hello, i seem to be having a problem with my truck, its a 1997 ford f150 4.6l w code 4x4, the coolant seems to be pressurizing all the time, so i changed the thermostat thinking it could be that, well that didnt work. So what i have been doing for the past month is having the cap on the resevior very loose as to let out the pressure. this has been working great and the truck has been running great.

but i have found another problem, there is coolant leaking in the v of the engine from my water pump were the the heater core hose connects to it , actually when i started up the engine i had my dad look in the v and he could see it leaking.

Now my question is.... how could a leaking heater core couse connecting to the back of my water pump cause my coolant system to become pressurized?

 

typically this is a sign of compression from the cylinders being leaked into the coolant system. (head gasket)

I cant remember exactly but typically that style of fitting has an oring to seal it, probably finally rotted out.

 

I thought the overflow tank was supposed to be slightly pressurized?

Not to thread hijack but if it is pressurized but the truck runs fine, heater works good, no oil in coolant or vice a versa then what?

 

yeah that is what im trying to figure out, the truck is running fine, the heater works good, and there is no oil in the coolant, all that is happening is that tube is leaking in the valley, so i hope when i replace that tube it will finally stop presurizing, and the coolant is still up to the line, it hasnt gone down much at all, and im not complaining for now cause its running great

 

Are you getting overflow coming out from the bottle?

If so, maybe you need to change out your radiator cap or overflow cap. If it is relieving pressure at less than 15psig you will get coolant blowing out when the engine is hot and eventually you will lose too much coolant.

 

i changed the cap with a known good one, but when its tightened up, clicking sound, then it wants to overheat, but when i loosen it up it releases the pressure and some coolant, but not alot though,

 

i changed the cap with a known good one, but when its tightened up, clicking sound, then it wants to overheat, but when i loosen it up it releases the pressure and some coolant, but not alot though, ive been keeping an eye on it

 

The cooling system is SUPPOSED to be pressurized - 16 psi. Do a hydrocarbon test on your coolant to check for a blown head gasket.

 

Oop, my bad I assumed he was referring to overpressurized.

 

If it overpressurizes, the cap should relieve the pressure to maintain it at 16 psi. If the cap is faulty and doesn't release the pressure, then it's going to leak out of all kinds of things.

 

Did you "burp" the system while refilling the coolant? Or enough? I've never not burped it enough to get problems so I can't say for sure your issue is this, just a thaught.

 

well im going to get a hydrocarbon test done on it today in my auto lab class, so i will let you people no what the results are later today, thanks for all the help

 

well the hydro carbon test came back negative, so i tried another coolant cap and it worked, so yay no more thoughts of a leaking headgasket!, thanks for all the info and helping me out, im pretty sure my waterpump isnt leaking cause i think it had it had antifreeze in the v when i changed the thermostat, so yup things are looking up lol