31 replies to this topic

[miniGTS]

Another thing to remember. The valve is only there to stop over pressure.

 

ps do your engine a favour and get the revs up to 5-5.5k. They will go way more on standard parts.

 

Ok, I'll see how it goes...

 

It gets to around 60km/h in 2nd gear at around 4000rpm and the speedlimit on the road around me is 60km/h... and I'm sure my neighbours already hate me for the noise 

[miniGTS]

So I added 3 washers to increase spring tension. At cold start it sits at around 550kpa so around 80psi

Once warmed up it drops down to around 100kpa so around 15psi at 1000rpm

Warmed up revving to 5000+rpm takes up to just over 400kpa, I'd say past halfway between 300 and 500kpa so maybe just over 60psi possibly.

Is that 1000rpm at 100kpa an OK result? I assume it's bearings or other internal clearances causing it to drop off to 100kpa regardless of relief valve tension.

I'll hopefully get my replacement pipe sorted next week for the Smiths oil pressure gauge that gives a better indication of pressure at 20psi increments.

I'll take it for another drive then and see what it says.

[miniGTS]

This short clip shows oil pressure going up when warmed up and taking revs to around 4000rpm.

https://photos.app.g...Rh46Ytra73zcVd8

[nicklouse]

You are still totally missing the point of the valve. It does not make pressure it is a relief valve in that it stops you over pressure it the engine. Adding washer only increases the pressure that it opens. As standard circa 60 psi it does nothing to the pressure below that.

 

the Mini pumps can produce too much pressure that is why you need a relive valve.if the rest of the engine is in poor condition it lets too much oil out and the pressure drops and the valve does nothing.

 

as Spider said he sees nothing wrong with the pressures you have given though in my head the tickover pressure is getting low.

Your above image does not work.

[miniGTS]

Thank you for clarifying that. In my mind, if I increased the resistance of the relief valve I thought it would help to also keep the pressure up when warm too.

I appreciate the time everyone takes to respond to all these posts, questions, etc. The knowledge on here is invaluable.

The video is a shared Google photos link. Sorry, didn't realise they don't open for everyone. I'll find a different video sharing option. It basically shows the pressure drop to around 15psi at 1000rpm then go up as the revs go up.

[DeadSquare]

My first car was a Marendaz, fitted with a Hudson straight six engine.

 

It had no oil pressure gauge, oil warning light, pressure relief valve or oil pump.

 

The big end caps "spoons" on them, which dipped into the sump oil, scooping oil up the stem, through the cap, to the bearings.

 

Not much of the scooped oil got to the big ends, most of it got flung up the bores and round the crankcase, which had grooves cast in it so that rivulets of oil ran down the webs to the mains.

 

Many people assume that the oil is just there to lubricate the engine, but its second job is to cool the bearings, so if your oil pressure is low, the oil is probably doing its second job, very well.

[Cooperman]

You are safe revving it to 6000 rpm and 5000 rpm is not regarded as high.

[miniGTS]

I've sorted the pipe for the Smiths oil pressure gauge. It shows a drop in oil pressure when hot to below 15psi. That's with idle at 1100 to 1200rpm. So a sign that things are not well inside the engine. Pressure goes up with the revs, around 60psi over 5000rpm and makes a brief whining or screeching sound when I lift my foot off the accelerator and the revs drop. This noise is only heard when hot.

There's no obvious knocking yet so thinking the bearings may not have reached the point where it caused other damage. Though I'd only know this once I've opened it up.

So, before I spend a fortune on having my other engine rebuilt sooner than I planned, I'm thinking of opening this one up and checking what's going on inside first. This engine is a bit of a screamer so want to enjoy it a bit longer before I kill it completely.

I know the bores are good because I checked them when I had the head off not so long ago... Probably did less than 100km since... The engine hasn't done more than a few hundred km since rebuilt 15 to 20 years ago... Clearly mistakes were made that I hope to not make again...this time I'll use new bearings and thrust washers after having the crank and block checked at the engineers and they tell me the correct sizes.

So that I can work out a rough cost estimate for parts needed, apart from bearings and oil pump, what else can cause low oil pressure?

I have a complete engine and gearbox gasket set. I'll just need to get a new head gasket.

Edited by miniGTS, 22 January 2025 - 07:35 PM.

[Earwax]

As Cooperman has intimated, a different oil could be a double check mechanism.... and the other telling point is the engine temperature/water temperature.relationship.

 

I can't help with info on S.A.oil brands but in my experience some of the available Aussie ( hot climate) 20W50 oils are too thin when approaching 220 F. Yes they all meet the appropriate standards but in my experience they can behave differently.

 

Please note : I am not suggesting you hide/mask any problem - i am just not sure you have an oil problem- are you sure your cooling system is keeping the oil in the right temp zone?

[Cooperman]

One of the best oils is Valvoline VR1 which is a US made 20w50 mineral oil, also known as’Valvoline Racing Oil’. I use it in both of my cars and it is great.
If you have 60 psi at 5000 rpm when hot you really don’t have much to worry about. My S will go down to 12 psi- ish at 2000 rpm when hot and it’s around 65 psi at 6000 rpm when hot.
So long as you have over 30 psi when running over 2000 rpm when hot it should not be a problem.
Sure, it might seem a bit low compared to a newly rebuilt engine, but it’s by no means worn out and in need of a full rebuild.

[miniGTS]

As Cooperman has intimated, a different oil could be a double check mechanism.... and the other telling point is the engine temperature/water temperature.relationship.

I can't help with info on S.A.oil brands but in my experience some of the available Aussie ( hot climate) 20W50 oils are too thin when approaching 220 F. Yes they all meet the appropriate standards but in my experience they can behave differently.

Please note : I am not suggesting you hide/mask any problem - i am just not sure you have an oil problem- are you sure your cooling system is keeping the oil in the right temp zone?

The Ravenol oil is a German company and the oil isn't widely available in SA. The one I'm using came highly recommended by some locals who have tried the Castrol GTX and Shell Helix which are the most widely available oils though there are some smaller shops that sell other brands like liqui moly, havoline, some are just store name branded, Petronas

I haven't seen valvoline in stores but it seems I may be able to order online.

The water temperature gauge hasn't gone over the normal mark. Usually sits below it when driving.

[miniGTS]

One of the best oils is Valvoline VR1 which is a US made 20w50 mineral oil, also known as’Valvoline Racing Oil’. I use it in both of my cars and it is great.
If you have 60 psi at 5000 rpm when hot you really don’t have much to worry about. My S will go down to 12 psi- ish at 2000 rpm when hot and it’s around 65 psi at 6000 rpm when hot.
So long as you have over 30 psi when running over 2000 rpm when hot it should not be a problem.
Sure, it might seem a bit low compared to a newly rebuilt engine, but it’s by no means worn out and in need of a full rebuild.

I think this, together with the other feedback puts my mind at ease. I'll just drive it and enjoy the car.... That's why we have minis after all.

I'll look into other oil options and maybe try something different with the next oil change. It is summer here and yesterday was a pretty hot day, 30something degrees and little wind...

I also considered an additive like liqui moly oil additive but decided against it as some mini related comments I found suggested that it's bad for our gearbox... Though some said it's good... But I'll rather not test it

[Spider]

,,,,,I'll just drive it and enjoy the car....

 

Hoorah !!!!

Other here will likely disagree with me here,,,,,,

Do yourself a favour,,,,,,,

Be sure you have a reliable Oil Pressure Switch, Lamp and if you like, a Buzzer with the light and disconnect your Oil Pressure Gauge or as I call them - " Worry Gauge "

I did run them years back and they'd worry me. I can't recall when or why, but I stopped fitting them probably 30 years back, maybe longer and never looked back. I now enjoy worry free driving,

[miniGTS]

 

,,,,,I'll just drive it and enjoy the car....

 

Hoorah !!!!

Other here will likely disagree with me here,,,,,,

Do yourself a favour,,,,,,,

Be sure you have a reliable Oil Pressure Switch, Lamp and if you like, a Buzzer with the light and disconnect your Oil Pressure Gauge or as I call them - " Worry Gauge "

I did run them years back and they'd worry me. I can't recall when or why, but I stopped fitting them probably 30 years back, maybe longer and never looked back. I now enjoy worry free driving,

 

 

      Yes, I asked myself why oh why did I insist on fitting one! It was initially because the light flickered while out for a drive but only when I stopped at a robot... and it was only when the revs dropped quite low (800 or less rpm) that the light flickered. I've adjusted the idle to be higher now. Anyway, then I asked on a local group and one suggested anything less than 24psi at idle is not ideal... another said 15psi for every 1000rpm is fine and this seems to be more inline with feedback received here... so it's fine

[Midas Mk1]

 

,,,,,I'll just drive it and enjoy the car....

 

Hoorah !!!!

Other here will likely disagree with me here,,,,,,

Do yourself a favour,,,,,,,

Be sure you have a reliable Oil Pressure Switch, Lamp and if you like, a Buzzer with the light and disconnect your Oil Pressure Gauge or as I call them - " Worry Gauge "

I did run them years back and they'd worry me. I can't recall when or why, but I stopped fitting them probably 30 years back, maybe longer and never looked back. I now enjoy worry free driving,

 

I agree on this, even on my 350z its a worry gauge when that idles at 18psi hot, you can't not watch it.

Aslong as you have a light with switch set at the minimum pressure, I wouldnt worry.