Overheating only with A/C on

[SC Rednek]

Hate to burst your bubble Iwannadie, but if you could reach 230* without venting steam everywhere then your old radiator cap was just fine.

Water turns to steam at 212* at normal atmospheric pressure (~15 psi). Higher pressure raises that boiling point, a 16lb cap will get you to about 250*. So if you could reach 230* without all your coolant turning to steam then you still had pressure.


I'm going to say your real problem is it's a jeep. The cooling systems just aren't all that great in 110* heat without upgrading, and your A/C just raises the temperature too much. Back when I had A/C, I could never run it when it was that hot.

Has anyone ever tried moving the A/C condensor to behind the radiator? Seems to me that it would reduce the efficiency of the A/C but would let the cooler air pass through the radiator first. Don't know if it's even possible.

 

[iwannadie]

Hate to burst your bubble Iwannadie, but if you could reach 230* without venting steam everywhere then your old radiator cap was just fine.

Water turns to steam at 212* at normal atmospheric pressure (~15 psi). Higher pressure raises that boiling point, a 16lb cap will get you to about 250*. So if you could reach 230* without all your coolant turning to steam then you still had pressure.

Well as I said I didn't have high hopes but nothing changed except the cap and ambient temperature being a little better. We'll see, I may be curious enough to just go for a drive right now but it's only 101* outside.

 

[iwannadie]

Another drive today and it was 102* in stop and go traffic for a while and no signs of over heating. It looks like it was the cap, maybe I was venting steam and just didn't see it, I consider myself pretty observant so who knows. Maybe the HD fan clutch was pushing enough air that it was breaking up the steam enough to make it hard to see.

I am again not holding my hopes high until it gets over 115* and I have no over heating but in the mean time I am living it up with the A/C blasting.

 

[87manche]

Hate to burst your bubble Iwannadie, but if you could reach 230* without venting steam everywhere then your old radiator cap was just fine.

Water turns to steam at 212* at normal atmospheric pressure (~15 psi). Higher pressure raises that boiling point, a 16lb cap will get you to about 250*. So if you could reach 230* without all your coolant turning to steam then you still had pressure.

you forgot to figure that ethylene glycol raises the boiling point.

It is possible that your cap was bad and it was venting into the overflow bottle. When it vented into there the steam would condense back into fluid because of the existing coolant in there. It's easy enough to miss the overflow bottle puking when you're going down the road.

 

[Crawler]

I wonder if you could run the heater hoses through the a/c condenser...
with the heater valve you could even control the flow from inside the cab...

:jester:

 

[ehall]

you'd only have heat when the A/C was running...

 

[SC Rednek]

you forgot to figure that ethylene glycol raises the boiling point.

Excellent point, forgot about that. What mixture are you running? In the desert probably should only be running 30/70, if that (I'm using almost pure water in all my vehicles since it's summer, I'll drain some and add antifreeze when it starts to cool off), so about 220* boiling point. 50/50 is 225*. But subtract 2* for altitude of phoenix.

But even with a new radiator cap I'd think it'd still be reaching the same coolant temperatures, if not higher because it wouldn't be venting off as steam (keeping the block cooler but the coolant hotter).

 

[Craigabooey]

I am having the same problem with my 97 XJ. Everything is stock and I am just driving back n forth to work. When its a hot day out, the temp guage will rise to 230 then I hear a beep and the check guages light will come on. I just flushed the coolant recently but it didnt help.

 

[87manche]

I am having the same problem with my 97 XJ. Everything is stock and I am just driving back n forth to work. When its a hot day out, the temp guage will rise to 230 then I hear a beep and the check guages light will come on. I just flushed the coolant recently but it didnt help.

has the radiator ever been replaced? it's 14 years old, it's time to seriously consider doing a new cooling system.

I dropped new radiaotr, water pump, thermostat housing , thermostat and hoses in my junk and kissed all of my cooling problems goodbye. I even tok off the electric fan tat I added way back when with no problems, my junk never had a factory E-Fan anyway.

SOmehting else to check that just popped into my mind, the thermostat housing. I coul never figure out why I couldn't keep pressure in my closed cooling system. I replaced bottles/caps, hoses just about everything. Then I took the thermostat housing off and one of the ears fell off in my hand. From the amount of rust there was in the crack it's been that way a long time and was likely the source of problems for a long time too. A new thermostat housing was less than $20. Something to think about.

 

[PRYAPSM]

Another drive today and it was 102* in stop and go traffic for a while and no signs of over heating. It looks like it was the cap, maybe I was venting steam and just didn't see it, I consider myself pretty observant so who knows. Maybe the HD fan clutch was pushing enough air that it was breaking up the steam enough to make it hard to see.

I am again not holding my hopes high until it gets over 115* and I have no over heating but in the mean time I am living it up with the A/C blasting.

Hows is your jeep running? Still running hot?

 

[LYKOS]

On this subject...

Mine does this too. But my fan doesn't come on with the AC. It comes on at around the 220* mark as it should but not with the AC.

How does one diagnose this problem?

 

[hubs97xj]

The 99-01(?) won't run the fan with the compressor; only when the PCM sees ~220*.

 

[LYKOS]

The 99-01(?) won't run the fan with the compressor; only when the PCM sees ~220*.

Well that was an easy diagnosis. LOL

Riddle me this, sorry for the hijack, somewhere I've read of a trick to make the Efan come on at a lower temp. Something about running a resistor inline?

Not going to do a bypass switch, I want it automatic. Any ideas?

 

[WB9YZU]

If you want a Modified Solution, you should post your question under Modified and stop hijacking this guy's thread.

 

[LYKOS]

If you want a Modified Solution, you should post your question under Modified and stop hijacking this guy's thread.

Sorry DUDE.

No need to get butthurt about it.

 

[scottmcneal]

Sorry DUDE.

No need to get butthurt about it.

:cheers: