Overheats with A/C on. Without A/C, can drive forever.

[mechjames]

Title pretty much explains it. For the past couple weeks, if I use the a/c in about 10 min, it'll be at 3/4 of the gauge (past the L mark) and it'll keep slowly creeping up.

If i don't use the A/C at all, it'll stay between 1/4 and 1/2, where it's always been.

This only started past couple weeks ago, but I did get stuck in a major mud puddle. I'm wonderin if its possible the rad / condesor could be clogged with mud or something? I'm going to pull the grille off and wash em out tomorrow.

I changed the thermostat for good measure (I did it a year ago) and put in a new rad cap today (stock one was on there, 280,000km). It's helped a little, but it still heats up.

Any ideas?

 

[MrShorty]

I'm wonderin if its possible the rad / condesor could be clogged with mud or something?

Definitely a possibility. Another possibility I would suggest checking is the fan clutch. Best test I've seen for a fan clutch came from a Mitchell manual: pull fan clutch, disengage thermostatic spring on the front and rotate 1/4 CCW, reinstall and test drive. If overheating problem is resolved, fan clutch is bad. If problem still exists, problem is likely elsewhere.

 

[inh]

Sounds like your radiator is clogged, either with mud on the outside (probably) or with corrosion on the inside (less probable)

 

[mechjames]

yea, i think the fan clutch is good, once the gauge goes past the halfway mark I can start to hear the fan noise while driving. but it might not be operating at full power.

i'm going to check for clogged mud in the rad area first. after flushing the rad last night, it did pretty well on the way to work this morning with the a/c on. We've been having some 30 degree mornings and 34 degree days here in Richmond.

 

[Mettler]

Ive been dealing with ac woes aswell. My truck has the r-134a compatable pump ( but it is charged with R-12 ) and everyone has been telling me that the condensor unit is a sponge filter with a sediment trap and to replace it. For vehicles as old as ours it is recemended that you replace the condensor unit as needed. As the sponge portion becomes clogged and not as effective as it used to be it causes the system to over work itself. Problem is finding a shop that will evac the R-12. No one has it accept grease monkey and napa service centers. Or so Ive found in my wonderings. If you do this get the system evac'd cause it gets all the old oil and gas out. Then go home replace the condensor (super easy) and refill with the R-134a coversion kit ( $47 at schucks) done, updated and cold. No more over heating. I belive the condensor is in the 100 dollar range.