TW 25 Lost All Oil Pressure.

FOMOCO Farmer · Nov 26, 2022

I think I know what happened but wanted to get others opinion. I've noticed a noise from the front of the motor the last few days. Tractor has been bushhogging. Not pulling all that hard. Yesterday, I smelled something that was not right. Noticed smoke or steam coming from the front of the motor around where the top radiator hose attaches, first thought was blown radiator hose. Tractor was not running hot. Started home, motor labored and quit. Pulled it home, cranked it over with kill switch pulled, no noise, pushed kill cable in and it started. No oil pressure in either port with a mechanical gauge. I'm pretty sure the oil pump drive idler gar has fallen off. Question is, right before it quit, it had excessive blow by. It blew out the dipstick and breather tube. After the restart, it had no blow by. Can anyone explain this? Motor ran fine. I did not run it long. I'm pulling the pan and see what I find. Probably pulling some rod caps as well. Anything that doesn't look right, motor is getting rebuilt. Tractor has around 5500 hours. Any thoughts, opinions are welcomed.

Bern · Nov 26, 2022

Early TW 10-30 oil pumps had an issue with the idler gear that would cause a sudden loss of oil pressure. This should not be happening on your model however. The biggest problem with TW oil pumps is that they're too big with regards to volume output. This puts too much stress on the relief valve and eventually side loads the bore in which it rides and causes the valve to hang up. Once the valve sticks open, oil pressure goes to near zero at idle. However, if you're getting nothing out of the port, it sounds like your pump simply stopped turning.

The most concerning part of your post is your note of the excessive blowby just before it quit. That's what happens when a bearing starts to seize, which is consistent with your laboring observation.

I fear you're going to find a bit of a mess in there once you drop the pan. Hopefully the crank can be salvaged.

chevytaHOE5674 · Nov 26, 2022

Like Bern says ill bet you find a mess in there.

My 8830 hung the relief valve open but it still made about 10psi at a hot idle and at 1k rpm made 25 or so psi. I bumped the low idle speed up until I had time to get it in the shop and replace the pump.

Had a tw35 stick the relief closed and blew the filters off at WOT.

Bern · Nov 27, 2022

Relief valve issues are exacerbated on the TW30/35 and 8830 tractors with the full-flow oil cooler. This is
because the smaller tractors use a bypass oil cooler, where a portion of the oil is sent to a cooler on the
bottom of the radiator and promptly dumped to sump. This can't happen on tractors with the full-flow oil
cooler.

Ford later on came out with a smaller pump for the non-turboed models. As I recall it was about 25% smaller
in volume output. I put one on a TW35, using the logic above. That engine would still peg a 100PSI oil gauge
when cold. In summary, the TW oil pumps are WAY too big, causing the relief valve issues you experienced.

TW 25 Lost All Oil Pressure.

FOMOCO Farmer

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Bern

Well-known Member

chevytaHOE5674

Well-known Member

Bern

Well-known Member

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