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"slow" Oil Pressure

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#1 need4speed

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Posted 26 March 2017 - 05:45 PM

The engine's a 1275 in a '92 BOC with about 75000 miles on the clock. It hadn't run for 7 years until recently and before I turned it over I changed the oil pressure switch for a new one because the light didn't come on at the turn of the key. Once the engine fires up (first turn) the oil pressure light takes a bit of time to go out - longer than anything normal. Oil and filter are fresh.

 

So, the question is, could this be anything other than a tired oil pump? I'm kicking myself for not changing it as a matter of course, but the car isn't mine and I wouldn't expect an engine of this mileage to need an oil pump. Technically it's not a challenge to do it, just that I'd rather not strip the clutch if I don't have to.

 

What do you think?



#2 RooBoonix

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Posted 26 March 2017 - 06:06 PM

Definitely check out the oil pressure relief valve, it might be stuck open and allowing oil to flow even at lower pressures. Plus it's quite simple to get to being on the front of the engine.

#3 need4speed

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Posted 26 March 2017 - 06:16 PM

Definitely check out the oil pressure relief valve, it might be stuck open and allowing oil to flow even at lower pressures. Plus it's quite simple to get to being on the front of the engine.

I was hoping somebody might suggest that!



#4 Spider

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Posted 26 March 2017 - 07:03 PM

It can't hurt to check the Oil Pressure Relief Valve, however, I'd be fairly certain that it would be the Oil Pump.

 

The Oil going through the Pump is unfiltered so they do suffer a high wear rate.



#5 tiger99

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Posted 26 March 2017 - 08:18 PM

It is usual practice on almost all vehicles that I have experienced, to fit a new oil pump every time the engine is rebuilt. The several reconditioners I have had dealings with over the years all do it. I hope that this will be of benefit to others who may do the same thing with unhappy results and lots of needless aggro.

 

You CAN change the oil pump without lifting the engine, but it depends on the new transfer case gasket being exactly the same thickness as the old one, or on having the correct test washers, dental wax and micrometer to measure and set the idler gear end float. The third method, with feelers, which perhaps most of us use, requires the engine and box to be split. Dome that in the car too, but do not recommend it! (But it does avoid messing about with the driveshafts and suspension.)

 

In the old days, pre Unipart, I was using gasket sets in MOWOG or BMC packaging, and relied on them being correct. Later, everything was Unipart, from the same factories. I never had problems with the idler gear. But it is a risk nowadays, with gaskets made from anything except the correct material.



#6 minimans

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Posted 26 March 2017 - 10:11 PM

First thing to do is check what the oil pressure is? That idiot light doesn't tell you squat about the oil pressure except it is over 7Ib's. Put a gauge on it and see what's what.



#7 dyshipfakta

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Posted 26 March 2017 - 10:31 PM

The other thing is how long are you thinking is long? Afew seconds is nothing really but can see like a long time

#8 need4speed

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Posted 27 March 2017 - 10:28 AM

The other thing is how long are you thinking is long? Afew seconds is nothing really but can see like a long time

 

3-4 seconds after starting given a blip on the throttle. I'm not going to hang about for ever to run a bearing.

 

Edit - to clarify, this is 3-4 seconds then blip and it goes out.


Edited by need4speed, 27 March 2017 - 05:51 PM.


#9 need4speed

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Posted 27 March 2017 - 10:29 AM

First thing to do is check what the oil pressure is? That idiot light doesn't tell you squat about the oil pressure except it is over 7Ib's. Put a gauge on it and see what's what.

If I had a gauge, I would. My logic is that if it's slow to get pressure it could be that even once the light is out I probably don't have adequate pressure. 

 

Sorry - being dim here: I'll get hold of a gauge - if the pressure is OK it'll save me an engine out - again.


Edited by need4speed, 27 March 2017 - 11:14 AM.


#10 need4speed

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Posted 27 March 2017 - 10:35 AM

It is usual practice on almost all vehicles that I have experienced, to fit a new oil pump every time the engine is rebuilt...

I agree, given the aggro of having to do it once the subframe has been replaced etc. It's not my car and it wasn't my brief to rebuild the motor. Apart from an odd oil leak everything seemed fine. The compression is good and equal on all four cylinders and it fires up very readily.  

 

I've not done a Mini engine/trans/clutch since 1978 so forgive me asking seemingly daft questions: I take it that the drop gear casing has to come off to get to the pump - which is on the end of the cam from memory.

 

I knew I shouldn't have lent my flywheel puller out in 1982! Never got it back...

 

edit - yes I see the drop gear casing has to come off.


Edited by need4speed, 27 March 2017 - 11:13 AM.


#11 nicklouse

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Posted 27 March 2017 - 11:21 AM

 

First thing to do is check what the oil pressure is? That idiot light doesn't tell you squat about the oil pressure except it is over 7Ib's. Put a gauge on it and see what's what.

If I had a gauge, I would. My logic is that if it's slow to get pressure it could be that even once the light is out I probably don't have adequate pressure. 

 

Sorry - being dim here: I'll get hold of a gauge - if the pressure is OK it'll save me an engine out - again.

 

you can get one to screw into the tapping on the block so you can read the pressure direct. great for checking things. no good when driving.



#12 dyshipfakta

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Posted 27 March 2017 - 12:19 PM


The other thing is how long are you thinking is long? Afew seconds is nothing really but can see like a long time

 
3-4 seconds after starting given a blip on the throttle. I'm not going to hang about for ever to run a bearing.

Yeah that is a while with a blip. Just saying it's not going to be instant and is v different to modern cars. But you obviously know this.

#13 tiger99

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Posted 27 March 2017 - 05:04 PM

That is slow. I have never owned a car that failed to pressurise immediately. I can recall some Triumphs needing a certain brand of filter to prevent it draining, and have vague recollection of something similar on a B series, but it "should" not be a major problem on an A series with vertical filter bowl that stays full. The pump "should" only need to fill the bits that can drain, basically the block and crankshaft drillings and feed pipe.

It seems that on this forum this is a fairly common problem, so I have to wonder if anything has changed in the last 20 years or so? Definitely better oils available. Filters from the major manufacturers unlikely to be inferior to the originals. Plenty of dodgy filters in the marketplace, a new problem since about 1995.

I have to conclude that it must be the pump or an air leak on the suction side, as there isn't anything else.

But something is still bugging me. Please be sure to let us know how this progresses and whether there is any visible wear in the pump.

#14 need4speed

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Posted 27 March 2017 - 05:39 PM

you can get one to screw into the tapping on the block so you can read the pressure direct. great for checking things. no good when driving.

 

I didn't know such thing existed until this afternoon when I got one on ebay. Quite a few kits out there calibrated to 500psi - not a lot of good. I found one up to 150psi.



#15 need4speed

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Posted 27 March 2017 - 05:43 PM

That is slow. I have never owned a car that failed to pressurise immediately. I can recall some Triumphs needing a certain brand of filter to prevent it draining, and have vague recollection of something similar on a B series, but it "should" not be a major problem on an A series with vertical filter bowl that stays full. The pump "should" only need to fill the bits that can drain, basically the block and crankshaft drillings and feed pipe.

It seems that on this forum this is a fairly common problem, so I have to wonder if anything has changed in the last 20 years or so? Definitely better oils available. Filters from the major manufacturers unlikely to be inferior to the originals. Plenty of dodgy filters in the marketplace, a new problem since about 1995.

I have to conclude that it must be the pump or an air leak on the suction side, as there isn't anything else.

But something is still bugging me. Please be sure to let us know how this progresses and whether there is any visible wear in the pump.

Yes, I would expect a quicker pressure first time after an oil change if I'd forgotten to prime the filter. I will update on this post with the outcome.







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