So I have a 98 f150 with a 4.2 v6. I did the head gaskets on it back in June, which seemed to have gone well. All except the valve seals were leaking. I figured of the things that could have failed on such a job, those were among the better. So I replaced the valve seals again. This time with the heads in the motor which is no easy task on a ford 4.2. Still smoked white/light blue on startup, and at high rpm's. compression was normal, and 150-160 psi across the board. must be valve seals, Right? Replaced them again, treating each one with the care of a newborn baby. STILL!!! Smoke on startup, and at high revs. still using/burning about a quart of oil per 40 miles. could this be an issue created by exhaust back pressure? I'm dead sure I have plenty of that. If not before, these cats have to be a solid chunk of carbon by now. What would you do next? do you think it could be the head gaskets? I think only coolant goes through the passages in the cylinder walls. The ones that pass through the head gasket. coolant could explain the white smoke. but I'm not loosing coolant, I am loosing oil though, with absolutely no leaks. There is nothing i can think of that a compression/leakdown test wouldnt tell me about. Any ideas?

 

How loose were the valve guides?

 

Didn't seem loose at all. when I did the head gaskets though. now that I think of it. I re-lapped the valves and cleaned off the shafts with 220 grit sandpaper turning them in the chuck of a drill. Think that may be the reason? I turned them very lightly and I'm sure i couldn't have removed much metal.

 

I don't think you ground off enough metal from the valve stems to matter. If the valve stem clearance is too much the valve seals won't seal well. I'm sure you've replaced the PCV? Right? Did you use gaskets or silicone on the intake manifold? I'm not familiar with the 4.2 engine design but it may be possible that if the intake is leaking it could be sucking oil from the valley under the manifold? Just wagging here.

 

I have not replaced the pcv's (there are 2 on the 4.2) but they function normally as far as I can tell. I will replace them just for gits and shiggles, cant be too expensive.. How would I test that gasket though? i guess i could with a vacuum gauge, but it wouldnt tell me conclusively that it was the lower intake gasket leaking. Just that there is one. The lower intake uses 2 gaskets that are 1/4" thick plastic/silicone. One gasket for each bank. there are also 2 rubber seals that span the length of the lifter valley that I think I used black rtv on, but definitely some type of silicone sealant as it said to in the book. I didnt like the way the gasket for the left bank sat when i had it on the alignment pins either. it seemed like the gasket was too big. big enough that being on the pins made the center of the gasket bow upwards about an inch at the apex in the center of the gasket. I guess the lower intake is next up, you could be right, sir.

 

Thanks for helping out, Roadie. You have pointed me in the right direction before, and I think you may be onto something again. I will let you know what happens, but it may be a week or 2. I'm freakin sick of working on this truck every weekend!! Thanks again, brothaman. Everyone who owns a ford should have a Roadie!! lol

 

I hope I deserve the praise. Let us know what you find. I'm not a mechanic but an engineer. I have been repairing my own vehicles for over 50 years so I have picked up a few things here and there. Oh, the 5.4 engine doesn't like aftermarket PCVs. Motorcraft is preferred. Don't know about the 4.2.

 

Well, Roadie... I think this truck is on its last leg. I have done literally everything that I can think of to fix it, but rebuild the motor. and that may be next.. That or a new truck.. I'm stumped. Thanks for all the help though, it is much appreciated!

 

Roadie, I hope you're still out there. I need to pick your brain again. I was coming down the I 70 hill west of the Eisenhower tunnel, and all of a sudden I lost all power. I have had similar things happen in the past where I had my 4wd shifter pop into neutral, and as soon as I put it back into 2wd I was fine. I think what is happening though is that my hubs aren't disengaging and the truck thinks it is in 4 low. What do you think? Does this truck even have disengaging hubs or does it just disengage the driveshaft to the the transfer case? I would think that it has hubs that disengage too so that the front wheels aren't constantly spinning the transfer case. So the symptoms are: it is shifting very quickly, as if it was in 4 low. It won't let me go faster than 35 or 40 without going into a limp. Tre transmission seems fine, but the transfer case is whining to high hell. What do you thing roadie? Should I throw a disengage solenoid at it? I feel like I want to verify this has locking hubs first. Do you know?

 

You should check your vacuum lines.

 

vacuum lines are all in order. Now I am starting to wonder if I didn't spur off some transmission issues because of this because it won't reverse. I think there must be something up with my shifter, if ut is the transfer case, and that's why it keeps going into neutral. But I don't know if neutral on the transfer case should translate to neutral on the entire transmission. Either way. I shift into reverse and all I get is grinding gears

 

Take a look at this video and see if it helps.

 

You do not have locking hubs. There is a vacuum-operated lock in the front differential.

Sounds to me like for some reason you ARE in 4L.

 

indeed, but it's a manual shifter, so if should switch out of 4 low when I put into into 2wd, right? Maybe you can answer this question for me. If I have my 4wd shifter in the neutral position, will the back wheels still spin in drive, or does that effectively disengage the transmission altogether? If there is something up with my shifter which is what I want to suspect at the moment, because its going to be a lot cheaper and easier to replace a transfer case than a tranny. The 4x4 shifter seemed to be working fine until a few minutes ago. Now if I move the transfer case shifter it makes a lot of grinding sounds. I think I f'd off the gears in my transfer case or something. Before it wouldn't reverse. Now it wont do anything but pop and grind. I can feel all of this happening through the transfer case shifter. It seems like something is not engaging now. I did all the vacuum line troubleshooting, and the solenoids, and actuator on the front of the transfer case seem to be working fine. I don't have a jack with me. So I am pretty much out of options for troubleshooting at this point. I think i t has to be the shifter for the transfer case. If it was my tranny the fluid wouldn't look bright red and smell brand new. I am about stumped.

 

It may be a lever, but it's not mechanical. It's all electric and vacuum.

With the transfer case in N, neither driveshaft should turn.