Now here's a funny thing!
Discussion
Has anyone else had this problem?
I am looking at a Mk. 2 Cooper 'S' fitted with an A+ block.
The engine has been rebuilt recently and when cold it has about 80 psi oil pressure (it has Duckhams 20/50). This stays high for the first 10 miles or so, but then the oil pressure figure on the gauge seems to steadily fall away until it's reading about 20 psi. Of course, as a Cooper 'S' it has no oil pressure light. If I then stop the car, switch off the engine, give it about 3 seconds, re-start it, the pressure immediately goes back up to c.70 psi, and that's when it's hot. Drive away and the indicated pressure decayes back to the 20 psi. Stop and re-start and it's immediately up to 70 psi again.
Now, before anyone says this, it's definately not the pressure relief valve sticking. I immediately suspected this and fitted a new plunger and a new 'S' spring. It has a plastic pipe to the gauge, by the way, not the 'orrible original pipe with the rubber bit in the middle.
In my mind I'm convinced the pressure is not dropping, but........
The owner is very worried, as you may imagins and I've got to sort it for him.
Any ideas anyone?
Peter
I am looking at a Mk. 2 Cooper 'S' fitted with an A+ block.
The engine has been rebuilt recently and when cold it has about 80 psi oil pressure (it has Duckhams 20/50). This stays high for the first 10 miles or so, but then the oil pressure figure on the gauge seems to steadily fall away until it's reading about 20 psi. Of course, as a Cooper 'S' it has no oil pressure light. If I then stop the car, switch off the engine, give it about 3 seconds, re-start it, the pressure immediately goes back up to c.70 psi, and that's when it's hot. Drive away and the indicated pressure decayes back to the 20 psi. Stop and re-start and it's immediately up to 70 psi again.
Now, before anyone says this, it's definately not the pressure relief valve sticking. I immediately suspected this and fitted a new plunger and a new 'S' spring. It has a plastic pipe to the gauge, by the way, not the 'orrible original pipe with the rubber bit in the middle.
In my mind I'm convinced the pressure is not dropping, but........
The owner is very worried, as you may imagins and I've got to sort it for him.
Any ideas anyone?
Peter
It's a brand new pump, bearings, cam, thrusts, etc. The block has done a genuine 8000 miles from new.
The pressure is fine for about 10 miles, but goes down to aprox 20 psi indicated over the next 2 to 3 miles and stays there at tickover. Just switching off, then immediately re-starting within about 2 to three seconds results in indicated 75 psi immediately, not a slow build-up.
I can't imagine it being an engine problem as if it were I woulod not expect the pressure indicated to go straight back to 75 as soon as the engine was re-started, but then againm those gauges are reliable and I can't ever remember ever having a problem in the past with one.
all suggestions are welcome.
The pressure is fine for about 10 miles, but goes down to aprox 20 psi indicated over the next 2 to 3 miles and stays there at tickover. Just switching off, then immediately re-starting within about 2 to three seconds results in indicated 75 psi immediately, not a slow build-up.
I can't imagine it being an engine problem as if it were I woulod not expect the pressure indicated to go straight back to 75 as soon as the engine was re-started, but then againm those gauges are reliable and I can't ever remember ever having a problem in the past with one.
all suggestions are welcome.
The oil pick up was cleaned and blown through with an air line prior to re-assembly.
It does seem very strange that only a couple of seconds after switching off, with the pressure reading about 20 psi and revving it not appearing to make any difference, that on re-starting it should immediately read 75 psi. It is not a slow build-up back to 75 psi after the oil has cooled, but an instant reading of 75 psi. The oil is fresh Duckhams 20/50, the filter is new.
I checked the site recommended, but in ther case the oil pressre only returned when the oil had cooled off.
It does seem very strange that only a couple of seconds after switching off, with the pressure reading about 20 psi and revving it not appearing to make any difference, that on re-starting it should immediately read 75 psi. It is not a slow build-up back to 75 psi after the oil has cooled, but an instant reading of 75 psi. The oil is fresh Duckhams 20/50, the filter is new.
I checked the site recommended, but in ther case the oil pressre only returned when the oil had cooled off.
I'd want to try another guage, or check the pressurea different way, i have seen the small flat rubber seal on the guage fail before too, doesn't always result in oil spraying all over the place either!! Easy ish to change the guage in position.
Edited by cambiker71 on Tuesday 14th October 15:25
cambiker71 said:
I'd want to try another guage, or check the pressurea different way, i have seen the small flat rubber seal on the guage fail before too, doesn't always result in oil spraying all over the place either!! Easy ish to change the guage in position.
I agree.. I'd try another gauge. Even if only a temporary fitment. And preferably, a mechanical one that works entirely independently from everything else in the car. IE, one that wouldn't be prone some possible electrical oddity within the car..Edited by cambiker71 on Tuesday 14th October 15:25
P,
I took it out for a 20-mile road test and it started off at 75 psi which it held for 8 miles. I stopped and let it tick over and it dropped to about 55 psi as I expected when warm. Then driving further it dropped to about 50 psi at 3000 rpm in top. I stopped, switched off, immediately re-started and it went to 75 straight away. After a further 5 or 6 miles it again dropped to about 50, so I de-clutched, switched off and then on again, let up the clutch and it went immediately to 75 again. I am absolutley convinced that there is nothing wrong with the power unit now and that it's a gauge problem. However, I don't have a spare one at present, so I'll cahnge it later. In the meantime I'm advising my customer to have me fir a 22 psi warning light next week as I think every Mini should have one and, of course, the 1963 - '71 Cooper 'S' never has one. It didn't have a rev counter either. Cheapskate BMC!
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