MF-135 oil pressure fluctuations

[flusher]

My 1964 MF-135 diesel is showing unusual oil pressure fluctuations. Oil pressure before this problem arose stayed in the 50-60 psi range constantly.

Now after engine start the pressure rises to 30 psi at 1300 rpm, fluctuates between 20-30 psi for 7-8 minutes and then drops to zero or near zero in about a minute. Shut off the engine immediately. Got a little coolant dripping out of the radiator overflow.

Repeated this behavior 3 times before stopping to think about the problem.

Checked the oil level; it's OK. Just a little oil leakage (less that a teaspoon) after engine shutoff, probably from the breather tube on the valve cover. No unusual smoke from the exhaust pipe.

The oil pressure gauge is a mechanical gauge with small diameter metal tubing to the engine.

Disconnected the oil pressure line at the engine and got a small pressure release and a little oil dribble from the fitting on the block.

There's a check valve on the outlet of the oil pump. Is this accessible by removing the oil filter plate on the block?

How about crankcase flush? Any recommendations?

Anybody have experience with Lucas Heavy Duty Oil Stabilizer?

 

[elad]

Small metal tubing may have some sludge. Remove gauge and blow
air through it. Gauge may be plugged too. Maybe new gauge before
you get worried about more serious problem. elad

 

[flusher]

Small metal tubing may have some sludge. Remove gauge and blow
air through it. Gauge may be plugged too. Maybe new gauge before
you get worried about more serious problem. elad

Good suggestion. The old oil pressure gauge was replaced about 8 months ago and used fairly large steel tubing (about 1/4" OD). The new gauge has the 1/8"OD copper tubing which I think is the standard size these days.

 

[Trac-Tech]

Flusher
I think the valve you are talking about on the head of the filter housing is the main relief valve for the lubrication pump. I'd check that first as it is easy to get at and it may be sticking. This could be the reason for some pressure and then none?

 

[Soundguy]

I'd go along with the other advice.. replace the oil gauge, and blow out the oil line.. reconnect and burp the line, then see what ya got.

soundguy

 

[flusher]

Flusher
I think the valve you are talking about on the head of the filter housing is the main relief valve for the lubrication pump. I'd check that first as it is easy to get at and it may be sticking. This could be the reason for some pressure and then none?

Thanks for the suggestion. The filter housing on my 135 has two bolt holding it to the block. The oil filter is the screw-on type. I think that valve is accessible by unbolting the filter housing, but I'm asking for verification before I do that.

 

[doxford jim]

Hi Flusher,

When was the oil last changed? If you changed the oil what colour was it (black, grey etc.) and what was the texture - any sludge come out?

There is the pressure relief valve near/on the engine driven pump. Could be the spring is weakening and allowing oil to return to the sump instead of all going to the oilways. Maybe valve sticking for some reason. There is also the relief valve in the filter head - it too could be sticking or have a weak spring.

I would do an oil and filter change first and then you know what you are working with. Maybe an engine flush and and drain, followed with a cheap ooil toclean out the engine. Then the good oil and filter. Not likely a new gauge is faulty, but is possible.

I don't know if this helps or not.

John Wood

 

[flusher]

Hi Flusher,

When was the oil last changed? If you changed the oil what colour was it (black, grey etc.) and what was the texture - any sludge come out?

There is the pressure relief valve near/on the engine driven pump. Could be the spring is weakening and allowing oil to return to the sump instead of all going to the oilways. Maybe valve sticking for some reason. There is also the relief valve in the filter head - it too could be sticking or have a weak spring.

I would do an oil and filter change first and then you know what you are working with. Maybe an engine flush and and drain, followed with a cheap ooil toclean out the engine. Then the good oil and filter. Not likely a new gauge is faulty, but is possible.

I don't know if this helps or not.

John Wood

Last oil change was 8 months ago. The old oil was black and grimy. The oil on the dipstick now is black and grimy.

I'll start with an oil change and new filter. Oil capacity is 6.5 quarts with filter.

I notice that some folks modify the normal procedure and use a quart of ATF in place of a quart of oil and run the engine for 10 minutes or so and then replace the oil/ATF and filter. The idea is that ATF is a light weight oil with detergents that cleans up the engine without damaging the seals. Apparently using diesel or kerosene instead of ATF can cause seal damage.

Never tried this method of engine flushing before. Need guidance here.

 

[Farmwithjunk]

Unless your Perkins diesel is different than any I've worked on, the only way to access the relief valve adjustment is by pulling the oil pan. Normally, that relief tends to stick and hold excessively HIGH pressure when the relief fails.

Do you still have the canister type filter, or has it been retro-fitted w/ spin on type? Canister type can internally bypass filter and drop pressure.

I'd start with a new pressure gauge and line to confirm pressure loss.

I recall someone reporting a simular incident, with a Perkins diesel coincedentally, where the oil pump pick screen up was clogged somewhat. Also I've heard of oil return passages getting clogged, not allowing oil to return from the top end, starving the pump finally.

Another thought, some of the earliest Perkins diesels had issues with oil pump pick-up falling off. VERY low rate of incidence, but a possibility none the less. (NOT likely though, as pressure wouldn't even read on start-up w/ no pick up)

 

[flusher]

Unless your Perkins diesel is different than any I've worked on, the only way to access the relief valve adjustment is by pulling the oil pan. Normally, that relief tends to stick and hold excessively HIGH pressure when the relief fails.

Do you still have the canister type filter, or has it been retro-fitted w/ spin on type? Canister type can internally bypass filter and drop pressure.

I'd start with a new pressure gauge and line to confirm pressure loss.

I recall someone reporting a simular incedent with a Perkins diesel coincedentally, where the oil pump pick screen up was clogged somewhat. Also I've heard of oil return passages getting clogged, not allowing oil to return from the top end, starving the pump finally.

Another though, some of the earliest Perkins diesels had issues with oil pump pick-up falling off. VERY low rate of incidence, but a possibility none the less. (NOT likely though, as pressure wouldn't even read on start-up w/ no pick up)

The oil filter is a spin-on type. I'll replace the gauge and see what happens.