xj will not stay cool

i have a new thermostat but my 88 jeep with the 4.0 will not stop boling the water out of its self is is common to lose a head gaskit and have that happen or should i look else where before doing all that work.

Does an 88 have the open or closed system?

The rating for the open system's radiator cap (non-pressurized overflow bottle) is 16 psi....

I'm not sure what it is for the closed system with the radiator cap on the overflow bottle. Open system has the radiator cap right on the radiator.

it should be a closed system but I am not sure how to burp it and if your supposed to when you change the thermostat.someone else will chime in though.:spam:

Does the cooling system pressurize as it warms up? Mine had a bad cap, and as the engine warmed up, the coolant would rise in the reservoir until it started to overflow. As this was happening I squeezed the top hose and noticed no pressure. Replacing the cap fixed it. Also make sure there are no cracks in the reservoir, and that the top of the reservoir isn't deformed making the cap not seal correctly.

Did you have this problem before changing the thermostat?

ps: mine is a '87 closed system

Mine overflowed three or four times...turned out to be AutoZone was giving me the 13psi cap instead of the factory 16psi cap.

Of course I have the open system with the cap on the radiator....

It wouldn't do it all of the time. I'd say three or four times in 2 months....but your closed system WILL react differently.

you can relieve air in the closed system by raising the rear of the vehicle, removing the temp sending unit for the gauge (rear driver side of the head), and filling though that hole until full....while cold!

or.....not as recommended (but has worked for me)-while hot or running loosen the top hose from the heater core (highest point in the system) and let the air escape. The air will be accompanied with very hot coolant, so don't burn yourself and attempt to keep the dist dry.

I assume this is some time after the replacement of the thermo. If not you may just need to let it warm to running temp and let it cool, several times. After each time it is cool, open the bottle and add coolant as needed.

If you did not get a thermostat with the burp hole, I suggest you do so. If not you can drill the hole. I usually ensure there is a hole about 3/8 at both 12 o'clock and 6 o'clock. MAKE SURE THE THERMOSTAT IS INSTALLED CORRECTLY!

Blaine B. said:

Does an 88 have the open or closed system?

The rating for the open system's radiator cap (non-pressurized overflow bottle) is 16 psi....

I'm not sure what it is for the closed system with the radiator cap on the overflow bottle. Open system has the radiator cap right on the radiator.

Click to expand...

The cap on the closed setup is 6 psi, giving you a max boiling pint of 235*F.

The plastic turtles can cause alot of problems, first it pressure not holding due to either a bad cap or warped bottle. If it looks like the original you might want to consider getting a replacment, you can get another plastic one or get a metal one, they are called 'surge tanks' and several companies sell them in varying sizes and shapes. The good part about those are is that they take normal pressure caps and actually have a provision for an overflow bottle.
There is nothing wrong with the closed systems, Ford has been using them for years, I just don't like the plastic pressure turtles.
If you do a search on 'surge tanks' you should get a hit I posted a few months ago with links to several suppliers as well as other suppliers others added to the posting.

235 degrees seems low, wow.

ya its got that closed system this is the first time i have ever seen one like this i think that the cap is lost i never thought that might cause a prob like that it will be the first thing i check i put the new thermostat in when i pulled a hose to get the a trany line that was leaking i lost all my water and never thought about it i just filled the tank and it didnt take any water out of it just got hot so i bought a flust kit to help me get the water in the system that was the best way me and my dad could think of not knowing any thing about this closed system and it worked well it ran about 200 with the new thermostat till i got stuck and had to work the motor and as soon as i his the power to it it got hot and boiled out the cap on the resavor looks like i should try a new cap then eh??????

You say the cap is lost? Well then yes, a new cap will help.

Assuming the bottle isnt cracked, when you put the new cap on use teflon tape around the tread and it will help ensure a tight seal. If you haver the time Id also flush the system with actual radiator flush, then when refilling use one gallon of concentrate, then one gallon of 50/50 and add a antirust additive. Did miracles on my '88 with a 195*F tstat.

If you have alot of time you could always pull the water pump and rent a pressure washer and spray out the block and head, then do what I said above.

And removing the rear coolant temp sensor is how to properly burp. Also the clossed systems are pressurized. So fill the coolant bottle until it over flows, put the cap on, burp the system, then refill the bottle of the missing coolant, warm up, let cool, add more, and youre done.

Not to highjack, but... how hot is too hot?
How hot (when overheated) can an engine go before something happens?
What are the symptoms if damage has occured.
Mine has been too hot a few times and I'm concerned.

Well when mine was new to me and hadnt been worked on for awhile it went deep into the red zone on the interstate. Let it cool and started back up with no problem, and 5,000miles later nothing bad, actually the engine seems to be much stronger after alot of the work I have done. Which will really be done for very little use since a stroker will be going in to replace all my hard work.

The coolant already has the necessary anti-rust chemicals in it......so it should be good enough.

You risk a leak if you use the chemical flush though, especially in the heater core. So take that risk! I think if you flush with the thermostat housing off and the water pump off, that's the best you can do.

ok cool by lost i ment lose my bad thanks ill have to get a new cap and give it a shot it dose not sound like any damage then i think mine boiled right at 212 or so with the lose cap and knowing how to burp it ill be gettin a lift and be goin to town in no time thanks

fordman125 said:

i have a new thermostat but my 88 jeep with the 4.0 will not stop boling the water out of its self is is common to lose a head gaskit and have that happen or should i look else where before doing all that work.

Click to expand...

Three possibilities...
First:
I have had thermostats that are new but bad. Take the thermostat and test it by hanging it by a wire and holding it in water on the stove and see if it opens. Your thermostat may still be bad blocking coolant flow to the radiator.

Second:
If you are overheating it is possibly because you are unable to thermally convect water properly through the motor to the radiator. Is your water pump moving liquid properly? You can turn your motor on with the radiator cap off and watch to see if your liquid starts to flow past the radiator opening before your engine overheats. I have seen water pumps running but with rotted, rusted tines in the pump they pumped little coolant.

Finally:
Hey... radiators go bad. An old Okie trick is to take a radiator off a vehicle, take off the cap, block the lower outlet with your hand, fill with water and then release the water out the bottom. If the water shoots more than 4 inches, your core is good. If less than 4 inches, your core is going or bad. From your description, I would bet you dollars to donuts your radiator core is chock full of crud. Also, get the most rows in your radiator you can. More flow, more convection and conduction. Cool physics in action. Good luck.

Is the upper radiator hose warm?

ya it gets warm

Well then we know the thermostat is at least working, but the radiator could still be clogged a bit.....when it's near overheating how is the pressure on both hoses?

Also take the cap off, rev the engine. Does the coolant get sucked in, and then pour over when you let off of the throttle?