Overheating only when ac is on....?

[mazdaspeeeeed]

I recently installed a brand new regular protege radiator along with 2 - 12" universal slim fans from pep boys and a brand new thermostat from napa. Well now my car is overheating only when i turn the ac on and drive for about 5-10min. The coolant level is staying full. The fans are both pulling the air into the engine and at very high speeds. Nothing really seems abnormal to me so i am stumped...

Any suggestions?

 

[Nc MSP]

no idea....maybe the water pump/alt belt is loose? idk just a shot in the dark

 

[Wheredjaredgo]

I have purchased a faulty thermostat that was supposedly new... I would try starting there if you still have the old one try replacing that... And just testing that the coolant lines are staying pressurized and coolant flowing. Does it only overheat with the ac on? Is your ac blowing hot when it's overheating or cold still?

 

[mazdaspeeeeed]

the coolant lines are staying pressurized and it only overheats when ac is on, but the ac always stays cold.

I read on the forums that there could be air bubbles causing this so i am going to run my car with the rad cap off and see if i can get some bubbles out of it...

next step will be thermostat.

 

[Spiced MSP]

my bet is on air pockets. If you didn't let the car run with the new radiator and coolant with the cap off before driving, you most definitely have air pockets

 

[mazdaspeeeeed]

Update: let it run with the cap off and ac on high for a good 20 min. No overheating for those 20 min.
Once i drove it again i got to work and sat in the parking lot with the ac on for about a minute and it overheated again...

 

[dacquesta1]

Bad Rad cap...worth a try.

 

[jdwk]

The A/C shouldn't cause the engine to overheat, it isn't that much load on the engine. The water pump and the alternator are on the same belt. The A/C and P/S are on the other.

I suppose it is possible the electrical load from the fans with the A/C on is causing the belt to slip on the A/C and W/P, but you'd hear it.

The thermostat is an easy check because you can feel the pressure in the upper radiator hose when it opens, which you've done. And if the car is not overheating without the A/C on, then it probably isn't the thermostat.

Air bubbles in the system usually cause the temp to fluctuate greatly as they pass the CLT, also the problem would be the same with or without the A/C on.

Have you run the car with heat on full blast and the rad cap off to refill the heater core?

 

[mazdaspeeeeed]

ok new problem...

I replaced the radiator cap. ran the car for about 20 min with the ac on high and the car sitting in my driveway and it stayed super cold and the therm stat stayed at normal range.

Then i drove the car down to the store about 20min away and it started overheating.
this time the reservoir tank had a crack/hole at the top corner and fluid was squirting out of it, the radiator fluid was boiling and bubbling inside the reservoir tank, and the tank itself was shaking because of all the bubbling.

After about 5min of sitting the car cooled off and i drove it again without the ac on this time. about 2min later it overheated again but only about 2-3 clicks past middle. As soon as i shut it off it cooled off again (perhaps the boiling fluid was causing it to run a bit hotter). I managed to get it home now and i am about ready to give up on it.

I have not yet run the heat on full blast with the rad cap off, didnt know about this step actually...

 

[mazdaspeeeeed]

also I am not 100% sure that the top hose holds pressure or not. currently there is no pressure at all, this would mean it was the thermostat, but why wouldnt the car overheat without the ac on?

 

[Teknic]

im having almost the same problem. my car is just sitting in parking lot. not sure what to do now. sub for info

 

[mazdaspeeeeed]

im about to go replace the thermostat it should be cool enough here pretty soon. I will let you know the result

 

[mazdaspeeeeed]

Replaced thermostat and reservior. Repurged entire system with ac on high and then heat on high.
Took it for a 15min drive and the cap got blown off my reservior tank and coolant sprayed everywhere... Overheated to about 3/4. Immediatly dropped to normal once i shut the car off...

Probably time to go to a mechanic...

 

[jdwk]

The resevoir is an overflow resevoir. It's not under pressure like some cars. The cap should not blow off. There is a drip hose on it so it's not even sealed. If you overfill the coolant to the point that it fills up the overflow resevoir it should just drip to the ground. I believe you meant to say your radiator cap was blown off.

Are you entirely sure the car is running perfectly fine without the A/C on? Also, are you sure your fans are working properly?

You said both fans are coming on at high speed. The fan on the driver's side is the cooling fan. It kicks on around 210 degrees and kicks off once it cools down to 190 or so. It also kicks on with the A/C. The fan on the passenger side is the condenser fan. It will kick on anytime the A/C compressor is engaged. The A/C will cycle on an off, so the fans will cycle on and off as well.

If you reach 235 the condenser fan will kick on to help out with or without the A/C on.

After replacing the thermostat, do you now feel pressure build in the top radiator hose? This is crucial. With the car cold, start the engine then just squeeze the upper radiator hose. You should feel it fill up with coolant as the tstat opens up around 180 degrees.

If coolant is flowing, it is either your fans or the radiator itself. Make sure both your condenser and radiator are not blocked by something. I once had a trash bag cover a part of my radiator and that was enough to send the temps soaring.

 

[BRIAN_MP5T]

You could try removing the thermostat completely.... to see if the car still overheats..

 

[jdwk]

Also a valid test. The car may throw a cel for not warming up fast enough, but that's not really a bad thing. It would at least rule it out.

 

[mazdaspeeeeed]

I will check to see if there is pressure in the top radiator pipe.

Both fans are kicking on still with the ac. I dont see any blockage.

I am not entirely sure the car is running fine without the AC but I know it isnt overheating. I have been driving it all week with no ac and 90+ degree weather and it runs fine. I will have time to mess around with it this weekend some more.

The resevoir is an overflow resevoir. It's not under pressure like some cars. The cap should not blow off. There is a drip hose on it so it's not even sealed. If you overfill the coolant to the point that it fills up the overflow resevoir it should just drip to the ground. I believe you meant to say your radiator cap was blown off.

Are you entirely sure the car is running perfectly fine without the A/C on? Also, are you sure your fans are working properly?

You said both fans are coming on at high speed. The fan on the driver's side is the cooling fan. It kicks on around 210 degrees and kicks off once it cools down to 190 or so. It also kicks on with the A/C. The fan on the passenger side is the condenser fan. It will kick on anytime the A/C compressor is engaged. The A/C will cycle on an off, so the fans will cycle on and off as well.

If you reach 235 the condenser fan will kick on to help out with or without the A/C on.

After replacing the thermostat, do you now feel pressure build in the top radiator hose? This is crucial. With the car cold, start the engine then just squeeze the upper radiator hose. You should feel it fill up with coolant as the tstat opens up around 180 degrees.

If coolant is flowing, it is either your fans or the radiator itself. Make sure both your condenser and radiator are not blocked by something. I once had a trash bag cover a part of my radiator and that was enough to send the temps soaring.

 

[Preferio]

The A/C shouldn't cause the engine to overheat, it isn't that much load on the engine.

Obviously, but the condensor is there for a reason. Do you know what that reason is? The refrigerant is pressurized, so when it's pressurized, it heats up, so the condensor is there to discipate the heat. A condensor can get hot and as the air flows past it, it goes directly to the radiator thus transfering heat. I have the same problem as the OP, but only when sitting in traffic or at a light- basically when the car isn't moving. I contribute that to the FMIC, because prior to that I had no issue. Hot FMIC > Hot condensor > Hot radiator. By the time that air reaches the radiator, it's gone through two other hot components. I'm also only running a single fan, so only use the AC when cruising.

OP, I know this may sound stupid, but make sure you've got your condensor fan wired correctly and it's not pushing air from the engine bay into the condensor because you would run into two problems- 1. It's hot air and 2. It would have a hell of a time trying to push that air while driving.

 

[BRIAN_MP5T]

The Fans are probably hooked up poorly, as in the way that they are attached is probably missing good seal..

It isn't like a fan that blows cool air on you... that it can just blow air on you.. the Radiator needs AIR FLOW (Through the Rad not on it)

NOTE: Just attaching them to the front of the AC Condenser will NOT make good airflow to the rad. People who try to run a pusher system like me, without removing the AC have to understand that the air will flow well past the condencer, but then do nothing to cool the engine. There is 1" of space where the air will simply blow around the radiator.

Mazda uses Puller Fans on the back of the rad..

BikingPro there, has them zap strapped over the oil cooler, AC etc.. His car will not cool itself no matter how fast he runs the fans... It will overheat stuck in traffic.

 

[mazdaspeeeeed]

Yup. Im thinking fans now too. Today is was about 90 out and after a lot of driving my car iverheated. This time without the ac on. The temp needle would go back down once i started moving again too. My fans arr pretty tight against the radiator with zip ties but they are obviousy not covering the entire radiator. Who makes custom shrouds for the regular protege stock radiator?