torque converter

[den]

I have a 96 jap mini cooper automatic with only 12000 genuine kms on the clock. One day the car performs faultless and the next it seems to be lacking power with erratic gear changing, the engine revs but the car drives very slow, similar effect to a slipping clutch on a manual car. No nasty noises or smells, its all new oil and the car is well serviced.
I think this fault has come on overtime I noticed it originaly when the engine was cold then improving as it warmed up.
Any advice would be appreciated

[69hcode]

It's possible the forward clutch is slipping. What oil did you put in it and how do you check the level? Could just be wrong or low oil. 

Also where are you located? Maybe someone close that could help with it.

[jockduck]

sounds like low oil level to me.
Jock

[wimfournier]

Low oil level I think too.
Do you know the special procedure to check the oil level with this particular automatic?
You must understand that the torque converter has quite a lot of oil in it. Because the centrifugal power the converter is filling itself up with a layer of oil inside 'the wall'.
So, when you check oil immediately after driving you'l find it 'low'. When you check oil level after the car stood overnight and check, you'l find it high, because a lot of oil came out of the converter into the crankcase.
So, the very moment to check the level is after the car stood overnight and you started the enigne en let is run stationary during five minutes. Shut it down and check. Now you can read on the stick if it is low, good or overfilled.

The oil you use should be ordinary engine oil 10W40.

[notamini]

There has been a good deal of commentary over many years now about oil levels causing 'hick-ups' for the automatic. My America can have anything from 1mm over MAX to 1mm over MIN and have no apparent differences. It isn't until the level goes below the MIN mark that I will find any issues.

As for checking it, yes there are many methods but with the aforementioned conditions, I can check it cold or warm but not hot and find very little differences. Keeping in mind that my drive train is exactly the same as any auto mini, I would think that you should all find the same situation.

The only improvement I have been successful with is changing to MA2 mineral oil. Thanks Richard for your information.

Mark

[den]

Many thanks Iam near to Chesterfield Uk
The car was recently serviced at a mini specialist in Sheffield
I will check the oil type and level
I have noticed that the fault is more prolific if the car has been not used for a few days and when the temprature is low
I will report back

[69hcode]

They may have put 15w40 in it. It's too thick and will act up more when the engine is cold. 

[limby2000]

Yep, there is plenty of these so called mini specialist that still put the incorrect oil in our auto,s.

[den]

Yep its had 20w 50 mineral oil put in. I will remove and replace with 10w40
and see if this cures the problem
Many thanks everyone

[richard1]

Tarija and Santa Cruz, Bolivia

20W-50 does not squeeze out of the grooves on the discs very well.
Note the surface (ignore how it is bent - long story).

As noted by "notamini" Do not use ordinary motor oil. Car motor oil has become super slippery for fuel economy. Great for new types of engines with roller tappets, but terrible for wet-clutches such as ours. You need motorcycle MA2 spec oil.

More on viscosity: 10W-40 pumps much faster and lubricates better than thicker oils. As I videoed this week, with 10W-40 I have close to 90 psi when cold, dropping to 42 psi for normal driving when hot. Any more would be going through the pressure bypass.

[notamini]

I can confirm those figures since my car runs the same 90 +/- 3,4 and 42 +/- 3,4. Richard, my name's Mark if you were wondering.
I'm now using 10W40 MA2. I only wish it was available in other places than bike shops.