12 replies to this topic

[oc1sup]

Model:MINI City 1000
Year:1981
Description of problem:Low initial oil pressure (about 30-40PSI) when cold then 0 PSI when warmed up.... does the oil pump suck through the filter or pump into it?
When fitting the metal oil pipe from the filter to the engine banjo inlet point, it's possible we've damaged it at the filter screw end (the bolt at the filter end seems welded to the pipe instead of spinning when we tried to undo it, causing the pipe to start kinking - so don't know if it cracked).
There's no leaks that are visible, but if the pipe has a hole in it and the pump sucks from the filter, then the pump could just be sucking air through the hole instead of oil from the filter..... can't seem to find a diagram or doc on the oil flow route in the engine.
Any ideas?

[Edmonds87]

the oil comes direct from the sump from the pick up out of the block from the hole at the top left hand side when looking at the engine head on. From there its pumped to the filter and back through the block to all the main gallerys.

Having probs with oil pressure myself. pain in the ass when the engine runs n thats the only thing holding you up!!!

Good luck

[oc1sup]

Thanks Edmonds87 - so crud from the sump goes through the pump before the filter... ace.... I wonder who has shares in oil pump manufacturers! I'm now assuming the pump is U/S.

I've ordered a new pump from Minispares; hopefully it'll arrive before the weekend and we can get things working again. Not looking forward to removing the engine again, but after changing the clutch with the engine in situ once already I think it'll be easier on my knuckles to remove it for this one.

Thanks.

[Guess-Works.com]

Check your oil pressure release valve first ( behind the domed nut on the front of the block) you should be able to pull it out with your little finger.

True path of oil is...

Pickup from the sump (gearbox)
up the back of the block and into the pump ( which sucks from the sump, and pushes it on it's way )
past the oil pressure release valve, excess oil is dumped straight back into the gearbox.
from the oil pressure release valve is goes up the front offside of the block, past the oil pressure switch ( or take off for oil pressure gauge ) and into the feed pipe to the filter.
It goes into the outer side of the filter and then up the middle into the engines oil galleries, and on to the engine components and head. If the filter is blocked then the oil passes through a small bypass relief valve in the filter head straight into the oil galleries, unfiltered.
Eventually returning to the sump by gravity.

Edited by GuessWorks.co.uk, 16 December 2008 - 01:13 PM.

[oc1sup]

Thanks guessworks. I already checked the bypass valve; the spring seemed the right length and the bullet end seemed un-scored and free moving in the hole, so decided that wasn't the problem. Now going to replace it with a ball-bearing version. The other mini, that we're just changing the front for a flip-front, has an adjustable valve, so may fit that for now as well.
In the meantime, we've just bought a new oil pump and are in the process of removing the engine to replace the pump. As a secondary problem, the clutch had started playing-up, so am reverting to a diaphagm clutch from the verto it had on it (new oil seal, diaphagm spring, plate, lever, slave cyclinder etc). Should know if it's fixed the problem by tomorrow evening I hope.

[fifeheadminis]

Thanks guessworks. I already checked the bypass valve; the spring seemed the right length and the bullet end seemed un-scored and free moving in the hole, so decided that wasn't the problem. Now going to replace it with a ball-bearing version. The other mini, that we're just changing the front for a flip-front, has an adjustable valve, so may fit that for now as well.
In the meantime, we've just bought a new oil pump and are in the process of removing the engine to replace the pump. As a secondary problem, the clutch had started playing-up, so am reverting to a diaphagm clutch from the verto it had on it (new oil seal, diaphagm spring, plate, lever, slave cyclinder etc). Should know if it's fixed the problem by tomorrow evening I hope.

the spring may have weakened abit l;etting the oil pressure to drop may be worth try a different one or a new one

[Jammy]

And turn your engine off immediately if the oil pressure gets much below 20psi, otherwise you risk doing the engine serious damage.

[flamenco]

I have the same problem on my 850. When cold, the pressure rises up to 70-80psi, but when the engine warms up, there is only 15psi at idle, and about 35-45psi when accelerating.

And when it's hot and I start it, the oil pressure warning light just stays on (i.e no pressure) for about 5-10 seconds and then it goes up to about 15-20psi.

However the engine runs perfectly. I will soon be replacing the pump and the crank bearings, but meanwhile I am still using it as it is my only little runner and I don't have time to replace the engine or money to overhaul it!!

[GraemeC]

oc1sup - did you prime the pump during the build of the engine or before starting the car?

[daemonchild]

My oil pressure varies a lot throughout the course of a drive.
Never below 20, but between 20 and 60.

Is this wrong?
If so - what do I need to look at please?

[oc1sup]

Hi GraemeC, sorry for the late reply! (came out in sympathy with the car - been ill....)

Yup got a new oil pump, primed with vaseline, installed it and now have 40-50 PSI, so I don't see that as a problem any more really - just the pump was U/S.

I've tried changing the spring with another I had around without any change to the pressure being seen - so either both springs are equally knackered or there's just a slight leak around the pressure release valve.

I got a ball bearing to replace the bullet PRV and will be fitting that shortly to see if it helps any - I'll leave the spring as is as the ball bearing will effectively shorten and thus stress the spring a bit more anyway....

[Guess-Works.com]

if installing a 9/16" ball bearing instead of the oil pressure relief valve cap, then you'll need to lob two loops off the spring, also I would recommend getting an adjustable dome cap so you can fine tune the oil pressure when hot... ( you can make these yourself but just a cheap to buy )

http://minispares.co...ty=pb&pid=34693

[oc1sup]

Thanks Guessworks, just thought I'd leave the spring the same size as a starter just in case it is weak, then cut it back in stages. Maybe not a good idea, so I'll start by cutting it down a little start with.

As I already have a spare domed nut, and spring that can be modified, I plan to drill the nut out and tap it to make it an adjustable PRV. I know it's not much to buy but every penny counts just now with all the extra I've spent on the car over the last few weeks... but just need time to do it.

thanks.