Hello All. Longtime reader of the forum, but first post here. I have a 1999 E250 with a 4.2L. it has 163K on it. Had the dreaded intake gasket failure at 148K and rebuilt the motor myself with the help of my neighbor (45 year Mechanic) and got away relatively easy. Had a bent rod on #1, cracked head at #3, and the intake gasket. Replaced EVERYTHING on the rebuild. Plugs, wires, coil pack, belt, water pump, camshaft sensor and shaft, injectors, fuel pump, radiator, all hoses, degas tank, EGR, PCV, all gaskets, timing chain, lifters, all bearings and seals. Even the O2 sensors-all 4. We left no stone unturned. After the rebuild, I was still losing an inch of antifreeze in the degas tank every two weeks or so. Neighbor said not to worry. We added a number of sealants and tried a number of different things to correct the problem. None worked. After a year on the rebuild, I started hearing a loud knock that would last 10 to 30 seconds on startup of the motor when cold. We thought piston slap, cracked flexplate, or lifters. But I still had the coolant loss happening. Lived with it for a few weeks, then upon startup one morning two weeks ago, I smelled coolant in the exhaust. I remember when the hydrolock happened that I had the same thing, with the coolant loss prior to that and thought "oh no...not again!" So I pulled the intake off again just to check that it had not failed. Upon removing the upper manifold, I found coolant leaking down the #6 runner from a 3 port valve that has 2 1/4inch coolant lines passing through and the PCV hose connects to. the neighbor agreed that I probably found the mystery leak, since the sealants we added to the coolant had coagulated inside the valve. So I bypassed this valve and capped it off, since the PCV connects to the intake up by the throttle body. Since I did that about two weeks ago, I have had the coil pack give a pre failure SEL, had the lean bank #1 &#2 p0171, p0174 errors repeatedly, and more importantly, a small amount of motor oil appearing inside the degas tank, floating on the coolant. Could the factory oil cooler have failed or be failing? It is the only place the oil and coolant pass each other short of the internal engine, but I am not finding coolant in the motor oil indicating a head gasket issue. So I doubt that is the problem. Also, the oil pressure is higher than the coolant pressure, so it would be easier for the oil to pass to the coolant side rather than vice versa. I found a bad gasket on the idle air control valve that might have been the vacuum leak creating the p0171 & 0174 errors, but the oil thing is perplexing. Any thoughts? Thanks!

 

It very well could be a blown/bad head gasket.
A long shot would be lower intake gaskets.
I'm leaning more to the head gaskets. Do a compression test and a coolant system pressure test. Then go from there.

 

Under the advisement of my neighbor, I did the compression test, all cylinders are within 5% of each other and the coolant system has not lost any fluid in two weeks since I blocked off that 3 port valve for the PCV system. Its holding tight. No degradation in driving performance either. In fact, it seems to be running better now than ever. Better gas mileage too. Just the oil in the degas bottle.

 

Not to be "smart" or anything, but if the lower intake gaskets or head gaskets had failed, how would oil that is not under pressure get into coolant passages that are pressurized to 16 PSI? The only part of the oiling system that is under pressure are the passages to the bearings and lifters. The passages through the head gaskets are drains bringing oil from the upper head/valvetrain area back to the pan. It wouldn't seem logical to have oil showing up in the coolant from those sources. Typically those issues put coolant into the oil pan. Just wondering how those issues could cause what I have going on.

 

Are you sure it is engine oil ? Not trans oil ? Or byproduct from the " sealers " used ? Just a thought !

 

In your OP you did not specify the coolant system was under pressure. You asked how oil can get into the degas/reservoir bottle, I answered. This was based upon my experience with this kind of problem happening to me in the past.Not to be "smart", in the future be more specific to how your Q?'s should be answered.

What would cause oil to leak into the antifreeze reservoir

 

Thanks for the replies! JWC3 definitely motor oil. brown not reddish. trans fluid was changed with filter at the engine rebuilt and is still bright red. BOF your right. I didn't specify the coolant system was pressurized. But under normal operation it is, isn't it? I was always under the impression that the coolant cap was designed to limit the pressure to its specification. In your past experience, did you have this situation occur when the cap was off or left loose? I could see that potentially allowing for the passage of oil into the coolant if the cooling system had little to no pressure as well. No disrespect intended.

 

I had a 97 4.2V6 with the infamous lower intake gaskets that were bad from the factory, along with the timing cover. They were replaced upon the recall. A few years later there was oil in my degas bottle. I did a compression check and eliminated the head gaskets. I did a coolant pressure check and it held 16 psi over 24 hours. I finally did a UOA and traces of coolant were in the oil.
Long story short, the lower intake gaskets failed, due to improper installation. Ford fixed it, problem solved.
I used to rebuild engines, mainly SBC. When head gaskets failed, were blown, etc. it would leave oil in the coolant and white, sweet smelling exhaust smoke. And, sometimes the coolant system would still be under pressure.
Each case is different. It's just a matter of doing a process of elimination, starting with basics then diving in deeper. For me, I have always been lucky to figure it out starting with the basics. But, I have had a few head scratchers, but eventually figured them out.

 

Ahhh...you been down that road before! I've read a lot about the early 4.2 issues. Supposedly they were all corrected before my engine was produced. I actually got to 148K before my intake gasket failed. Since it hydrolocked the motor, we had to pull it and rebuild. My first full rebuild, but I have done many a top end on various makes and models before. I installed the heads and gaskets while on a stand outside the vehicle. Also the lower intake was done on the stand, so I am sure the placement and all was correct. Since it was my first, I checked, double checked and then checked again. I used Felpro gaskets, which I understand is where Ford gets the factory gaskets from, and I know the gaskets could fail again, but I would seem unlikely since I am not losing any coolant. If the cooler doesn't correct the problem, I will most likely pull the intake again and replace the lower gaskets. I've had my share of head scratchers too. The newer ones are not like my 66 fairlane w/289. That one is easy to work on.

 

Glad I have an 05 with 175,000 miles and still running strong. I'd look at intake and intake gaskets. It sounds like new PCV might bye a remedy.

 

If the intake gaskets weren't replaced only 20K miles ago, I'd be looking that way. They are new Felpro gaskets, and I have no other symptoms of a possible intake gasket situation. No low coolant level, no vacuum leaks, nothing. PCV valve and tubing was all replaced with the rebuild and is clean inside. I even went back and retorqued the bolts on the intake-upper and lower. 89 inch lbs exactly in two steps. Only one or two had loosened a little bit, and not near the oil or coolant passages. I really don't want to have to pull the lower intake unless I really have to, since this is a van and the engine is centered under the dashboard with only 10" of room between the lower intake and the dash. It will be a 2 day nightmare for that one if I have to do it.

 

Hi All. It has been 3 months since I replaced the engine oil cooler on this motor, and I am happy to say, I think I have finally figured it all out. There is no more oil in the degas bottle (I found out lacquer thinner is a great cleaner to get the oil out of the bottle-with the bottle out of the vehicle, just pour in a couple ounces of LT and seal the openings, then shake. Cleans up like new and completely evaporates leaving no residue). Coolant and oil levels are holding fast without having to frequently top off. Van has been running great since all this was done. Don't overlook this solution if you have the same thing happening to you. Take Care!