Hello fellow campers, I have a growl on start up on my E300 1999 OM606. Did a code read from the climate control and got B 1416 which reads coolant circulation pump. From the "there are no stupid questions dept" is this my water pump or is there another pump? The growling I hear sound like it could be the compressor or the clutch but I have no codes for either. I do remember seeing a small pump on the exhaust side of the engine. Could that be the pump? Any input is appreciated. Have to get my ducks in a row for the first day over freezing . Thanks

That code is for the small pump on the coolant lines, down low under the air filter box on the passenger side. (The one you spotted on the exhaust side.) This pump keeps coolant moving through your heater core under low rpm conditions and also what makes the REST function work.

That said, if you are on your original belt driven main engine cooling water pump and thermostat, it may be a good idea to go ahead and replace that as preventative maintenance. Since you’re going to have to drain the system to change out that circulator pump based on where it is.

Proper fill is 1 gallon Zerex G05 concentrate and 1 gallon distilled water. They sell 2 kinds of Zerex, one that is full strength and the other has been pre-diluted. Much cheaper to buy one $25 jug of G05 and one jug of distilled water $0.99 at Publix….

Another hint, take loose the upper radiator hose when refilling (leave the hose attached to the thermostat housing), pour as much of the coolant and water in (take turns pouring some of each) as it will take, then hook it back up and put the rest into the expansion tank. It’s a good idea to go ahead and start the engine, put the heat controls on HI and drive around until the temperature comes up and you get roasted out of the driver seat.

This is necessary because if you get an air bubble trapped in the heat loop it can damage the head. The hot coolant flows out the back of the head and either gets sent into the cabin heater core or returned to the radiator by the control valves at the back right corner. If you get air trapped in this loop you will have flow problems through the head.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Thanks Jay Bob. Your info is greatly appreciated. I did a thermostat replacement this fall as temps never hit 180. New housing and thermostat. Draining the radiator was a thrill as it's a replacement (not MB but a Swedish brand) and the petcock did nothing. Hoses off and we were drained. I do have heat now but it's never toasty. Can I put this off till the spring? I'm working on the street and it's a cold street. Thanks again for your reply.