The E46 SMG pump systems incorporate a fluid reservoir designed to accommodate the additional fluid capacity required for the pump to achieve full pressurization. The reservoir is integrated into the intake air-box in all models except the CSL version. In the CSL model, the reservoir is a standalone component, attached to the shock tower.
It’s crucial to understand that regardless of the model – CSL or regular, the reservoir functions as an expansion tank and should not be filled to the top, especially when the SMG system is pressurized. Overfilling can lead to the slow release of system pressure over time, causing the fluid to flow back into the reservoir. If overfilled, the reservoir may overflow, leaking fluid through the breather port in the cap, which subsequently drips into the engine bay. This leakage may be misdiagnosed as a pump leak if not properly identified.
In non-CSL models, a check valve is located at the bottom of the reservoir tank. This valve controls the fluid flow when the pump feed pipe is disconnected. To ensure full fluid flow, the feed pipe should be inserted correctly and pushed all the way through to release the check valve. Failure to do this can result in SMG pump fluid starvation and the introduction of air into the system. This issue may arise after the system has passed the bleed procedure and could intermittently introduce air into the system once the vehicle leaves the repair shop.
For CSL type reservoirs, although there is no check valve, the long hose section is susceptible to air pockets. We recommend dismounting the reservoir and maintaining the feed line as straight as possible to facilitate the release of air pockets. If the problem persists, try removing the line from the pump until fluid flows and then reinstall it.
