Overheating with A/C

[menos]

I'm having a problem with my '91 overheating. It's only started now that the temps here are hitting 100+.

Symptoms-
Temp will start creeping up above 230 on both the highway and city streets. Turning off the A/C will yield a reduction in temp. While on city streets this reduction is pretty gradual but on the highway it is pretty pronounced.

The truck has a new 3 row CSF radiator, new water pump, all new hoses, new fan clutch, new dealer thermostat.

I do not notice an unusual drain on the power of the motor when the A/C kicks on, and the A/C seems to be cooling normally.

The higher temps only show up if I've been on the road for more than 30 minutes. Trips shorter than that do not result in higher than normal temps.

At no point do I notice any loss of power, so I'm thinking that the cat might not be the problem.

Should I be focused on the A/C compressor or could it be that that is enough load to push a system running on the edge over it?
Could there be another source of the excess heat? Tranny maybe? If I rig up a temp sensor for the tranny where should I mount it?

[mjma]

check to see that your electric fan kicks on when the AC compressor kicks on. Otherwise it may just be that your cooling system can just barely do it's job without the condensor working. Once the condensor starts transfering heat, the radiator can't cool the coolant down enough. This is when the fan should kick in to help pull more air....

[stewie]

x2 on checking the electric fan. also, did you completely change the coolant when you did the radiator? how is your coolant level, and how does the coolant look? does your cooling system need to be burped? my 95 would come close to overheating after i did the waterpump and again with a CSF 3 core. it turns out that it needed to be burped. i lifted the red safety lever on my rad cap slightly and a bunch of air went into the resevor tank. after all the air was out, it was cooling much better.also, have you hosed out your ac condensor in front of the radiator? if there is even just a little bit of debris in it, it could severly affect cooling capabilities. be sure to just use a garden hose, no pressure attatchements.hthstewie

[Gritts]

I think the 91, like my 90 has a closed coolant system. Assuming you haven't converted yours to an open system, you may have air in the cooling system. After driving the Jeep let the engine cool down for at least 20 minutes and then CAREFULLY burp the system by opening the cap on the surge tank (just a few turns) to let out the air. Retighten cap. You may have to do this procedure more than once.

Oops, didn't see Stewies post.

[Slo-Sho]

No mention of a new radiator cap?

[89CherokeePioneer]

The 91 has a conventional radiator cap-in the sense that it's open.

May want to burp, hows the coolant looking? Turn the A/C on and see that the electric rad fan is spinning-it probably is or A/C wouldn't be all that effective.

[menos]

Electric fan control is bypassed and is always on. All new coolant at 45/55 mix. New radiator cap. Open system. It is burped. I am frustrated

[Slo-Sho]

Is the belt tight? Look at the serp belt when the A/C kicks on and see if it's loose.

[Smittty9785]

Originally Posted by Slo-Sho

Is the belt tight? Look at the serp belt when the A/C kicks on and see if it's loose.

you from SLO by any chance?

[igotanxj]

Theres gotta be an air pocket in there somewhere, its the only think it could be unless you have some faulty part. The air pockets don't always work their way to the front top of the radiator. Ask around if someone you know has an air lift to put the cooling system into a vacuum before its filled, its saved my behind more than a few times. You have to completely drain it to work best tho.

http://www.brandsplace.com/0246-uv-550000.html

[jpcherokeekid]

chuck the a/c condensor, convert compressor over to oba, and remove doors. thats what i did.

[Ecomike]

Originally Posted by 89CherokeePioneer

The 91 has a conventional radiator cap-in the sense that it's open.

May want to burp, hows the coolant looking? Turn the A/C on and see that the electric rad fan is spinning-it probably is or A/C wouldn't be all that effective.

I would replace the radiator cap next (even if it is new replace it, get one that does not have the lever bleed valve on it!!!), at least 16 lbs, maybe even try a 17 or 18 lb cap, and make sure the E fan is not cutting out only durring the overheating episodes. maybe the fan or relay cuts out after a certain time, overloaded overheated electrical wire connection perhaps!!!!!!

Check for some partial restriction in the exhaust, or an engine running too lean. Exhaust leak heating the tranny, tranny fluid and eventually the radiator?

Also make sure you have the AC on Max, not on normal, and make sure the damper is closed to outside air and that the blend door is not letting the cool air reheat some from the heater core. Any of those can add overheating loads to the system.

[menos]

Well, after the temps here have gone up past 100 I've noticed that the problem is even worse than before. Having the A/C on makes the engine temps go up faster but it is still overheating without the A/C on. Today I ran home from work with the A/C off and the engine temps got up to 230 or so.

I've got a transmission cooler and temp gauge that should be here soon and I'll see if the cooler makes any difference. If that doesn't help I'm gonna try hood vents, but after that I'm lost.

[my2monkeys]

Don't forget your basics, like the boys say. Check bott. hose for spring inside, check pump flow at fast idle, and feel rad. hose when hot and make sure t-stat ain't malfunctioning.

[1familyxj]

I am having a similar problem. New CSF 3 core radiator, new radiator cap, new 180 t stat, New Flow Kooler Waterpump, and new engine (less than 200 miles on it). Mine overheats mostly in overdrive it seems. I have a high flow t stat and housing on order. Not trying to highjack your thread I just didn't want to start a new one since our problems sound similar.