Overheating... Only thing I hate about xj's

okay guys. I love my cherokee.. this is my second one. This is a 96 4door 4.0 4.5" rubi lift bilstein shocks, 4.11's, 33's, and all kinds of fun stuff.

BUT HERE IS MY ISSUE

Usually when I buy a used vehicle the first thing I replace is the temp sending unit. However for some reason I didn't replace the sending unit on this one until about 2 months ago... The second I replaced the sending unit it said I was overheating. Now let me say this 4.0 has 139k miles and dummy guages. The light doesnt just pop on like a bad signal. It slowly comes on and gets brighter as a drive. I went though and did the usual replacing of parts because I figured at 139k miles better to spend 200 and get all new stuff thats gonna last. So I did a flowkooler high flow water pump. A hesco high flow thermostat housing and new thermostat. The radiator is a 2 core aluminum that I installed not long after I bought the jeep because the radiator in it had a small leak.

I still gradually overheat even after 2 radiator flushes, new fluid, and new parts. There is no coolant in the oil so I know my head gasket is okay, and I replaced the fan clutch. And the fan shroud

HERE IS THE ONLY THING THAT SEEMS WEIRD

NO pressure in my lower radiator hose. I can squeeze it and it feels like its all air. However I know its not because with the radiator cap off if I squeeze that lower radiator hose fluid comes out of the cap..... I really dont want to spend another 200 to take it to some mechanic. Can someone please help... the only thing I havent tried is is running the engine with no thermostat. I live in the palm springs area and it gets really hot here so I can get away with it for a while.

HOW I KNOW THE WATER PUMP AND THERMOSTAT WORK PROPERLY

I did a thermostat flush after all those new parts were installed and to test the system I put a water hose in my radiator and removed the drain plug. I turned on the hose and watched the water come out. out came soapy sudsy water you can expect from the flush that is in the radiator. I let the hose run until the water was clear and flowing at the same rate the hose was putting out. I started the jeep and let it warm up... all while the hose was running. Once the jeep warmed up after about 4-6 min the thermostat opened and out from the bottom of my radiator was no long clear water flowing at the rate of the hose, but a soapy sudsy, hot steaming water that was clearly from the block. The water pressure come out from the drain plug would clearly spray faster as the water pump pushed the fluid through the system. I let that happen a minute or two to clear all soapy radiator flush out of the system. then I shut off the motor and let all water drain out. Once the water drained out I add plenty of 50/50 premix from autozone until I would not add any more. I then restarted the engine and added more( about a gallon and a half, which doesnt seem like much). I drove it a bit then parked and tried to burp the system a bit which allowed for about another half a gallon of mix... Roughly two gallons for the whole system. However I can drive farther now than I could before the overheating light starts to come on. A distance of about 8 min or 6-10 miles. Before all the parts were replaced with the new sensor I could drive 2 miles and I would start turning on. Someone please help me!!!!!

did you perhaps inadvertantly get a sending unit for a gauge when you have an idiot light vehicle?

I threw parts at mine.... the BTW brand sending unit(s) were both bad... When I spent the $40.00, the MOPAR read correct and I was never overheating....which I knew, since my non-contact thermometer on the rad and housing was where it should be. 92XJ.

I ordered a new temp sending that says specifically for dummy lights. I ordered it from rock auto. It should be here in 2 days

You say that you can squeeze the lower rad hose?

I thought the lower rad hose has a wire spring inside to stop it from collapsing, went the engine heats up?

lqguitarguy said:

.........The second I replaced the sending unit it said I was overheating. Now let me say this 4.0 has 139k miles and dummy guages. The light doesnt just pop on like a bad signal. It slowly comes on and gets brighter as a drive........ However I can drive farther now than I could before the overheating light starts to come on. A distance of about 8 min or 6-10 miles. Before all the parts were replaced with the new sensor I could drive 2 miles and I would start turning on. Someone please help me!!!!!

Click to expand...

I agree you have the wrong temp sender (for the gauge),
instead of for the light equipped. I don't think it's actually
overheating, and the new correct sender should work
properly.

You definitely have the wrong sending unit. The light shouldn't start dim then get brighter. It should just switch on if you were over heating.

on the lower hose(and upper hose for this matter) if the engine is cold and teh radiator cap is on the hoses will still be soft as there is no pressure. Once the engine is up to temp then the hoses should be firm. If not I would replace the radiator cap and check for leaks.

Talyn said:

You definitely have the wrong sending unit. The light shouldn't start dim then get brighter. It should just switch on if you were over heating.

on the lower hose(and upper hose for this matter) if the engine is cold and teh radiator cap is on the hoses will still be soft as there is no pressure. Once the engine is up to temp then the hoses should be firm. If not I would replace the radiator cap and check for leaks.

Click to expand...

The top radiator hose should get hard when the engine reaches normal operating temperature with a good radiator cap. The bottom hose not so hard since this is the suction side of the water pump,...thus the coil spring inserted into the hose to keep it from collapsing under high RPM.

The whole system will be pressurized so the lower hose should be hard as well. Especially at idle and/or with the engine off (hot).

Hey everyone thank you for the input. The new sensor came in yesterday and everything works fine. SOOOO FOR THOSE WHO HAVE DUMMY GUAGES AKA IDIOT LIGHTS DO NOT USE THE TEMPERATURE SENDING UNIT FROM AUTOZONE. ORDER FROM ROCKAUTO.COM OR WHEREVER JUST MAKE SURE IT SAYS FOR LIGHTS AND NOT FOR GUAGES. Also on a side note I have a perfectly good waterpump that I pulled and replaced with a flowkooler so If anyone wants it I am in need of a new steering stabilizer and would like to trade!!!!

I always like an easy fix.