98 Mercury Villager randomly overheats. New radiator, water pump, thermostat, hoses and cap. Correct coolant level and mixture, no leaks, or head gasket issues. Two-speed fan operates correctly and AC compressor correctly charged and works until temperature gauge rises near top marker. Small clicking noises (like switches) intermittedly sound as though coming from under dash, or near firewall. Occurs whether on highway, or in town. Often self-corrects after cooling for awhile. I've owned this vehicle for more than a decade and have done all repair work myself. Just cannot resolve this issue. I haven't done a block test, but no evidence of coolant contamination in crankcase. Any experience with these issues and thoughts would be appreciated. Thanks, Rique

Of the water is boiling them it has run hot. There is no way around this fact. Get a compression test done first. This should reveal if any damage has been done. Then address the boiling off problem. This can be a air pocket in the line, incorrect anti freeze mixture, sticking thermostat, water pump, cap, etc.

I would replace the radiator cap and then recheck for overheat

Exhaust Converter Blocked ?

Did you check for combustion gases at the
coolant or radiator fill

Your down to a head gasket or a crack somewhere

I would think the head gasket is common on that
motor possibly,research that

Timing Belt worn or jumped ?

engines overheat with no thermostats. Very simply put the water circulation is too fast for the heat to transfer to the air. Water pumps fail from bad bearings and pump seal but for no other reason. So back to basics Refit with a new thermostat put in properly. Have a flow test done on the radiator for blocked cores. have a coolant system pressure test done for leaks and cap failure.. have a compression test done to check for head gasket or cracks.. Check for correct ignition timing and air/ fuel ratio mixture. Run fault codes . when refilling with coolant ensure that all air locks are removed

Problem can usually be traced to 1 of 3 things:
Stuck thermostat; with a thermostat stuck closed you would overheat and eventually get backflow into the reservoir
Bad waterpump; a bad bearing or a leaking water pump would cause your overheating problem
Bad head gasket; these are accompanied by white smoke from the exhaust and a foamy appearance on your auto transmission fluid dipstick

If you did not replace the water pump it could be the issue. Or you still have air bubbles trapped in the system.

ENGINE NOT GOING TO START IF GET TOO HOT FIRST THING I WOULD REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP THEN ADD COOLANT UNTIL COOLANT LEVEL CORRECT THATS WHEN THERMOSTAT OPEN UP AND TOP HOSE HOT.CHECK FOR LEAKING RADIATOR HOSES CHECK TOP RADIATOR HOSE CHECK BOTTOM RADIATOR HOSE.CHECK FOR LEAKS AROUND THE RADIATOR LOOK DOWN BELOW COOLANTS FANS CHECK FOR LEAKS AT RADIATOR CORES OR LEAKS AT THE RADIATOR PLASTIC SIDE CONTAINERS. CHECK FOR LEAKS AT WATER PUMP WEEP HOLE AND CHECK FOR LEAKS AT THE HEATER HOSES AROUND ENGINE BLOCK TO THE HEATER CORE HOSES. THERE IS A REASON CAR OVERHEAT.IF CAR OVERHEAT WHILE DRIVING YOU HAVE FAULTY THERMOSTAT OR LEAKING OUT COOLANT OR BLOWN HEAD GASKET.IF ENGINE OVER HEAT WHILE SITTING DURING A LONG IDLING PERIOD.YOU COULD HAVE FAULTY COOLANT TEMPERATURE SENSOR OR FAULTY COOLING FAN FUSE OR RELAY.HOT WIRE COOLANT TO SEE IF IT RUNS IF NO REPLACE FAN MOTOR. IF YES FAN MOTOR COULD HAVE FAULTY WIRE OR PCM FAILURE. CHECK ENGINE CRANKCASE IF OIL LOOKS LIKE MILK SHAKE ENGINE HEAD GASKET LEAKING.

You have air trapped in the system. If you have cold air, warm air, cold air from your heater, then it's air entrapment. Very common these days. Go to a shop that uses vacuum method to refill cooling system & that will purge air.
Otherwise, you can try. Park uphill. cold engine - fill radiator to top with 50/50 mix of antifreeze. leave cap on but loose. fill reservior to 3/4 full. Turn heater to hot to allow coolant to flow through heater core. start engine, run at 1500 rpms until thermostat opens and upper hose is hot. tighten cap and let it cool down. after cool check level of reservoir. fill to top line on reservoir. it should **** coolant back into radiator as it cools down.
repeat if still an issue.

go to yahoo group for villager quest & join owner group for much more help. 2500 members.

Faulty thermostat, failed water pump, inoperable radiator fan, low coolant due to leak, faulty radiator cap, leaking head gasket, low oil, major exhaust leak near front, exhaust blockage, or incorrect ignition timing. If there is crust around radiator cap, cap is leaking. How long does it take to overheat? If it runs smoothly when cool, and all fluids are at correct levels, you can rule our head gasket, radiator cap, and ignition timing. If it overheats very quickly and fluids are correct, it is probably thermostat or water pump. If it seems to do better at higher speeds, it is probably radiator fan. You can check this by allowing vehicle to run in Park with hood open. Monitor engine temp on dash. When it is at or slightly above normal running temp, radiator fan should come on. Also note exhaust sound. If it seems loud and overheats gradually, you may have a leak before the converter. If the exhaust sounds quiet, but exhaust manifold is getting extremely hot (may glow red), there is probably a blockage. There will also be OK starting and idle but poor acceleration if exhaust is partly blocked.

COULD BE COOLANT SENSOR,HEAD GASKET,CHECK THE TIMING,THE PROPER MIXTURE OF COOLANT,WATER PUMP.DID YOU HAVE IT CHECKED OUT?ANY LEAKS?HEAT WORK WITH FAN?