Metal bypass pipe
 

Hi Everybody,
I have a '82 300d turbo and was curious as to the function of the small horseshoe shaped metal pipe that is connected to the water pump. It is attached by two banjo bolts. The best I can tell from looking around the internet, is that it's some kind or bypass pipe... but what does that mean exactly? I'd be surprised if it was "bypassing" liquid as it's very small in diameter. I really don't know, but mine looks pretty corroded. Also, what kind of symptoms would occur if it was bad/clogged? Do I have to drain the coolant to replace it?
I've really appreciated the bits of help that I've received on this forum and I'm looking forward to everybody's input. Thanks!

A picture may help your description.

The OM617.95 Engine Manual refers to the pipe as a vent line, but offers little insight as to its purpose. It would appear that it vents the head to the water pump housing or vice versa. Replacing it would require draining the coolant. Given the fragile nature of old banjo bolts, proceed with caution.

That's true. I'm going to try to add the part image to the post.. hopefully it works.

Thanks for the reply. I've also had a hard time finding it's exact purpose. Perhaps it's there to help vent small air pockets out of the system?

Yes it is a pump vent and they go bad. It will drip, drip, drip in the back. I tried JB Weld on mine and it did not work so I had Phil send me one from Fastlane. It was a cause of slow coolant leakage. Now I have no leaks in over 2 years. They are easy to relace. $37 I believe. U need drop leve a bit not entirely. Make sure u don't drop the sealing metal washers and clean mating surface good with some fine emory. It is super easy job, the kind we all like.

Thanks for the input! I also got another personal message that it vents air. I'm surprised this hasn't been discussed more because if it's not allowed to vent properly, I would imagine it would cause some random temp and pressure problems (depending on the blockage)? Has anybody replaced this metal pipe and found their car runs cooler and at a steady temp?

What I noticed on my 85 300D Kali Kar, and other 85`s, is they do not have this vent pipe. I have since added one.

Charlie