Temp goes up, when ac goes on

**SR71** · 08-24-2007, 06:25 PM

Okay guys, just like the title says. It's nothing drastic, but it's enough to make me want to take care of it before whatever it is gets worse. 98 T/A w/ 108k miles on the clock. The t-stat was changed about 20k miles ago and new coolant added then. Water pump changed about 35 thousand miles ago. Fans turn on okay because when i sit in my car at work sometimes about 10-15min with the ac on and it never overheats, so i know the fans are turning on and the tstat is opening. It's only when i'm driving to work when it "creeps" up. Maybe the dexcool needs to be flushed out? I checked the radiator for cool spots and it's warm all over. Sprayed it off, to no avail. Any tips would be appreciated, thanks.

Oh yeah, i'm in hot ass florida for my first summer too...came from B.R., Louisiana -- much hotter here though.

**LS2Tuner** · 08-24-2007, 11:26 PM

I'm in the Valley of HEAT...... How old is the rad. cap?
Also when you say the fans working is there a speed change when the A/C is turned on?
If not than ther is a problem.
Also are you going off the stock guage?
If so do you have access to any type of handheld scanner that reads live pids? If you do check that with the scan tool pluged in to see if just your guage is off.
It is almost 10 years old....... Stock sending unit too......?
I've seen them as far as 20* off.

**SR71** · 08-25-2007, 08:54 AM

I thought about the cap. Maybe going bad possibly? Yeah i am going off the stock gauge but i didn't think of the sending unit. Where is it located? Don't have a handheld to check it out though. Will try to change the cap and see if that helps. Thanks man.

**LS2Tuner** · 08-25-2007, 09:07 AM

If I remember correctly it's on the drivers head..... I think. I haven't done work like that on F bodys for years now.
Do any friends have a temp gun you could use to shoot the rad hose and radiator itself when she is "hot"?
Each pound of pressure lost makes like a 6or7 degree decrease in boiling temp.

**SR71** · 08-25-2007, 09:12 AM

Hmm, learning something new everyday. I just moved to Tampa a few months ago so i don't have all the "access" i had back home. Back in B.R., about 10 f-bodys and two mustangs would come running if i needed help. On my own now. Has to be out of the cap, sender, fluid. Everything else has been replaced. I read somewhere that it's good to replace the cap every few years or so. I'll try the cap and flush.

**B34M3R** · 08-26-2007, 08:55 PM

I think you guys are misdiagnosing this entirely.

Turning on your AC actually creates more heat for your car to be rid of, so the gauge/SU being inacurate is a non-issue. And the cap not holding pressure isn't likely to be causing such an effect either, since hes not really overheating, he wouldn't be reaching the boiling point, reduced or not. And if it was THAT shot, you'd be running through the coolant.

The problem seems to be with the rad itself not evacuating the heat fast enough to keep up with the extra heat from the AC. Now if there is one thing we have in freakin abundance in FL its BUGS. Oh, and tiny road debris from all the construction going on everywhere. Have you pressure washed your radiator ITSELF since love bug season? Get down there and take a good look at the front of your rad... a combination of bugs splattered all over, and your fins being bent from all the effing pebbles 'n shit thats on the roads down here would reduce your cooling effecency a ton. Which would cause exactly the effect you have described.