Supercharged Subaru: Minor supercharger tune-up

Getting started...

The first step is the empty the oil reservoir. Simply unscrew the oil plug and pour the oil out. If you want to have minimal residual oil, you will need to leave the supercharger inclined over a can for a little while. The is not a lot of oil in the reservoir, it's about 90ml for the M45 and 100ml for the M62.

Next, unscrew all bolts holding the snout to the rotor housing. When all bolts are removed you will note that the snout is still firmly clamped and won't come off that easily. This is normal since a silicone gasket is acting as glue. You will need to find a rubber or wooden stick and tap to snap it off. Getting it off might be tricky. The snout is 'glued' to a section on which the gears and rotors are installed. If ever you want to pry between the surface make sure you do not damaged the mating surface. First simply remove the snout portion and leave the gear section attached to the rotor housing.

(Pictures coming soon...)

Inspecting the snout

Verify the internal of the oil reservoir. Is there any contaminant that could indicate the gear are damaged. This should generally not be the case but perhaps a lack of oil could result in the gear failing. If you don't see anything special you can clean the snout portion using brake cleaner. Make sure you removed the coupler (black or green round shape thing attached to one of the gear or the snout inner shaft) before starting to spray brake cleaner.

(Pictures coming soon...)

Inspecting the gear

Next verify that the gear are in good condition. Also you can make sure the coupler fits tight. If the coupler is too loose consider replacing it with a new one. You can find coupler for a fair price on Ebay but I'm sure a little search on Google will find many supplier and maybe even one near you. I have diassembled two superchargers so far and in both cases the gears were in perfect conditions. These supercharger are very tough and made to last for the life span of the car it is installed on. Unless something bad happen like the supercharger swallowing sand, there is very little chance you will have damaged on the parts enclosed in the oil reservoir.

(Pictures coming soon...)

Rotors and housing

Probably the most important parts of the supercharger are the rotors and its housing. Anything else that air entering the inlet of the supercharger will probably endup damaging the rotors and/or the housing. Careful inspection on the rotor lobe is necessary. You should look for dents or various marks. You must make sure that the rotor are very smooth. Usually there is a coating on the rotors. Sometimes it starts to peel off, or some of it can have been damaged. It the peeling is too extreme you might need to consider removing the coating. I have read that it will affect how much boost the supercharger can provide. Removing the coating can reduce by 1% the amount of boost, so if you were aiming at getting 10psi, you might end having 9psi instead, which is not that bad in my opinion. At least you will be sure the coating will not endup in your intercooler, or even worst, in the combustion chamber.

Gasket remover can be used to remove the rotor coating.

Below you can see the rotor of my M62 unit. Some peeling was starting so I decided to remove the coating entirely. I simply used gadket remover, it works like a charm. Spray it, wait around 3 or 4 minutes and it will peel off very easily. Make you do a final cleaning pass with brake cleaner to ensure there is residual contaminant.