Very slow coolant leak?

[tmpnsnty]

Car: 2000 Camry Le (5s-fe) - around 165,000miles

Recently I've noticed my coolant reservoir has been going down very slowly. It took 1 month and a half, maybe even 2 months for it to go from the full mark to low. Right now I've just pour some distilled water to get it back to full, but what should I do now?

I've checked the hoses for leaks, but no cigar. Also, the hoses are replaced about 1 year ago, when the radiator was replaced. Should I just get my oil tested for coolant leaks? Possible head gasket problem? Or is it too minor that I should just keep refilling it with a 50/50 coolant mix once in a while?

Thanks
Jim

[carsrus]

Thats small enough where it could theoretically be just evaporation if the cap on the overflow is bad.

However, check waterpump weep hole for crustation and look at rad cap after a good long drive.

[Pvt-Public]

carsus, evaporation loss due to a bad overflow bottle cap? C'mon they all already have a vent hole so does that mean they are all bad? Bad radiator cap maybe, but overflow bottle cap, I doubt it. The weep hole is a good call that's where my really slow leak was, you could see the crud around it.

[fenixus]

yeah, if temperature levels in your area go past 100F for a long time, then the coolant will start evaporating from the return tank. I see the same here in NJ over our short (but hot) Summer. throughout 1-2 months it can drop half an inch from former level.

don't worry the system is not sealed on return tank side, so it's just evaporation. top it off with distilled water until level sits at LOW when car is cold and touches HIGH when car is fully warmed up.

[carsrus]

Originally Posted by Pvt-Public

carsus, evaporation loss due to a bad overflow bottle cap? C'mon they all already have a vent hole so does that mean they are all bad? Bad radiator cap maybe, but overflow bottle cap, I doubt it. The weep hole is a good call that's where my really slow leak was, you could see the crud around it.

Bad cap is an inherent design on these bottles. Look at the top of it one day, they slowly let coolant drip out. Its regular practice to top off coolant a cup or so each year, the vent tube allows minimal evap but combined with the bad cap it adds up.

[Zembonez]

It is possibly (at 165K) that the head gasket is seeping slightly but your problem sounds so minor that I would just keep an eye on the level and drive on.

[fenixus]

well, OP is from Texas, some long drought and heat wave over there. I'm not surprised that some coolant evaporated from the return tank over Summer months. I really wouldn't worry about it.

EDIT:
just noticed that you (Zembonez) are from Texas too

[Zembonez]

Agreed.

[tmpnsnty]

Thanks for the replies. I guess it's probably just the heat. It has been pretty hot this summer in TX. Almost the whole summer is over 100F.

I've checked radiator cap, it looks fine. Weep hole looks dry too. The head gasket is replaced around 120k miles.

[71Corolla]

Originally Posted by fenixus

...don't worry the system is not sealed on return tank side.

Yes and no. There is a pressure check valve that opens either when the coolant is being drawn from the tank, or being pushed into the tank. Otherwise, the system is sealed. For some odd reason it took me a long time to realize this, there is a valve on the cap. I know because I once put it on backwards which meant the check valve would only allow coolant to be pushed out of the tank and onto the ground.

[pmesfun]

^That is the system for J-vin cars?

[71Corolla]

I know the coolant overflow tank is different for U.S. made models (some at least) for whatever reason, so does that mean the cap doesn't have a check valve? I'd be surprised if it did not.

[fenixus]

well, yes, the cooling system itself IS sealed by pressure valve, but contents of the return tank are NOT sealed from atmosphere, that's what I meant.
my both cars have pressure check valves in radiator cap (1mz-fe on the block and 5s-fe on the actual radiator).

I made that mistake of opposite installation on my former 3.8L GM took me a while to understand why I had a problem with cooling there even was an arrow painted on the cap pointing the flow direction (must point to radiator) ... well I put it the opposite way hehe...

Originally Posted by 71Corolla

Yes and no. There is a pressure check valve that opens either when the coolant is being drawn from the tank, or being pushed into the tank. Otherwise, the system is sealed. For some odd reason it took me a long time to realize this, there is a valve on the cap. I know because I once put it on backwards which meant the check valve would only allow coolant to be pushed out of the tank and onto the ground.

[fenixus]

yeah, it must be it. I live in Jersey and we have short but hot Summer (tropical weather gets here) in our mixed climate zone (marine, warm and cool mixture depending on time of year). since I park my both cars on the streets and in open parking lots only they are subject to Summer heat (I think it gets easily to 150F under hood if car is parked in direct sunlight).

coolant level always drops a bit during Summer. I topped off 1mz-fe (was flushed) in beginning of Summer (or late Spring) and I can see now it's lower by around half inch .. that's only after a few months.

5s-fe did pretty much same (dropped coolant level a bit), but that car was barely driven in that time.

neither of cars "loose" coolant during Winter months though. so it's kinda a proof that it evaporates from the unsealed return tank when it gets really hot.

Originally Posted by tmpnsnty

Thanks for the replies. I guess it's probably just the heat. It has been pretty hot this summer in TX. Almost the whole summer is over 100F.

I've checked radiator cap, it looks fine. Weep hole looks dry too. The head gasket is replaced around 120k miles.

[fenixus]

US/Canada made/marketed cars have no pressure check valve in return tank's cap. there is no seal even, it's just a bare piece of plastic

as I mentioned above, the actual pressure check valve is under the radiator cap and that's the only one on my both cars. from pictures of pmesfun's Avy I can say his is same.

Originally Posted by 71Corolla

I know the coolant overflow tank is different for U.S. made models (some at least) for whatever reason, so does that mean the cap doesn't have a check valve? I'd be surprised if it did not.