I have a 1988 F150 with the INLINE 6 and i have low compression in cylnder 4 and 5. Cylnder 4 is at 90psi and cylnder 5 is at 45psi. It is pushing oil up and out of by the dip stick and it was comming out of the pressure release hose that leads into the air box. Does anyone know what this problem is?
Thanks,
I.6.O.D.

 

My guess would be that your head gasket is leaking. Sounds like your losing your compression into the oil galley holes that run through the head. So basically your pressurizing your crankcase with engine compression.

 

Your saying that my only problem could be my head gasket? Or what else would need to be fixed/replaced/
Thanks,
I.6.O.D

 

I'm not saying that's is your only problem or even definatly your problem at all, but if it was mine that I'd what I would put my money on. Did you overheat at some point recently?

 

I'd say that BigBlueOx is on the right track. Especially since it's on two cylinders that are right next to to each other.

 

I would say head gasket to , you can put a little oil in cylinders 4&5 & test it again & see if it changes ? ....Lew

 

i put a little oil into the cylnders and the oil pressure went up significantly. What does this mean?
Thanks,
I.6.O.D.

 

And i did not overheat recently. just thought ide add that in there because i forgot to before.
Thanks,
I.6.O.D.

 

And if it was the head gasket why would the oil be pushed up and out of the dipstick and the pressure release hose leading into the air box?
Thanks,
I.6.O.D.

 

cause the air that was in the cylinder could be making its way into the oil galley and going through the path of least resistance

 

....That indicates bad rings ...Lew

 

Ok. So if i have to rebuild both of those cylnders do i have to rebuild all 6? how much do you think it would cost to get the problem fixed at my local mechanic?
Thanks,
I.6.O.D.

 

Does anybody know about how much it would cost to get my engine rebuilt at my local mechanic?
Thanks,
I.6.O.D.

 

That all depends on the local machine shop , depending on what all needs to be done , they should be able to give you a price but its hard to tell with out taking the motor apart .....Lew

 

Did you put oil in all of the cylinders? New or old an engines compression will increase when oil is added to the cylinder because it gives a better seal.

I'm not saying it's not a good way to check for bad rings but you have to know what the specs are to properly diagnos such a symptom.