Hello. I have a 2003 300M with 120xxx miles. 2 months ago I changed the thermostat which led to having to replace the heater return tube. After sitting for two months, I finally saved up and bought the return tube (under the exhaust manifold) and after a few choice words and a pack of smokes got it installed. I bled the system the best I could and started home. After driving for maybe 15 minutes the car began to overheat. I pulled over and upon opening the hood there is a small puddle of coolant on the intake manifold just below the injectors. I thought that may be from bleeding the system (no tubing available) and that maybe i didnt bleed the system correctly. After the car cooled down i started it a few times but it stalled immediately. I let it cool completely at this point. Started it and drove about 5 minutes with the same results and scenario. Coolant seems to puddle on the intake manifold and on the ground below the passenger side of the motor. Any ideas as to where i should start with this one??? It has a new thermostat, coolant tank and heater return tube. Please Help!

 

did you grease and install a new o ring for the coolant tube,$2.37 from the dealer.

 

Thank you for the reply. Im not sure we are talking about the same part that was replaced. The pipe I replaced is the one that goes from the thermostat housing under the exhaust manifold and up the back of the engine. I did not remember seeing anywhere that an "O" ring would go. It had rubber hoses that clamped to the thermostat housing, coolant reservoir and the heater core. A different user said I should check the coolant system pressure to find the leak. Might be able to rent the tool this weekend and try that?

 

Oh I was thinking about the other coolant tube there is one that runs under the intake manafold from the front out the back of the lower intake plenum. These will leak coolant when they get old. The only way to get to it is to take both intakes off and unbolt the tube.

 

Do you have to take both the intake plenum and the lower intake off to get to that tube you speak of? Will the leak be visible on top of the intake manifold? No funds available for renting the coolant system pressure gauge this week. Looking at worst case scenario right now.

 

yes you must take both off to get to the tube. the o ring is $2.37 at the dealer part number 06505692AA and is speical order. If you are careful you can reuse the intake gaskets you will need to put RVT around the coolant inlets on the lower intake plenum. That is the 2 outer most holes on each side.