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Overheating Troubles

We’ve been having some overheating problems that no mechanic seems to be able to find the cause of, so here I find myself looking for deeper insight.

Towards the end of July our car had a new radiator installed. Our mechanic found a crack towards the top during a routine maintenance check before I our big move from Sioux Falls to Montana. We weren’t having any troubles, but he thought it best.

We moved towards the beginning of August. The car made the trip just fine and several trips between Billings and Bozeman without any troubles.

About a week and half after the move we went on vacation to Wyoming. The first night included camping in the Big Horns. As we were pulling into the campground the car overheated and we quickly pulled into a spot and settled in. After lifting the hood I discovered the reservoir and radiator we empty. I filled them both from our water supply and coasted into Buffalo the next day to find a mechanic.

After two hours no leaks were discovered and the thermostat and radiator were working properly. The mechanic suggested that it might be due to the abundance of dead grasshoppers on the front and preceded to clean them off and sent us on our way.

The next leg of the trip was from Buffalo to Laramie via Rawlins. We were fairly prepared to break down en route, but made the trip ok, the temperature gauge stayed in the middle the entire trip. After arriving in Laramie we spent the next week between Laramie and the edge of snowy range. I was keeping a close eye for leaks, but the car was running fine and not losing any fluid. Until, we made a trip further into the snowy range. On the way back into town the car overheated and sure enough the radiator and reservoir were once again empty.

I filled both from our water supply again and tried to make our way back down the hill into town. It was slow going. All of the fluid was blowing out through the reservoir and the car would promptly overheat. After struggling for about an hour, I managed to short the fans with fluid and decided to just call the tow truck to bring us into town.

The next day I filled the reservoir and radiator, changed the fuses, and drove to a mechanic. We left the car for the day and went on our errands in town. At the end of the day we got the call back. All the mechanic had found was the rubber stopper on the bottom of the radiator cap was missing. He said the head gasket tests were fine, the thermostat was working properly, and the radiator was flushing fluids as it should be. The reason we were losing fluid was the rubber stopper keeps fluids from flowing freely to the reservoir. He even took the car for a drive and said the temperature gauge stayed in the middle once again.

We went on to the next leg of the trip, to Guernsey. We stayed for about a week and made the trip home to Montana. Again, without any troubles. The temperature stayed central on the gauge once again.

The next week we made a trip to Billings without any trouble, and later a trip to Bozeman. After we were in Bozeman for a couple of hours the car overheated. The fluid was all missing as was the rubber stopper from the cap. We picked up a new radiator cap and fluid, and made the trip home without any troubles.

I called our mechanic in Sioux Falls to see if he had any insight to the problem. He suggests that it had to be the head gasket or a cracked head. ‘It’s the only way the radiator could build up enough pressure to blow the rubber stopper on the radiator cap.’

We took it to a local mechanic and gave him all the information we had. After looking at the car for a couple days, he doesn’t believe it can be the head gasket or a cracked head. It’s passing the appropriate tests (his aren’t probably as technologically advanced as the mechanic in Laramie, as this mechanic is a small town, one man shop). He also believes that the car should overheat fairly quickly in any instance, i.e. We wouldn’t be able to drive 400-500 miles without any problems. So far as I can tell, it seems to be linked with strenuous mountain driving, but performs fine on flatter ground.

Any ideas?

What year is this Camary? Does it have the V6 engine? How many miles are on the odometer? Does the radiator and reservoir lose the fluid with the gauge still in the middle position? When eveything is going well, has there ever been a case where the reservoir is empty but the radiator is full? Does the temperature gauge spike when it overheats? Has the water pump been replaced recently?

With the number of mechanics who have had ‘eyes on’ diagnosis here, this problem is going to be a tough dog to ferret out. If you find out the solution, please post back the answer so we can benefit from your experience.

It is a 1996 Camry with a 4-cylinder. I believe the odometer is about 145000. The engine is not the original and I believe would have around 67000 miles. The radiator and reservoir appear to lose fluid with it in the middle position. I have yet to notice an empty reservoir with a full radiator, but all the fluid seems to be going out the pressure valve? of the reservoir. The gauge tends to spike when it overheats. The water pump has not been replaced recently, but appears to be working properly. But again there seems to be a pressure build up in the radiator that is causing the rubber stopper on the radiator cap to disintegrate. I don’t fully understand the workings of flow system, but I imagine there’s small pieces of rubber inside the cooling system from the caps breaking/disintegrating.
Is there anything besides a head gasket/cracked head that can cause pressure to build up to 25psi? The cap is only regulated for 19.
As far as the mechanics go.
Mechanic 1: couldn’t find anything.
Mechanic 2: found broken radiator cap, thinks head gasket is okay.
Mechanic 3: hasn’t seen car, but thinks pressure is from head gasket/cracked head
2nd radiator cap broke, I replaced.
Mechanic 4: hasn’t found anything, but thinks had gasket is ok.

So, the mechanic that have seen the car and tested the head gasket tend to rule that out. However, the mechanic that I know and trust believes the only thing that can cause that pressure is the head gasket, incidentally, he hasn’t seen the car.
So I’m fishing for other possibilities before I have mechanic 4 tear into the engine, which he is reluctant to do, as he doesn’t want to charge me for something that he believes is working properly… nice guy, eh?

I have some other ideas that might be relevant. Either the cooling system cannot transport the heat away and a hot spot is boiling or there is excess heat being produced.

I am wondering if there may be a flow problem between the block and the head i.e. a plugged passage through the head gasket. A piece of debris may be intermittantly plugging the passage allowing one area of the head to boil water and push the fluid out. The entire cooling system only holds 1 gallon of coolant so the loss of a quart or two is critical.

You haven’t mentioned it but is it possible that you are getting detonation (ping) while climbing. Detonation can cause concentrated hot spots that become a boiling focus which would expel the coolant. Also consider that the engine oil cooler and transmission oil cooler could be overloading the cooling system capacity so check the transmission and engine oil temperatures when you get an overheat.

When you first warm up the car, does the upper hose get hard immediately? Even when there is no overheating, are you getting bubbling into the bottom of the reservoir?

Other than these I am at a loss for suggestions. Again post back when you find the solution to this problem.

This is an interesting problem. So you had the radiator replaced for a crack in it to begin with, although this is pretty uncommon did you ever see the old, cracked radiator? Sounds like maybe the radiator caps you have been purchasing are not compatable with the new radiator, or you recieved the wrong one to begin with, as this is when all these overheating problems started. You also stated that you filled the radiator with water. This works in desperate times but antifreeze not only prevents freezing, but also raises the boiling point of the water which your engine could very well appear to be overheating, but is really just boiling the water, not to mention add a bad cap and you’re really gonna spill some water.

As far as your head gasket goes, the tools are rather simple and universal so I wouldnt doubt the small town mechanic has and used them. I doubt you have a head gasket problem.

I would: flush system to remove all the old coolant/water. Fill with a 50/50 mix of antifreeze and distilled water, and get a radiator cap that works for your radiator. Also make sure that the cooling fans are working properly.