Mini Mayfair 998 my -88 automatic no drive

[juge]

Hi!
I'm new to this forum, which I found accidentally with help of Google.

We have this Mini Mayfair 998 cm3 with automatic gearbox, modelyear is 1988. Owned almost five years and the gbox has worked fine until now.

Mini was on idle on our yard while removing ski-box from another our car and putting it to garage. Every now and then I wen't to check that engine heat is ok, no overheating or so. I was suprised when I saw yellow light was ON but engine still running with no extra noises. Immediatelly turned engine off, started again and yellow light was still ON and tried all gears - no movement. Gave a little throttle, tested all gears still no movement. And still no extra noises from engine.

Ok, I have been collecting data about that gearbox and about what to do next. They say first thing is to check oil level, and it is as it should. Second is to measure oil pressure. Well, I'm a bit nervous to do that because of that yellow oil pressure light and might it possible that the engine will be totalled if I'm trying to measure the oil pressure. I have found out that some valve-table should be checked / cleaned and if I undestanded correctly it is possible without removing the engine+gearbox from car. But step after that requires removing engine+gearbox from car.

Can anyone say is it possible to measure the oil pressure without braking the engine? Some say that one possiblity is debree in some small valve which controls the oil pressure in engine. But now I can not say is that oil pressure regulator same and in same place as it is in Mini with manual gearbox.

All info and hints are welcome because I'm in Finland and classic-Mini with automatic gearbox is a bit rare here, so all the knowledge is found by Google...

[hbroodryk]

Hi juge

Welcome to the forum! I'm afraid I can't help you, but I am sure somebody will be along soon that can give you some more information and advice about your problem.

Regards (and good luck)
Hannes

[kalkat]

Do you know if the oil pressure switch is good? Take it out and test it perhaps?

The gearbox requires a far higher oil pressure to work as opposed to the engine which at idle would be happy enough with 25lb/sq.in. It is possible that there is an oil leak somewhere casing a lower pressure causing the gearbox to not work

[Stu]

Could you confirm whether or not you have drive in all gears?

It could be many things, but its most likely to be one of the following -

Faulty oil pressure light or wiring causing light to stay on.
Low oil level (perhaps not as you say it's ok).
Worn oil pump.
High engine operating temperature (perhaps not this as you say it was ok, but I'd still check it) A idling car causes high temps. Check the thermostat is working properly.
Oil pressure releif valve faulty.
Oil pick up strainer clogged.

It could also be a blockage in the valve block or pipework of the automatic transmission, but you'd be best to rule out the simple things first.

It cold also be due to incorrect oil grade. When did you last change the oil, and what grade did you use??

[wimfournier]

Because this came all of a sudden I'm afraid the car blew a gasket in the lubricating system.
Stu asked already what grade of oil you use.
It's quite cold these days up the en Finland, so turning at idal means a long time before the engine reaches 'working temp'.
I openend up and dismantled a Min Matic box recently myself to get an idea how it works and I'm thinking now about what part will give way first to an all to high oil pressure. I'm still puzzeled. So, please answer first our question about the oil grade you use.

[limby2000]

My money is on the oil pressure relief valve,which is easy and cheap to check/replace, if there,s sufficent quantity of oil in engine than it can only be the pump major fail, although very rare.

[jockduck]

Sounds either like oil pump drive failure, extreme internal oil leakage i.e. blown pipe or stuck pressure relief valves.
Jock

[juge]

Hi!
Thanks all for answers.

Stu: any of gears did not work, no reverse, no forward at 1., 2., 3. or at D. My dad is old-school Mini-man and he told me that there is no way that oil pump is broken, they just did not broke - or of it did it was very highly unlikely. Allthough we do not know is automatic-Mini oil pump different than manual-Mini. Oil has changed last year just before driving-season (summer season), just like I have always done, and between oil changes is maximum of 4000km which is about 2500 miles. Oil which I use in this Mini is Valvoline Racing mineral 20W-50 and it has worked perfectly.

OK, Mini has been in garage for few months and beeing waiting to be fixed...

Few hours ago I removed oil pressure light switch and installed oil pressure sender unit and oil pressure gauge istead. Started the engine and oil pressure 5.5 bar (79.7 lb/in2) when cold and idling. Vola, all gears worked... reverse and forward no problems at all.

Let the engine run and warm up till 1/4 of temp gauge. Tested several times all gears, everything worked. Oil pressure was 5 bar (72.5 lb/in2) when temp was 1/4 and idling.

When selecting any gear, pressure dropped to about 2 bar (1.8 bar 26.1 lb/in2) but increased immediatelly when gear was engaged to 4 bar (58 lb/in2). Sill all worked despite that low spot on oil pressure.

I can not believe that oil pressure warning light sender unit is broken because that transmission is totally mechanical, there is no electric-controlled things.

I wonder how precise this automatic is for oil level? Because place where Mini was idling at las November when that fault occurred, is where I usually keep my Volvo. And when I check oil level from Volvo in that same place, Volvos oil level is one "XX" line (there is XX lines in Volvo dipstick) more compared when checking it on level ground.

When I check oil level from this Mini on level ground there is enough oil. Allthough: There was no original dipstick with this Mini, and I have found out measurements of automatic Mini dipstick and made Min and Max marks by my self - OK, there is possibility for toss of 1 or 2 mm on those measures but still I believe that I have good amount of oil.


Sorry that long answer...

Any ideas...?

[Stu]

If you read my post I didn't say the oil pump could be 'broken', I said it could be worn. This means that the lobes to pump oil through the unit are worn which decreases its efficiency and ultimately the oil pressure. A worn pump could be the cause but unlikely considering the oil pressure you recorded in your latest post.

If you've replaced the oil pressure sender unit and fitted an oil gauge then you can rule this out as a cause.

Checking the oil level on an Auto is not the same as checking it on a manual, you knew this right? Could your oil level still be too low?

Dipstick readings must be taken on level ground. A characteristic feature of automatic transmissions requires that, after overnight standing, the engine is started before checking the oil level. Run for 1 minute, switch off and wait for 1 minute before checking. The difference between min and max is approximately 1 pint (0.6 litre).

I dont see the relevence of you Volvo's oil level in relation to your Mini's.

So you should be checking the following, which you have not confirmed you have done yet -

Faulty oil pressure light or wiring causing light to stay on.
Low oil level.
Worn oil pump.
High engine operating temperature (perhaps not this as you say it was ok, but I'd still check it) A idling car causes high temps. Check the thermostat is working properly.
Oil pressure releif valve faulty.
Oil pick up strainer clogged.
Blocked valve block oilway or pipework.

As a minimum I'd change the oil but switch to 10/40 and see if it improves. Id say its overdue an oil change if you've done 2,500 miles since it's last change.

[jockduck]

Can't be sure about more modern autos but oil pump drive failure is quite possible in early ones using the splined star drive, for some reason the way the parts are made the star coupling can partially disengage the pump spline, given enough mileage I'm sure the spline will strip. I have two worn ones in my parts box. I make a spacer to hold the star in full engagement on the spline. Other than that the auto oil pump is an excellent device.
Jock

[limby2000]

The 88 mayfair has the slot drive pump, pretty much indestructible, although anything can wear. Did you check the oil pressure relief valve, perhaps the spring has snapped.

[mra-minis]

Please note until I can purchase the MRA-Minis URL I can be contacted on [e-mail]

You have oil pressure this means the pump is at least turning, the main pump feed the transmission and the engine.

Getting your levels correct is important as is using the correct oil grade, 10W40 is good for the UK and most other countries with the same weather, Finland is a little different, you should refer to your owners handbook for your Mini.

The symptoms you mention, are not problematic, oil pressure diverts so you always get a spike in pressure as the oil changes course, I would be worried if the duration of low oil pressure increases in time as this can signify an internal fault, such as badly worn clutch plates etc. Although in the majority of cases this is insignificant you should watch out for delayed engagement and any slapping or banging into gear.

The auto pump is almost indestructible, but as above if it is the earlier splined type (pin type never got to production) the splines can fail, but there would be no oil pressure at all,

[juge]

Hello you all for a long long time!
At first, I'm deeply sorry that I have not been here for almost a year. Me and my missus have had all kind of experiences last year and the time has just - flew...


But to the point:
Our Mayfair Mini Automatic has worked very fine last year, no problems what so ever with the gearbox.

I have absolutely no idea what so ever what the fault was. Maybe it was the oil level - not sure. I got my hands on genuine my 1988 automatic plastic oil-dipstick and the oli level was faulty, but I do not any longer remember was it over- or underfilled...

Last time when I tested the gearbox was yesterday Sunday and it worked.

I would like to thank you all for your answers and patience for me not to been here to say that it still works fine (knocking wood...) 

[limby2000]

Lucky you judge,sounds like you,ve off with it. Probably was oil level as Stu indicated. I would however still recommend changing oil to 10w40 (ma2) at the very least.

[mra-minis]

I can be contacted on [e-mail]

Absolutely 20/50 is not good for the AP2 unit and will cause accelerated wear.