*91f150*

So I decided to pop the rad cap off while the motor was cold to see if I had any bubbles.
The coolant literally starts flying out of the rad cap right away. But the overflow tank has a little rubber hose the runs right to the top of the filler neck. Which is already pumping right away. Why is it already pumping coolant through the system? Themo stuck open? No thermo at all? If it was stuck open would this be normal?

*91f150*

I dont know what to think anymore about this truck. I've been through it again and again in my head "is it a blown hg or not"
I should mention thatthe first time out I pulled the rad cap off b4 starting the truck, and my truck revs close to 1200 rpm til I hit the gas once, yes just once, anytime, and it idles down immediately to about 600.
Anyway I went out and did it again. Started it first then pulled the rad cap, nothing at first. Then the coolant came up slowly a few small bubbles, but nothing I would call a bubble.....lol.
It is norma,l is it not to see the movement in the coolant almost right away? I mean like a swirling motion

transmaster

Yes, the thermostat is closed off so the engine can reach it's operating temperature soonest, more or less closing the radiator off you will see very little movement in the radiator. When the coolant temperature reaches the opening temperature for the installed thermostat it opens and coolant can then circulate freely throught the Engine and radiator. as for the coolant blowing off in your face, if the system is properly filled you don't take the radiator cap off at all instead you make sure the proper amount of coolant in maintained in the overflow,or expansion tank.

Go here to learn how your cooling system works:
http://auto.howstuffworks.com/cooling-system.htm

*91f150*

The truck was cold when I took the cap off, I was looking for bubbles as a headgasket sign.
And like I said the coolant is flowing full tilt as soon as the vehicle is started, and the reason it was blowing all over the place is bc the engine idles high when first started. Therefore turning the water pump faster, and throwing coolant around.......lol.
Going to change the thermostat this weekend, I head its a pain. I suspect there is no thermo in there.

Guillotine

What year is your truck and what engine does it have. Pull the oil dipstick and see if the oil still looks like oil or chocolate milk. If it looks good then I doubt the you have a bad head gasket.

*91f150*

91, 5.0
I've posted about this in a few other threads. But no, no chocolate or peanut butter just a little bit of froth on the end of the dipstick occasionally. The cap also gets a little milky sometimes. When I take the cap off after driving a little water drips off. Doesnt look like coolant or smell like coolant. Exhaust smells sweet, but not like coolant. No white smoke. the trucks been missing a little lately but I attribute this to the cold weather, poor plugs, wires and cap.

Guillotine

Your heater core or rad may also be getting gummed up if they are original. Start with the T-stat since that is the cheapest and report back.

*91f150*

Dipstick.....cold
https://www.f150forum.com/members/-9...5-img-0279.jpg

*91f150*

Under the oil cap....you can actually see the pure water droplets

https://www.f150forum.com/members/-9...6-img-0280.jpg

Guillotine

The oil looks fine. It's odd that there are water droplets under the oil cap after driving. I could see it if the truck sat overnight.