1999 Ford Ranger 4.0 4WD Auto. I just finished a successful transmission swap looking to fix no reverse and rough driving, but it has become apparent that u have a pretty good misfire.

I’m replacing valve cover gaskets to try to fix it because there was lots of oil on the spark plugs threads and the VC gasket is obviously leaking especially on the driver side. However while I’m here I thought may as well replace upper and lower intake gaskets and do a coolant flush/thermostat since it needs it bad anyways.

My question is do yall think I might be lucky and it really is just the lower intake gasket leaking oil into coolant, and if not how do I go about ruling out head gaskets/cracked cylinder? Also there is oil in the coolant but no coolant in the oil. Thanks!!






It could be leaking in the same spot on the other end of the gasket well

It looked like someone had used way to much rtv on the gasket where the coolant channels are on the firewall end of the intake, however I believe that is because the coolant channels don’t pass through into the intake as the intake side channels are blocked with metal.

 

I'll bet you ten dollars to a donut that you have a blown head gasket.These 4.0 OHV engines will not tolerate any "overheating". I have a 99 4.0 and I replaced my upper and lower gaskets, along with the VC's last year and I found NO sludge mix anywhere.

Here's the issue from where I sit. It's twofold. You are already this far into the engine. If you put it back together and the head gasket is bad you have wasted the time and money you spent for the gasket set. However, if it does have a bad head gasket and if the head is cracked, which is the common reason on these engines, things just got REAL EXPENSIVE to fix, but what choice would you have. You either fix it or let it sit!

FWIW, I would clean up those carbon deposits in the combustion chambers while I had it apart and I would also remove the injectors and replace the o-rings.

Good luck!

 

my thought would be I would do a compression test