Mysterious oil leak on my 289

[fasttback]

I have been trying to fix an oil leak on my 289 that has puzzled me for weeks. The leak is originating in the front of the motor in the vicinity of the oil sending unit, fuel pump, and oil filter area.

The leak only occurs under high rpms/higher pressure, usually when I driving under “extreme conditions.” Over the weeks I have replaced and/or cleaned the following:

oil filter
oil pan gasket
oil pressure unit and extension

There are no visible signs of leakage from the fuel pump to timing chain cover gasket, oil pressure unit and extension. The hard part about this is when it goes it sprays oil over everything in the vicinity, even upwards on the back-side of the power steering pump bracket.

I know it seems far fetch, but I am now looking at the fuel pump as the problem??? I know the fuel pump has access to engine oil through the timing chain cover, but it there enough pressure and oil that would cause this under high rpms. Second-guess, oil filter even though this is the second filter having the same problems as before. Has anyone experienced a similar situation or have other ideas?

 

[rbohm]

ok first make sure this is an engine oil leak, and not a power steering fluid leak. yes the fuel pump gasket may be leaking, since you indicate that this is a leak at higher rpm. the cause here is going to be extra pressure in the crank case that will blow oil out any area that is weak and leak prone.

did you put sealant on the threads of the sending unit or the extension? if not do so. i like teflon tape. and dony worry about a bad ground, the teflon tape is easily cut by the threads, and it bunches up at the edge of the opening where the seal is created.

 

[jcode68]

Are you sure it's oil?

Are you sure it's an oil leak and not a PS fluid leak? The higher the rpm's the higher the pressure in the PS system and connections. Sounds like you replaced the obvious problem points already. I tend to agree with you that the fuel pump connection would not be under high pressure, so if it leaks, it would leak 100% of the time while the engine is running. Did you also check the front oil seal in the timing cover? Same deal, if it leaks, it will do it all the time.

 

[latamud]

The oil filter might not be tight enough. Or, the oil pressure sending unit fitting might be leaking either where it meets the block or where it meets the sender. It might also be the valve cover.

I had a leak in the same place. It was the oil return fitting that I installed in the oil pan for the Vortech supercharger. I just put a bead of RTV around it and it sealed.
you

 

[fasttback]

Yes, this is an engine oil leak and not a power steering leak (fixed the red leak one a while ago). I recently had the engine cleaned thinking it would help me isolate the problem, but at under higher rpms while on the road the oil get sprayed all over that area.

When I did the oil sending unit and extension I used teflon tape and it showed no leak around the threads, even when oil was sprayed every where else.

The front oil seal does not show any signs of leaks, and oil was never on the front of the motor (just on the drivers side).

Since my last post, I was out in the garage reving the engine from the engine compartment trying to see some dripage...but nothing. So the leakage is sporadic and maybe under a load?

Another thought - could it be the head gasket? I was leaning against this because I changed them out in March of this year and it would be a hard to get oil on the back side of the power steering bracket from its position.

Any thoughts on what to change next? Here is my plan of attack (as it stands now):

new fuel pump
new oil fliter
new head gasket (hope not)

 

[fasttback]

Also, I tried to remove the oil filter when I changed the oil gasket. I could not twist it with moderate pressure and since I just changed the oil a little over a month ago I left it on (car is only driven about once a week).

 

[jcode68]

The only thing I would try to do before randomly replacing more parts is to further isolate the areas. If you can find a way to partition off the fuel pump using cardboard or something to see if it is in fact the source, same with the head gasket area. This might be challenging, but will cut down on frustration if you can isolate it a little better. Hate to see you replace head gaskets only to find out it had no affect.

 

[KreagerM]

I don't think it's the head gasket. I think if it was the head gasket you would notice oil leaking from the blow out spot. Is your oil filler cap on the drivers side of your car? Just an idea. Also maybe the exteme pressure is caused by a clogged PCV valve.

 

[fasttback]

I doubt the valve covers or oil filler cap are the culprit. I've been running Motorsport aftermarket valve covers with open breathers (no PCV). One leaked before on an old motor -and you will know when oil comes out of your breathers.

jcode68 - good ideas about isolating. Fuel pump isolation should not be a problem, but the head with a hot header close by...tough. I will give this a shot before randomly replacing things. Keep you posted.

Has anyone ever heard of synthetic oil leaking more than conventional oils?

 

[gtss]

It is possible that you have a small crack or porous section of the timing cover or something bizarre like that, and the leak only occurs when very warm. the speed of the engine fan would happily blow the oil all over. But instead of guessing and throwing more parts at it, take a trip down to your local parts store purchase a black light and some ultra violet dye that goes into the engine oil and take her for a rip. the dye will leave a trail so you can see where it is coming from. Failing that, close off your valve cover breathers, and all other crankcase openings, and apply some compressed air to the entire crankcase if it will leak oil the n the opening will be large enough for air to escape.
Gord

 

[2nd Mustang]

Has anyone ever heard of synthetic oil leaking more than conventional oils?

Aha, did you just change over from conventional to synthetic oil? If so, synthetic will create leaks where you conventional didn't leak. Once the synthetic creates a leak, it's almost impossible to go back to conventional oil to stop any leaks.

 

[TOM B]

I had the same oil leak that I think you have. I found out after weeks of looking that the junk FRAM filter I was using was leaking oil at high RPM's around the crimped seem. I took 3 of them back + a racing Fram filter. I finally told them where to go and bought a Napa filter and NO LEAKS

 

[iskwezm]

Has anyone ever heard of synthetic oil leaking more than conventional oils?

yes

 

[jcode68]

Just curious, did you ever figure out where the leak was coming from?

 

[MustangMatt1966]

yea, i am curious to know if it stopped also.

 

[fasttback]

Just curious, did you ever figure out where the leak was coming from?

To date I did re-clean the problem area, put up some cardboard to block off the fan and ran the motor in my garage. I brought the car up to temperature and would rev the motor off and on. As it was running I would go under the car (well secured and blocked) looking for the first signs of leakage, but nothing!!!

The Christmas thing has slowed me down, but I will back into it soon. My current thinking is this has to be a high oil pressure area, because I would have seen the start of a leak by now and when it goes it get all over that area. So, back to oil sending unit and head gasket areas?

 

[HistoricMustang]

Has anyone ever heard of synthetic oil leaking more than conventional oils?

Yep, again.

Check to make sure you do not have two oil filter rings. Sometimes the darn things do not come off and you put a new filter over the old ring.

Also, short burst at high RPM's should not cause a leak - high RPM's for extended periods of time will cause leaks. Been there and done that..........on a normal road circuit when the RPM's are up and down no leaks..........but doing an oval where the throttle is held open, I get oil leaks.
Then goes away.

HistoricMustang
www.historicmustang.com

 

[Tim65GT]

Sorry I did not catch this post the first time.

I had this EXACT problem before. I replaced the filter and the oil pressure sending unit extension making sure it was tight and sealed with teflon tape.

Nothing I did helped until one day I revved it up while looking carefully at the area right in front of the oil filter. It was getting sprayed by an oil mist out of the fuel pump "bleed hole"!

I don't know if all fuel pumps have this hole. (I don't have the original type fuel pump anymore with the screw-on filter) I think the purpose of the hole is to let the fuel run out onto the ground in case the diaphragm ruptures, instead of pumping the oil pan full of fuel.

Anyway whatever seals the crankcase from this hole failed and it was allowing the oil (assisted by excessive blow-by pressure) that lubes the pump arm on the cam eccentric in the timing cover to flow into the pump and out the hole. The hole is on the back side of the pump facing right at the oil filter and sending unit/extension.

I took the pump back to Checker Auto Parts and they exchanged it for free. No more mysterious oil leak.

Hope this helps.

 

[MustangMatt1966]

Sorry I did not catch this post the first time.

I had this EXACT problem before. I replaced the filter and the oil pressure sending unit extension making sure it was tight and sealed with teflon tape.

Nothing I did helped until one day I revved it up while looking carefully at the area right in front of the oil filter. It was getting sprayed by an oil mist out of the fuel pump "bleed hole"!

I don't know if all oil pumps have this hole. (I don't have the original type fuel pump anymore with the screw-on filter) I think the purpose of the hole is to let the fuel run out onto the ground in case the diaphragm ruptures, instead of pumping the oil pan full of fuel.

Anyway whatever seals the crankcase from this hole failed and it was allowing the oil (assisted by excessive blow-by pressure) that lubes the pump arm on the cam eccentric in the timing cover to flow into the pump and out the hole. The hole is on the back side of the pump facing right at the oil filter and sending unit/extension.

I took the pump back to Checker Auto Parts and they exchanged it for free. No more mysterious oil leak.

Hope this helps.

I beleive we have a winner!:SNSign:

 

[Dark Knight]

Wont be a head gasket, the only oil pressure in the heads is from the pushrods. Everything else is just drain back..

Check the sealing surface for the oil filter for nicks etc...and make sure you arent over tightening the filter... you ARE oiling the seal, right?