1997 BMW 540i Q&A
1997 BMW 540i Question: Car is leaking coolant and it drains quick from rear of engine and bellhousing.
Hi. The most common coolant leaks that we see on this engine are from the valley pan (aluminum plate w/ plastic cover on top of the engine block under the intake manifold) and/or the coolant tubes (2 aluminum tubes that run from the back of the water pump to the crossover tube on the back of the engine that attaches to each cylinder head. When those items leak, the coolant tends to run off of the back of the block and streams down the bellhousing. The way to verify this is to remove the top engine cover and use a flashlight to look under the intake manifold at the front and rear of the engine. A cooling system pressure test will also pinpoint the leak if there is any question as to the source of it. If the top of the engine is wet, you will need to remove the intake and replace the valley pan, the seals for the tubes and either remove and replace the water pump gaskets (good time to replace the pump and t-stat), or the crossover tube gaskets where they seal to the back of the heads (depending on which side of the engine you choose to remove the tubes from). You should also re-seal the PCV cover at the back of the intake manifold at the same time and change the thermostat housing assembly. The coolant sensor on the housing will leak internally and push coolant through the wires back to the Eng. control module. This is very common and when it happens, it is very expensive because the DME (ECM) is about $1400 (you can't just install a used module without also replaceing the EWS, and ignition lock cylinder and the used parts must be from the same car and can be difficult to source). I would be happy to visually inspect the leak and provide a complete estimate for the repair also. Good luck! James Wallace EuroAsian Garage Seatac, WA 206.246.3886 www.euroasiangarage.com - Jamesw