The BMW Mini M45 supercharger is based on Eaton’s well proven roots technology. Found in two variants in the R50, R52 & R53 models with early grey epoxy coated rotors and later black abrade-able coating. The BMW Mini Cooper S has been a great success and has attracted a host of modifications one of which being upgrades to the supercharger. This M45 is also an aftermarket choice for bolt-on supercharging of some Honda’s and Mazda MX5’s.
Although good, these superchargers can be subject to premature seal or bearing wear, and in some cases failure of the drive coupler. Rattling at idle is the first indication that something is going wrong, usually that a bearing is starting to wear, or that a drive coupler is fractured and failing. The important thing is to have them repaired when you hear early signs of something being wrong – if they are left rattling too long, the damage will spread from bearing wear, which is curable, to wear of the rotors and/or main casing, which can become bad enough to scrap the supercharger.
Please note all prices noted below unless otherwise stated include UK vat at 20%.
Not Your Typical Supercharger!
Just as many OE manufactures do, BMW have created a bespoke supercharger unique to the Cooper S. Using Eaton’s very dependable M45 rotor group they have created a supercharger that utilize the supercharger shaft to drive the water pump on the opposite end via a small gearbox (PTO gearbox).
Although this is very convenient and necessary to get such a supercharger in the confined space of the BMW Mini, it has also become the backbone of failures on these units. Premature seal failure leads to oil loss in the PTO (Power-Take-Off) unit, PTO gears then rapidly wear and fail losing all drive to the water pump leading to a host of over heating issues and supercharger noises.
Repair – this failure has previously been a potential scrapping issue with the worn gears not being available from BMW or Eaton. Repairs have been undertaken by sourcing good used condition gear sets, but these are hard to find with most people opting for the used market risking purchasing a similarly worn blower. Final choices have been to choose 1 of 2 aftermarket manufacturers of replacement gears but being forced to use their rebuild services at a hefty price tag to get them but NO LONGER.
We at Powerhouse are happy to announce that we can now replace the worn gears in your Mini, as well as all other bearings and seals, for brand new UPRATED GEARS designed and produced for ourselves at competitive prices. To our knowledge we are the only aftermarket company to have kept true to Eaton’s design features by incorporating their custom gear profile designed for the high-speed of the gears and lubrication. We have also upgraded the gears by opting for a wider gear to reduce the load per gear tooth and reduce the risk of total gear wipe-out as seen on some units.
M45 MINI REBUILD KITS
Replacing the bearings and oil seals in your supercharger will give it a new lease of life, and your own peace of mind. As long as issues are not ignored and repaired early, our Eaton M45 supercharger rebuild kits, which start at just £46 should fix the problem. You will need access to a workshop press but other than that the job is not beyond the ability of a competent mechanic.
M45 MINI SNOUT REBUILD KIT
If your problem is just a leaky snout oil seal, you have metallic supercharger oil or you’ve used a stethoscope to confirm a snout bearing needs to be replaced, then our Eaton M45 snout rebuild kit at £46 may be the most cost-effective way to have your car back to good health. The snout rebuild kit includes front and rear snout bearings, snout oil seal and the required oil to fill the supercharger after reassembly.
BUT – if there’s any doubt over the condition of the rear case bearings, it would be advisable to change them as well. The rear bearings are prone to failure; you may wish to avoid removing and refitting the supercharger and another strip down for the sake of two more bearings first time around by buying the M45 supercharger rebuild kit!
M45 MINI BASE SUPERCHARGER REBUILD KIT
For the BMW Mini, with the PTO adding extra parts we have created our “Base” kit which supplies you with all the base components found in most Eaton superchargers in order to rebuild and give your supercharger a new lease of life. Our Mini supercharger rebuild kit starts at £154 – which comes complete with all snout bearings, snout seal, 2 Eaton rear case needle bearings, case-pto seal plus replacement oil for the front gearbox & PTO gearbox. If you wish to or need to rebuild the PTO we offer additional kits to completely overhaul the PTO.
POWER-TAKE-OFF (PTO)
Our Mini Cooper S PTO rebuild kits provide all bearings and seals required to maintain your PTO and guard against the biggest known weak point on the Mini M45. If your PTO has already failed we can also provide new PTO gears, new PTO shafts, and seal repair sleeves to repair excessively worn rotor shafts. Our prices start at £61 for our PTO bearing and seal rebuild kits, these include a case-pto seal, PTO Shaft case needle bearing, PTO Shaft bearing and Outer PTO Shaft Seal.
Uprated replacement PTO gears can be purchased in pairs for £175, independent of a rebuild service. Our uprated PTO gears have been designed to maintain at our cost Eaton’s custom gear profile, a detail that others appear to have neglected to keep. Specified with high tolerances, ground finishes and hardened gears our PTO gearsets are the ideal replacement for worn OE gears.
PTO shaft replacements are also available for just £45, ground to exceptional tolerances and hardened to maintain life. You may wish to consider replacing if your PTO has run dry or been found with sludgy contaminants. These conditions are known to rapidly wear the sealing faces leaving new seals struggling to maintain a seal.
M45 MINI ROTOR PACK BEARINGS & SEALS
Our M45 supercharger rebuild kits do not include the pair of bearings and seals which live between the rotors and timing gears in the middle of the rotor pack. This is because at manufacture Eaton rolls the casting onto the bearing outer race, permanently sealing them in and meaning the casing has to be fractured to remove those bearings. That said, these are in an oil bath and rarely fail – when we are rebuilding superchargers we do not change the rotor pack bearings. If they do fail, some service providers in the US do offer rebuild of the rotor pack, but the Eaton Corporation themselves consider this to be an unreliable and often unsuccessful route to repair – when the rotor pack is worn out or damaged the only dependable solution is a new rotor pack.
If you want to attempt to rebuild your Eaton M45 rotor pack we can supply you the parts, but caution that it is not always successful. Our rotor pack kits are £84 and include both rotor pack bearings, 1 high spec aftermarket rotor seal with dual lip and FKM material for the higher temperatures + 1 Genuine Eaton Seal we have managed to source.