My '94 LT1 6spd has 90K miles

Lately I've noticed it running in the mid to high 230s, especially in hot weather (desert) driving. My AC has been blowing hot air when the outside temp is in the mid 90s and higher but blowing cold air in normal temps. Last year I had the AC checked (low refrigerant) at a dealer who wanted big $$$ to replace the condenser that they said had a leak (It does look like it was leaking). I opted to wait to replace it myself (haven't yet) - pick the car up from the dealer and lo and behold, the AC works great (I think the dealer recharged it and didn't charge me)and does for quite awhile. At least until my recent trip from Flagstaff, AZ to LA and back. In the high heat it blows hot air, and the rest of the time cold AC.

What's up? A recent article in Vette says that an overheating engine will cause the AC to blow hot.

I'm moving from AZ to CT in Aug and plan to drive the '94 there. I'm planning on removing, cleaning, and having the radiator flushed and replace the AC condenser before the trip.

I've read in other threads about removing the fan shroud and cleaning the radiator. Some posters have suggested for the time and effort of removing, cleaning, flushing it, that for the cost just replace it.


Thanks,
Carl

BTW, My Dodge Dakota w/183K miles is doing the same thing with the AC.

 

Higher underhood temps will reduce your AC efficiency. Those exposed cold lines going into your evap. will be comprimised by the higher underhood temps. 230* and higher engine temp. is too hot. You need to check your radiator for restrictive corrosion. And of course check for debris between your rad. and condensor. Make sure you are running 50/50 for coolent/distilled water mix. Also check that both of your aux. fans are operational. They should both be running with AC turned on....

 

Now theres a culture shock!

You'll quickly learn what the Texans refer to as damnyankees.

Yes, its one word....

Good luck!

 

Run the normal checks: radiator cap, hoses.....both upper and lower, clean radiator (flush) replace with 50/50 mixture of distilled water and Dexcool with the same color that came out. Make sure your thermostat is in good working order. Use tube insulation with zip ties on all A/C lines.

If the above doesn't work, check back with us. Theres more you can do to get under hood temps down.

 

I used to live in Flag myself, beautiful area. Personally, replacing the radiator with a new one is the same hassle as cleaning the old one, so clean the old one and be done with it. Use the same coolant that came out of the radiator, that is, don't put in dexcool unless that is what you already have or you will end up with jello in there. I put in a flushing kit with mine, and ran the electric wp while flushing. I also used a good flushing cleaner, Valvoline, if I remember right. I had crud coming out for about 15 minutes. The radiator was full of little rocks so I blew and washed as many of them out as I could. Now my 94 runs under 200 on all but the hottest days (deseret area currently running about 103* here but engine temp is 210).
Good luck!

 

"Now theres a culture shock!

You'll quickly learn what the Texans refer to as damnyankees.

Yes, its one word.."

Thanks for all the great tips. I'll do them when I get a chance in a week or so.

BTW, I grew up in AL, lived in PA, stationed in MA five years of my 26 1/2 in the Army, lots of time in NC and married a Texan. She's now my ex in Tex. I think I know about damyankees AND grits.

Actually, we have to make the move due to my mother-in-law's health and hopefully we'll be back in Flag after a year or two.

My wife knows the toys go where I go and she's cool with it. Two vettes, an HD and a truck....I've got a few x-cntry road trips ahead of me this summer.

 

I did three things that really helps keepit cooool. remove and clean radiator (most important). install manual fan switches for running in slow city traffic on a hot day, and replacing the original thermostat with a 160 degree unit. Very seldom gets over 190 degrees now. Runs great. Keeping it cool saves everthing in my opinion...

 

I used to live in Flagstaff also! We could have a reunion.
My 85 has run hot since new.
My Opinion: These cars were not engineered to operate in the southwest desert in the summer time.
I cleaned the radiator, installed a 180 thermostat, installed a throttle body coolant bypass, installed a 185-195 degree sending unit for the fan, and installed an Edlebrock hi-flow water pump. These mods only marginally helped.
I finally installed a new heavy duty AC delco radiator ($142) that is 1.25" thick vs the original that is .90" thick. I also installed an aux fan that goes in front of the radiator. These two mods lowered my coolant temps by over 25 degrees. I can drive in traffic and run the A/C and the coolant will stay around 200F. On the highway without A/C it runs about 185F.

 

[QUOTE=Vito.A;1561112438]I used to live in Flagstaff also! We could have a reunion.

"I love this town!"


My Opinion: These cars were not engineered to operate in the southwest desert in the summer time.

"I've had mine since Oct '04 and this summer is the first that it's run this hot."

 

Did you just clean the crud from the grills or did you flush/clean also?

 

Several quick tips to keep the engine running cool. Flush the system. Pull the radiator. Clean the outside of the radiator with simple green. While your at it clean the a/c as well. Make sure all of the fins are straight on both units. Use a 50/50 coolant mix. Get a new radiator cap. When replacing the coolant make sure the heater is on and burp the system.

I have heard that many owners have had positive results by insulating the a/c lines. If you check other posts you will see several ways it was done.

 

That will take care if it. Once the leak is fixed and the A/C recharged, you should get full time cooling. Don't EVEN consider replacing the radiator, unless the shop doing the flush tests for and reports a blockage, or less than ideal flow. And with your cleaned, flushed, and serviced, cooling system, your operating temps will be back to normal, if not better.

RACE ON!!!

 

Thats just not true. The large lines (cold) are the ones returning from the evap. and actually carry the heat which was absorbed when the freon entered the evap. as a liquid and boiled off as a gas. This process is how heat is removed. I know it sounds crazy that the warm line goes into the evap, and comes back cold, yet it is carrying the heat out. But its true. To get a better idea, look up latent heat and heat of compression.

 

OK, I haven't had a chance to work on 'er yet. Yesterday I took it for a long ride since I've been gone so much.

The AC blows well then after 15 - 20 minutes stops blowing. The AC line from the compressor, to the accumalator and into the evaporator were covered in ice. Once they thawed, the AC blew cold again. Think it could be the AC pressure cycling switch and/or refrigerant pressure sensor?

BTW, I have the electronic auto AC and I ran trhe diagnostic per the FSM with no trouble codes. The temp set (left/down side), off, auto and recirc buttons often stick . I know I have to clean them.

 

If the evaporator is freezing, you are probably low on freon.
Probably a leak somewhere.

As for cleaning the radiator, the best thing I did for mine was replace it -- not clean it.
My radiator had the fin area filled with small sand like particles -- and I tried everything to get them out. It just didn't work.
The interior of the old radiator was like new -- it didn't need cleaned internally.
A new OEM radiator and special foam rubber "sealing" strips between the radiator and the fan shroud forces all air to go through the radiator without bypassing it. Then, I sealed all the holes (especially, the hole where the A/C condenser lines go in) in the shroud with stainless tape.
In Florida, in 101 degree days, my in traffic temps are about 185 to 200 degrees (my fans kick on at 195 rising and turn off at 185 falling).
I couldn't get anywhere close to that before replacing the radiator.

I now think of the radiator as a "road filter" that needs replaced when the sand-like particles get it plugged.
When you follow traffic, small particles are "whipped up" in the road draft. And, the "bottom breathing" air intake of a C4 is like a vacuum cleaner.
With my new radiator, I don't follow traffic closely anymore.

Tom Piper

 

Yes, I believe there is a leak in the condenser. I plan to replace it with a used one I bought off the forum.

My radiator has 2 1/2 years of 700 mile weekly round trips between Albuquerque, NM and Flagstaff, AZ totalling about 30k miles. I can just imagine the crud in there. Would you suggest changing the water pump while I'm in there? I was planning on it.

Carl

BTW, I was team mates with a guy named Tom Piper in Alex, VA working for the Defense Dept from '97 to '99. He was a gear head, too. Last I heard he moved to GA. Any chance you're one and the same?

 

With high miles, I would consider doing the water pump.

As an engineer for GE on CAT scanners, I worked with another Tom Piper.
But, I'm not the one you are speaking of.


Tom Piper