Hello All

First I would like to say how valuable these forums are to the regular amateur mechanic out there. I had a coolant leak on my 300. I read all of the posts about it possibly being the water pump. I took it to a couple of shops in my area and they seem to point in the same direction. I finished changing out the pump over the last 3 days. I put everything back together very methodically.. When I finished,I had a 13 MM bolt left over. For the life of me, I can not figure out where it goes. There are 4 bolts holding the pump to the engine 3-13MM, and 1 hex head. 3 bolts holding the tensioner bracket 1-19MM Holding the tensioner on. I fired her up and lo and behold my leak is back. If any one can possibly tell me where I might have Brain Farted please let me know. I swear, I did a real clean job, used the cdrom, and took plenty of time. What else could cause the leak. I put all new seals ,Water pump,thermostat,heater line.Any help or suggestions would be welcomed because I am at a dead end. Luckily it is not my daily driver,


Thanks Much
Bob Bridges


1972 Silver 280 SE
1989 Silver 280 SEL

Did you remove the water line that runs across the front of the engine? Or is that bolt 10 mm.

Anyway, check the heater hose connection at the rear of the head -- it's sealed with an o-ring and held in place with a metal clip, and the o-ring goes bad and dribbles.

Did you replace the short hose between the water pump and the thermostat housing? If not, you need to, it's likely to be bad.

The sealing surface for the water pump must be completely clean, so must the groove in the pump, and you should not use oil or grease on the o-ring, else it dribbles.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks for the post Yall


Comes to find out I did'nt tighten down one of the hoses, right now she is dry as a bone. I still don't know where the extra bolt came from. Oh well.




BB

Some of the water pumps M/B has been giving out has an additional brass fitting that you need to pop into the back of the water pump like a freeze plug.
Theese are universal pumps that some need the plug pounded in and some have another water hose that bolts to that portion of the pump.

You may have a big hole in the rear of your water pump that you can't see but you have to remove the water pump and get that brass fitting.
They call for an orange goop to put around the fitting before you tap it in.

If you have this pump and you need the fitting, the dealerships carry them.

I have to admit, I got burned on that one myself once, and it will never happen again.
They just went to this update not too long ago with this universal pump and the parts guy did not tell me about the fitting plug so I mounted the pump in record time, feeling all good about my acheivement, but when i poured the coolant in, it started running out the back of the pump.
Say what! I said to myself, so I had to r=r the pump again and knock in that little plug.

I had a 13mm bolt left over when I did mine. I'm sorry, I can't remember where it went, but I did dig down and find its home. Good to know I'm not the only one. Seems like maybe it went in the back of the PS pump or tensioner.

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2012 E350
2006 Callaway SC560