leaking radiator cap

[Grimm5577]

Sometimes you have to push the cap down with a fair amount of force til it catches the threads.

I'll try it again, but I gave it a good push, thought I was going to bend or break the overflow tank mount, the under side of the green cap has a center column (pressure vent?) which wouldn't fit into the neck hole of the overflow tank.

 

[old_man]

Take it to your local mechanic and have him put a sniffer in the radiator or use a bubble tester. These look for combustion gasses in the radiator and will pinpoint a blown head gasket.

 

[Grimm5577]

I took cruiser's advice and gave it another go with the green volvo cap. I really gave it some force and got it on, it threads on tight, and fits very snug. I drove it on two 2+hour trips this weekend and not a drop of fluid leaked out.
Thanks Cruiser!

 

[cruiser54]

You're welcome. The first cap I got, I thought it was wrong.

 

[gameface87]

Hey guys, I am at a loss. Is there anyother causes of a leaking radiator cap? I have no other symptoms of a blown head gasket, no water in oil, no white smoke, no bubbles in reservoir. Any other causes? I dont have a fan shroud. that wouldnt matter right? thanks again

 

[gameface87]

Figured it out! Looks like the thermostat was busted. Replaced the tstat and the housing with a new gasket. Also swapped out the idiot lights for real gauges and replaced the oil pressure sender and coolant temp sender. It runs at 210 all day!

 

[montanaman]

If you were just putting around the yard and lost coolant without being overheated, that could mean probable head gasket failure. It is likely the radiator developed a leak from being overpressurized.

Just my buck oh five..

I've heard of that before, but I don't understand ... isn't the radiator cap designed to relieve pressure @ 16 (or 13) PSI before the radiator gets over-pressurized? When pressure gets too high, doesn't the cap allow some fluid to escape into the overflow reservoir?