Got a 93 F150 with a 5.0 that is continuously running low on coolant. had a small leak in a water pump seal that has been fixed. I cant seem to find a leak anywhere on the engine or the radiator. Oil runs clean with no indication of coolant in it. I'm stumped

 

Check the passenger side floor- is it wet?

Also, if there is a leak above a manifold, or exhaust pipe, the coolant could hit that and evaporate before you would ever see it. Then, when the truck shuts off, the pump no longer pumps, and there is no leak! Many garages can add a die to the coolant then look under a black light to see where the leak could be.

Good luck

 

Could also have a head gasket leak into the piston
bore. Sometimes you can see a bit of a fog (mist)
out of the tail pipe after the engine is warmed up.

Have your system put to 15 to 20 lbs of pressure
and see if it holds with the engine off. You might
even hear a hiss.

Good luck..

 

heard i could check the spark plugs to see for abnormal discoloration to check if it was leaking into the piston bore... that true? if so what kind of discoloration?

 

im having the same issue in my 95, the truck never overheats always stays in the normal range.

 

I've actually seen it go into the transmission before also (if its an automatic) because of a bad radiator

 

In cooler weather you can keep your radiator cap loose.
The result will be, not letting your cooling system build
up any pressure. This in turn will *sometimes* stop
any coolant from being forced into a piston bore *if*
you think you may have a head gasket problem.

This may take a day or so to make sure no more coolant
is being lost. If no coolant is being lost after a few days
of driving, tighten the radiator cap up again. If coolant
is being lost again, you found your problem. Head
gasket on the right or left bank. Change both..

 

check all your hoses, the shop marked me down with a major defection in the motor because they found coolant on the engine somewhere and then a month or so later i found a loose coolant hose with coolant all over the engine under it

 

could be a leaky freeze plug....