Another Oil Pressure Question

[Paul B]

Doesn't matter where in the line the NRV is, it will prevent oil drain-back through a worn pump!

No, it will stop oil drain back through the NRV.

Your filter, NRV, whatever, is on the outlet of the pump, right, so oil will drain straight down from the pump, leaving the pump empty and spinning on air, unable to suck oil.

[badger]

No, I disagree. For oil to drain back to the sump via the pump, it has to flow from somewhere, the only place it can flow from is the gallery's which have to be drawing/allowing air in to replace the oil that flows out via the pickup back to the sump. Insert an NRV anywhere in this line (anywhere between pickup filter and gallery) and you prevent reverse flow. You cannot simply allow oil to flow out without something (air in this case) being drawn in - that creates a vacuum. If the NRV is in the filter, and is working, then in theory there would have to be a leak path somewhere for the air to be drawn in to allow the oil to return to the sump. if the leak were internal (pickup pipe gasket for example) then fair enough, nothing would show externally. If however the leak path is external, then it'd also leak oil out when pressurised unless it is the pump base gasket on the suction side, but even then I'd expect to see a leak after shutting the engine down.

[Paul B]

So, if you get a milk bottle full of oil and turn it upside down, nothing will leak out because it doesn't have a hole in the top?

Ok, not a good analogy, but oil can and will still slowly drip and trickly down from the pump over a few hours/days, especially if it is hot and watery when the motor is shut down.

[Mike n Helen]

This afternoon I have removed the oil pump gears, and oh dear they are very scored, i'll get some pictures later on. The pump base housing off to my remote filter is also scored but I should be able to get this dressed up. The front housing will also need replacing, looks like it's been sand blast inside the pump housing.

Just one problem I can't get the front pulley bolt out, any suggestions ??

Mike n Helen.

P.S. The oil filter does have a NRV.

[badger]

Paul B, I agree with your milk bottle analogy, but that's not what we're talking about here, is it?

Take a pipe, about 3/8" bore and 20" long, fill it with oil and seal both ends of it. Suspend 1 end about 12" above the other, form a small loop near the bottom of the pipe, the bottom of the loop being roughly 2" above the lowest end of the pipe. That represents the pickup, pump and gallery to the heads. Now unplug the bottom end - a little oil will indeed come out slowly, being replaced by air as you rightly say. The oil in the "loop" and all above it will stay where it is however, representing the fact that the pump gears remain primed for next startup.
Now, introduce a running clearance across the many bearing shells etc within the engine by making a hole - lets say 3mm, not unreasonable - and watch almost all the oil vanish down the pipe!
Here's the important bit...... fit an NRV anywhere in the length of pipe and the loop representing the pump will always stay full!!!!!!

Try it if you don't believe me, but don't shoot me down in flames before you prove me wrong. I didn't spend 26 years working with fluid dynamics and hydraulics in the aviation industry for nowt.

[Paul B]

Paul B, I agree with your milk bottle analogy, but that's not what we're talking about here, is it?

Take a pipe, about 3/8" bore and 20" long, fill it with oil and seal both ends of it. Suspend 1 end about 12" above the other, form a small loop near the bottom of the pipe, the bottom of the loop being roughly 2" above the lowest end of the pipe. That represents the pickup, pump and gallery to the heads. Now unplug the bottom end - a little oil will indeed come out slowly, being replaced by air as you rightly say. The oil in the "loop" and all above it will stay where it is however, representing the fact that the pump gears remain primed for next startup.
Now, introduce a running clearance across the many bearing shells etc within the engine by making a hole - lets say 3mm, not unreasonable - and watch almost all the oil vanish down the pipe!
Here's the important bit...... fit an NRV anywhere in the length of pipe and the loop representing the pump will always stay full!!!!!!

Try it if you don't believe me, but don't shoot me down in flames before you prove me wrong. I didn't spend 26 years working with fluid dynamics and hydraulics in the aviation industry for nowt.

Hmmm, I'll have to fall back on my previous statement here. (backpeddles furiously)

....Unless I am visualising the pump incorrectly. It is a couple of years since I had mine in bits.....

I was thinking the pump setup is similar to a Chevy, with a direct line down to the sump, but after a little research it appears the pump sits in a sort of 'sump' or low point in the system, where the oil shouldn't drain from, even if the pump is worn and there is no NRV. So, unless the pump is stripped apart completely it should never actually become dry.



So, unless a pump is so badly worn that it just cannot suck enough oil to prime itself, even when wet, then oil draining off should make no difference.

I guess that means the pump in question is totally tatered.

When I last pulled my pump I primed it by squirting a bunch of oil in through the two plugs on the pump body.

[Mike n Helen]

Well here are a few pictures of the offending parts, I think it's fair to say they are worn.







All I need to do now is find a new timing cover, not as easy as I first thought, people are telling me they are no longer made for the SD1. I was advised a Buick one is the same, can anybody else confirm this?

Mike n Helen

[katanaman]

buick is the same as the older P6 cover. I will have a look down the garage tomorrow and see if I have a good SD1 one. I know I have about 3 of them just cant remember what their condition is. Have you had the sump of yet as that looks like something has been dragged through the pump. Top and bottom marks are standard on a well used one but the sides look sand blasted. Nothing should ever actually make contact with the sides.

[Mike n Helen]

I will have a look down the garage tomorrow and see if I have a good SD1 one. I know I have about 3 of them just cant remember what their condition is.

If you do find one let me know as I've had no luck in finding one so far.

Cheers,

Mike n Helen

[katanaman]

one I have is pretty scored up the other I have has a few marks but isnt bad but the water connection on the back of the pump is pretty corroded so you probably dont want it. I do have a pretty good RR 4x4 one but you would need to change your pump and pulleys.

[Mike n Helen]

one I have is pretty scored up the other I have has a few marks but isnt bad but the water connection on the back of the pump is pretty corroded so you probably dont want it. I do have a pretty good RR 4x4 one but you would need to change your pump and pulleys.

Thanks for looking, I'll keep them in mind if nothing else turns, didn't really want to start to change the water pump too. I can see me having to get a Buick one at this rate. You said it's the same as the older P6 cover, what does that mean if I'm to fit it on an SD1?

Mike n Helen

[katanaman]

smaller oil pump and you will need a new distributor as the newer ones wont fit. I cant see you getting a Buick one very easy anyway as it was the 60's early 70's that they made the 215.

[Mike n Helen]

Didn't manage to find a new timing cover housing, but have seen an older thread stating that dressing it up should be OK.

Everything back together now with new gears, and the good news is, there's no rattle from start up and I have instant pressure. The bad news is, from cold, it only gets up to 1 bar, once its hot it drops back down to zero on the gauge at 800 rpm, but still no rattle.

I have also noticed the gauge sometime fluctuates and goes totally off the scale up to 7 bar for a second or two and then back down again, it nver did this in the past. It's a Smiths telemetric gauge with a pressure transducer, was wondering do I need to bleed the pipe to the gauge, is it possible I have an air lock in the pipe?

Mike n Helen

[katanaman]

looking at the pics you have a badly damaged front cover which cant be dressed up. The pump cover can but the rest cant without destroying the clearances.