What if the coolant keeps leaking on a Mercedes ml 430?

Answer 1

It depends what kind of leak you are referring to when the engine is cold. If coolant level comes down low after driving, you are loosing coolant while the coolant system is under condition of hot and higher pressure. You can be loosing it through pin holes in hoses, cracked hose, loose hose connections (this condition is cheap to fix and can be done by yourself) or through defective or deteriorating cylinder head gasket (expensive to fix). If you see coolant drippings on the floor under the engine compartment area, you can trace the source of the leak up above. It could be coming from a defective water hose, loose hose clamp, or just like my case, the water dripping was coming from the auxiliary coolant pump cap. The auxiliary coolant pump is under the hood on the passenger side of the engine. The auxiliary pump is an electric driven vane type pump device that supplies coolant to the primary pump of the cooling system. You will find this by tracing the water hose from the coolant tank to the top (inlet or suction ) side of the auxiliary pump that feeds the coolant to the cooling system. There is a second hose on the pump cap (outlet or discharge) side. When I inspected the pump assembly, I found out that the cap flange of the pump shroud (made of phenolic plastic) has eroded right exactly where one of the four screws holds the shroud cap directly down to the pump housing. This eroded section of the cap and housing was the source of the leak. Why or how it eroded, I cannot explain. After loosening the strap clamps that held the hoses, I pulled up the pump assembly together with the rubber mount that held the pump body. The rubber mount slips off a metal bracket. Jiggle while pulling upward the rubber mount to loosen its bond on the bracket. There is a wire cable attached to the bottom end of the pump assembly. Keep this cable attached as you don't need to disconnect it to fully inspect the pump assembly. I scraped and cleaned the eroded portion of the shroud and pump body assembly. The hold-down screw got exposed completely and it wasn't holding on any solid part of the pump assembly. Behind the screw was a gap on the pump cap flange where the leak was coming from. Somehow the seal between the cap flange and pump body got open due to erosion. This gap is where the coolant is oozing out. I applied a blob of Locktite epoxy over the eroded section as a temporary measure to prevent further leakage. It has held for over three months since but I occasionally had to check whether it still leaks underneath. It is still holding and counting. You can buy this twin barrel Locktite epoxy mix at 99¢ store or hardware store. Meanwhile it gave me the time to search the internet to buy the replacement auxiliary coolant pump with no rush. An internet search showed prices between $150 and $210 for the new part.