Weird cooling system happening

[Bradjon]

I am getting ready to g to bill be to install a new water pump and injectors in my90 . Water pump seal is starting to leak just a little .about 12 oz a day . When I drive the car it doesn’t leak in fact doesn’t start leaking till about 1 hr after I shut it off . There stranger thing is she has sat for 3 days and went to fill turned the radiator cap and it went poof like the system is still pressurized? Huh I don’t understand had to add 24 oz of water but the system is still under pressure. Have taken the car on a 80 mile drive as kinda a test to see if would be ok to make the 460 mile trip and she ran between 87 /89 celcius and seem ok to go any idea why it still holds pressure after 3 days ? Help

[Bradjon]

I guess it won’t pull coolant from the overflow tank when there is a leak ?

[Ccmano]

The main pump shaft seal can be that way, especially when not driven for a long time and then suddenly driven fairly frequently. Seals dry up and leak, then plump up as their driven more. If you confirmed that the pump shaft seal is leaking, coolant dripping out, coolant residue below the weep hole, replace or reseal the pump. When your done recheck the system with a coolant system pressure gauge to make sure there aren’t any other leaks.
H

[Bradjon]

Thanks Hans just got a new water pump from Jerry as well as a. new set of injectors . Going out to bills on Monday to work o. The car for a. Few days fix the stereo plus maybe the air depends on money

[32valvesftw]

Radiator cap malfunction?