Dual circuit brake system with 4 piston calipers
- Brake pedal
- Master cylinder
- Fluid reservoir
- Push rod piston circuit
- Intermediate piston circuit
- Double adaptor
All Type 3 Variant vehicles for export to Sweden are fitted with a modified braking system (M 594).
On the front axle, double calipers (4 pistons each) and modified brake discs are installed. The diameter of the tandem master cylinder has been changed and it now has six outlets. The lower pistons of each caliper and the right rear wheel cylinder are operated by the push rod piston and the upper pistons of each caliper and the left rear wheel cyllnder by the intermediate piston in the master cylinder. This ensures that when a brake circuit fails there is always braking force on the front axle end one rear wheel. The calipers have 6 bleeder screws of which 3 are for normal bleeding operations and 3 are for brake fluid changing purposes.
The image and description of the Swedish 4-pot brake system come from Dave Hall of the UK VW Type 3&4 Club:
4-pot are calipers with two cylinders and pistons *each* side. It makes the Swedish M 594 a very safe option for braking, but since virtually every part apart from the fluid is special for this system, it's probably an almost impossible task to find bits for it outside Sweden. They had twin pipes and hoses almost everywhere, too. I think it was an answer to Volvo for its accent on safety. The front-rear split we have isn't as safe as a pot each side for the front and one rear side on each circuit. Dave. UK VW Type 3&4 Club www.hallvw.clara.net/