[bamato]

So a while ago I posted a question here about my yj runnin hot. Well the problem still exists, and has become more perplexing than ever. I changed the thermostat and tightened the belt, and flushed the system. And what do ya know? It ran fine for about a week, then started running like crap again. It runs at like 230-240. It never gets hot enough to overheat (yet, knock on wood) but I just dont like having it run that hot. Short of replcing my water pump, which I did just only 2 years ago, I dont know what else to do. There's is a black dust all over the front of my engine block, which leads me to believe that the belt is shredding itself on something. But what I can't figure out. And besides there being a very very slight glaze on the back of the belt, it seems in pretty good condition. I'm basically clueless, and would like any help someone can offer.... Thanks everyone

[domdan69]

I had to replace my radiator. Even after flushing, with the chemicals, it was so built up in there and the flakes of deposits wouldnt all come out. Since then all is well.
Got my replacement at a privately owned pars place (not a napa or autozone) for about 140$. Autozone wanted twice that.

[bamato]

My radiator was replaced at the same time as the water pump. And water flows through it very easily. Wish it was that easy.

[geabaldyvx]

Bad gauge or Sensor maybe? Does it seem to get to full temp overly quick? You said it doesn't overheat but are you getting fluid dumping from the pressure cap?

[bamato]

I'm starting to think its the sensor. Every once in a while when the car is warming up the gauge will jump suddenly then lower back down. I know it's got to be runnin hot because the jeep runs like crappola when its hot. And yeah it does heat up pretty quickly. As for the pressure cap I don't think there is fluid dumping. I'm sure it's probably dumping to the resovoir tank when it needs to, but its not spilling everywhere if thats what you mean. How hard is it to change the water pump? And is it a PIA? Cause I don't want to have to do it, spend the money and time, and that not be the problem ya know? Diagnosing cooling systems is quite difficult.

[goatboy]

Naw, I'm thinkin' you've got a cracked head, or maaaayybbbbeee a bad head gasket, more like the head...when I had the headwork done on my 258, the shop said that it's pretty common for them to crack due to heat...do a leakdown test on your cylinders, although for higher mileage vehicles, that's not an end all to beat all test due to other factors... I can just about guarantee you it ain't the water pump or radiator, if you think it's the sending unit, replace it and see what happens, but bottom line is that you're probably gonna yank the head eventually. When a head cracks, the problem can come and go, as you describe...good luck

[EABiker]

I've never seen a water pump cause overheating unless it was leaking and allowing the pressure to escape. Remove the belts and see if the pump turns relatively easy by hand; if so, the pump itself is not causing the belt to slip. Next, check the fan clutch to make sure it is not freewheeling. Excessive advanced timing, or a lean mixture can also cause operating temps to rise.

[bamato]

Well I replaced the crank fan with an electric one. Goatboy, what exactly does a leakdown test entitle? Also, it runs fairly close to normal operating temp in the morning when its cool out. It just seems unusual that a dlight temp decrease in the outside air would really matter that much. Why do I drive a jeep again?

[wolf3902]

Just throwing this out there cause it happened to me. But check the fan clutch. They can go bad and cause that.

[bamato]

No clutch, electric fan

[goatboy]

Leakdown test should be outlined in yer shop manual...it's when you pressure up the cylinders with compressed air and see how long it takes for the air pressure to leak down to a certain point...kits are available thru KD Tool etc...you might be able to rent the tool at yer local auto parts store... when you have a leak in the cylinder, either via burnt valve, a cracked head, bad head gasket, worn rings, what have you, the cylinder in question won't maintain air pressure... and theres no such thing as a cylinder being able to maintain pressure forever, it's just the rate at which it leaks is the deal...never had occasion to do it myself, never needed to, but I'm somewhat familiar with the process...there might be someone else out there that might have some more info, or who might think I'm fulla hogwash!!!

I don't think the air temperature had anything to do with yer deal, frankly...just a coincidence...

[yooperlou]

Just want to throw this in because it happened to me. Did everything you have done except I never replaced the radiator cap because it was less than a year old. After replacing the cap everything ran normal. Just a thought but you probably already checked that.

[bamato]

another peculiar fact is that it gets hotter at freeway speeds..... id figure all the extra air flow would cool it off ya know?

[483Fitter]

radiator is probably bad, ive gone through a few in the yj. Around town it was fine but once i got a little speed going it would get hot. Get a 3 row off ebay.

[UncleWaldo]

Maybe the elecric fan is the problem?? I tried an electric fan on my ZJ when the clutch fan went bad. The electric fan did just fine around town but at highway speeds the jeep ran hot. I spent the money on the new clutch fan. No more problem.