Hello everyone. Thanks for all of your help in advance. Here's the story.

I've got a '95 F-150 with a 351W and 181,000 miles. Last week I had a pretty bad exhaust leak from the headers, bad enough that it was melting spark plug wires. Unfortunately this all happened about 100 miles from home. I drove the truck about 15 miles or so, with no wire on the #4 cylinder until I could get to a tow truck place and have my truck towed the rest of the way home. I took the headers off and determined they were badly cracked, so I replaced them. However, my truck had to sit outside for about a week while I was waiting for parts to come in. It has rained a few times (I had the hood shut), but it is possible some moisture may have gotten in the heads.

Once the parts came in, I put it all back together again. New headers, new EGR valve and down tube (I broke them taking it apart). I also replaced cap, rotor, wires, and plugs. I started it up, and now I've got huge clouds of smoke coming from the tail pipe. I drove the truck, hoping it was just some moisture built up in there. It filled the street with smoke. Turns out its burning oil pretty bad. I even had oil leaking from the new headers, at the collector where I needed to tighten it up because it was still leaking a bit.

I pulled spark plugs and found that the #8 cylinder's plug had oil all over it. I cleaned the plug off and reinstalled it, but the oil just fouled it out after about 30 seconds. The smoke is definitely present at idle, but gets much worse up from idle. I'm thinking (and hoping) its a bad valve seal, but it seems strange that it would just happen all the sudden and be so bad. As far as I can tell, the heads are not cracked, and I didn't see anything abnormal while installing the headers. The valves looked good from what I could tell through the exhaust ports. They were covered in soot, but its an old truck. It ran like a champ before all of this happened. If anyone has any thoughts, I'd appreciate them. I welcome any help I can get, and apolozige for the novel I've written. Its just been one of those weeks and I'm about at my wits end here.

Thanks again, everyone.

 

Only thing I can think of that with the plug wire disconnected from #4, the injector was still firing, thus washing the cylinder down, diluting and ruining the crankcase oil. I'm a bit surprised though that #8 appears to be your only oil fouled plug. Either way, if you haven't changed the oil and filter, now would be the time to do so. I use a clean, yellow drain pan, so I can see any metal from the oil after it has sat for several hours and then drain it into a suitable container with a mesh screen. Since the oil was diluted, any number of things are feasiable.

Do a compression check on the cylinder's and that will give you a better idea. Hope this helps. Some auto part stores places rent compression testers, so that would be a start.

EDIT: Also be sure to check that the PCV valve is working properly. Perhaps you have a blowby condition and the valve is sucking in large amounts of oil. This would only apply if you have the PCV hose connected to the rear of the Plenum and not specifically to the Vacuum tree located in the center of the Plenum. Ford changed the PCV routing due to damage to the #8 cylinder. Since it was last in line and the PCV was located thus at the rear of the Plenum, it allowed for the #8 cylinder to suck in all the trash, sludge from the escaping blow-by gasses. Have also heard of it destroying th #8 piston, etc.

 

Dang, never heard of that. Could be the answer to my long standing mystery of a broken oil expander ring on my #8 piston (I've since replaced the long block). Thanks timbersteel!

 

Ok, so an oil change just might fix my problem, or at least help? I sure hope so. I'll check all the plugs on the passenger side as well, but #8 was the only one that was fouled on the driver's side. I was running out of time, and the driver's side seemed to be where the problem was coming from so that is the side I checked. I'm not real sure how oil could get into the cylinder though, even if it is ruined by fuel. Could you please explain? Thanks again. I hate it when my truck is broken, but I hate it even more when I don't know what the problem is...

 

If the problem was fuel dilution, and it would be there with raw fuel being sprayed into a cylinder without ignition, it will escape through exhaust valve and also down the walls of the cylinder. It's like watching water on a clear drinking glass when you wash it. It just runs down the sides of the cylinder pass the rings and into the oil pan where the crank is churning the oil and the splash was lubricating the cylinders. More and more destroyed any lubricating/cooling effect the oil previously had and thus the rings wear down due to the "viscosity breakdown". I suspect the oil ring is shot if the PCV valve isn't the problem, but with the oil no longer being able to perform it's job, the mains and rods bearings were taking a heavy toll as well.

Hopefully someone else may chime in with more help.

Also to GoinBoarding, have you since re-routed your PCV valve? This would be a Great time. I did and I also installed a MoshMito Oil Catch can in-line with it. In 1000 miles, 8 ounces of oil I collected. It's been great to keep most of the blow-by oil and trash from going back through the intak and coking the Plenum and intake manifold with sludge.

 

Sorry, I got mis-directed on my previous post about your question on how oil could enter the cylinder.

It can enter it from blow-by being sucked in through the intake. It can also happen when the valve guide seals are shot and leaking oil directly into the cylinder and when the oil expander ring is cracked, broken allowing oil to enter the combustion chamber.

 

I have not. Instead of the PCV plugging into the fitting on the back of the upper plenum you tap it into the little 3-way tree thing thats more on the center of the plenum? With an oil catch in-line?
A picture would be great.
To the OP, I sure hope its the PCV for you. Otherwise, time for an upgrade! (I mean rebuild).

 

Yes GoinBoarding. I just connected the brake booster line to the rear of the plenum and ran the PCV line to the center of the vac tree. I will post pics in my album. I will also take pics of my oil catch can setup tomorrow.

 

So, the problem could also be a bad PCV valve? I'm not new to working on cars and have done some pretty serious stuff before, but I definitely don't claim to know everything, so forgive me if I sound a bit dim. I guess what I really asking is how you would recommend going about diagnosing and fixing this. I know it could be a number of problems, I just need somewhere to start. This is my daily and I need to get it up and going if possible. Honestly, I'd love to go into resto mode with it and rebuild the whole thing like Goinboarding said, but time and money is tight and I don't have anything else to drive in the meantime.

I don't think there is much damage to the bottom end, but I could be wrong. Its not knocking and runs strong and as smooth as normal until that spark plug fouls.

Thanks guys.

 

Check my album for locating the PCV valve if you are unsure of it's location. remove it and check to see if there is large amount of oil in the PCV line. If you remove it and oil is running out of it and/or line, that may be the problem. "May" is the key word. There are baffles @ both the opening for the PCV valve and also the oil filler neck. They "baffle" to prevent oil from being blown/sucked out of the opening's in the valve cover. I would perform a compression test. That would help is starting with a diagnosis. Many others will suggest the test as above.

As far as knowledge, one only learns from asking. That's why most of us are here and also share.

Also, with an oil and filter change, stay away from FRAM, also known as the the Orange Can of Death. This brand has been known to destroy engines. I'll post a pic tomorrow in my album of my recently acquired '90, 302 truck engine that came with a "Tough Guard" Fram filter. Stick with Motocraft, Napa, Baldwin, Wix for oil filters.

If I missed anything, hopefully another member will chime in/elaborate on your problem and correct me if I misguided you.

 

I'm with you on wishing/hoping that it's the PCV valve (which we used to jokingly call the CeeMeePee valve in auto shop class), but I suspect something to do with worn/broken oil control rings as mentioned above.

Do compression test (dry and then wet), and/or a leakdown test first.

If a ring problem is confirmed by the above and you want to keep driving it, install a spark plug non-fouler on #8 and add some STP oil additive (the thick honey-like mixture) and/or switch to straight 40W or 50W motor oil (used for motorcycles mainly). You can also install a hotter spark plug in the cylinder(s) that is/are burning excessive oil. If your engine needs a rebuild anyways, you may be able to eek out a few more miles with these tricks.

Good luck and let us know what you find. If the #8 plug only is fouling out that quickly, that doesn't sound good and points toward a problem inside that cylinder.

 

I'll definitely check the PCV valve, and hope thats the culprit. Unfortunately I have to tend to agree with you that it may be something more serious. I would think that if the PCV valve was sucking oil back through the intake it would be feeding it to all of the cylinders, or to at least more than just the one. I'll do those tests as well and see what happens. It just seems crazy that it can be running fine one day, then the next I could be having all these serious problems, even with the oil being dilluted. I would've thought I'd be seeing some symptoms beforehand, and the oil dillution would've been the last straw.

Thanks guys. I appreciate it, despite the bad news.

If you think of anything else, keep the suggestions coming.

 

I'm not sure what the intake manifold looks like on a '95 351 but on older 460's the rear vacuum port is in the #8 runner.
A leaky master cylinder or transmission modulator will affect that one (#8) cylinder exactly as you say it's doing.

I suggest you do a compression (or better yet a leakdown) test to see how that cylinder compares to all the others.

 

When all of this happened, just before I had the truck towed, a little poof of smoke came from under the hood. I pulled over immediately and when I opened the hood, there was brake fluid everywhere. Some of it landed on the left side header, which is where the smoke came from. I'm sorry I forgot to mention that before. I've pumped the brakes and checked it for leaks, but havent found any. I'll look and see where the vacuum line goes into the intake. If anyone knows, please chime in. I left the truck at the shop where I work, since I can't drive it anywhere, so I'll check it out as soon as I can and hopefully be able to do the compression and leakdown test then as well. I suppose just pulling off the hose to the intake and looking inside will tell me if thats the problem. Hopefully thats it. I'd much rather change out a master cylinder than rebuild the engine.

Thanks again.

I'm all ears to any further ideas.

 

If the master cylinder is leaking into the brake booster you won't see any fluid externally.
You could just disconnect the hose at the booster check valve and see if it's wet with fluid there.

If it is, I'd suggest replacing the booster and M/C as a unit.
Once the diaphragm inside gets brake fluid on it the rubber won't last long.

But, again I'm not sure that this is your problem.
Good luck and welcome to the forum red351W.