Car overheats when AC is on (1999 Mazda 626 LXv6)

[RigoVernon]

Can someone help me with this. Since last summer I noticed that my car would overheat a few minutes after I turned the AC on. Because of this, I did not use the AC all summer long. This past January I took my car in for some needed work. They changed all my belts(including timming belt), spark plugs and wires, oxigen sensors, and water pump. Because of the amount of money I had to pay to get all this work done, I did not even mention my problem with the AC and the engine oveheating, but I was hoping that by replacing/fixing any of the parts they were already working on, would solve this problem.
A few days ago we had temperatures in the mid 70's here in the northeast, and on my lunch break I turn my AC on. After about 10 minutes or so, I notice the engine temperature was steadily going up. So I immediately turned the AC off; obviosly the problem didn't go away!

Does anyone have any idea what could be causing my engine to overheat when I turn the AC on? I have checked for fluid leakage and everything is fine. Also, the AC cools pretty well. The only problem I have is that it causes my car to overheat... I really don't want to go through another summer without AC.

Thanks

RigoVernoN

[ViciousLoki]

Look into Vapor Lock

[TonyMazz]

Originally Posted by RigoVernon

Can someone help me with this. Since last summer I noticed that my car would overheat a few minutes after I turned the AC on. Because of this, I did not use the AC all summer long. This past January I took my car in for some needed work. They changed all my belts(including timming belt), spark plugs and wires, oxigen sensors, and water pump. Because of the amount of money I had to pay to get all this work done, I did not even mention my problem with the AC and the engine oveheating, but I was hoping that by replacing/fixing any of the parts they were already working on, would solve this problem.
A few days ago we had temperatures in the mid 70's here in the northeast, and on my lunch break I turn my AC on. After about 10 minutes or so, I notice the engine temperature was steadily going up. So I immediately turned the AC off; obviosly the problem didn't go away!

Does anyone have any idea what could be causing my engine to overheat when I turn the AC on? I have checked for fluid leakage and everything is fine. Also, the AC cools pretty well. The only problem I have is that it causes my car to overheat... I really don't want to go through another summer without AC.

Thanks

RigoVernoN

When is the last time you had your coolant system flushed ?

Reverse flush the coolant system, replace the thermostat, clean the leaves, bugs etc from in front of the condensor coil, radiator.

Also check your radiator cap and replace with a good new cap...

Finally check your water-pump , fan clutch and make sure they are working properly...

[zmweaver]

The additional demand put on a motor with A/C on is no more than driving the car hard. Meaning that if your car overheats only overheats with the A/C on, radiator performance is not a likely suspect. Leave your motor running while parked with the A/C OFF and monitor your temperature gauge with the hood closed. Wait until the cooling-fan kicks in and observe the effect on the temperature gauge. Once the temperature is stable, turn on your A/C and see what happens. Make sure the cooling fan doesn't cut out when you turn the A/C on. If your temp. gauge fluctuates rapidly, you need to replace the thermostat. More information is required to accurately diagnose your problem.

[ardnum]

I used to have the same problem on a 1998 Mazda 626 (6 cyl.). Every time I turned on the AC, the car would start heating up. The temperature needle would start going up and came close to the "danger zone" but never hit the "danger zone."

I took the car to a dealer who was close to work. At that time, I had an extended warranty that was still in effect. The dealer replaced the entire AC system under the extended warranty. However, the car still overheated. When I informed the dealer that the problem was still there, he said "well, that's the way Mazdas are and at least the temperature needle is not hitting the "danger zone."

Anyhow, I decided to replace the thermostat and flush the cooling system. I did that, but the problem was still there.

A few months had passed and my extended warranty was over.

Then, one day, I took the car to a different dealer. This dealer told me that "based upon experience, the radiator needs replacement." I was a little hesitant because there were no leaks in the radiator. Anyhow, I authorized the work. The dealer replaced the radiator. And the problem got fixed.

Summary: The radiator in this car can get clogged or blocked; replacing the radiator may fix your problem.

Another time, I had overheating problems (with or without using AC), it turned out to be a cracked radiator overflow tank. This tank is notorious to fail. I am already on my third tank.

[MazdaOwner]

Hello:

I have had numerous problems with leaking overflow tanks on my 2000 626. I am now on my fifth tank. The loss of coolant can lead to severe overheating and loss of A/C. Two tanks failed in less than 12 months. A week after my most recent failure (requiring another system flush), my radiator failed and had to be replaced.

I have the last two tanks and the leaks are obvious. If you have similar problems again, I suggest you have the mechanic look at the tank closely.

Also, call and complain to Mazda. I did and they reimbursed me even though it was out of warranty. They know it's their problem.

[RigoVernon]

Sorry it took me so long to respond to your comments, but after monitoring this message board for a couple days after I posted and not getting any response, I thought I would not hear from anyone.

Its funny you guys have mention the issue about the cracked reservoir tank, because I also had to have it replace like 3 years ago when my car started overheating on me. It didn't occur to me that this, again, could possibly be the cause of my current problems. But here is an update to my original post:

I basically avoided taking my car to the dealer because of their overpriced fee and also because everytime I take it to get fix I always end up paying and fixing more than I thought was necesary. They always find a way to make you spend more money, even when you really don't have it. So I decided that I will drive my car throught the summer without using the a/c to prevent this from happening again.... Well, guess what? eventually my car starting overheating without the a/c on. An like some of you mentioned it would go up really high but never really hit the danger zone. As time went by I realized that this was happening more and more often, to the point where I was only able to take short trips in a warm summer day.
At first I decide that I would give it a try and attemp to fix my car myself, so I went to an autopart store and bought the repair manual for my 99 626 and read it, pretty much didn't get to far but, in examining the engine compartment while the engine was running I discovered that my cooling fan was not working. So at this point I needed to find out if the fan was indeed bad or if there was something that was not letting it start. I had my brother inlaw test the relay and they appeared to be working fine, I also checked all the fuses and there was nothing wrong.
So I took the car to a small shop that I know and explained to them was going on. The mechanic found something wrong with the sensor and replaced it, this got the fan working again. He test drove it and the car worked great! I was so exited. I could finally turn my A/C on and make it through the remaining of this warm summer. So, that afternoon, I picked my car up, paid the 100.00 that he charged me and drove off with my A/C blasting! I got on the highway to head towards a friend's house and as I started climbing a relatively steep hill on the highway, my car started to overheat again! I immediately turned the A/C off and drove to my friends house. I called the mechanic to report the problem. I had to take the car back the next day. The mechanic test drove my car for a long time and could not get the car to overheat again. He examing the system and found that there were air packets in the cooling system, which he got rid off and ended up adding an additional 1/4 gallon of coolant. He test drove it again with the A/C on and could not get it to overheat. When I got out of work I went to the shop, and test drove the car with him in it, with the a/c on, on the highway and through the city and the temperature remained stable. I was so happy, finally my problems were over!
I took my car home.... the next day, while I was shopping, the mechanic called my cell phone to tell me that I had left my briefcase in his shop, so I headed over there immediately to pick it up. After I picked it up and was headed back home, the car started overheating on me on the same hill it did before, however the temperature did not go up as high as it ussually did in the past, so I decided not to do anything about it and wait it out. Drove my car several time without problems. This last monday I took the day off from work and went out shopping for a new washing machine. It was a warm and sunny day. Except for a few instances, the car will mainting proper temperature as long as its moving and the breeze is blowing. I was getting ready to enter a shopping plaza, and as I stopped at the light waiting for it to change, I looked down and saw it again, slowly but surely the temperature was going up gain. The light changed and as the car started moving, the temperature when back to normal. That was the only time it did it that day. Next day I was on my way to work and hit some traffic that made me slow down and I saw the temperature going up a little bit. When I got to work i called the mechanic and told him what was going on and I dropped it off yesterday morning for him. At this point neither him or myself new for sure what could be the problem but since its an inexpensive part, I requested that he replaced the thermostat and so he did. After he replaced the thermostat he test drove the car with the A/C on and this time around, while he was testing, the A/C and the fans shut down and the temperature starting to rise. But the said that when running without the A/C, the temperature was fine. He told me that in the past he had a Toyota corolla do the same thing and that the problem was with the relay, that once he replaced it on the corolla the problem was solve. So now he believes that my problems are caused my electrical issues and he recomented and replaced the relays.... I really don't know what to do.

This morning I drove my car in for work with the A/C off, and the temperature started going up when I stopped at a red light.

Ealier this year, like in january, I had taked my car to the dealer for service, where they replaced all my belts, my water pump and a couplen oxigen sensors.

Now I have a new temperature sensor and a new thermostat and I am still having problems.

[mazdatech177]

check cooling fan operation when ac is on... both fans should be on while the ac compressor is on... ive replaced numerous cooling and/or condenser fan relays on 98-02 626. the fan motor itself is a possible, yet, much less common problem. these relays should be right behind the engine compartment fuse box. there should be three right in a line. the faulty one will rattle like a babys toy when shaken usually.

[RigoVernon]

Both fan appear to be working fine. Even when the A/C is not on, if the car gets hot enough, both fans will run. But the temperature is still going up. To be on the safe side, I went out and bought brand new caps for the antifreeze reservoir as well as the radiator. Y also bought some brand new relays and replaced those myself over the weekend. That didn't really make a difference. However, I noticed something that has me thinking. Saturday when I got back home after a drive, I open the hood while the engine was still running, just to verify that both fans were running. And, they were. But, I put my hand in front of each fan to feel the air. I noticed that the primary fan does not blow air as strong as the A/C fan. I don't know if this is normal, but in made me think that even though this fan is working, its not working as strong as it should.... What do you guys think? I don't know what else to do, the only two things I have not replaced yet is the fan and the raditor.

[briman15]

I have had my 626 for 10 years and the overflow resevoir was replaced by the dealer because it was cracked 7 years ago. Recently it started overheating when the AC was turned on. I inspected the overflow resevoir and there were fluid stains on the underside indicating a CRACK.
I bought a new one ($113). It is a better design than the one I had so Mazda fixed an issue they said did not exist.? The repair is SIMPLE. Remove two screws and then two clamps (from hoses), reinstall the hoses with the clamps to the new resevoir, then reinstall the two screws. Total time 12 minutes. Overheating problem Fixed!