2012 Scion xB
Runs freaking great at 126k. Literally never had any other issues than brake pads and wiper blades...
and I'm just now starting to burn a l'il oil.... about a qt every 3k.
Last winter. I hit the A/C button and blew a hole in the line.... ran without A/C all summer and finally got it fixed
this Fall. Weird enough though. And I'm not sure these 2 things are related because they didn't occur simultaneously.

But now my car is losing Coolant at an extremely rapid rate... 1/2 gallon a day??
There are No Visible leaks anywhere.
Took it too same mechanic as A/C hose issue and we did a pressure test on the system but it came back perfect. held pressure.

So when the car is running,.. heat gets HOTTTT inside then the coolant dissipates or goes away and it gets cold inside the next day....
both the top and bottom radiator hose get "warm" but not terribly hot and neither one seems to have much
"pressure" when you squeeze them... seems like there is no coolant flowing through them as it should be "under pressure"???

Any thoughts appreciated,

-Roy

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Hello Roy,

any check engine lights? is the exhaust fumes white? the cooling system is a sealed system, places that you could be loosing coolant are hose clamps, water pump, heater core,radiator, radiator cap, coolant reservoir cap.and head gasket.

 

Give your engine oil dipstick a look see. If the oil looks like swiss mocha, you [may] have a blown head gasket. If so, your mysteriously missing coolant might be in the crankcase.

 

My Scion has 267,000 miles, I am experiencing the same condition as Roy. Coolant is disappearing, did pressure test all is well no sign of a leak, checked my exhaust for white smoke, checked my oil for mocha residue, took out my plugs checked in there, everything is fine.
Yet the car indicates overheating, the coolant in the overflow disappears, half of bottle is used to refill. Also I have a purge flow problem and cylinder 2 misfire, rough idle. those are simple fixes, my main concern is the coolant.

Any help is greatly appreciated.

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ShortyRus - Pressure test. For the coolant system? I'd also do a combustion test on the cylinders. You might have a blown head gasket.

This will tell you if you have combustion gases in your coolant:

https://www.harborfreight.com/combus...tor-64814.html

 

Good place to start and there is also a test you can do on the coolant itself to see if it has any indications of combustion gases being pushed into it. Pressure testing the radiator isn't going to tell you if you've got a head gasket issue unless it's really bad. 12-14 psi might not be enough to push coolant into the combustion chamber and cylinder but 125-140 psi coming out of that cylinder has a good chance of pushing the other way, into your coolant system.

You said you pressure tested the system but did you also pressure test the radiator cap? I'd make sure that still tests as good as that would be an easy and inexpensive fix. I'd also look at the thermostat to make sure it's still good and not stuck closed or just partially open.

If you're pushing out 1/2 gallon a day it's obviously going somewhere, and it's none of the aforementioned tests you've done so far, I am going to bet it's a head gasket.

 

Thank you all so very much will let you know the outcome. Planning to get started on it tomorrow. I’m thinking it’s a head gasket.

 

This may help

 

thanks for the video definitely will help

 

perhaps your coolant tank or cap is leaking. Also check the hose running to it