Just got my 6.0 LQ4 in and fired up, seems to be blowing a lot of coolant out of the overflow tank. First startup with this build, just want to be safe. Also does anyone know if the overflow should be mounted higher than the top of the radiator (the same as a stock truck)? Using all stock components (radiator, hoses, overflow, etc.
This is in a 72 c20

 

Overflow should be highest point. You probably have air in system and it's overheating.

 

Edit>Sorry for the repeat. I agree with "tarinitup".

 

Make sure your air bleed tubes arent restricted.

 

like they said up there, also could be a bad head gaskets, or sense its a new build, are the heads torqued right ?

 

YEP ^^^^^^^^^^ All the above

 

Could be a bad cap also?

 

Yeah, forgot to add that it's a new build with a used stock longblock. Ran fine before putting it in the 72 C20. Just the overflow issue. I think the height is going to be the issue. Right now it's about even with the top of the radiator.

 

Does any company offer a cheap kit to test for exhaust gases in the coolant system?
I know the dealers can do it.
Planning on lifting the overflow tank as high as I can today. I'll let you know if it fixes the problem

 

you can buy a pressure tester for the cooling system that screws on to the top of the radiator or overflow, has a pump that you pump up the system with and it should hold pressure. if it looses pressure its leaking somewhere and you may be able to see it leaking. they are pretty cheap.