I have a 92 AWD 4.0L van. She has lots of miles (295K Klm/ 184K Mi) Anyway works great runs smooth and all that but I get a smell of burnt oil after driving for a long period of time. I guess oil must be leaking on the manifold somewhere but being an Aerostar the engine is totally invisable. To the point, what would be the most likely leak point on a 4.0L? Any chance of valve covers or should I look elsewhere? I know there is an Aerostar guru out there with the answer.
Thanks

 

on a list of likely suspects ,the valve covers would be on the top. i have a 91 4.0 litre with 196 thou mi. those bolts seem to vibrate loose over the miles, mine had the same odor .its more in controll now. i periodically reach in when able and tweak the valve cover bolts. the most likely spots are the drivers side rear, and passenger side rear bolts (were on mine.) if you pull out your engine cover you will be able to see them.also get underneath and look up on the sides of your engine block. you may see oil residue on the block, coming down the sides from the valve covers above.
i clean the engine some each time i open the hood, or change oil. it keeps me up on what is going on .my problem of leaking oil was major. a garage wanted 700$ to replace the valve cover gaskets. i chose to watch and tweak...doing very well lately. i also used some engine degreaser on the sides of the block cautiously, trying to reduce the built up deposits. good luck rick

 

The earlier model 4.0 engines were prone to rear main seal leaks. There is an exhaust cross pipe that runs under the engine at the engine/transmission juncture, just at the point where the drip occurs. Could be the source of your smell.

 

On my 1990, the major leak(s) was (were) from the valve cover gaskets. The replacement gaskets were over $50 at the delaership. Since I had Ford's ESP when I got the van from the previous owner, I had the dealership to it for a $50 deductible. I think it was worth it.

I still have leaks, one of them is from the oil level switch, but I can't really figure out where else they might be coming from. Probably from the rear main.