77 245DT oil pressure help

Trailfarmer · Oct 20, 2015

Some-time lurker, new member.
Tried lighter weight oil during recent oil\filter change on my 77 245DT with about 1500hrs. Now after warming up oil light comes on when tractor is at idle. Revving engine makes light go off. According to dip stick oil level is ok. No problems like this before the change.

Need heavier weight oil? Saw a comment in another thread that lighter oil may not be best choice for older engines.
Oil pump going bad?
Oil sensor going bad?

I am reasonably competent at working on my own stuff but don't have any pressure testing equipment, etc

Local dealer is $75 hr (+ transport) so I'm hoping you folks can help me figure this one out at home

Trailfarmer · Oct 20, 2015

Some-time lurker, new member.
Tried lighter weight oil during recent oil\filter change on my 77 245DT with about 1500hrs. Now after warming up oil light comes on when tractor is at idle. Revving engine makes light go off. According to dip stick oil level is ok. No problems like this before the change.

Need heavier weight oil? Saw a comment in another thread that lighter oil may not be best choice for older engines.
Oil pump going bad?
Oil sensor going bad?

I am reasonably competent at working on my own stuff but don't have any pressure testing equipment, etc

Local dealer is $75 hr (+ transport) so I'm hoping you folks can help me figure this one out at home

BigBoyToys · Oct 21, 2015

What were you using and what weight oil did you put in?
In general a lighter weight oil will result in lower oil pressure.

Trailfarmer · Oct 21, 2015

I switched from 10W30 to 15W40 and it is the kind for diesels.
Changed it about a month ago, weather was 60s--80s.
Been busy with some many other projects, but need to get it figured out so I can get some fall\winter chores done.

Would a continuity tester or something similar tell me if the oil sensor is bad?

varmint · Oct 21, 2015

Greetings, Trailfarmer! I lived in Greater Lafayette (and W. Lafayette) for most of my first 37 years.

That said, go to an auto parts store, and buy a cheap mechanical oil pressure gauge. Most should come with various adaptors. I installed one on my old '87 B8200 Kubota quite easily, by installing a brass tee (male/female/male if I remember) where the oil pressure sender on the side of the engine block screwed in, taking the new gauge line off from the tee and screwing the idiot light sender back on the other side of the new tee. That way, you will see what the pressure actually is at various RPMs. And, 15w40 is heavier, not lighter, than the 10w30 you say your started with. That would worry me!

repete · Oct 22, 2015

Perhaps the heavier oil is unable to push through the filter when cold and therefor lower pressures on the downstream side of the filter.

varmint · Oct 23, 2015

15w40 isn't exactly 50w, and wouldn't the filter's bypass let oil thru? Don't think this is figured out yet...

lakeridge · Oct 23, 2015

The camshaft has a machining plug on the end of the shaft. This plug can fall out and creating a big enough within the lub. system that the pump cannot keep up at idle.
When you throttle the engine up the pump flow increases to compensate for the leak. I ran into this problem many years ago. Plug is pressed into the hole and simply feel out.

BigBoyToys · Oct 23, 2015

You said you changed your oil, how long has it been since the filter has been changed?

The bypass valve in the filter will open for a few reasons...
1. The filter is clogged/dirty.
2. The oil is too "thick" at cold temps.
3. If you were to accelerate hard and build up oil pressure too quickly. (Unlikely in a tractor).

The bypass valve opens in these conditions so the engine isn't starved of oil. "Unfiltered" oil is better than "NO" oil!

Most tractor manufactures seem to recommend 10W30...try going back to it.