The girlfriend has been driving my 99 cherokee sport the last couple days and as she was headed to the house last night the temperature gauge shot to 250 but being smart as she is she killed it right after. When she did the relief on the radiator let all the coolent out or atleast what I'm assuming as of now. Took me and her dad an hour to get it 6 miles to the house. Looks like I have a little project on my hands. Any ideas? Thinking maybe the thermostat is stuck closed. It'll run for a few then gets hot and you have to kill it.

Needless to say she w as pretty pissed when she called me on the side the road.lol

 

Yup, replace the thermostat and see what happens. Cheapest, easiest place to start when you have and overheat and boil-over.

 

What maintenance has been done? Girls like driving reliable vehicles (their dads like reliable vehicles also, tells dad something about his daughters boyfriend, LOL).

 

What is the history of ALL cooling system maintenance?

Along with thermostat, a fresh radiator, radiator cap, water pump, and hoses is money well spent if you plan on keeping the vehicle.

Dollar for dollar, there is no better money spent, than that spent on cooling system maintenance. These systems are too often ignored until problematic.

Good luck!

 

Youre right...BUT, if this is an isolated incident and he wants a fix NOW, the best thing to do is START with the thermostat. Fix that, start her up and see what happens. Might be your only problem.....might not, but its the best place to start.

 

Update. Flushed the radiator and a new therm and still over heating. Thinking possible water pump problem?

As far as up to the cooling system I have no idea. None that I know of. It will be getting an over haul after I get back fronm the beach in a couple weeks. Not driving it down but for now I just need it running.

Yes she does like driving something that is reliable.lol I'm in the mix of just redoing a lot oif things oin the jeep now but its as I have the money. So this problem is first.lol

Water pump next possible thing? Thanks

 

It might not be the best way to go about it, but this is the way Ive always trouble-shooted (yes, I know) vehicles:

Overheat and a boil over: Change the thermo and flush/fill, see what happens.

No change, change the waterpump & see what happens. Worst comes to worst youre spending small cash (A lifetime waterpump from NAPA is under $50 bucks) and getting a new waterpump, thermostat and flushing out the system and putting new coolant into it. Things that should be done at this stage anyway, along with new hoses.

Ive never had a code reader, etc., and this is the way I grew up fixing vehicles. Now, back in the day we didnt have all the computers, sensors, etc., so you might have a sensor or something gone. I dont know squat about sensors in our XJ's (Im learning from this site though) so maybe someone here will chime in and say its a sensor, but for me personally Id move on to the waterpump and see what happens. There are only so many things that'll cause a major overheat.

Did you fill and burp the coolant correctly so its actually full?

Do you have any signs of a blown head gasket (coolant in oil, oil in coolant?)

 

First, make sure you don't have a leak, most garages will have a radiator pressure tester, use one they work great in finding cooling system problems. Then get a meat thermometer and check to make sure the thermostat is opening at the correct temp and that it is opening completely. Next, check that the fan clutch is working properly. Last, make sure the electric fan is coming on when it should come on.

 

Same thing happened to me when my water pump blew out last year. I replaced the water pump, thermostat, radiator, and fan clutch. The temp gauge still read up in the 230-240 range. I gave up and took it to my mechanic, and he figured out (after putting a temp gun on it) the temp. sender unit (the one on the back of the engine in my '96) was reading way too high. It apparently got damaged when the temp shot up while I was driving. He replaced that and found that the engine was actually running around 200.

 

Start it up and see if both heater hoses are getting hot, if one is cold and the other one is hot your heater core is plugged. If its the heater core just take a pipe and join the 2 hoses together until you can get it fixed.

 

check the fan clutch my rubicons fan clutch went out but when i was going down the road it went back to normal. thats how i knew what it was

 

If the T-stat is now good and you flushed the radiator and the entire cooling system of any possible blockages.....AND ALL TRAPPED AIR BUBBLES, then the only other thing it could be is a bad water pump. Water Pumps usually start leaking out of the weep hole when they go bad, though. It is sometimes hard to see the water leaking from a water pump weep hole because the fan usually blows it away as it comes out.

 

Update, after a couple hours of working last night all I have is more head scratching from me and my cousins. didn't replace the water pump but now have the anti freeze shooting out of the resivor(sp?) Instead.

Still probly will replace water pump. Had thiought oif the fan clutch and going to try that tonight it had gotten to dark and late last night to work any longer.

Wahoo both hoses do get hot.

Thanks for all the help so far.

 

Forgot to say that it don't look like a blown head gasket oil looks fine.

 

Make sure both hoses for the heater core and radiator are getting hot!