27 replies to this topic

[Spherix]

Hi everyone,

After having read a bunch of low oil pressure topics I fear I might be answering my own question here, but I hope I'm simply missing something.

First off, I'm running gauges from a Porsche 911, so reading are a bit different vs Smiths.

When I initially installed my SPI engine I instantly after starting had just over 1 bar of oil pressure on the gauge. As I hadnt driven it during setup, I don't know what it was during hot rides yet. Seeing as the oil light on the dash goes off within a second after starting, I didn't worry about it.

Note, senders for temp, pressure and warni g light have been matched to both Mini and Porsche instruments in the car.

Recently I've been able to take the car on some first shakedown tests. No major problems occurred until I took a longer highway drive in warm weather, I noticed the oil temperature running hot, but the Aux fan of the SPI hadn't kicked in yet, which I found odd, and blamed it on Porsches perhaps having a lower heat scale tolerance due to being air cooled.

When I arrived at my destination however, the oil warning light on the dash came on whenever the car dipped under about 1000 rpm. Readings on the Porsche gauge barely show 0,5 bar, but I'm a bit sceptical in how accurate they may be. Barely a change on the dial when revving it to 3-4000rpm either at the moment.

Since its back in the garage I've flushed the oil and changed the filter; still lower than 1 bar on the gauge after startup. I then inspected the pressure bypass, which showed quire some scoring but came out without any resistance. I hoped it was stuck open earlier, explaining the loss of pressure and high oil temp.

I have since replaced it with the ball bearing and slightly shortened spring, but that doesn't seem to make a difference either.

I have not let the car run warm/hot since as I'd want to avoid damage. If I let it idle briefly and turn the engine off, the oil lamp comes back on after about 4 seconds, so there is still some pressure I'd say.

To note;

- Oil filter is Minispares
- Oil is 20w50 castrol mineral
- There is plenty of oil in the car

While I would like to test this again with a mechanical gauge (sourcing parts now), I do find it odd that not just the Porsche gauge reads lower than it did initially, but the Mini's warning light also coming on/off when it was proper hot depending on the revs.

Other than the pump suddenly going (barely any swarf/metal was in the oil change fyi) I was wondering if perhaps the channel to the oil pressure sensor could be blocked somehow, reducing pressure getting to it?

Any tips welcome, I hope to connect the mechanical gauge this weekend, but otherwise I think I might need to pull the engine and replace the pump, which I obviously would want to avoid.

Edit: To add to that, what should I be seeing in terms of oil flow through the filler cap? While everything did seem oiled there, I did not spot any form of flow while idling the engine.

Edited by Spherix, 25 May 2023 - 03:37 PM.

[Lplus]

Firstly there's no real visible flow through the filler cap.  as long as it looked oily it should be fine.

 

Secondly the standard mini oil pressure switch illuminates at about 7 to 10 psi which would  approximately agree with the 0.5 bar shown at hot tickover.  The pressure should be 60 psi at 3000 rpm hot, which would be over 4 bar.  Something doesn't sound right at all.

 

Replacing the bypass bullet with a ball bearing and a shorter stiffer spring was the cooper s set up which on mine gave 90psi + cold and 75psi hot at 3000 rpm.  I went back to standard.  Using a shorter standard spring should still give about 60 psi.though the pressure might drop a bit after the ball lifts.

 

There is no actual flow to the sensor so a blockage would have to be almost complete.

 

The mechanical guage will be the true test.

[Spider]

I'd suggest confirming the readings with a known gauge, though given the light comes on, it's probably correct.

If this is right, then regardless, the engine will need to come out.

If you are looking to hopefully sort it in a minimalist way, then start by checking the Oil Pump. It may just have a blown gasket or be worn.

You'll also want to check the strainer on the pick up isn't blocked, in which case, you'll want to strip much of it down to not just clean it but find where the debris came from that blocked it.

[cal844]

I'm afraid that the light coming on is bad news.... Light works as it should so it's engine out and a full strip down IMO

[Cooperman]

On a Mini the oil light will come on at tickover at c.7 psi, which is 0.5 bar.

However, you should be seeing 5 bar cold and 3.5 to 4 bar when hot at anything over about 2500 rpm.

 

It seems that you have two choices:

 

1.  Fit a mechanical gauge reading in psi. Mini Spares do a good kit.

2.  Pull the engine out and check everything. I would do no.1 first, then only pull the engine if the new mech gauge still gives a very low reading.

 

Personally I don't like the ball bearing relief valve arrangement, but if using a plunger make sure that it moves freely and is not sticking.

[Spherix]

Update now that I finally have the mechanical gauge sorted, these are the readings at 1000 rpm cold idle. Close to 70 psi If I read things correctly. It gets there nearly instantly, but raising the revs to 3000 rpm (while cold, I dare not to fully heat up the engine now..) only makes the needle move a hair, barely noticable.

Im not sure what would make the pressure be there instantly and then fail to build further, but I'm not sure I have other options than to pull the engine. Unless anyone else has a guess?

Edit: Thinking while rereading the posts, this pressure does seem better than expected as well. That would imply the sender or pressure electrical gauge may be incorrect, but should I not see an alternating pressure on the gauge?

Edited by Spherix, 06 June 2023 - 12:45 PM.

[KTS]

i would think that's the maximum pressure the relief valve will hold.

 

when the oil has warmed up i'd expect the pressure to be less at lower rpm and build up as revs rise

[Lplus]

Update now that I finally have the mechanical gauge sorted, these are the readings at 1000 rpm cold idle. Close to 70 psi If I read things correctly. It gets there nearly instantly, but raising the revs to 3000 rpm (while cold, I dare not to fully heat up the engine now..) only makes the needle move a hair, barely noticable.

Im not sure what would make the pressure be there instantly and then fail to build further, but I'm not sure I have other options than to pull the engine. Unless anyone else has a guess?

Edit: Thinking while rereading the posts, this pressure does seem better than expected as well. That would imply the sender or pressure electrical gauge may be incorrect, but should I not see an alternating pressure on the gauge?

That looks just fine.  The relief valve is blowing off so the pressure will only rise a small amount more as revs rise and more oil is pumped.  With that pressure the engine appears to be in good health.

[StefanMini]

Hi Robert,
That oil pressure is perfect. Most important is when the engine oil is at operation temperature the pressure don't go under 10 psi at idle, and when you will rev the engine it has to be around 60 psi when hot.
Stefan

[Spider]

Seems healthy to me while cold.

That you aren't seeing a rise beyond 3000 RPM is OK too, as KTS and Lplus has suggested, that's just the upper limit as set by the Relief Valve.

Let it warm up and see how it is then.

[Steam]

The ball bearing setup is a great idea but it needs to be fine tuned. I spent a day messing with spring lengths until I got what I wanted. And no 2 engines are alike so a shorter spring is only the stating point. You cannot just fit and forget.
The bullets can stick in the bore which is why I use a ball.

[Spherix]

Thanks for the confirmations! I had in fact refitted the normal relieve valve and spring after the ball and shortened spring did not solve things. Easier to do elimination if you don't change too much at once and all that.

I'll be taking my gauge and sender to a local specialist, a retired man who used to be the head of the tech department for VDO, so he knows these instruments well. I'm assuming something in there is faulty, and he's got test setups in his workshop.

Per Spiders comment I will do another run soon with the car warmed up, the warning light is still wired up as it's normal in the Mini, with the exception that the sender unit is not stock, but was matched for correct sender values. It could be a coincidence ofcourse that the valve stuck open causing the oil light go on, which in turn brought my attention to what the gauge was reading as I hadn't paid much attention to it.

As I'm not in the country for a bit, I'll update in a few weeks. At least it feels nice that the chances of the engine having to be taken out seem smaller now.

Edited by Spherix, 07 June 2023 - 07:01 AM.

[mini13]

in terms of hot readings, your likely to see @25 psi at idle, and i wouldnt be to concerned if its a bit lower as long as it picks up when you blip the throttle.

Ive been through the "ball bearing " thing before, and they can give erratic readings, as the oil flows around them causing them to bobble/oscilate ( like a malteaser in a stream of air) this can be remedyed with a " cup" behind them to stabilize them, but thats a lot of effort, in most cases you are probably just better off with the std shuttle.

[Steam]

in terms of hot readings, your likely to see @25 psi at idle, and i wouldnt be to concerned if its a bit lower as long as it picks up when you blip the throttle.

Ive been through the "ball bearing " thing before, and they can give erratic readings, as the oil flows around them causing them to bobble/oscilate ( like a malteaser in a stream of air) this can be remedyed with a " cup" behind them to stabilize them, but thats a lot of effort, in most cases you are probably just better off with the std shuttle.

Been using a the ball on various engines for years and never had that issue.

[Spider]

 

in terms of hot readings, your likely to see @25 psi at idle, and i wouldnt be to concerned if its a bit lower as long as it picks up when you blip the throttle.

Ive been through the "ball bearing " thing before, and they can give erratic readings, as the oil flows around them causing them to bobble/oscilate ( like a malteaser in a stream of air) this can be remedyed with a " cup" behind them to stabilize them, but thats a lot of effort, in most cases you are probably just better off with the std shuttle.

Been using a the ball on various engines for years and never had that issue.

 

 

There is some damping in the gauge and usually, because of the way they are installed, also adds to that damping, so it most likely was occurring, you just weren't aware of it. For a road car, they are not a good idea.

 

https://www.theminif...huttle-vs-ball/