Hey all,
I have a 2003 lm7 5.3. I decided to ditch the expansion tank and go with a moroso filler neck. What psi radiator cap are you guys using? I just tried to run a 16 psi one and I overheated within 2 miles of driving.

 

I have the exact same engine in my Scout, donor vehicle was a 2003 Tahoe.

Temperature stays rock steady (so far) at 190 F. My cap is a 16 PSI.

Running this radiator:

RnD Fabrication 1965-1971 International Scout 800 & 800a Downflow Radiators

Hope this helps, good luck.

 

Thanks!

I think we finally came down to the issue of their being air still in the system. I think all of the coolant sprayed out of the overflow trying to get it back to the shop, so tonight we are going to try to properly throw coolant in their with a coolant funnel. Hopefully we see better results tonight.

 

I run a 18psi cap from a Fbody

 

I run a 16 psi cap on the filler inline with the top hose no problem.