I know it's impossible to troubleshoot an engine via e-mail, but thought someone might have experienced symptoms like this... 1) Check engine light comes on...goes off after 10-12 starts. Turns back on after 3-4 starts. 2) Sometimes the engine starts, runs rough, misses, check engine light flashes...shut engine off, re-start, and it purrs like a kitten. Only happens with warm engine. 3) OTC Code scanner reports P0133 error, O2 sensor slow to respond. If I cross reference the error code with a chart in the Haynes manual I get upstream sensor bank 1 (OK, where is that?). A mechanic at the local Ford dealership said the engine is burning water in the #4 cylinder, coating the converter material with water vapor, causing the O2 sensor (converter output monitor) to light the "check engine" lamp. He also said to check the plugs for a yellow/green tint...bottom line, bad head gasket, replace the engine. What I know: There is a thin film of black engine oil in the coolant recovery tank, been there for several months, doesn't seem to get worse. Uses (leaks?) about a pint of coolant in 3000 miles. All three plugs in the front bank have a yellow/green tint, all three plugs in the rear bank look blacker (rich mix?). #4 cylinder is in the rear bank I believe. There are no signs (no foam, no drops...) of water in the crankcase oil, oil level goes down with miles. Cardboard under the car engine indicates slight oil leak, slight coolant leak at front of engine, and slight leak from transmission pan. Car is Ford Windstar, 1996, 3.8L 128K miles. The big question...is it the head gasket, or just an O2 sensor? Any suggestions, comments, thoughts would be appreciated? What the dealership says...does not compute in my tiny brain. The same dealership refused to align the car (after I replaced struts) without drilling the rivets from the upper strut mounting plates (adds $70 to the bill). An independent alignment shop (2nd opinion) said the camber was right in spec, didn't touch the plates, corrected toe-in, and now the car drives fine. Thanks for reading... Bill

The check engine light will go off after "three normal run cycles" as long as the problem does not reoccur per the Ford manual. When the computer sees the same problem three times without three normal start run cycles between them it turns the check engine light on. Antifreeze will ruin an O2 sensor, and could be the cause of the check engine light. Sounds like a cracked head or blown head gasket on the front bank as the spark plugs on that bank have the yellow/green tint on them while the rear bank is running rich. You can have a slow coolant leak for quite a while. I had a Ford Escort several years ago with a cracked head. I drove it for 6 months like that, just had to add water once a week or so. Finally pulled the head and replaced it. Your van has four O2 sensors. One on each bank before the cat (upstream) and one for each bank after the cat. Sounds like the Ford mchanic is right about the head gasket. Question is, who pays for the work? Chuck

I'll bet if you show the service manager enough evidence that this problem is common (lemonaidcars.com, autosafety.org, and other sites) they may pay for some of the repair. You can always go to small claims and argue a defect (which most likely it is). Worked for me on an out of warranty Chrysler transmission (http://mypeoplepc.com/members/tjk).

Bill, your 3.8 is acting much like the 3.8 we had in our 1989 Sable. You have a minor head gasket leak. I think what's happening is when you shut the engine down, there's no longer compression in your cylinders and coolant can leak in through the bad head gasket. Then you end up with the green plugs and O2 sensor. This is what happened to our's (only in one cylinder, though), and it was the running rough (due to the fouled plugs) that was the first real clue of a problem. If you rev the engine, do you see bubbles in the coolant reservoir? That would be another clue. The oil in there sounds ominous, though. We didn't have that. The Sable went at about 75K miles. I pulled the heads, had them resurfaced and a valve job, then put it back together. Funny thing, I don't think it completely cured the problem. We still had occasional bubbles in the reservoir, minor coolant loss, but no more fouled plugs. I think we were lucky that I got to it before we had coolant in the oil. Drove it that way for another 2 or 3 years and then traded it in on the Windstar. Took a while to find a used Windstar with a 3.0L, but there was no way I was going to buy another 3.8L. I expect next time we align our Windstar that they may tell us that we need to drill the towers. But we don't have odd tire wear and it doesn't track funny, so if that's the case who cares if the specs aren't perfect? Hope this helps. Mark Salvetti Saugus, MA 1996 Windstar 3.0L 2001 F150 SC 4.2L