Oil leak assistance ideas

[Mark Roth]

I have recently been plagued by oil leaks on my 65C. 12,000 miles since a complete rebuild by a reputable shop in CA. I have run Redline 10-40 for years.
No problems until now except minor weeping from the sump studs.

There has been a minor crankshaft leak for a while but the current situation is new. I started noticing oil on the horizontal sheet metal around the dipstick. I resealed the oil filler can gasket and the crankcase ventilation hose connections even though there wasn't much leaking. Not enough to get the sheet metal wet. Then I went for a drive and pushed the engine to 4,000 - 4,500 rpms and sustained driving of 70 or so. Oil started pouring out of the bottom of the engine. Eventually, it was discovered that the seal in the fuel pump around the plunger that keeps the oil in the crankcase had failed which produced a major oil leak. That leak only appeared after a hard load. That was fixed. The sheet metal leak continued. I switched dipsticks with a friend when we went on a hard drive and there was oil all over the engine compartment. My friend's dipstick area was clean. I cleaned off the engine and took it into a shop. Oil on the dipstick surround sheet metal only. They cleaned the area and I drove the car around the block a few times to see if it would leak. Didn't. I did notice that the engine had taken on a loud roar over 3,700 rpms that I had never heard before. Not an exhaust leak but a deep internal roar that seemed to be in the muffler. Engine has never run better and there are no holes in the exhaust system. It seems like the sound of the muffler has gotten deeper and louder at the higher rpms. So then I ran the car on the freeway for a half hour at a brisk speed and went through the gears a few times. There was oil around the dipstick area and around the junction block where the oil gauges and oil lines connect. Photos are attached. The shop changed the oil lines and reinstalled the junction block. The also changed the seal in the dipstick and replaced the oil filler cap gasket and the hose to the air filter from the oil filler can. Air flow from the filler can to the carb is clear. I think that there is more oil around the top of the carb under the air filter then there used to be. The dipstick is tightly in the tube. They also did a leak down and compression test. Results looked good. Results are attached. The mechanics thought that the amount of crankcase pressure seemed normal based on their observations. I drove the car home at speed. There was oil around the dipstick again. I cleaned the area and taped gauze around the dipstick tube under the dipstick but not on the sheet metal. Today I went to a car show at speed. There was oil around the junction block and the dipstick. The gauze was saturated. The photos are from today. The muffler is still abnormally loud. I don't know if the muffler sound is related to the oil leaks. Any ideas would be appreciated.

[Mike Wilson]

Mark:

Lots of people have read your post but, like me, maybe scratching their heads for answers. I'm just spit-balling but hopefully it will elicit better advice.

Oil line journal: looks like the sealing washers are in place but was sealant used on the fitting in the case? Also check the hollow bolt and oil lines.

Dipstick: the O-ring was replaced. Check. Is the dipstick tube tight in the case? Is it wet underneath the L bracket that is bolted to the case? If so, maybe someone used the wrong size 6mm hex bolts and the one went into the case?

12,000 miles, the rings should have seated.

Oil sump studs wet: check flatness of sump plate and screen. Were the studs sealed in the case?

I know you will get better and more definitive help from others...

Mike

[Vic Skirmants]

"is it wet underneath the L bracket that is bolted to the case? If so, maybe someone used the wrong size 6mm hex bolts and the one went into the case?"
WHAT?
Those bolts go through an external web; nowhere near going into the case.

[Mike Wilson]

Thanks for the correction, Vic. I confused the L bracket with the tin behind the crank pulley.

Mike

[Ron LaDow]

Mark,
Starters:
1) R&R the oil 'tower', paying attention to the crush washers; I think the filter feed line wants aluminum parts. If it still leaks there, do it again with really careful inspection; that assembly should NOT leak if the surfaces, the parts and the fasteners are 'normal' and not damaged.
2) I'm an 'interested party' in that Pre Mat sells a replacement for the sump plate, but it is my considered opinion that the factory considered that a 'consumable' by the 20,000 mile range and hoped it became a revenue source. Yeah, you can knock it mostly flat, but you're gonna have to get that rivet to quit leaking also (I used to be on the '#10 allen-cap-screw/nylock-nut' side of that discussion).
3) BUT, 18% leak is getting to the limit and you've got one more at 15%; you have more blow-by than the factory intended and it is going to go somewhere. Are you sure the vent to the air filter has not gotten plugged in some way?

[Sean M Rooks]

What are you running for crankcase ventilation? Do you have the oil filler connection venting to carb or to atmosphere?

Do you have ventilated valve covers or non-ventilated?

I had a similar issue after doing a bunch of engine resealing. My car came with a ventilated cover on one side and the oil filler vented down by the dipstick tube. After fixing some leaks (notably pushrod tubes) and putting stock non-ventilated valve covers on, I had leaks at the block and oil filler.

Switching to the ventilated valve cover solved my problem. Not a scientific analysis at all, and perhaps treated only a symptom but it worked for me.

-Sean

[C J Murray]

I am guessing that there are 2 problems, a leak at the oil union area and blow-by pushing oil from the dipstick tube.

The oil leak at the union looks like the filter return line bottom fitting or the gasket under the union. Don't over tighten that fitting though. Those threads can't be repaired easily. New gaskets or a change to aluminum gaskets with rubber o-rings bonded to the ID might solve that. I would get the engine very warm and then degrease it via your favorite method. Then take the car a very short distance, maybe a mile, at high rpm and stop to inspect for leaks. Repeat until the oil shows itself. The objective is to catch the leak as it begins to appear and before it goes all over.

[Mark Roth]

Thanks for the suggestions. I’m thinking that maybe there is too much blow by which is causing the loud sound when the explosion goes into the case. BUT there is no blue smoke out the exhaust and the oil is nice and clear. The crankcase vents to the right carb as designed and that path is clear. Just to be clear, would too much blow by be causing the leak at the junction block? Is Ron correct in that the leak down and compression tests indicate too much blow by?

[C J Murray]

Hi Mark, the blow-by could possibly be making a leak where the oil filter return line attaches to the crankcase but that is a long shot. The connections at the union are under full oil pressure, no crankcase pressure, and I have seen leaks there before. There is so much going on there that it would be best to see it start to leak on a clean engine.

Drag racers rebuild engines when they get to like 3% leak down, because they are crazy. Your leak down does sound to be high for a recent rebuild. Was there an effort to make the rings seal with low to mid rpm full throttle acceleration?

[C J Murray]

What P&C set was used?

It is odd that it doesn't smoke. How much oil is it using?

[Mark Roth]

Used a quart about 500-750 miles while driving at 70-80. The only time it smoked was once after a large oil spray over the engine which led to the repairs to the junction, etc. No smoke was ever seen before or after. Even when cold starting.

[C J Murray]

That is a bit high oil consumption but leaking doesn't count.

[Wes Bender]

For the leak at the junction block, check that the vertical fittings have copper washers and the horizontal fittings have aluminum ones, and that they are the correct size. As far as I know, the gasket sets have the correct ones. Even "experts" have been known to install these wrong. As mentioned previously, don't over-torque the fittings here.

Did you check the screen in the right hand carb air filter where the vent hose attaches? if it is blocked you'll get excessive pressure in the case. Doesn't take much to block it. Take the hose off of the oil filler can and blow through it. Shouldn't be any appreciable resistance.

[Mark Roth]

Thanks Wes and CJ. Anyone have more thoughts about the compression and leak down numbers? What other tests?

[David Green]

Mark,
I had a leak at my oil union (tower) that I tried fixing with various combinations of copper and aluminum crush washers with no success. The solution was to use high-pressure-rated metal-bonded sealing washers I got from McMasters.
David

https://www.mcmaster.com/catalog/124/3333