lost oil pressure

[spike]

Hi had a good and bad weekend.
fitted new cowl to rad to try to stop over heating, same time put new ( put one in was not fitted) thermostat in,
replaced engine oil W30 fitted new oil sender, and bulb for oil light, started it up and great oil light came on then with slight revs goes out ,

but engine temp on tick over hit red, removed thermostat temp ran at low normal.

put topper on mowed some old thick grass for an hour then oil light started to flicker then 20 mins later it will only stay out at half revs, engine temp was running at 165% normal run temp.

so any ideas i am thinking the worst and a big bill ££££££££££££££££££ any suggestions will be great, please don't say scrap yard.

thanks

[alang]

Spike,
You're not alone - mine does just the same. A bit of flail mowing, the temperature gauge gets to normal, the oil pressure drops and the light comes on when you drop below 580rpm. Same tends to apply to my Grey Menace to be fair and that's had an engine rebuild.
The tractor is quite happy on road runs, harrowing or rolling on a cool day but I've decided her days of hard PTO work are now over.
My Dexta was made in 1958 some 10 years after me, so I've been through what she's going through

[jambug123]

Have you fitted a oil pressure gauge to the tractor as these can tell you what is going on as it could be main bearings on the crankshaft that are worn.
The oil light will come on when the pressure drops below it's set figure which is usually around 3-5psi.
My 1959 dexta did exactly the same I checked it with a gauge and found the oil pressure was good until it got hot the it dropped down, a crank regrind and new shells cured the problem.
Regards
James

[spike]

thanks both
just getting a T adapter and gauge and will fit them may be over weekend also got 20w50 oil see if the thicker oil my help.

just thinking ahead if the bearings need replace can you drop them out form the bottom with out removing engine?

and i have seen conflicting post about dropping the sump, some say remove front axle some say you can do it with axle in place

what is correct axle out or not, was hoping to leave it in as don't have a lifting crane.

thank you

[Jerry Coles]

Hi Spike

A word of caution if you are thinking of replacing the big end bearings. When you release the shells if you push the piston and con rod up out of the block then OK. BUT if you let the piston and con rod go down too far (ie letting the con rod go past the journal by rotating the crankshaft) then the lower part of the piston will come out of the cylinder and the oil rings will pop out of the groove. You cannot draw the piston and con rod out of the bottom of the block as the casting will foul the piston skirt. In other words the only way out is UP!! If you have this happen (yes that was me!!) then to remove the piston and con rod you will have to break the oil ring to remove it so the piston skirt can then re-enter the cylinder. Good luck )

Jerry

[spike]

thank you
i was hoping not to remove the pistons just replace big end bearings from the bottom if that is possible? if you remove the crank the pistons will not just drop out "would they" i would hope the rings are tight enough to hold them in place, but i have never worked from this way round "bottom up" done hole rebuild on a ford escort mk1 but we just lifted the engine out with ropes and 3x3 posts and 4 guys. i was a lot younger then.

can i just drop the sump to look at the oil pump, and remove one of the con rod ends to see the state of the shells (bearings), i would think nothing will drop out as the crank will still be held in place

thank you