Okay i'm losing my mind over this one!
I have a new pump, new thermo, new radiator but the engine doesn't always cool....

it works for a while, then stops then works again. Every time it stops working, i no longer have a heater which leads me to believe the water is not circulating....now when it does not cool and temp gets to about 210 before i shut the engine off, i go to the front and the cap has let water out all over the engine. Is it supposed to do that or should it just release pressure into the overflow container?

Anyone looking for a truck? i'm selling this one!!!
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I'm thinking replace the radiator cap and ur flex fan is crapping out on you and not pulling enough air through the radiator.

 

the cap to me makes sense...i'll try that first thing tomorrow but the fan doesn't because wouldn't i still be circulating hot air through the system and thereby still have heating?

 

Yes the cooling system will still be circulating but if there's not enough air coming through the radiator to cool the fluid you will run hot every time.

Does the truck get hot if you let it sit and idle in the driveway or when ur driving it?

 

sounds like an airlock somewhere in the system

i nearly overheated mine refilling the system after the plenum fix b/c a large amount of air in the system wasn't allowing the coolant to circulate, finally the stat opened and i was able to add more, the overflow was half full, let it sit overnight and went back to check it, the system had drained the bottle

 

it does sound like air in the system.

if a new radiator cap does fix it, you should do a pressure test on the coolant system to see if you can find a leak.

not wanting to create panic, but a leaking head gasket or head can can pump pressure into the system and cause similar problems.

if you run it in the driveway with no cap, and see an endless supply of air bubbles coming out of the radiator, thats another indicator of a compression leak. a compression test on each cylinder can usually confirm or rule out.

 

Could be as simple as a stuck t-stat!

 

^ th thermo has a jiggler valve. i found best results when thats facing te manifold....firt time i did it i had no heat, second time, i made jggler face manifold now i have hot air....but i could have gotten all the air out of the system and thats why i have hot air now.

 

that jiggler valve isn't on all thermostats. i know failsafe has one and my stant that i just put in there doesn't.

 

This is exactly what I would do to determine the cause. this isn't always a sure fire way of telling a blown head gasket but check your oil for water and just because its a new thermostat doesn't mean its a good one you might pull it back out and check it in a pan of boiling water. And I assume you properly burped your system whick can be a PIA if your t-stat doesn't have the little hole drilled in it.