Folks,
Interested in views on what might have taken place with my car yesterday (1275 A+) - I noticed that the hot oil pressure (at speed) is 70-75psi. The car has always done 50-55psi. Recent oil change (XLD before and after), and an oil cooler recently fitted. Drove around today without the cooler plumbed in, and no change - still 70-75psi. Oil filter changed late yesterday and cut open for interest's sake - almost no material collected. Oil pressure relief ball & spring removed & checked, no worries there.

As I have an adjustable oil pressure relief cap, I could wind it back to give, say, 60psi hot, but I can't help but think something has caused this - but what! (Oil pressure is normally too low, not too high!)

Thanks in advance,
Matt

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'68 Deluxe w/Metro engine

Bypass in the filter housing was open before and now closed?

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the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

Thanks for the reply Mickmini. What would have caused the bypass valve to close, given that I still have this high oil pressure after the filter change?

Is it realistically possible to have 70-75psi hot on an engine of unknown age/history, running a cheap mineral oil?

One option is for me to screw out the pressure relief valve (I have an adjustable one) down to say 60psi, but this would only deal with the symptom, not the cause.

I substituted in another Smiths gauge yesterday, but no change to the readings.

Could be worse I suppose, it could be low oil pressure - but it would be nice to pinpoint a cause.

Cheers
Matt

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'68 Deluxe w/Metro engine

Double check the relief valve, I'm not sure how the adjustable ones work (are they a ball??) ....when mine was sticking one time (standard bullit shape one) it jammed closed and my oil reading went off the scale (100psi plus) and sometimes would jam open and give very low reading.

I normally tend to get a reading of around 65-70 hot at speed (and it's not a new engine). The standard valve is supposed to give around 70-75psi max I believe.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Thanks Phill. Mine is a ball bearing, with a cutoff bolt up the guts of the spring to give it support - took advice from this forum on that issue a while ago. Just took it out and it all looks the way it should...
Interesting that you get 65-70 hot - I didn't know that was possible. What oil do you use?

Matt

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'68 Deluxe w/Metro engine

I dont know how to fix ur issue but i run 75-80 psi hot and the engine was rebuilt over 15yrs ago?

Thanks - it sounds like the oil pressure I'm seeing isn't a real problem - but how it came to jump 20-25psi is a real mystery. I wonder if it passed a stone?

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'68 Deluxe w/Metro engine

The Doc was a supporter of the ball for a long time but I seem to remember he changed his recommendation back to using the standard arrangement in the last year or so. He may come on to elaborate, or do a few searches and you may find the post with the reason(s) he reverted.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

When i changed my oil and filter last time... My gauge went from 75 all the time to 50 on idle and 75 while driving? Dunno why either but all seems be going fine

Valvoline XLD classic. Although that is now mostly no longer available and is being replaced with XLD premium.

I just use the old standard bullet shaped valve.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

I am still using a ball in mine, but I've seen some problems with this mod, unless you use a new spring.
If the spring gets bent it tends to push the ball sideways, off its seat. Putting a bit of straight 5/16" steel rod inside works, but you want the spring straight to avoid problems. So don't use the old spring if it's bent at all.

IMO the original valve works well, as long as metal shavings in the oil doesn't jam it. This is really its only problem. The ball avoids this as it is smaller diameter and there's plenty of clearance.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

That's belting along at 110 kmh, idle is usually around 25psi.

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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

THe bypass valve is just a ball and spring. It could get jammed by crud just like the releive valve. You can take the housing off the blockand check it is closing properly.

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the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

Gents. I seem to recall a similar issue being described to me when I visited the Willson's in Hobart many years ago.

The car was a Clubman with excessive oil pressure, so excessive that a test gauge was spat across the workshop!

The usual suspects were checked and the pressure relief valve was fine.

What was eventually found, and it took a lot of head scratching on the Willson Laddie's part, was this:

The pressure relief valve seats on one end of a pressed-in sleeve that also incorporates the relief hole that allows excess pressure pushing past the relief valve back to the system.

This sleeve had come loose so that under pressure the pressure relief valve, and the sleeve, were being pushed up the bore against the spring. This meant that the sleeve was covering the return hole in the block casting and causing no regulation of pressure. With no regulation, it just keeps going up until the leakage limit of the oil pump, or something else in the system, is reached.

Once they worked this out and were able to glue and stake the sleeve back where it should be, the problem went away.

It's worth mentioning that until I heard about this fault, I had no idea that the seat for the oil pressure valve was a separate part. I always assumed it was simply a bore in the block. Shows to go you never stop learning! (and you probably should look closely at cutaway drawings as well!)

I thought I wote this fault up in the Mini Experience magazine, or possibly in "Inside the Greasy Bits" but can't find it so far in my archives.

Worth checking anyway as it's a likely cause of your symptoms.

Cheers, Pottsy

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Smile Up at The Trucks!

Yes The relief Valve Seat is a removable part. There is also a difference between the one in a manual Block and the Auto Item. To remove this seat one has to normally tap a thread in it and use a long enough bolt to pull it out. I remember changing the one in the 1380 engine which I changed from Auto to Manual.

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