'97 Jimmy Overheating - please help

08-27-2004, 05:32 PM
ok for some reason my jimmy is overheating, there is no leaking coolant, the radiator appears fine, just put new water pump in this winter, new thermostat last week, radiator has been flushed... it used to only overheat while the A/C was on today had to drive home with the heat on to keep it at 210... please help quick, its like 85 out and driving around with the heat on is not right... thanks...

08-27-2004, 05:40 PM
Did you use dexcool or regular antifreeze when you did your new water pump and stat?

08-27-2004, 05:53 PM
regular antifreeze 70% anti, 30% water

08-30-2004, 03:33 AM
Possible faults:

Thermostat defective (even if new). Remove and test in water; heat it up from cool with thermometer to indicate temperature.

Lean fuel/air mixture. Check spark plugs for deposit colour (grey/white = lean, beige/toast = correct). Check for correct grade of spark plug. Check fault codes for clues eg O2 sensors, AIR injector.

Ignition timing retarded. Check and correct. Use inductive pickup timing gun and follow the VECI label instructions on the bonnet/hood slam plate or radiator cowl.

Air trapped in coolant galleries. Start engine from cold on at least 30 degree slope, radiator upslope, rad cap off. Top up coolant, refit cap. Raise revs to 1500 for 10 seconds every 40 seconds. Repeat ten times. Open bleed points (if any) to release trapped air, then close. Switch off, allow to cool, recheck coolant level and header tank.

Bottom hose collapsing. Observe while engine running. Be careful of rotating fan and belts. Increase revs to 2000 and observe hose. New hose fitted with spiral wire support if collapsing.

Brakes binding. Raise wheel off the ground. Properly cleaned brakes will allow the wheel to be turned with one or two fingers on the tyre sidewall.

Belts slipping on water pump. Check belt tension.

Radiator finning clogged. Soak with solution of dish wash. Wash out after 20 minutes from FAN side. Don't use a power washer, just a hose with an adjustable nozzle to get a jet of water.

Sludge in coolant galleries. Long job. The only effective way I've found to remove sludge, is to remove the core plugs and dig the stuff out in flowing water.

If electric fan cooling check circuit, thermal switch and fan.

Good luck


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