overheating

[ninetysix-ex-jay]

If you said it ran fine with the thermostat out just try replacing it.

[Riot]

So my dad just took it out for over an hour, let it sit in the driveway for like half the time. Goes a bit above 210, thermostat opens, goes back down. Who wants to bet 10 dollars, I go to drive it today and it overheats?

[crosbike]

my brothers 5.2 zj was doing this. Would shoot up high then dive down to running temp and kept doing that. Replaced the water pump and its good to go. It could be that the water pump fins are gone so its not pulling coolant.

[Wide-J]

Definately swap the thermostat. If the cap is cool, it could be that the thermostat is closed causing the coolant in the block to heat up and spike. If its closed, it wont allow that hot coolant to excape out of the thermostat housing and go into the radiator where the cap would then get hot. Also, the lack of heat sounds like thermostat too. Yes you have hot coolant in the block, but the blocked/defective thermostat isnt allowing the coolant to make it to the heater core so you arent getting heat. My only concern is that brown sludge you were getting. Between the sludge in the coolant and the spikes in temp, there is always the option of a headgasket problem.

[ninetysix-ex-jay]

Does the coolant stay at the same level in the expansion tank or are you constantly replacing it? If its at the same level that would rule out the head gasket. If you are replacing it I'm not saying its a 100% the head gasket but its possible like Steve said.

[JustTorchIT]

hmmm i like this thread... sounds exactly like the problems i had with my jeep for the longest time.

my jeep had 92, 00 on it when i started having problems....

i think i figured everything out and it turned out that the previous owner put that fuckin stop leakshit in, because the radiator had a slow leak, and they ran strait water, so it fucked the thermostat and all the cores in the radiator. so the water was like brown sludge, and the water pump barely had any fins left on it. so now a year later, and everything to do with cooling has been replaced, and i finally have almost green fluid running through my jeep.

i know i sound like a jack ass... but just keep flushing that thing, and id suggest even get a new radiator and water pump and thermostat. i probably flushed my jeep 20 times in the past year just trying to get all the shit out. ive gone through 3 radiators, and a couple thermostats a waterpump and lots of chemical flush shit... good luck to ya

[Riot]

At this point the thermostat appears to be opening because as it reaches slightly above 210 (which it didn't used to do) it ends up going back down to 210. I do have heat now, even last night when it overheated, which is why the plot thickened even further... Anyhow...The coolant was green all day today after last night's overheating, and that's about where we are now...

Green coolant.
Heat works.
Overheating.
Cool Radiator Cap.
I'll replace the thermostat this week. I need to find the money for a new one. Anyone know anywhere hiring? lol...

[xjeeper]

mcdonalds is hiring and a t-stat is only like $5. take both the upper and lower hoses off the radiator and put a garden hose in the top and just let it run through it until clear water comes out the bottom.

[88XJchief]

Maybe you put the thermostat in wrong.

[Riot]

I didn't put the thermostat in, my dad did it, and even assuming he made the mistake, the mechanic would have caught it. Or even someone else along the way..

[ninetysix-ex-jay]

So you put in a new thermostat?

[Riot]

Nah we washed the old one because it was all sludge.

[Dr. Thunder]

Decent chance that after you fixed it the first time and it overheated again there was an air pocket, now it has probably worked it's way out.

[Riot]

I'll try tonight I just don't wanna go to far from home.

[Riot]

It's not overheating, but it's running hotter than normal.
I haven't gotten around to trying anything yet due to my extremely busy schedule. ;]
Just throwing it out there.