Car Help! (Coolant)

[LVSteve]

Sorry I should have been more specific. I did not remove the radiator cap, just the lid from the reservoir. There is a hiss when I do this to fill the reservoir, even when the car sits overnight.

This implies that the system is remaining pressurized. You may just be getting the last of the air out. My SUV is a bear to bleed properly and the best advice was to drive it for a week or two and keep a close eye on the levels. That seemed to work.

One thing baffled me when researching this kind of thing. Lots of folks were getting pressure checks that were good, but they were still losing coolant. Of course, the pressure checks were done with the engine cold so that opens up the likelihood of a leak that it only present when the motor is hot.

Safe travels, and carry extra coolant.

One thing to add, the sealed cooling systems on modern cars work rather differently to what I was used to with 1980s motors. What we used to call the "expansion tank" is now part of the pressurized system, and coolant can move freely between the radiator and this tank. The tank has a pressure cap that in extremis will release and probably dump coolant in the street. The radiator has it's own cap set at a higher pressure than the tank cap. I think it is there to prevent a cooling system blow-up if the tank cap fails and won't open.

 

[rwsmith]

Be really careful...

I had repairs made to the cooling system and the warped heads after a bad overheat. I thought I was in the clear, when out of the blue, the same thing happened. I had to junk the car. Keep a really close eye on your temp gauge and stop immediately if the temperature starts going up.

I don't know how compatible with today's cars this is, but you might carry along a can of 'stop leak' if you can't find the leak.

One problem with filling it up when needed is that the radiator really needs to cool down or when the pressure is released, the coolant will flash into steam and lose about half of your coolant. You will need plenty of patience.