20+ Things You May Not Know About the R53 Cooper S But Should Know

posted in: GTT Blog & News


These are just the most common observations we have made over the years based on working on around 2000 of these cars.  Lots of important things here for people to look out for and other things that may be concern but is actually not a problem at all.


  1. Engine. Low level oil is the most common issue we see. Running it too low will destroy the big ends in a very short period. Very expensive as usually a new crank and even con rods will be required so check fortnightly. It’s no good topping it up after you’ve noticed the engines developed a loud ‘dak dak dak’ sound! The damage is done.
  2. Sparkplugs really need to be 7 grade NGK Iridium IX on any modified R53, but the biggest problem is limp wristed under tightened ( read not tightened at all) plugs. These unwind then strip out the last 3 threads. There’s no need for this it’s just lack of care, spinach or knowledge. The compressible washer as its name suggests should be compressed.
  3. Bypass Valve. A distinct lack of power often on a ‘52 or ‘03 plate can be attributed to a broken supercharger bypass valve. This can lose up to an estimated 50 bhp (yes 50) from it. Interestingly it doesn’t usually show on diagnostics so even a car that’s regularly serviced by Mini may exhibit this fault. It can be checked in less than 10 seconds! We have seen cars that according to the owner have had the fault undetected for up to 5 years.
  4. A modified R53 requires Super Unleaded fuel, to protect the engine from detonation when driven hard. Preferably use 99 octane. Shell V Power is best..End of! Drive flat out in 6th gear on 95 Ron and you’re asking for trouble.
  5. The standard air filter gets very dirty very quickly. Most look like something dug up from a dried up swamp. This is mostly due to the standard air box air entry point which only takes air from the dirty front grille area. Change at least once a year despite what the service schedule says. Induction kits such as our GTT Cold Ram that utilize a second air inlet from base of windscreen area stay a lot cleaner.
  6. We are starting to see cars with stripped oil drain plug threads. The trend here is the opposite of the spark plug scenario .i.e. they are often grossly over tightened resulting in a stripped thread. We now have tooling to fix this in situ with a new M16 Fine thread and new oversized plug
  7. Broken Oil dipstick …If this is starting to fall apart (Usually 4” from the top then change it NOW! If you leave it and it breaks in half you will probably have to take half the car apart to retrieve the bottom part.
  8. Gearbox /Clutch….The 6 speed gearbox is VERY strong. People confuse this with the awful 5 speed Midland box used on early One & Cooper..It’s not the same.
  9. Standard clutch is a LUK item. This clutch when new will easily handle 300+bhp and the massive torque from a turbo no problem and still not slip. Part of the reason it’s so good is due to the large diameter flywheel which has corresponding large frictional surface area.
  10. As the clutch ages they get stiffer/notchier but only start to slip when very worn. A brand new STD LUK clutch will have a lovely light action to boot.
  11. Clutch bleeding can only be done with the clutch cylinder clamped in a fully compressed state.
  12. The dual mass flywheel when worn can transmit some pinion chatter through to the gearbox. This only occurs in neutral with foot OFF the clutch pedal. Some noise here (worse when hot) is not really a problem. A rigid flywheel will make the noise more pronounced. A very lightweight flywheel will benefit from having the idle speed raised by 100rpm to prevent stumble or stall.
  13. The most common oil leak is the crankshafts rear main oil seal. This is an engine issue really but mentioned here as it makes sense to replace this when you replace the clutch as is very little extra labour on what otherwise would be a mammoth task. They ALL leak from here to a greater or lesser extent and in most cases is not a problem if the bottom of the engine to gearbox joint is just wet rather than dripping.
  14. WHEELS & TYRES. Most minis wear out tyres on the inner edges first which is easily missed on a quick visual inspection. Get your knees dirty and look underneath closely. Oddly the old style Dunlop Run flats (SP9000) were the worst for this.
  15. Run flats are not only harsher than conventional tyres but noisier to. The Kuhmo run flats particularly so.
  16. If you find the gearing slightly long (tall) on your pre- facelift 2002-2004car, try changing all 4 tyres to 205-40 17” tyres in lieu of the standard 45 profile tyres. Lowers the gearing marginally, looks better and slightly cheaper to. If you want the look as well go for 215-40 17”.
  17. Standard wheel offset (ET) on the 17” run flat wheels is around 50mm. Most aftermarket wheels are around ET37/38. That means assuming both are 7J width rims the new wheels will protrude 13mm or ½” further out …Normally not a problem and looks better to.
  18. DASH WARNING LIGHTS. Airbag light is common on earlier cars and we see many cars for sale with ‘just needs resetting’ in the advert description. Although early cars can have a problem with connections under the passenger seat the problem may well be more serious such as an ‘airbag deployed alarm’ or ‘internal error’ etc and this will NOT reset. A new module + fitting +reprogramming could land you nearly a £1000 bill so be careful.
  19. ASC /DSC Light. This will come on automatically each time 17-18psi of boost is reached, so is common on modified cars when driven hard. It will stay on until ignition recycled… It’s actually no bad thing as the system in our opinion is more of a hindrance than a help under hard driving conditions so the auto turning off is no bad thing .It will store P0108 as a code as well due to increased boost …all normal stuff.
  20. Emission Light ……Often can come on even without a code. Has to go through a number of drive check cycles before it will turn off ….In this case nothing to worry about. Worth running fault code readout anyway as can come on for a number of reasons including misfire and cat below efficiency.
we keep stressing how important it is to get every supercharger rebuilt if it has never been done.
Leaving it until it starts to get noisy is risky and leaving it longer and continue driving will severely increased chances of it becoming unserviceable or extra expensive rebuild. This can damage sealing faces and bearing seats beyond repair.
Even just stopping driving the car and leaving it can cause damage. It needs to be removed instantly and inspected / rebuilt. As you can see sometimes the coolant breaks into the PTO and severely corrodes the rotor drive shafts oil seal face. Leaving water/coolant inside will rapidly rust.
Bolt-on VS Interference Fit Supercharger Pulleys
Often discovered during rebuilds damage has occurred to drive pulleys’ shaft… this is usually caused by aftermarket “bolt-on” type pulleys.
These “bolt on” type pulleys can come loose & slide along the shaft, this makes the supercharger pulley out of line with the other pulleys which causes the belt to wear very quickly or even jump off.
With some brands of reduction pulleys’ we have noticed the supercharger seal retaining clip (tab seal) has had to be removed to fit this pulley in the correct position. This is not ideal, and could result in the seal moving and leaking (one image shows how one of these brands has damaged the seal retainer clip as not enough clearance).
Another image shows where Superchargers Snout outer oil see has been severely damaged due to the seal retainer being spun around with the “bolt on type” pulleys inner sleeve.
‘Bolt-on’ type pulleys are known to slip, slide and even fall off on rare occasion.
Identifying the problem… A sudden loss of power will be caused by this as the supercharger has lost all drive, or intermittently as the pulley jams then slips repeatedly. This means the water pump will too! Over heating is inevitable as the water-pump is driver by the supercharger, if not fixed, worst case could result in catastrophic engine damage!
On some occasions the free spinning of a loose pulley on the shaft wears it so severely it is no longer serviceable.
GTT Supercharger reduction pulleys use an interference fit system to the shaft (same as OEM pulley) so why risk it?
Why Not To Use — DIY Supercharger Oil Replacement Kits With Syringe
We have seen this a few times where people use these kits to refill/replace the superchargers oil through the drain plugs. This is highly risky as you do not know the condition of the internals and by topping up you unknowingly are mixing new oil with all the old sludge/swarf/dust etc making a sort of grinding paste that destroys your PTOs internals… and in some instances beyond rebuild.
BMW can now only supply recon units from Eaton at a whopping £3450 (inc vat) and above…,second hand units of ‘unknown condition’ becoming both scarce and more expensive, a GTT rebuild on your own charger makes much more sense.
Engine Coolant Inside R53 Superchargers PTO?
This is a rare case (we currently have seen around 10 cases) where the water-pumps seal fails and coolant forces its way into the Superchargers PTO ….
The water pump and PTOs… mating surfaces corrode together making a seal, so the coolant may not even be coolant dripping on the floor at all.
Some incidents we’ve seen the coolant get through the second oil seal in the PTO (under small gear) and into the rotor housing..
The seal behind the fork drive is also replaced during a GTT PTO rebuild. We also strongly recommend a new water pump is fitted at the same time.
When coolant breaks into the PTO it severely corrodes the rotor drive shafts oil seal face. Leaving water/coolant inside will rapidly rust! remove right away and get rebuilt!