Cooling system help

[JL7mgte]

Hey guys, I need help figuring out what's wrong with my cooling system. Symptoms:

1) After driving the for about 20 minutes, the coolent will overflow out of the radiator.

2) After this happens, the coolant level in the radiator is low and is not is not re-filling itself from the overflow bottle.

3) The heat is not working.

I believe I have ruled out:

1) Water pump (because it's new)

2) New radiator.

3) Not a BHG. Passed NAPA coolant test, also had mechanic check for BHG.

I've had a pressure test done on the coolant system with dye in the system and the mechanic did not find any leaks. He also checked to see if the heater core was blocked and it was in good shape. Right now I'm at a loss as to what is causing coolant to back out of my system. Any Ideas? :1zhelp:

 

[Silent Smith]

Weak rad cap maybe?

 

[JL7mgte]

Weak rad cap maybe?

I wish it was that easy. I have a new cap and radiator.

 

[mrnickleye]

Mine did what yours is doing. The top hose would get very hard, then finally the cap would let the pressure over to the bottle.

The BHG just didn't show up. I burped it several times over 2 months. Finally, after 3 test over 2 months, the block test chemical showed a BHG.

When I got it apart I saw a "tiny" spot where it was allowing compression into the coolant. I believe it only did this during combustion, when the pressure was at its highest.

 

[suprastanger507mgte]

Napa block tester is garbage: Do a leak down test.

 

[JL7mgte]

Well, if it is a BHG, it's still under warranty because the mechanic just fixed it a couple months ago. He's doing a leak down test now. Thanks for the replies.