Hello Everyone!!

I've searched the forum and I can't find a solution to my problem.

Here's the deal:

I replaced my 150,000+ mile engine with one that's barely over 50K mi., and it's overheating while driving at highway/freeway/motorway speeds. During idle, and while running errands, it doesn't overheat, but once I hit 50mph sustained for a while, the temp gauge just keeps creeping up and never cools back.

1. No thermostat is installed, in Puerto Rico temps rarely lower from 80F.
2. The water pump is brand new.
3. No coolant is leaking, and the cooling system holds pressure well.
4. The radiator (2 row) is new (recored), and after the engine was installed, it's been flushed TWICE to remove all the junk left over from the engine re-build. PLUS, it's been rodded, just to make sure.
5. Plenty of water and coolant...

I'm running out of options, aside from installing a 3 row core. Engine compression is good, and I doubt the heads are leaking, since the coolant doesn't go anywhere, except when it boils over.

The radiator cap is NOT OEM, I'll be looking for an OEM soon, just to be sure.

PLEASE help meeeeee...I'm out of my wits with this one. <img src="/forums/images/graemlins/scared.gif" alt="" />

Thanx!!