I have had the heater on the entire time. Air never got hot.

 

Went out this morning and both the radiator and expansion tank were low. Took about half a gallon to fill both. I didn't run it but I plan on checking again when I get home and try to flush the heater core through the outlet hose and then run it and re burb the system by leaving the rad cap off. Hoping that a lot of air has escaped letting it sit.

 

Did u say u installed a NEW rad cap?.....the rad cap is critical to an "open" cooling system like yours. U do not need to turn the heater controls on to "burp" the heater core....your '99 does not have a heater control valve....coolant flows thru the heater core (presuming it's not plugged) the moment the motor is started. As soon as coolant flow starts (motor started), air is pushed out of the core.

For several days, motor COLD, continue to remove the rad cap to check coolant level in the rad and check the coolant level in the bottle as well. Eventually the rad will get to the point that coolant level will remain at the very top, motor COLD. When coolant level in the rad remains at the very top, the system is fully "burped". If coolant does not remain at the very top of the rad after several days of checking, the rad cap is malfunctioning or there is a internal/external leak somewhere and leaking coolant is being replaced with air.

U MUST remove the rad cap, motor COLD, to see if the cooling system is taking care of itself (coolant returning from the bottle to the rad as the motor cools). If the coolant level is not at the very top of the rad, motor COLD, it ain't taking care of itself. Keep topping off the rad, motor COLD, 'til coolant level remains at the top of the rad.

 

That is what I plan on doing. Its my daughters jeep and she needs it back for work, I just don't want it overheating on her.


When the car is shut off after running, should the top radiator hose be hard as a rock like there is a ton of pressure in it? Kind of concerned me last night like something was plugged.

 

Yes......all of the rubber hoses will/should be rock hard ('til the motor cools off). It's a pressurized cooling system. Pressure is what raises the boiling point of the coolant and the correct pressure rad cap would be 15-16 psi. Each psi raises the boiling point 3 degrees. A 16 lb cap will raise the boiling point from 212 to 260.

Again, I can't stress enough the importance of a properly functioning rad cap.

 

Went home, level down a little bit. Pulled the Heater core outlet hose and ran water through it so it came out the inlet hose(Pulled from Tstat housing of course) When I pulled the inlet hose from the housing, nothing came out, normal? When I flushed the core water came right out Clear, then rusty red, then green. So I filled the outlet hose with water and put it back on quick, did the same with the inlet hose. When I get home in a few hours I will give it another whirl. Probably replace the Radiator cap too. Keeping my fingers crossed.

 

Got home started it up. Burped the system replacing coolant as I went, after about 10 minutes, no more bubbles, both heater hoses warm and heat out of the heater vents. Take it for a test drive and it stays around 210, maybe a little lower. Drive to my daughter about 12 miles away about 65-70mph on the freeway. The temp creeped up to about 215-220 but seemed to be ok. Keep in mind I had the heater running the whole time.
Anyway, three hours later, txt from my daughter, almost overheated after 3 miles. WTF!!! She said it happened at a stop light and pulled over to let it cool for 20 minutes, temp went back to 210-220 and she made it home. She did say that she was not running the heater at all when she popped the hood, the upper radiator hose sounded like it was sizzling and maybe was seeping, but no coolant under the Jeep. I am getting really confused!!! To me all signs are pointing at another head gasket. I told her to check the coolant in the morning and then fill it if needed and maybe take it for a drive close to home, but keep the heater going. Any ideas?

 

Other than the water pump and t-stat, what cooling system components have been replaced? A new radiator and fan clutch would just about complete a total cooling system overhaul.....the major cooling components anyway.

 

That's about it. I told her to take it in and get the head gasket tested at my buddy's shop before I throw any more money at it. The fan was working fine when it was sitting in the driveway. the electric fan was kicking on and the other fan was blowing air as it should. The fact that it didn't overheat on me because I was running the heater and circulating more coolant leads me to believe it's the head gasket. Hope its not, already replaced one 2 years ago.

 

Have you tested the fan clutch. Just because the fan spins doesn't mean it works. The fan always spins with be engine but until the clutch engages its "useless" in a sense. Also, what coolant are you using. What brand tstat is in there. What kind of radiator cap. We need more info to help you further if it isn't the gasket

 

About $135 gets u a new fan clutch AND new radiator. The XJ cooling system is not something u want to take lightly. If it's running hot this time of year, you.....not your daughter, need to take seriously replacing all of the cooling system components.

As stated, just because the fan spins doesn't mean squat. Is the fan shroud intact and in place?

 

Fan shroud is in place. And yes I am taking this seriously. I am not going to get into family issues but she is lucky that I am even around after all she has done but that is beside the point. Basically an New Autozone Tstat and Radiator Cap ( Could not find a Stant yesterday) but I will probly replace those along with the radiator and fan clutch once she gets it tested. Not sure if the radiator has ever been replaced. I really do appreciate all the help with suggestions. Suggestion on radiator? I will probably get a gates fan clutch since I have always had good luck with those. The reason I don't want to throw another $200 at it before she gets it checked is because if the Head Gasket is blown we are getting rid of it. We planned on selling it soon anyway. Someone can turn it into something. I know its worth $1000 to the right person and yes I will disclose everything.

 

AutoZone and others sell the radiator for about $100 and the fan clutch for about $35.

 

Fan clutch test is easy. Drive til warm for a bit. Stop engine. Spin fan by hand. It should not spin easily. As for the radiator, advanced auto had one and with coupon codes you can save a good amount of money. I just bought the upper, lower hoses, radiator and coolant or $108. Save $50 on coupons

 

All fan clutches gradually loose performance starting day one of use and over time/miles just get weaker. Does the spin test tell u the clutch is at 100% peak performance?......installing a new clutch does. $35 for a new one eliminates the guessing as to how well the fan clutch is performing.