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Another Toyota Lemmon Overheats with AC on

My 2003 Sienna minivan overheats when the AC is on. After about 10-20 minutes of running the AC, the air starts blowing warm. There is a humid and musty quality to the air, and then the temperature gage quickly rises. When I turn off the AC the temperature quickly cools and the car runs with the gage positioned right in the middle range. I have recently had fans replaced, $450, which fixed the problem for three weeks. It started again. I was then told it needed a new radiator and thermostat. These were replaced, $500,even though I told the mechanic the car runs fine with the AC off. Again problem was fixed for two weeks. Now it’s starting again. Besides getting to the bottom of what is really wrong and fixing it, one of the things I find strange is that both times the mechanics worked on the car the symptoms temporarily stopped. If they have not addressed the problem, why would this happen, and could it be a clue as to what is wrong?

Well I don't think it has been fixed.  Different things have been tried, but not the right ones.  

My guess, would be an air block or a water pump problem.  Other possibilities would be a hose that is collapsing (maybe internally so you can't see it) 

I would not worry too much about it not causing problem right after it was worked on, I just thing they did not get down to the real problem yet and the fact it did not act up right after they worked on it is a red herring.

Why does your mechanic’s inability to repair the problem make the Toyota a lemon?

I think you need a better mechanic. Sounds to me like someone is throwing parts at the problem, hoping one of them will work.

I suggest taking the van to a shop that specializes in automotive AC. These are usually radiator shops, and they are experts at cooling and AC systems.

I agree with the other posters. Sounds like the mechanic has the problem. It might just be a simple relay since you say the cooling fans were recently replaced. I don’t like “shotgun” maintenance.

Could be a relay or temperature sensor, have you checked to see if the electric fans are running when it is overheating?


The mechanic changing parts blindly is the lemon, not the car.

There’s probably a loose electrical connection or flaky relay etc. that gets wiggled or disturbed when they change parts under the hood.

Thanks for your advice.
I forgot to add one more element to the overheating puzzle: At least for a period of time after the cool air first begins getting warm, after about five or ten minutes, the cool air kicks in again, then it gets warm again, and at some point in this cycle it gets very warm and then the car begins to overheat.

The car HAS BEEN A LEMON since I got it. It had the “gelling problem” many of these cars had. Fortunately the subsequent damaged block was fixed under an extended warranty (they were forced to have due to a law suit). With less than 55,0000 miles, the timing belt broke and was replaced along with the water pump, then with less than 65,000 the transmission went out, then it needed a valve job. And oh yes, I had to change three of the four motor mounts. The brakes only last about 9-10,000 miles because this model they put a heavy minivan body on a Camery chassy without making any adjustments. I’ve ended up putting in over $6,000 last year on a car that is currently worth only around $4,000. I just wanted to hang onto it for another year or so, since so many of the car’s parts are new, including its tires and current brakes.And with one exception, all the Toyota dealerships I’ve dealt with locally in the San Fernando Valley have lied to me (one even sent me away, saying the motor mounts were fine, (since they apparently got paid less to fix problems under warranty) when in fact they were damaged and were soonfixed at another Toyota dealership in orange county, where I first bought the car new.

Thanks for your input. I’ll follow up with your suggestion.
Do you know of any good, honest, and reasonably priced mechanics in the San Fernando Valley, CA area?

I’d love to know all of the tiny details behind these major problems this car has been having.
There’s something going on here.

I tend to agree.

Talk to your friends, neighbors and coworkers. Wen you find a mechanic mentioned by a few of them, try him.

Me, too. I have a 2002 Sienna, bought new right after 9/11. 168,000 miles. At 85,000 miles a mechanic said the front pads were low, so I had them replaced. But when we got them apart, they were well above minimum, and would have easily gone 100,000 miles. Mostly highway driving. At 168,000 miles original rear brakes have plenty of shoe left.

To need brakes at 10,000 miles indicates severe driving practices, OR something seriously wrong in the braking system. I suspect the latter, but who knows? All these repairs sound like a car that has won the Baja 500.

If the car has been driven moderately, then I would agree this is a lemon.

As far as the sludge, I have felt to change oil per the manufacturer’s recommendation on cars with known sludge problems is not a good idea, but most people are going to trust manufacturer’s recommendation.

For most people, if a car goes a year or two trouble-free, and then something happens, then they don’t call it a “lemon.” Lemons usually have problems from day one.

Who did you have to sue, the extended warranty company or Toyota?

Did you buy this vehicle new or used? If you bought it used, how did you ensure the car was properly maintained and in good shape when you bought it?

Nothing broke until you had the vehicle for how long? Two years? Three years?

How often did you have the oil changed?

With 65,000 miles on the odometer, how many times had you changed the transmission fluid?

Are you sure about the reason for your quickly-wearing brake pads? My mother’s 2002 Sienna (the same model as yours) doesn’t have this problem, so it sounds to me like you might have an undiagnosed problem with your brakes.

How much money did you put into this vehicle for maintenance before you started having these problems?

I had the same thought. I have posed some questions above. Hopefully, the OP will answer them.

Like irlandes, my mother has a 2002 Sienna. Maintenance is expensive, but the vehicle made it past 100,000 miles without any major problems. It might have helped that I knew about the sludging issue, and insisted my mother have the oil changed every 5,000 miles.

According to Wikipedia, the first generation Sienna was made from 1997 to 2003. If that is true, the OP’s Sienna would have been a model that had been in production for six years prior to its purchase. I find it hard to believe that in all that time, Toyota would have let a problem like that continue.