket
seized or free-wheeling fan clutch
bad radiator cap
collapsing lower hose
Running too lean

Lots of things it could be. Have any more info?

[J10/J20 Project]

I would first look into the fan clutch.
Is there any visible fluid around the front?
Make sure fluid is full and fresh. Even though it looks green it may loose all it (glyco)(sp)
Flush and drain if needed. and good time to really check the radiator for flow.
It could be a thermastat on the fritz. but usually they work or they don't.

[BRAIN]

no visible leaks. fluid level stays full.
radiator appears to have sludge floating around.
one day overheats next day just fine.

[AMX factor]

If there are floaties in the radiator it's time to do a good flush. Might be half your problem.

[BRAIN]

i think i will get the radiator flushed and see
what happens.

thanks

[illegalFSJ]

Best way to clean it is to remove it and take it to a radiator shop. They will "boil" and "rod" it out, making it as good as new.

[Don S]

..
BRAIN;

... You need to at least pull and replace the thermostat and to reverse flush the engine. Remove both radiator hoses. Use a garden hose where the lower hose was and put as much pressure as you can in it. Pull the heater hoses and flush the heater core.

other good reading below;
link> OVERHEATING & AIRFLOW 101 (http://groups.msn.com/ATexasOklahomaJeepClub/ouraycotopic.msnw)

Have a good one, http://www.michiganjeepers.com/forums/images/graemlins/wave.gif and … CUL.. Don S..

[ February 04, 2004, 05:45 PM: Message edited by: Don S ]

[partywagon]

you might just have to flush it out real good mine would overheat real fast so i just flushed it out until all water coming in and out was clear then got a new thermostat and haven't had a problem since

[Banks]

Was it overheating before the new t-stat?There are 3 kinds of t-stats:1-cheapest,2-cheap,3-best.Always spring for the best. Marc