300SEL 4.5 water pump replacement

[WANT '71 280SEL]

Other than the notch in the balancer to access the bottom water pump bolt, is there anything else I should know before tackling this job? Looks pretty straight-forward but time consuming.

Thanks

David

[Tony H]

Do you have the new pump? you can look at it to insure you got all the bolts. Some are different lengths so insure you don't get them mixed up. I can post a pic of a engine with the pump removed if that would help.

[WANT '71 280SEL]

I don't have the new pump in front me. I ordered it and it should arrive tomorrow. How long did it take you to do the job?

Thanks,

David

[werminghausen]

Hi David,
I just had to take out my pump on the 3.5 because one of the 3 bolts of the upper pump housing broke off(thread sticking in the main housing)! I had to remove the bolt because I needed to repair a coolant leak.
What a pita to get the pump out (in order to get the broken M8 steel screw out of the aluminum body. All steel bolts were so heavily corroded... so that another M8 bolt broke off (2 of 3 bolt broke).
I hope your pump is in better shape without much corrosion.
The pump housing has 3 bolt sizes connecting it to the block: One very long and the others medium and short size (all M8). they came out easily as their threads are in the steel block.
You need to rotate the crankshaft for matching the notch with the position of the 2 lower screws. This part is easy as it sounds.
What is wrong with your pump? Mine was perfectly fine after 43 years... However I had a slight leak at the lower hole when I installed the pump again and had the system pressure tested with 1 bar. Weird thing is that the leaks seemed to have stopped then the pump was running at a test drive today. I have to watch the coolant for a while I guess.
I would have also a new pump installed if I had access, but no chance in Oman. It cost me $45 just for removing the broken bolts in the old housing. What can you do in Oman.
Anyhow I am driving.
Martin

[WANT '71 280SEL]

Thanks for the write-up Martin. My lower weep hole is dumping out fluid. It only seems to do it after driving for awhile so keep an eye on yours.

Thanks,

David

[Mike D]

Martin, if the pump is leaking at the "weep hole" then your pump is on its way out. I've seen them last for months and I've seen them puke immediately after they begin leaking. As much work as you've put into your car I'd hate to see it roast.