1999 F150 4.6 Romeo Motor.... I have an issue with excessive pressure in coolant system. I was wondering if a leak in the intake manifold could cause this. I know a head gasket will do this, but motor is not producing any white smoke, oil is clean, and there is no oil in the water.

It will also spike the temp gauge 10-15 min after initial start-up, turn motor off.... wait 2-3 min, start it back up and the temp gauge is normal...... strange.

Coolant will push out the overflow cap on long drives.

Anyone have any idea's .... really puzzling !

 

i had a 96 with a 4.6 that blew a head gasket but never gave me signs of doing so except for the problems your having i changed everything before doing the head gaskets and that solved it but yes a blown intake can do that

 

what color is the coolant does it look like a muddy river