Hello guys! Hoping to get some advise here! I will try to keep it as short as possible but also mention all important info at the same time. Replaced parts are underlined.

Had my R53 (2003) for 5 years now, been replacing what soon feels like every component in the entire car, it came as no surprise to me when it suddenly lost drive on the way home from work one day. Dailying an R53 you kind of just drive around waiting for stuff like this to happen. I was pulling away in 1st gear when the car suddenly lost drive and engine revved up. Same symptom as if I would hold the clutch pedal down. Pedal felt normal but the car would not drive forward no matter what I did to the clutch or shifter. Gear shifter felt normal, gears would also go in as if the clutch was pressed down but even with the pedal up the clutch would not disengage and car would not drive.

Towed the car home and ordered a new slave cylinder as this was my first suspect without beeing able to look under the car. Replaced this, found that the brake line going to the slave cylinder was very rusty and even broke on disassembly so ordered and replaced this as well. Bled the slave cylinder properly and made sure it pushed the lever on the outside of the gearbox. Put the car back on the ground, hoping that I had found the cause to the problem. Tried the car, and it was working! Let it warm up, went for a 10-15 min test drive and still working. Then on the way home the exact same problem occured again... After maybe 30 minutes of driving. I was pulling away in 1st gear when it suddenly slipped out of gear and engine revved up. Gear stick would go in any gear but nothing happened when pressing or releasing the clutch pedal.

Towed it back home and decided to change the gearbox oil as I read that the gears are held in place by hydralic pressure. I had noticed some leakage from the drive shaft seals as well, so replaced the seals on both sides. When changning the oil only about 20cl came out, and almost 2 liters in (Redline MTL). Knowing this I felt pretty confident that I had found the real root cause of the problem. Put the car back down, let it warm up, went for a test run and everything seemed to be working. Went for a longer test run this time, slow driving in 1st and 2nd gear over speed bumps etc. Some high speed, going through every gear. Maybe 45 min test drive this time, everything worked and the car even took me back home. Then the day after, after about 15 minutes driving, the same thing happened again! This time when driving on the highway in 6th gear. Totally relaxed on 2,5K RPM, it just slipped out and engine revved up before I released the throttle and started rolling to the side. At this stage the car was rolling but no gears would work. Gear stick felt normal but the problem was the same as before. It behaves just as if the clutch would be working and you press it in, like the clutch is engaged. Then I towed the car back home and there it has been standing in shame for 3 months now.

I'm not in the need of a daily car right now so I haven't found the motivation to fix my beloved Mini until now. But I'm really hoping to get some pointers in the right directions from you guys and then find the motivation to get it back on the road! But at the moment I have no clue what the problem could be. Both times I felt so sure I had found the issue when the car was working after replacing those parts. Worth noting is that when the car was not working, it was 100% not working. It went from working perfectly to not at all. Not some re-occuring issue that the gears slipped out and then back in or anything. So I find it very strange that the car would go back to "working" both times after obviously replacing the wrong parts. Or at least haven't found the root cause yet.

Like the first time I only lifted the car, changed slave cylinder, brake line, bled the system and put it back down. Result: Working again for 30 min.
2nd time I only lifted the car, emptied the transmission fluid, put new shaft seals in, put new fluid in (about 10x more than came out lol). Result: Working for 1 hr, broken day after.

Why would it work if I haven't found the problem yet? I still haven't opened the gearbox and would like it if I didn't have to. I can see the slave cylinder working when I press the clutch pedal. It's pushing the lever on the gearbox all the way in. So I don't think the problem is on the outside. What I haven't checked yet on the outside of the gearbox is the shift wires. Could faulty wires cause this? The problem is as if the clutch is broken, but the opposite. It's not stuck in gear, it's not able to engage any gear.

Please, very thankful for any advise!

 

Driveshaft piping out. Have you tried searching that here?

sorry to hear of ur troubles, bummer

 

Well it's not the slave cylinder.

 

Well it's not the slave cylinder.
maybe the diff.

 

I'm surprised the severe lack of lubrication apparently wasn't also accompanied by terrible noises.

I would think the shifter would feel different if one of the shift cables was bad, but I've never had that happen in my Mini. The difference was noticeable in my Audi when a bushing in the shifter linkage broke.

 

https://www.northamericanmotoring.co...to-wheels.html

 

Oil doesn't keep the gears in place. I accidentally drove my R50 around the block a couple times after replacing the clutch last month with no gear oil in the car at all and it shifted great.

What you have here is indeed a very strange problem. The fact that it is intermittent rules out some normal clutch/trans related issues. I'm guessing the amount of heat in the engine bay has no effect on this issue? Once it has started to slip it will not stop even once everything cools off again? Are you sure the gear selection linkage is working properly? Can you feel the car going into gear with the shifter even when things are slipping? Maybe the car is becoming stuck in neutral somehow?
The popping out driveshaft of ssoliman is an interesting one. How would the drive shaft be putting it self back in though I wonder? The low trans fluid could be a result of this driveshaft pop-out. If you lose one driveshaft you'll lose all forward drive, so its a sound theory. The only thing holding the left side shaft in place on the trans is a C-clip in the middle of the drive splines, so maybe that clip is broken or something. Maybe get under the car and see if you can move the driveshaft in and out of the trans by hand. You shouldn't be able to. Normally you need a crow bar and moderate force to pop the driveshaft out of the trans.

Why don't you just put the car up on jack stands and get after it? It is just sitting there collecting dust anyways. That'll give a chance to have a look at the drive shafts and if its not that then you are almost certainly going to have to take the transmission off, so why not just get in there and see what you can see? Its not really that hard- its just a lot of bolts! Hahaha. Clutch replacement parts are easy to source and not that expensive. You could get a complete gear box from a salvage yard pretty easily too- this might be a good time to swap in the ZF trans from the post-LCI R53.

 

I am having nearly identical issue. So bizarre as I would expect normal failure to make it as if the clutch would Not release. This is like it is fully released.
Did you resolve the issue? What did you find?

 

I'd assume it's a pressure plate issue...OR the dual mass flywheel failing and not applying sprung pressure. Maybe once warm the metal arms are too weak to maintain propper clamping force causing it to not hold in gear...

 

I'd suspect a drive-shaft slipping out. Is the car lowered?

 

Not lowered, and both driveshafts are in place. I am suspect of the clutch. It is just odd that it failed randomly, then worked as normal for a bit, and failed again. This time I do have a light flutter noise from the clutch area when clutch is pressed.