Oil Pump Woes

vaultsman

Well-Known Member
#1
Tooling along in the outside lane at 70....suddenly sounds like a bag of spanners rattling under the bonnet.

Checked the gauge....zero oil pressure. Managed to get over to the hard shoulder without incident....recovery truck home.

Took the distributor out to find the pump drive shaft seized. Stripping the pump down shows....this:



The driven gear's lost a tooth, taking out the pump driving dog at the bottom of the distributor. I fitted the spacer plate/taller gears conversion 8 years ago.

Thoughts, anyone? Anyone else had this?

EDIT: The gear cavity in the front cover appears fine with no evidence of scoring or damage, and the driven gear turns freely on the spigot.
 
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harveyp6

Well-Known Member
#2
I've never seen that.

Presumably that's an OE gear which would make it even more strange that it's broken.
If it's a repro part then it would be difficult to know, but I've never heard of it either.
 

vaultsman

Well-Known Member
#3
Not sure whether it would be OE, Harvey, as it came as part of the higher-volume upgrade kit. It could be an OE SD1 idler gear, but certainly the driving gear isn't as it's the SD1 size gear, but with the slot rather than tongue for the drive.

Bit of a puzzle that there's no evidence of what caused the fracture. If the gear was cracked when I fitted it I'd have expected it to fail before now.

I'll have a word with Real Steel on Tuesday. Need to source a 35D8 distributor shaft as well.

Wouldn't have one in your box of bits, would you? ;)
 

SydneyRoverP6B

Well-Known Member
Staff member
#4
Hi Stan,

The only things that spring to mind would be either a fault in the manufacture of the gear that failed, or a suitably sized piece of debris became caught between the gear and the housing, resulting is what you see.

I have not seen that happen before either, although I have heard that the gears can jam when the conditions are right.

Ron.
 

vaultsman

Well-Known Member
#5
Thanks, Ron.

Still remains a puzzle to me though....a suitably-sized piece of debris to cause that failure would surely have left its mark in the aluminium. So, even though it's taken 8 years ( :eek: ), I've got to go with a material/manufacturing fault.

I'll reassemble it all with a new idler, change the oil & filter, fit a new distributor/shaft, curse the gods....and see how I go. ;)
 
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vaultsman

Well-Known Member
#6
Well, the woes are not banished yet. :(

Couldn't buy just the idler gear, so I had to get a new complete kit from Real Steel, but found the gears were 4 thou deeper than the existing which meant I'd need a thicker gasket. Thought it best to do the job properly so I took the timing cover off, fitted the gears to give 2.1/2 thou end float and packed them with Vaseline. Refitted the timing cover and spun the pump with a priming tool. Pressure started coming up....which was good.

All back together, spun the engine on the started with ignition disconnected.....and not a flicker on the mechanical gauge I have fitted. Took a chance and started the car and the needle came off it's stop, but the pressure steadfastly refuses to rise above 20 psi. It dips slightly now and again, then recovers to 20 psi. Varying the revs between 550 idle and 1200 makes no difference to reading. So not a happy bunny....

It's suggesting to me the relief valve isn't seating properly, although it seemed OK in the bore when I had the pump on the bench.

Unless.....the original mishap totally shafted the bearings....

Thoughts, anyone?
 
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clive P62

Active Member
#7
Hi Stan.
I would recheck the relief valve again just in case a bit of swarf has jammed it (happened on my sd1)
On my first p6 I bought as a non runner
It still had 30psi but nocked badly, No shells or crank left when stripped.
Hopefully not damaged in your case as you noticed fault straight away.
Clive.
 

vaultsman

Well-Known Member
#11
Took the relief valve out, cleaned out the bore as best I could with a small brush, and dressed the plunger face and chamfer with a stone. Refitted, but sadly there's no change.

There's no change in the 20 psi pressure anywhere between 550 and 2000 rpm.

Even with a low reading like that due to worn shells, I would have expected to see some variation at different engine speeds. Or am I wrong in that?
 

harveyp6

Well-Known Member
#12
There's no change in the 20 psi pressure anywhere between 550 and 2000 rpm.

Even with a low reading like that due to worn shells, I would have expected to see some variation at different engine speeds. Or am I wrong in that?
If it's making 20psi at 550rpm and thet's enough to bring the PRV off it's seat then no matter how hard you rev it it won't make any more pressure. You need to up the point that the spring allows the valve to come off its seat, either by changing the spring for a stronger one, or preloading the one you've got to see what happens. If you're worried about the possible condition of the ends and mains causing genuine low pressure, then on an "S" it's simple just to drop the sump and have a look.
 

vaultsman

Well-Known Member
#13
I hear you, Harvey.

So you'd agree there should be some variation, and you're suspecting the PRV spring pressure? But wouldn't the spring weaken over time, rather than suddenly? Before these shenanigans, Occie would always hold 50 psi at 2000 rpm when cold.

I know, I know....my head's going round with it all.
 

harveyp6

Well-Known Member
#14
The problem you have is that the guage is reading low and because you're not certain that by revving to increase the pressure you'll do further (serious) damage, I'd probably have a look at the shells. You only need to look at a couple of mains in the cap and a couple of ends in the rods (not the big end cap). I'd agree the PRV spring should get weaker over time rather than suddenly after this incident, but whether it's the spring, or the shells I think I'd want to look at the shells just in case. You would expect an increase in pressure with an increase in rpm, but if for whatever reason the PRV is opening at 20psi and you get 20psi at idle, then the pressure won't ever go up from that.
 

vaultsman

Well-Known Member
#15
Thanks Harvey...that's clear.

I'm away from tomorrow for a few days, so I'll drop the sump when I get a chance....hopefully next week.

Cheers.
 

cobraboy

Well-Known Member
#16
Am reading this with interest but am afraid I cannot suggest an answer. Only thought is to check the side clearance on the gears in case the cover has been blown out by the exploding gear and there is a gap big enough to impair the efficiency.
I would like to ask ..... if the end float is supposed to be a couple of thou and the gears are tight how does one achieve the clearance ? double up on gasket, or is there another way ?

Thanks
 

harveyp6

Well-Known Member
#17
if the end float is supposed to be a couple of thou and the gears are tight how does one achieve the clearance ? double up on gasket, or is there another way ?
There are varying thicknesses of gaskets, although they're not itemised as such, you just have to take pot luck with the thicknesses of the gaskets you buy. IIRC the genuine ones are a lot thicker than the pattern ones. Worth noting that some pattern gaskets have one of the holes that should be there not stamped out.
 

vaultsman

Well-Known Member
#19
Am reading this with interest but am afraid I cannot suggest an answer. Only thought is to check the side clearance on the gears in case the cover has been blown out by the exploding gear and there is a gap big enough to impair the efficiency.
I would like to ask ..... if the end float is supposed to be a couple of thou and the gears are tight how does one achieve the clearance ? double up on gasket, or is there another way ?

Thanks
As Harvey says, the genuine gaskets are thicker at .010/.011" than the pattern ones, which are usually around .007/.008". The high-volume kit also comes with a .004" gasket (that needs the missing hole cutting out).

When new, the gears should stand proud of the gear chamber in the front cover by approx. .006/.007". When the gasket's fitted, this then provides the end float between the gears and the pump cover.

I remember when I first fitted the high-volume kit 8 years ago I had some problems finding the right thickness gaskets to get the end float correct. Obviously, if the clearance is excessive, oil pressure will suffer. The tips of the gears should also have no more than .002" clearance to the gear chamber walls.
 

cobraboy

Well-Known Member
#20
Thanks for that info I appreciate it.
My gear tips have .004" so I will see how it goes on pressure.
I read an interesting piece on drilling the relief valve spring cap and tapping for an m10 fine thread and using a bolt and locknut to preload the plunger to give 10 psi per thousand revs.
What could possibly go wrong ;)
 
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