91 plymouth sundance is overheating i changed the thermostat and the radiator and the car is still overheating and the reserve tank is spitting out coolant

Indicative of a blown cylinder head. Gas from combustion pressurizes the cooling system. Get the radiator pressure tested. They pump air into the radiator and watch a gauge. If the pressure goes down either coolant is going into the combustions chamber or air is coming out of the reservoir. You may just need a new cap.

It's located on top of the fuel tank. You may have to drop the fuel tank slightly to get to it.

If the unit overheated and there was no coolant flowing into the reserve tank, then there is two possible issues that must be addressed immediately. Either (1) There was not enough coolant in the system. This is because when the coolant heats up it expands and will go to the reserve tank. The fact that there was going to the tank indicates that the system is less than full, or (2) The radiator pressure cap is defective.

I would flush the cooling system, clean the reserve tank, replace the radiator cap, and refill the system and retest.

You change the head gasket

The spitting is cylinder pressure or combustion
gases blowing out coolant

you have a blown head gasket.. doesn't have to have coolant in the oil for a blown head gasket... if hoses are rock hard when running then you have exhaust leaking into the coolant via a blown head gasket...

hi there,you should take your car to a radiator shop and have them clean the radiator.To do this they dismantle it and clean all the tubes etc.This is not a job to do at home.They radiator electric fan shoud not run all the time only when it is switched on by the water temp switch which could be faulty.It sounds most likely that your problem is more associated with a partially blocked radiator.

Your radiator might be air bound or clogged. When the car gets up to temperature and the thermostat opens shut the car off and try to feel all the corners of the rad. if its cool in any spot you might need a flush or new radiator. (When thermostat opens let car run for about 5 min before shutting down) Hope this helps

To the rear of the gas tank under the car.

When the car is completely cool,check the electric fan(s) for smooth rotation.

Clean/check/change the thermo sensor,contact and wire.

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Excavate air pocket in coolant system / check for head gasket leak

This test will kill two birds with one stone.

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MAKE SURE THE COOLANT SYSTEM and ENGINE IS COLD!

RAN THIS TEST IN A WELL VENTILATED AREA ONLY!

You will spill some coolant during this air pocket purge test.......BE KIND TO THE ENVIRONMENT and ANIMAL please clean up after the test!

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Put the front end on a pair of ramp or park your car on a VERY STEEP HILL (radiator facing top of the hill) .

Top of the coolant reserve tank

Let it ran for 10-15 minutes.

Monitor for air pockets escaping from coolant reserve tank.

Small amount of bubbles is OK at 1-5 minute mark

After the thermostat open up (after 195 F warm up) at
5-12 minute mark or after high idle you should see less bubbles.

If you do not see any in rush of bubbles then your thermostat may be partially stuck or rusted badly inside the thermostat hosing.

Give the thermostat host few gentle taps.

If you see larger bubbles surfacing after 15 minutes then should do a hydrocarbon (HC) dye test to test for potential head gasket leak.

Let engine cold down and top off coolant reserve tank.

Start monitor for coolant lost

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A coolant flush is require every 2 years or 24,000 miles.

I recommend the thermostat that has a relief pop-let to reduce the change of burst radiator and coolant hoses.

Make sure you get a new thermostat gasket,black RTV and fresh coolant for the job.

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My girlfriend has a 91 sundance. I solved that prob by doing a coolant flush and replacing the radiator cap. The gasket was torn to shreds on the cap