Hey all! I ran the A/C on my '88 for the first time in about 10 months! I rarely run it, because it wastes gas and with the prices these days, I'm not wasting what I don't have to!

Anyways.. it was a really hot day outside. About 90-some degrees and the humidity was killer. So I decided to run it. The first thing I noticed was that it only ran cold when I was on the move. If I would stop at a light, it would slowly become as warm as it is outside. Then I would start moving again and all would be well once again, icy as the north pole (maybe not, but it felt good!)

So I get to work and turn the car off and I hear this REALLY strange noise coming from my engine bay. So I pop the hood and take a look inside and I hear what sounds like coolant racing through all of the the hoses. I didn't think too much of it (well a little worried, but I didn't have time) so I put the hood back down.

So I'm standing next to my car and I'm getting my shirt on (yes, in the parking lot) and my brother comes out of nowhere and we start talking. So I look over at my passenger-side headlight and I see smoke coming out of it!!!!

I pop the hood again and see that my coolant is BOILING! From looking in the resevoir, it looks like it turned brown, too!

I'm 50% on A/C compressor and 50% on me not filling the coolant. But I'm leaning further away from the coolant, because I'm usually quite religious about filling it up. (I owned an '86 Ford Tempo...... enough said... )

Thanks in advance, guys!

~Derek

 

Derek,
I am alittle confused by your symptoms. It seems you are addressing two issues; 1) A/C only working at cruising speed and 2) Your engine coolant brown and boiling.
Issue 1: You should check for leaks in your A/C system, then assuming you have satisfactory results, have it recharged.
Issue 2: It is possible that your upper and lower radiator hoses are older and have lost theit firmness. You should check this by raising the hood and withthe engine runing, give it some throttle. If your hoses are bad, they will collapse due to the waterpump drawing water volume into the engine. Result is that at speeds otehr than idle, the uppoer hose is collapsed and coolant cannot be returned to the radiator for proper cooling. The coolant remains in the engine for extended periods and the temperature gets dangerously high. Have you noticed your temp gauge, is it high or does it heat up quickly? Back to the results; once you reduce engine speed (idle), the collant returns to the radiator, supe heated and then boils over into the reservoir.

 

Your fans may not be working, should be on with A/C. With the fans inop, the a/c would only work while moving. If you were going kinda slow, the car would overheat.

 

Good idea to look at the fan. With a/c, Main Fan Relay is going to be grounded by the ECM when the fan switch opens - about 220 psi on the high side. It will continue to run until pressure drops to about 170 psi. The switch is on the smaller line from the condensor to the evaporator, next to the high pressure switch. Disconnect it and the main fan should come on, usually proving that the ECM is ok (granted you'll probably disconnect both to find which one turns on the fan - plug the one that doesn't back in). Then, to get a rough idea as to the status of the switch, let it heat up a bit with the a/c on and the fan off and then put a meter across the terminals. With some heat, it should read open. If not, I'd drive it around a couple of blocks with it disconnected (assuming the fan comes on with it disconnected) and if the overheating goes away and the a/c stays cool, drop by a Dealer for a new one. Now if the fan doesn't come on with it disconnected, you've either got a faulty relay or the ECM is bad. Post what you find out for further help.

 

I see that your car is an 88. Has your refrigerant in your AC been changed over from R12 to R134A. The new "environment friendly" R134A does not cool as well when stopped. GM switched over to it in the mid 90's.

 

Plus if fan was not coming on you would have high head pressure in the a/c system and it should shut off the compressor, might even have blwon some freaon out of the pressure relief valve on the compressor. It all points to the fans not coming on.