Super Major Engine Oil Pressure

David M · Post by **David M** » Sat Apr 26, 2008 4:26 pm

Hi,
Our 61 Super Major was leaking coolant into the engine oil. We fitted new liners, pistons etc. and this cured the problem.
However during its first days work the oil light came on at low revs. We checked the pressure and found it to be around 5 psi at low revs and 10-15 at mid-high revs.
The oil light never came on before the rebuild and the crankshaft mains appeared okay.
Could this problem be the oil pump itself and how would we check the pump for wear?
Any help appreciated.

Post by **Brian** » Sat Apr 26, 2008 6:23 pm

Its easy with hindsight but it would have been best to have had the crank checked and also the camshaft as both these can cause loss of oil pressure/low oil pressure.

The pump wear is checked by eye and there should be a light rubbing contact between the rotor and the outer ring as the pump is turned. The second check is to mix about a pint of 30W oil with 1/2 gal. of paraffin. With the pump held in its operating position with the filter immersed in the mixture, the pump should be rotated at around 60rpm. It it is OK it will lift the paraffin/oil mixture.

Majors never had a very high oil pressure. Around 20 to 30 PSI when run at 1800 rpm and around 5 PSI on tick over is quite normal have seen them run for many years with only 10 PSI at 1800.

You would also need to check the PR Valve in the pump body but I would suspect your problem is more likely crank/camshaft related..

David M · Post by **David M** » Sun Apr 27, 2008 9:43 pm

Thanks Brian,
The pump lifted the mixture so we will turn our attention to the crankshaft next. I'll let you know what we find.
Regards,

David M · Post by **David M** » Tue Apr 29, 2008 12:22 pm

The crank has some marking on the mains and feels uneven when you run your fingernail across it. I expect this is the problem.
I'll now go and weigh up the costs between a regrind and new crankshaft.

Post by **Brian** » Tue Apr 29, 2008 2:02 pm

David,
Regrind is the cheapest and best way to go. Those cranks would take a number of grinds without any problems. We used to have service cranks down to .030.

I would also check the cam shaft and bearings.

David M · Post by **David M** » Tue May 13, 2008 11:37 pm

We finally decided to fit a new crank.
Although it was a little cheaper for a regrind + bearings + gaskets than a crankshaft 'kit' the machine shop was quoting a turnaround of months rather than weeks whereas the new one was here next day.
We eventually got it fired up around five o'clock on Saturday evening getting around 35 psi on tickover. We re-assembled the tractor and gave it a bit of a run then got ready for a road run on Sunday.
All went well until, 3 miles from home when water started squirting out of the head gasket.
On to the next job...