I have a '98 Ford Ranger with the 4.0, it has about 190,000 miles on it. I purchased the truck from my dad about 2 years ago, it had 178,000 miles on it then. When I bought it from him, it had fouled the #1 plug and noticed some slight coolant loss. The problem didn't happen again for another year or so. Now, I fouled a plug in less than a month, and coolant is disappearing a lot quicker. It seems like I might have a head gasket leak, but I've also read that it could be the lower intake gaskets.

Is there some way to determine between the two? I have noticed a hissing sound like a vacuum leak, possibly the lower intake leaking? Any opinions helpful!

 

Well, to start, are you leaking coolant on the ground or is the truck burning it off? I'm not sure what they use, but if you suspect the lower intake is leaking, you can spray something (brake cleaner?), not sure though, around the lower intake and if the rpms change then you know you have an intake leak. Someone on here with more expertise than me can tell you for sure what to use. If however, the motor is burning to coolant, its either the head gasket or the head itself that is bad. Pressure test the suspect cylinder and if it doesn't hold pressure, that would tell me that the head is cracked. If you still have the old plug, what was the condition of the electrode and the porcalain around the electrode? Those two things would be big clues. Just my two cents. Hope this will get you started.