Freak oil pressure problem, anyone have this happen??

[sd455dan]

Yesterday had to mow a field of tall weeds , it was about a 4 hour job with my Rhino 554 and a 6 foot brush bull. tractor is a 1993 with 1100 hours.

Tractor ran well, engine temp at or below 190 degrees, oil pressure about 30psi at idle and 55 psi at 1600 rpm, outside temp in the 80's.

Anyway , finished mowing- loaded the tractor (8 mile trip home) after refilling with diesel. this morning decided to unload the tractor . she fired right up but 0 oil pressure . Shut it right down and checked the oil, right on full so I cracked the oil pressure gauge line and rolled the engine over with the comp release pulled.
No oil came out. At this point I tried an old trick I learned on an old Buick that would not pump oil and unscrewed the oil filter and cranked it over again and in a couple seconds oil was making a mess of my trailers floor. tightened everything up and started the tractor up and everything was normal , the pressure was right where it always is,

Thinking that, because this tractor has the style of oil sump and pump which mounts the pump above the oil and has to draw the oil up a siphon tube to the pump- that the bouncing and such from moving it and leaving it for the night let the oil drain back cavitating the pump...

It seems to be set up like most engines, in that the only anti -drain back valve is located in the oil filter itself... Restarted the tractor 8 hours later and had instant pressure again... Will keep a close eye on the pressure and if it happens again I will install a new oil filter to eliminate the drain back possibility


Soo has anyone else run across this with their tractor?

 

[Baby Grand]

Very interesting. So the pump lost it's prime?
Didn't even know that could happen, since they're usually positive displacement pumps with very small lift heights.

 

[doxford jim]

I had a similar thing happen on my F250 with the IH 6.9 Litre diesel engine.
I also noticed that when the oil warmed up the pressure dropped off. I fortunately had a "preluber" oil priming pump on this engine, so when the oil pressure dropped off I would switch the preluber pump on to get me home (I used the truck locally only while I had this problem).
After a lot of checking and including replacing the filter head (suspected sticking valve) and no changes, I went to a local International truck centre.
The IH truck place removed the sump pan and checked the engine and found that the lube oil pump "pickup tube" had a crack around 70% of the outside. There is a clamp on that engine to prevent the pickup tube from vibrating, cracking and completely failing. Guess what, the clamp on my engine came apart and the pickup tube vibrated and failed - nuts and clamp found in the sump.
With cold oil, the pump would pump fine as the oil vicosity stopped and air being sucked in. Once the oil warmed up, air started to be sucked in the pickup tube.
I had a new oil pump and pickup tube installed, new main and bottom end bearings installed. The old bearings started to show some scuffing marks. My situation worked out fine as I was able to stop serious engine damage.

For you, I would install a second oil pressure gauge (mechanical) to substantiate your findings one way or another.
Can't help on your solution, but am able to explain what happened to me and how things worked out.
Good luck and please update on your situation.
Thanks
Jim

 

[sd455dan]

Thanks for the replies Guys

The tractor has started and built pressure normally since being (home). I'm guessing it didn't like being bounced around on the trailer and then left overnight before being off loaded. The oil pressure gauge is mechanical and believe it is working as it should , would probably replace it but it is plumbed with a solid metal line and Chinese banjo fitting...

Thanks again , Got plenty more work to do so just have to see how it goes...and if it does act up I'll use the other tractor and tear into the Rhino a little deeper

 

[Gale Hawkins]

Had this happen in the 2002 SUV with GM 5.3L engine and it would only do it hot and I think it was the pressure relief valve sticking open. This was following an overdue oil change. I ran about 8 oz of Sea Foam in the new oil for 160 miles and the problem went away totally. The oil was really black after 160 miles. It was not thick but just very dark. When we drained it we went back with 10w-40 Mobil one high mileage motor oil and 3000 miles later still no sticking of relief valve in oil pump.

 

[sd455dan]

thought it would be good to update- oil pressure has built up quickly every time since the oil filter was loosened /re-tightened in the original post...

also the oil / filter change only had about 20 hours on it after mowing, Normally run Shell Rotella T but there was a great deal on Mobile Delvac oil. the filter is a Fleetguard...