I have a 1987 XLT V6 that is in excellent shape. Bought it new in '87 and the last big issue was a blown head gasket at 100k. When that happened I had the valves ground, belts and hoses replaced etc. and now I'm at 242,000 miles and this engine still starts right up every time. It doesn't burn a drop of oil and still has good power and compression. Amazing.

But, there is an oil leak I can't figure out. Clouds of smoke come up from between the firewall and rear of the engine on the driver's side when the engine warms up. It's way down in there too far to see from above, and when I look up from below with a flashlight the source of the smoke appears to be up too high to see. (I don't have a lift.) Weird.

Assuming maybe the rocker covers were leaking way in the back I replaced them to no avail. I've thought maybe the main seal (its plenty oily down under things) but that's below the exhaust headers where the heat is causing the smoke- I think. Could it be the oil sending unit? Intake manifold? This is so bad I can't drive the truck- in fact, I was shocked they passed it for smog because reams of smoke were billowing out the open top even as the tech was measuring the high idle exhaust. He didn't even care! So much for legitimacy of smog regs! What a joke... Any help appreciated. This truck is too solid and spotless to consider trashing!

 

How long ago did you replace the valve covers? The valve cover bolts on my truck loosened up over time and I could smell oil burning. I could faintly see wetness around the back side of the valve cover and checked all the bolts and sure enough they were loose. Tightened them up and haven't had an issue since.

 

Yeah, I was thinking that, too. But I checked and the valve cover bolts are all tight. The smoke seems to originate from a spot halfway down the engine or so, in an area that's virtually impossible to see from above and below. What lives in that area that could be a source of leaking oil? Seems too low for top-end stuff and too high for bottom-end (pan, main seal etc.) I'd better get out the Chilton's and look more closely...

 

its the rear main seal. mine ate oil and p!ssed it everywhere then started most of the time. for all the fail engineering in these motors im suprised they work as well and as reliably as they do.