Car still overheating


#1

Ok I’ve already replaced in the past week a thermostat, waterpump, radiator, cooling fan, temp gauge and both sensors. The colling system works. But as soon as I turn on the ac the car over heats. Condenser is not clogged and gets plenty of air. Any ideas?


#2

Also the engine bogs down dramatically atleast 2k rpms. When ax is turned on.


#3

Maybe the compressor is faulty?


#4

How do I know if it is? The air blows ice ice cold.


#5

@pilotcar94‌

Pop the hood and start the engne

Does the compressor make an awful racket when the clutch is engaged?


#6

No no racket or strange noises. Just Boggs down. Immagine pressing the gas in park and then just letting it go. That’s how it is at idle. From normal to way to low.


#7

“Also the engine bogs down dramatically atleast 2k rpms. When ax is turned on.”

How can idle drop by 2000 rpm? Normal idle speed should be under 1000 rpm. Do you mean it drops by 200 rpm? That would make more sense.

PS, sorry I hit the “disagree” button with my fat finger by mistake and can’t undo it.


#8

Does the secondary fan kick on with the ac?


#9

Open the hood and turn on the AC, do the fans come on? If not, that is the problem. The condenser sloughs off a lot of heat when the AC is on and if the fans are not running, it causes the radiator to get hot.

Also replace the radiator cap.

A 200 RPM drop would be normal for a carbureted car, but the IAC (idle air control) should compensate on your vehicle. The IAC may not be getting a signal because someone fiddled with the throttle stop screw or the TPS (throttle position sensor) isn’t working. A non working TPS should throw a code and a check engine light.


#10

Has anyone hooked up a set of manifold gauges to the AC system to check the low/high side pressure readings?

If the high side pressure is too high, there may be a problem with the expansion valve at the evaporator. If the pressure is too high, it creates greater heat out of condenser in front of the radiator, causing the engine to overheat.

Tester


#11

Every mechanic I take the car to won’t lok at the ac they just say an A/C system can’t cause a car to over heat.


#12

Then those mechanics don’t understand physics on how an AC system functions.

Tester


#13

If those mechanics think that then their A/C knowledge is very shallow. Very.


#14

pilotcar94 What is ax? The common abbreviation for air conditioning is AC.


#15

AC can indeed cause an engine to overheat. The most common causes would be the AC compressor is binding, or the engine fans are not turning on and/or spinning as fast as they should be when the AC is on.

Edit: Less common, but if there’s something wrong with the engine or cooling system the AC might produce enough extra load on the engine to cause it to overheat, even if the AC compressor and fans are working correctly. But check the most likely problems first.


#16

@sgtrock21; I’m sure the OP meant AC…as the X is right next to the C on the key board.

Yosemite


#17

If that were true, then the radiator fans wouldn’t always come on when the AC is switched on.


#18

Fans are wired to run on high all the time. Going to take car to A/C place tomorrow to have it looked at.


#19

Also the 2k rpm drop I spoke of is at highway speeds


#20
Fans are wired to run on high all the time

Remember that just b/c the fans are wired to run on high doesn’t mean they are actually spinning as fast as they should be. The fan motors or their bearings could be wearing out. And that would be even more likely in your case since they’ve been hard wired to run at full speed all the time. The fan motors aren’t designed to be running all the time.

The actual fan speed can be easily measured and compared to the factory service manual spec with a relatively inexpensive rpm measuring strobe-light instrument.