Lehman Leak

[Island15]

My 1976 120 Lehman has just started leaking. Just over 5000 hours runs great and has not used or leaked oil in the past. Maybe a half quart between changes.
It has a leak on the port side very near the motor mount very close to the starter. I cannot see exactly where it is coming from, hopefully some can tell be which casket needs replacing?
I'm hoping to be able to replace without pulling the motor!

Thanks for any advice.

 

[RT Firefly]

Greetings,
Mr. 15. You might try a fluorescent leak detecting dye available at most auto parts stores.

 

[Xsbank]

Dollars to doughnuts it’s the lift pump gasket.

 

[525cj]

I just had a similar issue. Check your valve cover bolts. Mine had worked their way loose. Oil dripped over the edge and pooled near the top of the motor mount.

 

[psneeld]

Lift pump is on other side, could just be dripping down fron valve cover as my aft motor mounts usually have a bit of oil in them after a long run.

 

[Xsbank]

You’re correct, the lift pump is not on the port side. Rats.

 

[BruceK]

Cleaning the area using degreaser may help find the source.

 

[Airstream345]

I agree, most likely a valve cover gasket

 

[grahamdouglass]

Take your big flat head screwdriver and tighten your valve cover. A 1 min fix

 

[Island15]

I'll give it a try as soon as it gets light! I sure hope it's that simple.
Thanks

 

[psneeld]

Dont sweat leaks, sweat gushers.

 

[Larry M]

Do not over tighten or you can distort the cover. If it still leaks after, remove the cover and take a 2’ or so metal straight edge and lay it on the inside lip where the the gasket goes. Check to see if it’s flat. It can be straitened out if it’s not. I think the torque valves for the cover are 12-18 lb ft.

 

[psneeld]

One trouble I have noticed is the cork gasket hardens pretty fast...read some place it is a one time use gasket...so torque values might have to be "adjusted" to get all the screws tight and thd whole gasket to seal.

I may switch over to a home made neoprene (or similat to meet chemical and temperature nedds) gasket.

 

[C lectric]

If the valve cover gasket is leaking a trick car builders used was small pieces of 1/4" thick flat steel to spread the load. Often the valve cover sheet metal would deform under the screw heads. THe screw was tight but the deformity would bottom out before the metal between screw heads would snug down.

If there is room on the flange to make such they might help where the gaskets are not quite doing the job.
Of course don't over tighten or you may deform the cover flange regardless.

It will depend upon your unit if there is room on the flange.


And yes you might need to get down there while running to inspect to find the leak. When the engine is hot the oil will be hot and run very readily dripping from points that leave little trace. That UV dye mentioned can help as even a small trace will show under the UV/blacklight.

Just be carefull and wear GOOD hearing protection if you do enter while running.

Any oil hoses in the area? If so a pinhole or a loose fitting or clamp, even a tiny one, can cause a stream under pressure that can spread oil.

 

[Russell Clifton]

I went down in the engine room after reading this and found every bolt on both engines loose.

 

[Sabre602]

I went down in the engine room after reading this and found every bolt on both engines loose.

Would you please clarify this? Every valve cover bolt or EVERY bolt?

 

[Russell Clifton]

Sorry... Every valve cover bolt.

 

[Larry M]

Here are some pics of what C-electric was talking about. These are for Chevy’s but I’d think they’d be some for Fords.

 

[Sabre602]

Sorry... Every valve cover bolt.

Thanks! Gonna check mine this afternoon.

 

[kchace]

Just remember that stamped sheet metal valve covers like the type on the Lehmans should not be tightened too tight or the sheet metal will distort and they can actually leak worse.

Ken

 

[BruceK]

If it is a valve cover leak you ought be able to see the source. If it is, you might need to remove the cover, clean and apply some sealant, as it`s true the gasket hardens. Replacement would be good.

When you tighten, work your way across it and along, like tightening head studs, to get it evenly tensioned. You might need to go over it twice, tightening one screw can ease tension elsewhere.
Depending how close the engine is to the underside of the floor a good size screwdriver may be too tall, I used a socket extension on a socket wrench to get access to some screws.

 

[psneeld]

Its my guess thats why the machine screws have round, slotted heads for a screwdriver (at least on mine) instead of hex heads for a socket and wrench.

 

[Boat]

Another Chevy reinforcement part. No idea if they would fit.

 

[Island15]

Thanks all!
I was able to tighten each one about 1/8 to 1/4 turn hopefully this will take care of the problem. My engine is very clean but I just could not find a source for the leak

 

[Comodave]

I have a coolant laek on one of mine. I just put some dye in it and am going to run it to see where the dye shows up.

 

[BruceK]

On 120s, maybe others, the large tube leading down from the expansion tank gets eaten away, and needs replacing, it involves welding a tube on, or repairing what is there. We did one a few years back,and checked the other which appeared to have been done. So it had, but due to poor welding/thin material, it developed weep holes just above where the hose was clamped on. Obviously tightening the clamp didn`t help,and the thing would leak coolant which ran along the head/block join mimicking a head gasket leak. That one has been redone, with a scrap alum pipe which came with a flange one end, facilitating a good weld repair.

 

[Brooksie]

Perkins has a similar valve cover with cork gasket. My engine is horizontal so always leaked. Many years ago I made a silicone gasket and hasn't leaked a drop since through several removals and replacements.
Clean the cover well with solvent, fill the gasket area with silicone caulk (LifeSeal has best adhesion), flip it over on a piece of waxed paper or polyethylene on a flat surface, let it cure completely, trim off excess inside with a razor blade, install. Minimal torque needed for complete and lasting seal.

 

[Yakobi51]

I have 2 120 lehmens in my boat, I have the same problem. I did the research and found out that there is a freeze plug on the end of the cam shaft it is common to leak there.

I have 6000 hrs and both are leaking as little, you have to pull the transmission out and bell housings and flex plate to get to them. while we are in there I am changing the flex plates also. I hope that helps.

 

[jpar1972]

Reply

Loose bolts on exhaust manifold, maybe gasket, I had the same thing happening this solved my leak

 

[Island15]

Ok, so it is not from the valve cover. But it is still leaking, after tightening.
If I wedge half a diaper between the rear port motor mount and the stringer it will get get pretty much saturated in about 6 hour of running but the rest of the area under the motor stays drip free. Until this issue I could go between oil changes and never need to change out the "Pigs" bright and white! I wound say about 1/2 quart in 6 hours.