I'm at 115k miles on my 2008 GL450 and doing some preventative maintenance. I'm going to go ahead and change the 2 drive belt idler pulleys as well as belt tensioner. I follow this subforum fairly regularly and never see posts about water pumps on our motors going out. I did see just one or 2 posts when I searched, but thats it.

What are y'alls thoughts on the mechanical water pump replacement?

 

I would do it. Was the only thing that ever completely failed on my GL besides the air struts. That's around the time it failed.

 

how do you bleed the system?

 

Counterpoint, I’m at 215k on the factory pump with never any loss of coolant and I’ll leave mine alone until signs of impending failure.

I’d put this one squarely on the “while you’re in there” / “if it ain’t broken, don’t” terminator line; but if you must - DO USE OEM quality parts and fluids.

This requires a drain so a good chance to flush the system as well.

 

Which system are you talking about - coolant and air was talked about in the sentence you quoted.

 

I'm at 225K with the original pump without any play in the pulley or leakage. It is the only rotating thing on the front of the engine that hasn't required replacement or repair. They seem to last a long time. I'd be inclined to leave it alone if it isn't leaking out of the weep hole since a replacement may be a remanufactured part with questionable durability.

 

At 13 years you might as well replace the 15-year G05 (gold) antifreeze your vehicle originally came with with current G48 formula (blue) antifreeze. Gold no longer available from Mercedes.

my dealer of course suggested water pump replacement when I requested this, but I declined. Water pump previously replaced on this diesel a few years ago, another replacement not really currently needed.

now both my cars use same antifreeze.