Hello, I have 92 cherokee... It coolant overflowed today, I checked the cap and it was tight. Checked the color and it was clear. When I was driving i was looking at the temperature and it never made it to 210. So I was wondering what else could cause this problem?

 

Is it possible that you might have overfilled the coolant overflow reservoir? I know that on the later model xj's there is are cold and hot fill level marks on reservoir. Just a thought.

 

I overfilled mine and it spewed over. As the days get warmer the engine will get warmer while running. It is possible that if you filled it up in the winter the extra didnt overflow until now.

 

nope It was level before cause it overflowed last week but I think i left the radiator cap lose. But I know the radiator cap was down today..

 

when you say clear as in green or just water? cuz if there is no antifreeze/coolant it will boil over/expand where it can get out

 

its mostly water since i had to refill it. It actually has a rust tint, not milky or anything just a brown tint.

 

how long has it been mostly water? Mine was when I got it and had to replace the almost new waterpump because of rust. Unfortunately I now need to flush the system AGAIN. I would say flush the system and fill back up with a 60/40 or 70/30 coolant mix. 60% Coolant and 40% water.

 

My gf jeep did this it had a blown head gasket it would build pressure and push all the aintfreeze out had me wondering for awhile. It didnt smoke our anything just a thought hopefully that aint your problem

 

I hope everyone knows to ONLY use distilled water with their concentrated coolant if you didnt buy 50 50 pre mix. Normal water contains minerals that will clog your radiator. You should flush the cooling system to clear out any deposits. if you have a radiator leak replace the radiator. If your cap popped off your bottle you need to replace it because the cap and/or bottle threads could be compromised. The pressure will build up again and just pop the cap off. The system needs to build pressure to work properly.

 

yeah i used distilled water

I forgot to say it only goes over after i stopped and turn of the engine. Its fine while the engine is running the about 2 mins after it start going over.

 

Replace the radiator cap, drain and fill the system with a 70% water to anti-freeze mix.

 

Because of the lack of circulation of coolant through the system and air past the radiator, the coolant temperature increases after engine shut down resulting in an increase of the system pressure. The radiator cap is supposed to allow the expanding coolant to flow into the expansion/overflow reservoir. Your cap sounds as if it does not. Radiator caps are relatively inexpensive. And make sure that the line from the radiator neck to the reservoir isn't stopped up.

 

its going into the reservoir... its overflowing the reservoir... nothing is comping out the cap or anywhere else that i can see.

 

Correct me if I'm wrong, but '92s have an open cooling system with a radiator cap on the radiator itself.

Because of the law of the conservation of matter, the reservoir can only overflow once unless you add more coolant to the cooling system. The same applies to the older closed system where the pressure cap is located on the expansion tank (reservoir).

If you let it overflow and then cool overnight, what is the level of the coolant in the reservoir? What is the level in the radiator? Reservoir level should be higher than the hose attachment point. Radiator level should be to the top of the neck, up to the radiator cap.

You probably know the rest of this, but if both coolant level conditions above exist, drain the cooling system and refill with distilled water. Run the engine and turn on the heater until the thermostat remains fully open and the coolant circulates completely. You'll need to repeat until the water in the system is clear and that which you can't drain out is essentially all distilled water. (To get it all out, you'd need to use vacuum.) It will take three refills if you can add six quarts of distilled water after draining to reach 87.5% distilled water. A gallon of distilled water costs a dollar at the grocery store, so you may want to use tap water first until the water drains clear.

Then fill with six to seven quarts of 100% antifreeze. Top off with distilled water. Run the engine and turn on the heater until the thermostat remains fully open and the coolant circulates completely. Tighten the radiator cap, and fill the reservoir to the MAX level indicated. Allow to cool completely (overnight). Check levels in radiator and reservoir. Radiator should be full. Fill the reservoir to the MIN level indicated.

 

Your right about the open cooling system but the expansion tank has a line that goes from the bottom of the expansion tank to the radiator. So when the engine cools it sucks coolant from the expansion tank to radiator and when it heats up it goes into the expansion tank.

Maybe thats it when my engine is off the line is in between the fill and full line. But how do I know if the thermostat is completely open or not while the engine is on?