I just put in a new radiator in my 1988 f-150 i6
It’s holding pressure in the radiator, I just checked the coolent after letting the truck sit for a week. There was enough pressure to spew coolent out of the radiator when I took off the cap. Any suggestions????

 

Put a new radiator cap on it.

 

I have a brand new cap on a brand new radiator

 

A small amount of air trapped in the system would cause that, with some driving it should work its way out.

 

Which brand? Which PN? From where?

 

Any name brand cap designed for your vehicle will do fine. It is not necessary to use a Motorcraft. It's likely made by a big maker anyway such as Stant in a plant somewhere in Mexico. I haven't used an OEM cap in over 30 years and never had an issue.

 

I bought the radiator and cap from O’Reillys auto parts

 

My temp gauge barley works, most days it doesn’t read, others it moves up just a little bit
any suggestions?

 

Verify the operating temperature of the engine.You could warm up the engine with the cap off, measure the coolant temperature with a meat thermometer. Coolant should be around 195.Or after driving,if the upper hose is very warm, you likely have a bad sending unit for your gauge.It is a single wire unit and is difficult to see and access. It is screwed into the block on the passenger side, slightly in front of the starter area.

Replace the thermostat (195 degrees) if the engine is running a lot cooler than than 195, upper hose is not vaery warm and you have no heat.This is where I would use a Motorcraft thermosat if possible. A good alternative is a Stant Superstat.

 

If it is rated for the specified pressure, it should be fine. No rocket science with a radiator cap.