oil is breaking down in '50 cub

[Matt Kirsch]

Frankly I wouldn't even know if my engine oil was getting thin. I pull the dipstick, and the correct amount of oil is on it, so I wipe it and recheck. If it's the same I replace the dipstick and run the tractor.

How are you determining that the oil is getting thin?

[Puffie40]

I concur that you are either running it too hard or have cooling issues. Pop the water manifolds off and blast the pressure washer into the water jacket.

[flipklos]

When I overhauled the cub 5 years ago the block was power washed, caustic boiled, and washed again. Same with the head. The oil pressure does drop off a bit as it gets to temp but it is still plenty high.

The temp was taken on the water neck. I will try to get a temp inside the top of the tank. I will go to the park and mow the fishing trail tonight so you have some info.

How do I know the oil is breaking down,

15W40 don't run off a dipstick like water when it is cold. I am an industrial mechanic. This is a clear cut case of the oil thining due to the viscosity improvers breaking down. The used oil when it is cold and you drain it has the viscosity of 5W-20.

[pickerandsinger]

I had a few issues with tractors which I attributed to multi viscosity oil……I switched to straight TSC detergent 40 weight and they all disappeared…..I won't go in to the issues in detail to save discussion on my high school Auto mechanics Dinosaur BOCES education in 1964, but the 40 weight worked for me in old engines some of which I rebuilt…My tractors are all working tractors... :hat tip: Dave

[flipklos]

Ok here we go all temps in Fahrenheit,
measurments taken with a multimeter temp probe and temp gun,

Outdoor temp 78.6
Humidity 52%
34 psi cold
32psi hot
220 coolant in top of radiator
215 neck
128 return pipe
147 outside of pan
142 inside pan

15 min mowing half deck with a woods 59 in 20" grass half in 10" grass.
10 min driving to and fro,

Oil temp is not real high but the city actualy mowed most of it for once. Oil was awful thin at start.

Interpret this how you want. Has anyone taken similar observations.

[havoc1482]

Thats not a bad oil pressure to be honest. If I remember correctly anything around 40psi is what you want. I'd say 32 is perfect. My SA runs around 35-40

[Eugene]

The oil pressure relief valve in a Cub is suppose to be 35 psi. 34 cold, close enough, no problem with the oil pressure.

[flipklos]

I shimmed the spring a bit during the overhaul. Always do. Not so much to increase pressure but to compensate for wear.

As for straight weight oil. I have no issues with it but I would never get anything started at -20F with 40W in it. One would have to run 10W to get it to spin at all.

There is a reason that there is not much use of straight weight oils anymore. My uncles run them in air cooled engines that are used in the summer............Don't know of anyone else that uses them much anymore.

[indy61]

I use the old oil I drain from my truck to run in my Cub. Works great.

[Slim140]

I use the old oil I drain from my truck to run in my Cub. Works great.

I use my old oil I drain from my truck to burn brush piles. Works great.

[Matt Kirsch]

Well, either you're running way too hot or the oil just isn't up to the same quality as it used to be.

Since it's happening so quickly, I would switch to a different brand and see if it makes any difference. Should be pretty easy to tell in short order if the oil is breaking down because of the tractor, or the oil.

[Eugene]

220 coolant in top of radiator. 215 neck.

To hot. Should be 200 degrees or less. At those temperatures the coolant should be steaming. Most automotive thermostats are 190 or 195 degrees F.

I have operated my Cubs in 100 degree temps for hours and not had steaming or boil over from the radiator. Since my Cubs are mostly used for mowing, I have to blow out the radiator fins every so often.

Check the ignition timing.

Clean the radiator fins.

[havoc1482]

220 coolant in top of radiator. 215 neck.

To hot. Should be 200 degrees or less. At those temperatures the coolant should be steaming. Most automotive thermostats are 190 or 195 degrees F.

I have operated my Cubs in 100 degree temps for hours and not had steaming or boil over from the radiator. Since my Cubs are mostly used for mowing, I have to blow out the radiator fins every so often.

Check the ignition timing.

Clean the radiator fins.

Most modern automotive coolant systems will hold it at around 210-212 F. Its in a pressurized system, so keeping it at the boiling point of water. Most modern systems are pressurized to raise the boiling point because the higher the temperature difference to outside air, the better heat transfer occurs through the radiator. A higher temp also makes combustion more efficient as well.

Now in a thermosiphon system like the Cub, yes that number should be lower because at those temps listed your coolant is going to boil away.

[flipklos]

mowed the yard tonight, took 40 min or so to do it here are the numbers,

34 psi oil cold
32 Hot

218 on the neck
135 return
213 in the radiator
156 oil temp

68 degrees out.

I don't find these temps to be insane considering the nature of thermosyphon cooling. There is a reason that the farmall A eventualy got a water pump,
As far as trying a different oil in this..............Why I have used and still use rotella T3 15W40 in many different engines. Allis WC, Ford 8N, 49 F6 ford truck with a flathead, 64 F100 292, Several 300 six fords. Never have I had any issues whatsoever with the oil. Runs clean and is good on price. No I don't think the oil is to blame.
I wish I could blame it on hydraulic oil or gasoline but nothing indicates that. Timing............Move the distributor at all from the factory setting and you loose power.
Cant see bubbles In the coolant.
No white exhaust.
The radiator is not plugged.
This thing always runs warm It will cool down to 190ish on a hot day if you idle it for 10 min.
Just to check mayby I drain the coolant and give it a rinse?

All I know is an oil I have used for years is getting its arse kicked buy a lil ol cub

[Eugene]

218 on the neck. 213 in the radiator. Cant see bubbles In the coolant. No white exhaust. The radiator is not plugged.

All I know is an oil I have used for years is getting its arse kicked buy a lil ol cub

Let me be generous, faulty temperature testing instruments. Other wise I'd just say BS. 218/213 degrees F. and no bubbles in coolant. Yup. Right. What do I know from up? Nothing.