Mikeythrash

I am not really sure what is going on with my xj it is a 96.i noticed my thermostat is all over the place.So I put coolant in since it was low.i used a entire bottle and what was left of the bottle I put in the overflow tank.after doing that and driving temp seemed fine.til i drove it a second time I gunned it and temp flew up.then it started to come back down a bit.i drove to a parking lot parked engine did not seem like it was overheating or even nearly as hot as the gauge said.went into the store and came back jeep wouldn't start.open the hood and the engine is hotter then it was before.keep it open let it cool and it finally starts unplug my coolant sensor I believe it is located in the right near then2 fans and my cooling fan comes on plug it back in and it goes off.i am sure I need a sensor and probably a thermostat.but where's all this coolant going from the overflow tank? The jeep runs really ruff and at idle it's even more ruff.could this be a gasket issue or water pump? I am not really sure what to do here.i just got this jeep about 2 months ago.and just started driving it recently.please help and answers will be great.

Battle

Overheating under load is usually a sign of a bad headgasket. Have you checked your oil cap for sludgy buildup? Do that.

You also could have built up air in the system if you recently replaced something in the coolant system. You might want to try and burp the coolant to make double sure.

PocketsEmpty

The coolant will burp itself with an open system. The cap handles it--No need to do anything fancy.

OP, pick up an infrared thermometer from Harbor Freight if you can (like 20 bucks I think), and point it at the thermostat housing when it happens. Verify gauge reading. If it's running rough, it could be your head gasket. When it's running, check out the exhaust for white smoke, or a coolant smell. Might be worth a compression test also.

Mikeythrash

About a week ago I checked the oil it was fine smelled it no coolant smell.my engine light is on and one of the codes that came up was a temp sensor code.and something about a vacuum leak.i have driven every day and for good amounts and I don't see how it would allow me to do all this driving especially on the highway it runs smooth.if it is a head gasket issue??? I have seen white smoke out of the exhaust but it's only like that when I first start it in the morning and it's cold all night then goes away but I thought that was normal.how much does this kinda thing cost to replace the head gasket ?

PocketsEmpty

If you have a code for coolant temp sensor, start there. Get a new sensor. That will also affect when the e-fan comes on. If that doesn't solve your issues, then look around for a vacuum leak. Listen for a hissing sound when engine is running. Also, do your dash vents work properly? Another sign of a vacuum leak is when the vents go to defrost and won't switch to dash or floor.

As far as head gasket replacement (if that's even the issue), shops can charge anywhere from 500-2500. It's a crapshoot, basically. If you're somewhat mechanically inclined, you could do it yourself with the right tools and research.

Mikeythrash

I have the sensor problem and a head gasket is blown.took it to a mechanic today I am gonna have someone fix it for under 800$ it is a 96 very clean and only has 98,000 miles on it.i really don't wanna see it not be fixed when I just recently got it and did not do even close to what I want done.i know the e fan doesn't come on when it's supposed to cause I have to keep the hood open after I park cause if not the engine gets super hot