:: G60 - Photographic Rebuild::
The G60 powerplant is an awesome engine capable of some serious power outputs, but as most G60 owners are aware, the charger requires regular servicing. Although VW never specified a rebuild/overhaul interval, the bearings and seals within the charger have a lifespan considerably shorter than that of the rest of the engine. As a result the charger should be overhauled on a regular basis, with the interval between overhauls dependant on the charger's state of tune. The following can be used as a rough guide:
In addition to this the small drive belt that links the main drive shaft with the G60's auxiliary shaft should be renewed annually. As this is an ú8.50 part you have no excuse for ignoring it!
These are rough estimates and there are a number of simple inspections you should make on a regular basis to keep an eye on the condition of your G-Lader, [these will be covered in the forthcoming"G60 Tips" section].
Failure to service the charger will ultimately lead to it failing terminally, at great expense to you.
--- a brief word from our sponsors ---
--- and back to the article ---
Rebuilding an expensive supercharger is not an easy task and if you are in any doubt about this process, we cannot stress highly enough how important it is to seek the advice of a professional company such as JMR
The article is not designed to be a DIY guide but instead to give you an insight into the rebuild process and help you understand the G-Lader a bit more. If you have any questions about the process or have problems with your own charger then please get in touch with John at JMR, as he is an expert, not us.
The rebuild basically involves stripping the charger down, cleaning the casing and inspecting all parts for wear before reassembling it with new oil seals, apex strips, bearings and drive belt. As manufacturing has moved on since VW designed the G-Lader, Experts are able to reassemble the charger using higher specification parts than the originals so in theory the rebuilt unit is essentially better than new.
You can either remove the charger yourself and ship it toJMR or you take your car down to their South Coast workshop for them to remove and refit the charger for you. We opted for the latter as we were going to be there anyway to watch the process...
Firstly, pop the bonnet and allow the engine to cool, you do not want to stuff your hand down the side of a roaring hot charger! Remove the air box or induction kit as well as the charger inlet pipe and any induction kit heat shield. Remove the plastic radiator cover, alternator cover and soft rubber charger outlet hose (the one that goes from the charger outlet baffle box to the plastic pipe that runs to the intercooler) and put these parts to one side. Disconnect the boost return pipe from the top of the charger and push to one side. if you run a cotton gauze performance filter now would be a good time to treat it to a clean and re-oil.
Remove the securing nut from the top of the charger belt tensioner and remove the top of the tensioner from its mounting (the bottom of the tensioner can remain in place). VW have a special tool for this but if you have a Jabbasport pulley and tensioner cap, your tensioner will be upside down and the tool cannot be usedů. get the brute force and ignorance out of the tool box at this point! This will release tension on the serpentine belt, allowing you to remove it from the alternator and charger pulleys. Then remove the plastic baffle box from the charger outlet (or RSR outlet if you have fitted one of these). Disconnect the braided oil feed line from the charger and tuck it under the oil filler cap so it doesn't drip everywhere. Then disconnect the rubber oil return line and leave it hanging free under the charger.
Charger with inlet, drive belt and tensioner removed
The blower is now ready to be removed but in order to access some of the allen headed securing bolts you will need to remove the drivers side headlamp and grille (on a Corrado). You will only need to remove the grille if you are working on a Golf G60. Remove all the allen headed securing bolts and carefully withdraw the charger from the engine bay.
Charger ready for removal
G60 being removed from engine bay
Engine bay sans charger
The charger is now ready to be stripped down. Firstly the plastic cover is removed from the toothed drive on the auxillary shaft. The pulley can then be removed from the main drive shaft and the two toothed drive gears removed from their respective shafts along with the small drive belt, remembering to carefully set aside the woodruff keys. These parts need to be put to one side as all but the toothed drive belt will be reused.
G Charger ready for strip down
The two halves of the charger casing are then separated by removing the allen headed bolts. The displacer and main and auxiliary shafts are now removed. The auxiliary shaft is then broken down and the counterweight removed but taking care to set aside the woodruff key as this will be reused. The apex seals can then be removed from both sides of the displacer and casing halves and discarded.
The springs behind the apex strips are kept as, unless damaged, these will be retensioned and reused. The oil seals and bearings then need to be removed from the casing and discarded. There are a number of circlips holding the bearings in place which must be removed with circlip pliers and retained. The bearings are removed by heating the charger casing with a hot air gun which causes the casing to expand which frees the bearings. The oil seals often give the first indication of charger wear. Oil is fed to the bearings under pressure and if the seals are not 100% then oil is forced passed the seals into the charger internals or out of the charger casing round the drive pulley.
Separated halves of G-Lader
This charger was in pretty good condition inside and out but JMR were able to show us a few examples of chargers that were somewhat past their prime.These components were obviously beyond repair but looked worth keeping for entertainment value alone.
If your charger internals look like this then seek professional help!
Once everything is stripped down the casing halves are chemically cleaned and carefully inspected for damage and excessive wear. Assuming all is OK, the casing internals are masked off and the casing is sprayed with a durable silver coating. The displacer is also carefully cleaned and checked but using a regular de-greaser as the chemicals used to clean the casing are far too aggressive for the magnesium displacer.
Supercharger displacer mounted on main drive shaft
Masked and painted charger casing
It is possible to modify the charger by porting the internal parts, in particular the charger outlet and upper inlet chambers. This will increase the amount of air that the charger can flow thus increasing its efficiency and overall boost levels. My charger had already had some porting work performed at the last rebuild so no additional work was required this time but such modifications would be carried out before cleaning and painting the casing. Specialists can do pretty much any level of porting work and offer a standard rebuild, a stage 4 upgrade which involves enough porting for most people's requirements as well as a "race spec" upgrade. Pictured is a charger which has been built to race spec. This has been ported to within an inch of its life and every possible angle and corner had been smoothed and every opening enlargedůvery cool!
Check out the exhaust porting on this race spec charger [right] vs. Si's stage 4 item
The auxilliary and drive shafts are also cleaned in degreaser and closely inspected for wear. If the engine has been run on poor or dirty oil then this will show up as burnt on deposits on the main drive shaft. Such deposits are removed if possible. The oil ways within the main drive shaft are checked for blockages, carefully cleaned, and blown out to remove any dirty oil or debris.
The charger components ready for reassembly
The charger is now ready for reassembly. New bearings are fitted to the casing halves by heating the casing until the bearings merely drop in. They can be fitted with a press, but if the bearings are out-of-alignment, damage is almost certain to occur to both the bearing and charger. The circlips are reinstalled to hold the bearings in place [taking great care that they are aligned so as not to block the oil ways that feed the bearings with oil]. The oil seals are pushed into place and care is taken to ensure that the external seal on the main shaft is not pressed flush with the casing as fitting them to sit flush will obstruct the oil way that feeds the bearing.
Bearings being fitted to casing using heat, not press
Bearing in place with circlip oriented to avoid obstructing oil way
The apex seal tensioner springs and new apex strips are installed in the displacer and casing halves. These strips create a seal between the displacer and the supercharger casing. If they are worn then the lack of adequate seal will reduce the amount of boost the charger produces as well as possibly cause the main drive shaft to run out of true [which will further accelerate bearing and oil-seal wear]. If the apex strips become extremely worn then they can jump out of place and jam the displacer - usually at speed!
The apex strips are made from a Teflon-based composite and look like a mix between plastic and rubber with a copper grease coating. The strips arrive in sets but arrive slightly too long which allows rebuilders to trim them down to an exact fit. Strips which are too short can move around during use and possibly jump out of their retaining groove. In addition, the strips shrink naturally during their lives, so a good fit from the outset is paramount.
New apex seals
Grooves in charger casing for apex strips
Apex strips being fitted to displacer
The displacer is fitted to the main shaft and installed in one half of the supercharger casing along with the auxiliary shaft. A special grease is then applied to the charger's internal surfaces where apex strips will bear against. Although the strips are self lubricating the grease helps ensure that the strips make a perfect boost-tight seal.
The charger halves can then be put together and the toothed drive pulleys refitted to the main and auxiliary shafts. A new drive belt is fitted to link the two shafts taking great care to ensure that the two shafts are aligned with one another and thus correctly "timed". As standard this belt is 6mm wide but JMR fit a wider 11mm item that fits on the standard pulleys whilst being stronger and more durable than the original. The main drive pulley is now fitted to the drive shaft and the G-Lader is now ready to be refitted to the car.
Half of charger built up with drive and auxiliary shafts in place
Before refitting the supercharger it is important to manually rotate the main drive shaft. It should be tight to turn (implying a good seal between displacer and casing) but smooth and should rotate without any obstruction. Refitting, as the Haynes manual says, is the reversal of removal but if you are still running the original VW oil feed line then JMR replace this with a stronger Teflon lined pipe as part of the rebuild.
The original line is a simple rubber inner with a steel over-braid and the rubber disintegrates and collapses with age and heat. This blocks the line and can starve the charger of oil. The new line is much better quality and should never need replacing. The oil return line is a larger diameter line and tends not to need replacing so is just re-attached to the charger. Once the charger is in place the induction kit/air box can be replaced along with the inlet pipe. The charger baffle box and rubber outlet pipe can also be refitted and one is then ready to test the rebuilt G-Lader.
Spangly new charger being reinstalled in car
Before starting the engine it is important to prime the charger by turning the engine over for 10 seconds or so on the starter motor (Simply disconnect the hall sender to prevent the engine from firing). This will fill the charger with oil so when the engine is first started the charger bearings are not dry. Allow the engine to get up to temperature and check for oil leaks from the charger and oil feed and return-lines as well as boost leaks from the intake pipework. Assuming everything is OK the engine can be stopped and the radiator cover, alternator cover, headlamp and grille can be refitted.
Charger being run and tested for oil leaks
Following a rebuild the G charger needs running in for a period of 250 miles. This is done simply by keeping the revs below 4,000rpm (assuming you are running a 68mm pulley) for the first 250 miles. If you are running a std pulley you can run the engine to about 4,200rpm and if you are running a 65mm pulley I would limit yourself to about 3,700rpm. After this the charger should be absolutely spot-on and ready for a decent bit of right foot!
If you are in the market for a supercharger rebuild, we would STRONGLY recommend the services of John at John Mitchell Racing.
G60 The Basics [new]
G60 Tuning [new]