Sudden Blow-by

[Mac AR]

I was working my '51 today, and its suddenly started smoking from the crankcase and the exhaust. If its under a good load it mostly goes away, but when coming up from idle it smokes pretty good. It looks like oil smoke rather than water, so I've ruled out a blown head gasket. Oil pressure is excellent, nearly pegs the gauge at full throttle, and is centered with the "I" on the gauge. I admit to being stumped, so if anyone could point me in a different direction I'd appreciate it.

Mac

[Eugene]

Compression tests. Dry first then wet.

If you think it's burnt oil in the exhaust, then rings. Rings are about the only way oil gets in the combustion chamber. Minor amount of oil could be drawn past the valve stems but that is normally inconsequential.

Blow by, rings.

[Waif]

Checked your oil level for excess fluid?
I've had the touch control leaking hydraulic fluid into crank case when the pump o-ring was bad . Not uncommon.
Gets messy though when oil is overfilled and thinned out!

[Mac AR]

That's what I was afraid of, Eugene. She was running fine last Sunday, and now today she's started smoking. I don't have a way to do a compression test, but I guess I'll have to get a gauge. I've not noticed a loss of power, if that's an indication of anything. Do you think I could've stuck a ring in a weeks time? Just thinking out loud. The engine was overhauled 2 or 3 years ago and wasn't used much until I bought it in the spring. It just seems oddly sudden, I guess. When I get a tester I'll let you guys know the results.

Waif, that's a good thought. It wasn't over filled best I can remember when I checked it before starting today. I'll check again in the morning and see though, that may be part of the issue.

Thanks again,

Mac

ETA: I went out to the shop and checked, it looks like the oil is just a fuzz over the line, and seems thin. I think I'll change it, just for the heck of it. Can't hurt and I'm sure its about due to be done.

[Don McCombs]

Check the Touch Control level, too.

[BigBill]

Wash the crankcase breather in kerosene. The old cars with no pvc system we washed the crankcase breather in kerosene when changing the oil. Then add seafoam to the crankcase with new gas and to the gas tank then run it.

[outdoors4evr]

Rent a compression tester from Autozone. They refund your "rental" in full when you return the tool.

[ricky racer]

Rent a compression tester from Autozone. They refund your "rental" in full when you return the tool.

[Mac AR]

Well folks, looks like I've figured out the cause of my smoke. When I checked the oil last night, I marked the stick with soapstone, and rechecked it. Up to the line, no higher. This evening, it was almost a 1/4 inch over the soapstone line. This leads me to believe my pump is leaking. I understand its just a fifty cent o-ring that goes bad. Any idea what size I need? Also, any pointers on replacing it? I'm certainly not afraid to tackle it myself, I'd just like some advice from y'all that have done it before. As always, thanks for your help.

Mac

[Waif]

Pump shaft needs to be inspected for wear where o-ring rides. A groove defeats the seal.

Here's a mention of a different type of ring with double edges I believe. Could straddle the groove. Not saying you have a groove though. O-rings just plain fail too.
viewtopic.php?t=81109

You might consider replacing the rest of the seals , and a new gasket too..
Here's Rachel if you need morel support..
https://www.steinertractor.tv/v/touch-c ... /65479902/

[Bob McCarty]

Pump shaft o-ring is a dash 112, buta-n. The pump can also be machined for a seal if it's deeply grooved. With the seal you can place the lip on a smooth area of the shaft.

[Glen]

Hi,
Below is a listing from TM Tractor for the pump shaft o ring.

http://www.tmtractor.com/new/hy/396fp.htm

Below is a listing for the pump rebuild kit, it has several parts, among them are, a gasket for the top end of the Touch Control tubes, and o rings for the lower end of the tubes, and a gasket for where the pump bolts to the engine.
There is an o ring for where the 2 halves of the pump join together.

http://www.tmtractor.com/new/hy/288fp.htm

The pump is held on the engine by 2 of the 4 bolts in it. Looking forward from the rear of the pump, the upper left, and the lower right bolts hold the pump on the engine, they go through the pump.
Don't remove the other 2 bolts until you get the pump to a bench, it can fall apart.
You can loosen them though, while the pump is bolted to the engine.

The pump drive gear should have a lock washer that bends over one flat of the nut, to keep the nut and gear from falling off.
You have to bend the washer away from the nut to remove the nut.
The washer has to have a tab that sticks into the keyway of the shaft, to keep the washer from turning. Sometimes the tab breaks off, then it needs a new lock washer.
TM Tractor has a new lock washer.

Wash the outside of the pump before taking it apart, if it is dirty. Be careful to keep all dirt out of the two holes in the end of the pump.
Work on the pump in a clean area.
Use plenty of new Hy-Tran fluid when putting the pump together.

Below is a pic from TM Tractor of the lock washer.

[Gary Dotson]

You might be jumping to a premature conclusion. When a Cub engine is shut down and the oil checked, it will be at a given level on the dip stick, as it sits, the oil will drain from the filter housing to the oil pan, raising the level on the stick. Did you check the fluid level in the touch control?? If it's not low your pump is not leaking.

[Don B.]

So, will a bad hydraulic pump seal cause a sudden blow by condition?
From what I see in this thread, it sounds like it can?
Considering it was sudden, I was leaning toward a broken ring or some other such ring problem, but maybe not?

[Waif]

When my pump o-ring seal went from mildly bad to bad and over filling engine crankcase , there was oil droplets falling on the hood from exhaust.
With the attendant "smoker" syndrome.

Did not go farther in checking things out beyond than having o-ring replaced ,oil changed.

Was thinned oil getting past rings? It was getting in the fireboxes from somewhere.....

Not being over run with hungry machinists , I had the pump replaced with one in better condition when the original started leaking again.