Oil leaking? most common problem areas please!!

[old_blue]

I have a small drip (what I thought was anyways) but I jsut popped the hood to check how low it was and it was atleast a quart low if not a little more. It drips onto the H-PIPE from the tranny so I can only figure that it is drip from the back of the engine and then while driving it gets pushed down the tranny line. I have replaced the rear main seal so I dont believe that is it. Only other thoughts are the back of the heads or the oil pan itself. Does anyone have any ideas or problem areas from their mustangs? Thanks
Jon

 

[Michael Yount]

The back of the valve covers are notorious for leaking - and it does leak down the back of the engine/bell housing. A couple of things I'd recommend. First, clean the engine really well with a degreaser (be careful of water/electrical connections). With the engine clean, you'll be able to easily see where the leak is coming from. Second - be sure your pcv system is functioning properly. Many times, the pcv system is clogged up so crankcase pressure builds and isn't vented properly. When the pressure builds it can force oil out of perfectly good/new seals and gaskets. If the engine is old/tired/high mileage, and you have increasing amounts of blow-by, this contributes to the crankcase pressure issue.

 

[old_blue]

Yeah it is 120K+ miles so I am sure I have some blow by especially when I down shift. I am about to put some heads on (I hope the engine can handle it) so I will be replacing all the top block gaskets. Thanks for the info, MUCH APPRECIATED!

 

[Michael Yount]

tba - if I were you I'd run cranking compression and/or cylinder leak down tests before I put the heads on. If the motor's got weak cylinder sealing you want to ID that and fix it BEFORE you start asking it for more performance. Like the Fram oil filter commercial - you can fix it first, or you can pay more to fix it later.

 

[old_blue]

WHat kind of numbers should I see from the cylinder compression??

 

[87'GTstang]

Anything below 100 psi is a bad sign. !50 psi or so is fairly good, anything higher would be better though. If you start pushing 200 psi then you may be having too much buildup problems in the combustion chamber and need to probably be inspected (unless running high compression numbers).

 

[Michael Yount]

I would add - it's not an exact science. Cams with a lot of overlap bleed off more cylinder pressure -- they will read lower numbers, and that doesn't necessarily mean there's a problem. They should all be within 5%-10% of each other whatever they are. 7 cylinders reading around 140 psi, and one reading 80 psi is a problem - you probably want to run a leak down test on the low cylinder. Some folks say to test with the engine warm - that's a good idea I think. Some folks say to run a full set of numbers first; and then to squirt a bit of oil into the cylinders and run them again. The rationale is that if the numbers go up significantly with the oil, that you've got a ring sealing issue. Not sure if I buy that all the time or not. I'd run the numbers and post them - see what kind of trouble you stir up.

 

[88stangmangt]

if it is that bad go to a thicker oil like 20w50 and that will help till you can tear it down.

 

[old_blue]

sweet thanks for the info. I was thinking of running one of those high mile oils. I run castrol but I also heard valvoline makes a good one

 

[old_blue]

I will do a pressure chk this weekend and post numbers when I get them!

 

[battyice]

Small block fords are also notorious for leaking oil from the rear of the intake. Worth checking it out as long as you're in there.

 

[old_blue]

kewl, thanks

 

[87'GTstang]

I would add - it's not an exact science. Cams with a lot of overlap bleed off more cylinder pressure -- they will read lower numbers, and that doesn't necessarily mean there's a problem. They should all be within 5%-10% of each other whatever they are. 7 cylinders reading around 140 psi, and one reading 80 psi is a problem - you probably want to run a leak down test on the low cylinder. Some folks say to test with the engine warm - that's a good idea I think. Some folks say to run a full set of numbers first; and then to squirt a bit of oil into the cylinders and run them again. The rationale is that if the numbers go up significantly with the oil, that you've got a ring sealing issue. Not sure if I buy that all the time or not. I'd run the numbers and post them - see what kind of trouble you stir up.

Yes I fully agree. These are about all of the procedures I follow when doing so on compression tests. What I stated was for obviously a basic stock engine. The point of doing it when the engine is warm is because expansion has already occured and you are testing the engine as it would be when you are driving as usual. Yes the ring sealing issue is supposed to hold true as well. It is supposed to help with sealing from above the piston. I've seen a few engines read as poorly 80 psi and then with oil added it came to 125 psi. Come to find out the rings were worn down to almost nothing according to specs.