Oil leak...can't find it

[merc123]

I have what I assume to be an oil leak. It loses a random amount of oil, depending on how I drive it. I can't find the leak though. I can smell oil if I am on the gas to say 3500-4000 RPM then have to get on the brakes hard. On occasion if I get to 4000 RPM and just let the car idle back down instead of shifting into 2nd (traffic) I can occasionally smell the oil. I washed the motor off on top and just can't seem to find any oil.

The only thing I could think of was maybe the PCV valve was misting on the passenger side valve cover?

 

[1fun281]

This things burn oil, especially on big down shifts, or revving to 4k then jumping on the brakes, being at 4k rpm with the throttle body closed causes a huge vacuum, which dumps oil through the pcv

 

[bhuff30]

How many miles can you get before the oil is a quart down? I personally wouldn't be concerned until you get less than 1000 miles per quart, but I believe ford says it isn't a problem until something rediculous like 4-500 miles per quarter. If you were burning or leaking that much oil, you would know it!!!

Anyway, the most likely problem is the valve stem seals, assuming you have replaced the PCV valve. Seems pretty common for these engines to have leaky valve stem seals. Mine does, and I usually only catch a tiny puff on start up on rare occasions.

 

[JymboSlice]

head gaskets, oil pan gasket, rear engine seal.. to name a few.

 

[merc123]

I had the tranny out to replace clutch and it was doing it before then and no signs of oil from rear main.

I don't think it's burning oil because there is no smoke at all. I think it's just leaking it out somewhere. Even if I get on it hard there's no smoke (someone driving behind me).

No leaks around the oil pan. It's gotta be leaking onto th eheaders or something because where ever it is it is burning up before I can see it.

 

[N8Dogg98]

When I replaced my clutch, the plate on the rear of the engine covering the rear seal was leaking. Replaced the gasket on that cover and no more leaks.

Could it be a cam cover gasket? Have you had the cam covers off for any reason? Do you see any smoke in the engine bay when the hood is open and the car is running?

 

[merc123]

Nothing's been taken off the motor except the transmission, starter, plenum, and the intake. I don't see any leaks on the timing cover though. No smoke either. I've tried to duplicate it to where I smell oil then pull over immediately and look for it but don't see any. It's not burning oil, it's just a strong smell of oil.

 

[N8Dogg98]

What kind of exhaust do you have? When I had a o/r mid pipe I smelled exhaust frequently when I was driving.

 

[merc123]

Mac O/R but it's not exhaust. Car only has 104k miles on it.

 

[N8Dogg98]

If it were the PCV valve you'd see it missing there. Have you jacked the car up to take a look underneath to see if you can identify the origin of the leak?

If it's dry under there and based on the circumstances when you smell the oil, I tend to agree with bhuff that it's likely the valve stem seals. This is nothing to worry about unless you're burning more than 1 quart every 1K miles as bhuff said.

 

[merc123]

Yep, crawled all over under it trying to find it.

 

[bhuff30]

Does it leave oil spots around?

Again, how many miles to the quart of oil?

It is completely normal for engines to use a little oil between changes (down to even 1000 miles per quart). It says nothing about the engines health, efficiency, or otherwise. In fact, burning that much oil may not even produce smoke.

Yep, crawled all over under it trying to find it.

 

[merc123]

4100 miles and its 1/4" below min mark. Two days and 400 miles ago it was above min mark.

 

[merc123]

No oil spots

 

[bhuff30]

I'm guessing that is around a quart every 2-3k miles, which is really nothing much to worry about. Did it use oil before, or suddenly start now?

My 97 GT has burned about a quart every oil change since we got it with less than 50k miles on it. It has over 188k miles now, and is still going strong, not really using any more than it always did.

If you ever see a puff of blue smoke, here are some indications to the problem: blue smoke under accel is often badly worn rings. A blue puff on start up or after prolonged idle can mean bad valve seals. White = coolant/water. Black = very rich.

4100 miles and its 1/4" below min mark. Two days and 400 miles ago it was above min mark.

 

[merc123]

It has been doing it about a year now. I parked the car while I was in Afghanistan and when I came back it started doing it after a few months or so. At first I just assume it was from where I had spilled oil on the valve cover and it was running down the back of the motor.

There is absolutely no smoke. It's not a constant use of oil though. I can go 1,000 miles and it never move. Make the 200 mile journey to/from work and it'll go from full to half of the crosshatch. Go another 2,000 miles and it never move. Then it'll drop like it has now.