Does this sound like a bad thermostat on my 05 Camry?

I have an 05 Camry. My wife was driving it and said the AC wasn’t working and needed recharging. I had just used it in the morning and it was fine. I took it for a test drive and the AC pumped out cold air off and on and the temp gauge was half way, where it should be. A few more minutes of driving and the AC wasn’t sending out cold air any more and the temp gauge said it was hot. Also the check engine light was on, but I don’t have a code reader, so not sure what it was saying. I went a few blocks to home, and checked the coolant, and the overflow reservoir was empty, even though when I checked it a few days ago it was full. Nothing was leaking under the car. I filled it up, started up the car, ran it for a few minutes and all the coolant was gone again.

I suspected that I needed a new thermostat, but have never changed one before. I looked up how to do it and how to diagnose it. The car had cooled down by then. Looked in the radiator and I can see coolant to the top. Started up the engine and now I’m getting cold air out of the AC and the temp gauge is half way again. However, the coolant overflow tank is empty again, yet nothing is leaking. The radiator cap never got hot after running it for about 10 minutes in the driveway, but the upper radiator hose was hot and the bottom was warm. And now the check engine light was off. Seems like the thermostat was working again.

Does this sound like a bad thermostat, that is now temporarily working? Anything else I should check or should I just replace it?

If the engine is losing coolant, it’s not a thermostat problem.

The engine has a coolant leak somewhere. And if you don’t see coolant on the ground, pull the oil dip stick out and see if the oil looks like this.

Tester

Thanks for the suggestion. Just checked the oil and that looks normal, and was half a qt. low, which isn’t surprising since it does burn oil. Doesn’t look diluted or a different color or anything.

If this helps, when the car is cold now, the coolant level is about 1 inch from the radiator cap (I assume that is full?), even though the coolant level in the overflow tank is empty after just filling it and before running the car. Should I keep adding coolant to the overflow tank?

Yes.

But also locate the coolant leak.

Tester

Possible, but seems unlikely. Next time it overheats, pull over, keep the engine idling, and check if the engine compartment cooling fan(s) are spinning. If they aren’t, that’s got to be addressed first.

Beyond that, you are losing coolant and you need to find out where it is going. It’s possible you have an external leak, but it is a slow leak and it all evaporates on hot engine parts before it reaches the ground. Or the leak is inside the car, so check for coolant under the carpets. Any sort of leak like that makes it impossible for the cooling system to hold pressure, and that almost always causes overheating.

Good idea w/this symptom to warm the engine to normal operating temperature with the radiator cap off. As it warms up look into the top of radiator, bump the idle rpm a little, checking for streams of small air bubbles coming up through the coolant. If you see tiny bubbles, have your shop check the engine for an incontinent head gasket. If you see a few big bubbles, like the radiator is burping, that may not be a head gasket problem, but what happens when you have an external cooling system leak.

Finally, if this car still has the original thermostat, no harm done to just replace it. While I doubt it is the cause of the symptom, it probably is on its final legs. On the V6 3L engine it looks to take about 1.5 hours, so not too big of a job. It’s also possible while replacing the stat that you’ll see coolant stains somewhere , indicating a leak.

In an emergency it’s sometimes possible to cool off the engine by turning on the heater to max, and heater fan to max.

Thanks everyone for the tips. I refilled the coolant overflow reservoir again, ran it again and looked for leaks. I did see a little liquid pooling on the engine in a divot where the alternator connects to it, as if it’s leaking out of the valve cover gaskets and dripping down. I opened up the oil fill cap and it was smoking (coolant burning off?) and when I dip a paper towel in there, in seems too liquidy to be just oil (but then again it was also hot at this point, so not sure). Checked the oil dip stick again but now that seems to be more liquidy too. Also the reservoir is down to 1/2 full after running the car for about 10 minutes.

Not sure if this is related, but the car also has been burning more oil than usual in the last couple months.

If there’s coolant in the engine, does that mean this car is ready for the junk yard?

That’s an external coolant leak.

Bring the vehicle to a shop close by. And ask that they do a cooling system pressure test to locate the leak.

What they find will determine the destiny of the vehicle.

Tester

Do you see anything unusual, milky, cottage cheese like stuff, on the underside of the oil fill cap? Likewise on the underside of the radiator cap. If not, focus on what’s causing the known external coolant leak first. You know you have an external leak b/c you can see the coolant pooling on the outside of the engine.

It does sound like it could be a hose, but could also be another cause, if the leak is coming from the base of the cylinder head. Does this have the 2.4L engine? Hopefully not.

I don’t see a mention of the engine size. If the mechanic suspects a blown head gasket, it is possible you could have a problem of the 2004-06 2.4 liter engine. A head gasket will blow. When they tear down the engine for repair, some of these have stripped threads in the engine block.

The good news is there is a repair, other than replacing the engine.

One thing the video doesn’t say if mechanics found it was 3 bolts that commonly failed, not all. This saves on the repair. This video shows what he did to fix the repair, what he expected to find, and the actual blown head gasket… more than you probably need. He used a different product.

“This is how we repaired a 2.4L 2az-fe engine in a 2006 Toyota Camry using helicoil bushings from the NS300L kit.”

Yup, it has a 2.4L engine.

I greatly appreciate all the help everyone! Will post a photo of the pooling liquid in a few moments.

There is a little bit of crusty pink stuff on the edge of the radiator cap, but nothing unusual under the oil fill cap.

Ok, here’s a photo of the pooling liquid on the side of the engine, near where the alternator connects. Look in almost the exact center of the photo at the dark oval. That is where the liquid (coolant?) is pooling. Not sure where it is coming from. At first I thought it may be dripping down from where the valve cover gasket is, but that could just be old oil stains that I see.

Nothing seems to be dripping from the radiator hoses.

That looks like an external head gasket leak.

Because to the right in the image, i can see the heat shield for the exhaust manifold.

How much do you want to spend on this vehicle?

Tester

Thanks for the video. Yeah, this Camry has 210k miles on it. I’m obviously not a mechanic and probably wouldn’t pay too much to fix it since it’s probably only worth $1,500.

Don’t want to spend too much … probably not much over $500. Does it cost a lot to fix an external head gasket?

If it’s the external head gasket, does that mean that coolant isn’t mixing with the oil?

We know there’s an external gasket leak. So coolant isn’t mixing with the oil. Yet!

But it can turn into an internal gasket leak. And when that happens, stick a fork in it., it’s done.

To properly fix this requires removal of the head to replace the head gasket. And unless you have the tools and experience to do this type of repair, the cost to have someone else do it will be greater than the value of the vehicle.

You could always sell it on Craigslist as a repairable for $500.

Tester

Thanks for the idea to sell on CL! Didn’t realize people would pay that much for a repairable. Otherwise, it runs and is in good shape, except for a slow leak of the power steering fluid.

Probably, but let a shop verify that before making any decisions. They’ll pressurize the cooling system and then it will be easy to see where the leak is occurring.

If it is an external head gasket leak your car should be pretty easy to sell to a diy’er type, as that problem is considerably easier to fix than the type where the coolant and oil mix, or coolant gets into the cylinders. Conceptually replacing the head gasket is simple: The head is just a hunk of metal that sits on top of the engine block (where the cylinders are). There’s a gasket in between those two parts. So you just unbolt the head from the block, remove the old gasket, put the new gasket between the head and block, and bolt the head back on again. the problem is that the head is sort of like the engine’s grand central station, with air and fuel going in, and exhaust going out. So there’s a lot of stuff connected to the head, and it has to be disconnected first, which makes the job very time consuming. It’s also possible when the head is removed a problem will be revealed which will require a machine shop to fix, more time & another expense.

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Great advice … thank you. Any idea what most shops charge for the pressure test?

Also, any harm in keeping the radiator filled with just water for now, since it goes through it so quickly? Or do I really need a 50/50 coolant/water mix to keep the engine cool enough?

I’ve never had that test performed so don’t know. You could do it yourself with this.

https://www.harborfreight.com/radiator-pressure-tester-kit-63862.html

So it would be hard to charge more than $90 for that test I’d guess.

The cylinder head is aluminum and will corrode quickly w/plain water, so don’t do that.

If you’re serious about getting rid of it, And if it’s only an external coolant leak, I’d try something like Bar’s Leak Head Gasket Fix, $25.00 Might get you a few more months out of the car.

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