351w oil leak when engine cold

[Texasdoc]

1000 miles on a recently rebuilt 351w. I've noticed that when the car sits, it drips oil. Not much - maybe an ounce. It appears to be coming from the front of the engine, but I cannot tell where exactly. It does not leak when the engine is running or when warm - only after it has cooled off.

I recently changed the oil after the car sat for a few weeks. Drained the old oil, then put in Royal Purple. I noticed a small oil puddle on the floor after filling the oil. This was before the motor was run with the new oil. Looked around the engine but couldn't find a source.

Yesterday I put the oil dye in the system and drove it around for 10 minutes. Didn't see any oil (or dye under the UV light) after the drive. I will look again tonight to see if anything has dripped and see if I can find a trail with the dye.

Any thoughts?

[LMH]

If it's center of the front of the engine, I'd look at the front main seal on the crank. There's also the filter and sender attachments though, so those should be checked as well.
Larry

[Barnsnake]

Check closely above and ahead of the oil filter. There is an oil pressure sender port and the fuel pump in that area. A leak there can look like a front main seal leak.

[Texasdoc]

Checked the oil pressure sender port and the fuel pump block-off plate. No leaks there. No leaks around the oil filter. Haven't been home yet to check with the UV light. I don't understand why it would leak when pouring cold oil into a cold engine, but doesn't leak under pressure/hot engine. Were not talking a big leak. Less than half an ounce over 3 days.

It dripped when I poured cold/new oil into a cold engine. The oil should go to the top of the head, thru the head drains, into the block around the cylinder or the lifter valley, then down into the pan, right? It should not go to the timing chain area, fuel pump block plate, fuel pressure sending unit. Right?

I guess some could fall from the lifter valley onto the crank, then run forward along the crank to the timing chain area, then out the front seal. Hard to believe it would go that far forward from just pouring it into the valve covers. To my thinking, most likely would be a little draining out of the valve covers and draining down the outside of the motor... but I can't find a leak source/trail.

I'm thinking somewhere a gasket is not quite tight but when the metal heats up, it seals. I was hoping not to have to take off the crank pulley and balancer.

[CowtownCobra]

Tom, its a new motor and until it breaks in it may blow a bit out of the breathers.

[olddog]

My memory plays trick on me. I confuse and mix things. I may remember a dream and think it happened.

That said, I think the timing chain gets lubricated by drain back oil from the front of the head. If the leak is where the timing chain cover seals to the oil pan, then pouring oil in the valve cover near the front of the head could allow oil to leak. This would explain what happened.

My 5.0 leaked there and I pulled the oil pan and resealed it. Problem solved.

[DAVID GAGNARD]

First thing is to check the valve covers,sounds like the one that you used to re-fill with oil after your oil change is "seeping".......

I doubt it's from your front crank seal, if it was the source of the leak, it would POUR oil with the engine running.....

Being the leak is only when the engine is not running, leads me to think something needs tightening and I'm betting a valve cover.....

David

[sllib]

Mine did the same thing. I bought one of those fancy timing pointers to replace the coat-hanger special I used to set TDC and forgot to tighten the bolts that held it to the timing cover, one of which replaced a shorter bolt down near the oil pan. It drove me crazy for weeks. I even crawled under the car while it was running (not recommended for the sane!) but couldn't spot it. Finally, after removing the pan and most of the front of the engine I discovered what I had done. I wouldn't talk to myself for a month.
Bill

[roadrod2000]

Maybe it's like like one of those Blackbird planes. They leaked like crazy on the ground but once you got them up to speed they sealed right up. Your problem is your driving too slow

[Texasdoc]

Thanks, guys. The only thing I could find with the oil dye was some where the oil pan joins the block on the passenger's side. There isn't any on the balancer. None on/around the heads.

I just replaced the oil pan gasket with a new one. I put in a windage tray and used a one piece rubber gasket. It was leaking like this before installing the windage tray and changing the gasket. I didn't think it was the pan since the leak continued the same after the install.

It looks like I'm gonna have to take everything off and reassemble. I did the tray install with the motor in the car and it was a PAIN.

Sounds like a winter project - remove the tranny, radiator, and electrics. Remove the engine from the car. Remove the balancer and oil pan. Check all seals. Reinstall. Thinking about using "The Right Stuff" Gray gasket sealer with the rubber one piece gasket upon reassembly.

I'm just going to leave it for now, unless I find a different source for the leak. (I thought of valve cover gasket too, but they look dry and tight.) It doesn't leak enough now to waste the summer months driving.

[mln385]

Oil pan may be weeping at the crank valley,apply silicone in the valley as some pans do not conform to the radius well and the gasket is not thick enough to allow for excess.

[DAVID GAGNARD]

Originally Posted by Texasdoc

I just replaced the oil pan gasket with a new one. I put in a windage tray and used a one piece rubber gasket. It was leaking like this before installing the windage tray and changing the gasket. I didn't think it was the pan since the leak continued the same after the install.

It looks like I'm gonna have to take everything off and reassemble. I did the tray install with the motor in the car and it was a PAIN.

FWIW, I let the local parts house guy talk me into using the nice new, shiny, expensive, blue, one-piece oil pan gaskets, TWICE!!!!!!!!! one on a 302 and the other on a 351, both leaked like crazy and I had to replace both!!!!!!!!
I've never had an oil pan gasket leak one drop using the oil style 2-piece cork and rubber end gaskets!!!!!!!!!!!!!!
I guess I learn the hard way.....

David

[LMH]

Originally Posted by DAVID GAGNARD

FWIW, I let the local parts house guy talk me into using the nice new, shiny, expensive, blue, one-piece oil pan gaskets, TWICE!!!!!!!!! one on a 302 and the other on a 351, both leaked like crazy and I had to replace both!!!!!!!!
I've never had an oil pan gasket leak one drop using the oil style 2-piece cork and rubber end gaskets!!!!!!!!!!!!!!
I guess I learn the hard way.....

David

I've found the same thing. The old standby works the best. I put some silicone in the corners where the rubber meets the cork. Never say never but usually don't have an issue.
Larry

[DAVID GAGNARD]

Originally Posted by LMH

I've found the same thing. The old standby works the best. I put some silicone in the corners where the rubber meets the cork. Never say never but usually don't have an issue.
Larry

Same here, a little dab on the corners and I like to put a "light smear" on the outside of the rubber cap gaskets for insurance and I honestly can't ever remember having one seep, much less leak.........

Old school STILL does work in a lot of cases........

David

[Texasdoc]

I did this. A dab of RTV in the corner where the pan meets the crank. Also a dab/light smear where the timing cover meets the block. Also a bit around the corner of the pan. Both front and back.

Still the same drip with the old-school cork and rubber and with the new one piece rubber gasket.

[LMH]

Are you using an oil cooler or remote oil filter? Wondering about plumbing points.
Larry

[Texasdoc]

Nope. Filter on the block.

[Clois Harlan]

Take a white paper towel and rub around the area where the intake meets the block in the front and the back. Do the same around all the valve covers. Then, check your dip stick. I use to never run a dip stick for that very reason. Oil never gets more than 500-600 miles on it anyway. Dipsticks notoriously leak on FE Engines.

Clois

[DAVID GAGNARD]

Originally Posted by Texasdoc

I did this. A dab of RTV in the corner where the pan meets the crank. Also a dab/light smear where the timing cover meets the block. Also a bit around the corner of the pan. Both front and back.

Still the same drip with the old-school cork and rubber and with the new one piece rubber gasket.

Possibly a hairline crack in the timing chain cover??? when the engine warms up, the aluminum "swells" up and seals the crack????

Do you have access to a lift???? if so, I'd clean up everything as much as possible and put it on a lift and try it again while under it to see if you can find out where the leak is coming from..

David

[Luce]

Lay a piece of sheetrock on the garage floor under where you park. Replace it twice a year. Oil is cheap enough. It's supposed to leak.

After fighting the Canton oil pan into place after my cam fiasco, I'll roll the car over the next time I need to drop the pan.