A/C - Overheating woes...

[Saurian]

So Jeepy's air conditioning runs great, blowing ice cold and making me happy... But when I run the a/c, the temperature enters the danger zone, and my check gauges light comes on... Now, under normal operating, it's running hot, about 220, never used to go a lick above 210... The electric fan is switching on and running when it gets up there, and I cleaned the radiator, ran water through, over, and in it till it came out clear...

My theories...

Something, somewhere, in the system is not working properly, causing it to run hot.

The radiator is still muddy, and I just didn't clean it well enough...

Something happened to the coolant when it boiled, and now it is not as effective, a coolant flush, and I'll be right as rain...

What do you all think?

[90Xjay]

I think when you recently went muddin' your radiator fins are not totally clear of the mud. The mud will insulate heat and not let the radiator exchage it properly, you know that whole thermodynamics thing..

Clean the raditator fins good, also in the radiator, try straight water for a while, it runs cooler than water/glycol mixed.

Or, try not running a 50/50 mix in the heat, run maybe 70 water 30 glycol

Just my thoughts...........no charge of course

[Saurian]

I am skeptical of the radiator, only because I must have flushed gallons and gallons of water through it since I was at the Mounds...

On the other hand, though, Mounds mud is a fine powdery sand-mud, gets into everything, and damages anything it touches, seems like...

So it could still be a little cloggy... Maybe if I get the time, I'll just pull it and spray it out properly, sure I could get it better if not in the Jeep...

[graewulf]

could be as simple as a stuck t-stat too...

[Saurian]

Now, is the thermostat the little thing with the wires going into it, that screws in to the thingamabob where all the hoses go, or is it the thing inside the thingamabob where all the hoses go? I noticed that when I unplug the wires, it throws a Check Engine light, and the electric fan runs nonstop.

[XJNick]

Hi,

So Jeepy's air conditioning runs great, blowing ice cold and making me happy... But when I run the a/c, the temperature enters the danger zone, and my check gauges light comes on... Now, under normal operating, it's running hot, about 220, never used to go a lick above 210...

If you say the Jeep has been running hotter than 210 lately without the A/C on, then the problem is a result of your cooling system doing a poor job to begin with. Turning on the A/C just makes things worse as you've got the now hot A/C condensor sitting right in front of the radiator, and the same fans trying to cool both it and the hotter-than-normal radiator.

Maybe the radiator is full of mud as you say, or perhaps you have a bad thermostat and/or air in the cooling system?

-Nick

[Saurian]

Still problems...

The radiator is clean; there is no mud in it whatsoever, I could read a book through it if need be... I replaced the thermostat yesterday, and she was running fine, but then began leaking from around the thermostat housing gasket. It began to overheat again (guessing air was entering through gap). I re-replaced the gasket, making sure this time to scrape well... No leaky. But still running hot, runs at 220? on freeway with air on, shoots up to 250 as soon as I get off freeway, goes back down to 225? within 30 seconds when I put the heat on, then go with only cold vent, no air...

I don't know what shape the coolant is in right now, with all the topoffs and such, but it's not looking a particularly brilliant green, and if it was sucking the sludge from the bottom of my reserve tank, that would be a very very bad thing, I imagine. Based on this info, the only things I have left are air in the system, or bad coolant. How do I get air out of the system, and/or, how do I do a coolant flush on the XJ?

[TwistedCopper]

For your next step, I would flush and refill the radiator.

You have a new thermostat, the system is full, and I'm assuming you verified the water pump is pumping.

I suppose it's possible that the newer style coolant did not react well form excessive overheating. If it is dirty or damaged it will not do it's job properly and could allow corrosion to occur in addition to not keeping the motor in proper operating temperature.

How is the motor performing strength wise and on gas economy? One other possibility is you have engine trouble causing it to run hotter than the cooling system can compensate for. I hope you didn't damage it when you soaked it

[Saurian]

Jeepy is running happily and well, no noticeable engine degradation of any kind...

I think my next step is to pull the t-stat, and see how it responds then. How does one do a coolant flush on the I-6?