Losing oil pressure

[Saw-sick Steve]

My 50 year old MF 135 is struggling to maintain decent oil pressure. Starts off fine but then gradually drops as the engine warms up until after about an hour or so the gauge barely registers on tickover. Problem seems worse in the summer, I can only work a topper or mower for a couple of hours before having to switch off for fear of seizure - not so much of a problem in winter on processor. Oil is black, not losing any through leakage or burning - any ideas?

[ballibeg]

Oil pressure relief valve stuck? Worn oil pump? Think it's a sump off job and replace pump with valve as a whole.

 

I'm no expert though.

 

Dave

[treequip]

Classic symptoms of a worn out pump

[doobin]

Whack some Lucas oil stabilizer in it, it works well. You want the heavy duty one, not the synthetic one.

 

Lucas Oil Products (UK) - Heavy Duty & High Performance Lubricants

 

I use it in my motorbike after a shot air filter led to half the compression that there should be. Being a tough little Honda, it now runs almost as good as it should. So good that I can't be bothered to replace the pot and piston.

 

I also use it in my tracked machines, to help provide engine protection when climbing the steep slopes we work on. It's a regular part of my service program. No bull, you can hear the engine run smoother. I'm not one for snake oil, but for my particular circumstances this product is the business.

[doobin]

Oil is black, not losing any through leakage or burning - any ideas?

 

If it's black, I'd start by changing it...

 

If it's your usual 5 years since last changed old tractor oil, it's probably giving you as much engine lubrication as water. Add the Lucas stuff at a rate of 20% to the new oil, give it a new filter and see how you get on.

[TimberCutterDartmoor]

My 50 year old MF 135 is struggling to maintain decent oil pressure. Starts off fine but then gradually drops as the engine warms up until after about an hour or so the gauge barely registers on tickover. Problem seems worse in the summer, I can only work a topper or mower for a couple of hours before having to switch off for fear of seizure - not so much of a problem in winter on processor. Oil is black, not losing any through leakage or burning - any ideas?

 

Whack some Lucas oil stabilizer in it, it works well. You want the heavy duty one, not the synthetic one.

 

Lucas Oil Products (UK) - Heavy Duty & High Performance Lubricants

 

Had exactly the same with International; red hot in summer, no pressure registering at 1500 rpm let alone tickover. Really need to take out the pressure switch and test with gauge if you can. I also used Lucas Oil Stabilizer but in this case it made no difference whatsoever; though I do believe it works in the majority of cases. Fearing the worst I changed the oil and just like that - problem solved.

 

However, bear in mind that these old'uns were designed for sub 250 hour oil changes on SAE 30 oil and when 15W40 replaced this the O&F interval became 100 hours - very short and goes before you know it. Your oil shears down pretty rapidly thus. The pressure at the switch is static pressure so doesn't really give an indication of oil flow - most likely the thinned oil will be plentiful at the top end but not maintaining MOFT in big end bearings and crank journals so the oil change is recommended. Look for a 15W40 with the highest HTHS you can find and highest viscocity at 100 degrees possible.

 

JD Plus 50-II would be a good start.

[aspenarb]

My 50 year old MF 135 is struggling to maintain decent oil pressure. Starts off fine but then gradually drops as the engine warms up until after about an hour or so the gauge barely registers on tickover. Problem seems worse in the summer, I can only work a topper or mower for a couple of hours before having to switch off for fear of seizure - not so much of a problem in winter on processor. Oil is black, not losing any through leakage or burning - any ideas?

 

I would change the oil and filter then get the pressure checked with a gauge. The original may be telling lies, they are supposed to run 25-30 psi @ around 1000rpm so its not that high anyway.

 

Bob

 

Some Gumph.

 

Data Specifications

 

Cylinders 3

Bore 3.6” (91.44mm)

Stroke 5”

Displacement 152.7 cu ins.

Compression Ratio 17.4:1

Firing Order 1,2,3

Power 37 bhp

Location of No. 1 Cylinder, Front of engine

Cylinder Liners, Chrome plated

Fuel Pump Static Timing, 18 degrees B.T.D.C.

Letter On Fuel Pump Rotor, E

Letter on Hydraulic Head No. 1 Delivery Port, W.

Inlet Valve Opens, 13 degrees B.T.D.C.

Exhaust Valve Closes, 10 degrees A.T.D.C.

Valve Overlap, 23 degrees

Valve Lift, 0.36″

Tappet Setting (Hot), 0.010″

Tappet Setting (Cold), 0.012″

 

Tightening Torques lbs./ft

 

Cylinder Head Nuts, 55-60

Con. Rod Nuts, 70-80

Main Bearing Setscrews, 110-120

Flywheel Setscrews, 75

Balance Weight Setscrews, 50-55

 

Pressure Setting (injector bleeding pressure), 120 Atmospheres

Operating Oil Pressure, 25-30 p.s.i. or more at normal speed

Relief Valve Setting, 50-65 p.s.i.

[Saw-sick Steve]

Thanks for the replies lads, this place never fails to come up with the goods.

[predator]

if you can get at the relief valve check it over it could be fouled one way or another ??

 

ps i have seen the relief valve spring shimmed with thin washers to raise the oil pressure a tad .Also your oil pressure switch if its electric some put low oil pressure light on at 7lbs and some 11lbs hot on tick over on the old girls so if its around that ticking over somethings a miss