So few months ago, I did a head gasket job on my '94 F150 with a 300.


Ever since, the engine ran rough and shakes at cold idle, but smooths out once warmed up, and had some puffing blow by out the oil fill cap (just like when the head gasket was blown).



This is my winter truck, and I'm just putting it back on the road as of this week for winter, and after a 18 mile trip to work, I noticed it puked out coffee/oil from the crankcase breather hose, into the air box and leaked down the inner fender and onto the ground. I took out the air cleaner, looked in that hose, it was full of coffee colored oil.


I taught ok, PCV clogged? I replaced it, and engine runs much better cold now (still not perfectly smooth, but much better, and has LESS blow by, but still some present).


I cleaned the coffee mess it did yesterday, drove to work again today with the new PCV, same thing. Puked out more coffee from the crankcase breather. The oil is brand new in the engine as of 2 days ago (2 oil changes in less than 80 miles, to make sure all the coolant from the blown head gasket was out of the crankcase) I am running 10W30 diesel oil in it.

And now I have a leak between the engine and tranny, I haven't looked at it closely yet to see if it's coming from the rear main, or pan, but the pan is new from 5 years ago, and looks dry all around so....



Any ideas? Is there some other vent? Or something else can be clogged?

 

Your rings are bad and/or the head needs machined. It does not take long for a bad head gasket/cracked head to ruin the rings. Do a compression test...

 

"Do a compression test..."

x 2

 

"Do a compression test..."

x 3

And be sure and put tablespoon of oil down the spark plug hole for the second reading for each cylinder. First test each one record its reading nothing added then once more with the oil.

If its worn rings the reading will rise considerably with oil down the hole help them seal, if its a failure such as broken ring or blown gasket the reading will only rise a little if at all dependent of course on the severity of failure.

That will help you narrow it down to a single cylinder if it's limited to one, and to what degree its damaged before tearing into it, what to look at once inside.

 

I just did the head gasket on it not long ago, put like 300 miles on it so far.


I had the head machined down (it was warped), cracked checked, suck test the valves, and I replaced the valve seals.

Head came back 100% in great shape.

Inside the engine was extremely clean, cylinder walls all looked brand new! No wear marks anywhere, all factory cross hatched still there (engine only has 98k miles).


I will do a compression check to be safe, but I seriously don't think rings has to do with this, i've seen what kind of blow by broken rings give, and this is not even close to being it.


All I have is small puffs of steam from the oil fill cap, but if you feel it with your hand, theres no pressure coming out.

 

Mis read your OP, re reading it yea sounds like coolant issue rather than crankcase blow by. Pressure and with it coolant from the cooling system is entering into crankcase.

 

Where can it enter it from other than the head gasket....witch is new?

 

If the drain back holes are clogged it could cause the oil issue you are having.

If I remember correctly from when I had mine apart, the only drain back holes in the head are the ones for the pushrods.

So all the oil would end up going through the lifter area.

If the lifter area's drain back holes are plugged, or mostly plugged then it would fill with oil over time. Eventually filling up the valve cover area and spitting out the breather.

Also, if your side cover has a bit of a leak, it would run out of it, onto the block and back down until it comes out of the rear of the block. Which would explain your new leak around the block/trans area.

Personally, I would still do a compression check (would have a long time ago actually) as it can't hurt to know one way or the other, but I think restricted drain backs under the side cover is a good possibility.

You might be able to check it by running the truck down the road a fair ways, then sticking a screwdriver in the valve cover before it has time to drain back down. (I'm guessing the holes are just restricted, not plugged all the way)

There is a baffle in the valve cover, and it will keep you from putting a screwdriver down far enough to check, but if I remember correctly one of the holes in the valve cover doesn't have a baffle - well, it has a horizontal one, but that won't get in the way of the screwdriver.

I don't remember which hole, I think the rearmost one, which should have the pcv valve in it, but I have seen the pcv and vent switched.

Edit: Without seeing it I can't say for sure, but I wouldn't worry about a little bit of steam when you open the oil filler. I see you live where it gets a bit cool. Its probably just some water from condensation boiling off. If its a lot and/or you are losing coolant than that would be a different matter.

 

Compression check will tell. Like I said, it doesn't take long at all for the rings to go from a bad head gasket. cylinder walls tell you nothing about the condition of the rings. I'm telling you this because the same situation happened to me, the cylinders looked good but the rings were bad. Let us know how it turns out...

 

He's complaining of coolant mixing with oil in the crankcase, you don't get that from bad rings.

If the head and head gasket is 100% and you're sure of that? then it's possible it has a cracked block, crack between water gallery and push rod bay for example?

Many years have past since the last time I was into a 300 six, perhaps don't recall coolant passages oil returns etc all that well but its about all that's left. Water pump doesn't pass through a timing cover like the v8's bolts directly to front of head, doesn't enter intake etc?

Be somewhat rare but not entirely impossible (depends on the shop and the guy actually doing the work) that they missed a crack in the head when they checked it, the original problem especially if symptoms are exactly the same as before you removed the head now that its back on.

 

Just wanted to share my experience...

My old 302 had similar problem. It would puke coffee oily mess out the breather box. It had terrible blow-by. It looked worse in cold weather because it was exiting the breather hose and cooled rather quickly since it wasn't warm enough to burn the moisture off. Cylinders had, 140-150, but it just couldn't prevent the blowby.

I never saw where he mentioned loss of coolant. I've been following his threads and so far it was when the head gasket blew.

Perhaps IDIdieseljohn can chime in and clarify my last statement.

 

I took out the air cleaner, looked in that hose, it was full of coffee colored oil

This is the comment I based it on, yea its possible I'm wrong but to me that says oil that has been mixed with coolant.

Missed that at first and partly due to the treads title 300-6 PVC question and choice of words happen to use blow by, puffing out oil cap etc. Yep jumped right on the "blow by" bandwagon.

Reread after he questioned our suggestion found those little details missed first time around.

Heck 18 mile trip it created enough of the stuff to make it all the way to the ground.

puked out coffee/oil from the crankcase breather hose, into the air box and leaked down the inner fender and onto the ground

 

FIXED.


My crankcase breather hose was clogged up with that coffee oily crap, as well as the tuna can thing on the valve cover that connects the breather hose from the air box.


Cleaned the hose, and that tune can, no more blow by, running great, still slightly rough idle when cold, but no blow by.


Oh and that leak I had between the trans and engine, that only happened for 2 days, went away much before I resolved the problem completely.



It looks like the coffee that was stuck to my oil cap and inside the valve cover is also gone now as well.


Boy i'm glad that's all it was.

 

Good to know its running better.