50.Cal

94 grand 4.0. When I drive about 15 to 20 miles or more my temp stays around the middle and sometimes 3/4. When I stop im shooting out coolant, guy before me took off the over flow tank. Im going to get a new over flow tank but why is it doing thay every time? Maybe a new stat with a lower temp is needed? I flushed the radiator about a year ago and it wasnt that dirty.

extrashaky

Sounds like a blown head gasket. Get a combustion leak tester and test for the presence exhaust gases in your coolant.

CrazyMacaw

The pissing at stops will stop when you replace the overflow bucket, it's meant to flow back and forth as the temperature changes. (Assuming it's the open bucket line that's leaking out coolant)
Replacing the thermostat with a lower temp one is a band-aid at best, there's a reason it's running hot. You might check the thermostat to make sure it's the correct one for the vehicle and that it has been installed correctly. Also, check to make sure it has the correct radiator cap and that it's functioning correctly as well.

Like extrashaky said it could also be a blown head gasket.
If you had the overflow bucket it might reveal itself as a stream of air bubbles in the bucket. It might also present itself by turning your oil milky and a bit frothy looking.
A compression leak tester is the most accurate though.
Good Luck -

50.Cal

Thank you both. Ill start with the easy stuff first. If its the head gasket I think ill tackle it myself. There isnt any curve ***** I should watch out for is there? I know I have to remove the lifters which shouldnshouldnt be bad as long as I keep them in the correct order.

dave1123

I hope you mean the rockers because the lifters won't come out until you pull the head. I know some of the older jeeps use a pressurized overflow tank instead of a vented one. Which do you have? Is the pressure cap on the radiator? I may be thinking about the really old Cherokees (XJ) on this one. I do know that the closed system can be converted to the open system easy enough.

Anyhow, without the proper pressure in the system, once the coolant flow slows down, there will be hot spots in the engine that will boil and cause steam to bubble up thru the radiator into the overflow tank. Without the tank, it's going to spew out anywhere it can. Remember coolant will boil without any pressure at about 215*F. With 16 psi pressure, it goes up to around 260*F. Jeep systems are design to run between 195*F and 210*F.

If you do pull the head, use new bolts and make sure the bolt on the front driver's side has sealant on the threads or it will leak coolant. It also shouldn't be torqued over 100 lb/ft.

50.Cal

I did mean rockers, good call. The problem with my jeep is the guy I bought it from turned it Frankenstein. The jeep is a 94, he put a 98 engine in it and parts from multiple other cars. He workd at a wrecking yard. The cap us pressurized but i did just notice, in the box of parts he gave me, there is an old over flow tank. Not sure if its cracked. Ill put it on today and maybe get a new cap just because.

extrashaky

It's a little better than that. 50/50 mix of ethylene glycol and distilled water should boil around 223°F at sea level. Water alone has a boiling point of 212°, so the coolant wouldn't be doing much if it only raised the boiling point 3°.

50.Cal

Oh man, that makes sense. I was in a pinch a while ago and I put mostly water in the radiator. That was a dumb move on my part.

extrashaky

It's better than overheating. You do what you have to do. But once you're not in a pinch any more, it's a good idea to drain and refill with 50/50 mix (or 65% coolant/35% water if you're in a really cold climate).

It's also a good idea to use distilled water for the water portion of the mix, since tap water has minerals in it that like to deposit themselves in your radiator and heater core over time. A lot of these guys you see posting on here with no heat have scale from tap water minerals built up in their heater cores that has to be flushed out. Some of that could be avoided by not using tap water.

dave1123

Oh, you mean like my well water that's more liquid limestone than water? Yeah, I know it well! I buy premix now.

JimmyBo1313

Check your radiator for air flow. Not much light was coming through this puppy! LOL