....it is making all kinds of noise and there's spray everywhere. I bought a thermostat today. I might as well change that too.
I guess I shouldn't drive her, right? It sounds like grinding metal.

__________________

1976 280C
SLOWER DRIVERS KEEP TO THE RIGHT.
DRIVE RIGHT PASS LEFT

It's hard to tell if you're being facetious or not...

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Since you have to change the water pump, you might as well change the front crank seal as the vibration damper on the M110 has to be removed anyway to remove the water pump (balancing disc behind the damper to be removed for seal removal). And since you're back there with the pump removed, this is also a good time to change the short hose between the thermostat housing and lower radiator hose pipe. And of course the only practical way to change this hose is to remove the thermostat housing.

__________________

Don't Chrome them; polish them

Are you sure the vibration damper has to be removed? I gave it a glance and it looks like the only thing in front of the WP is the fan/clutch assembly.

__________________

1976 280C
SLOWER DRIVERS KEEP TO THE RIGHT.
DRIVE RIGHT PASS LEFT

The bottom WP bolt (possibly 2) cannot be removed without the vibration damper being removed first. It also disallows enough space to remove the bottom lip of the WP. You also need adequate space to clean the mating surface behind the WP. The damper is simple to remove, the balance disc - if you replace the crank seal - is more work.

__________________

Don't Chrome them; polish them

He's giving you the straight poop regarding the lower bolt. Oddly enough, on the 280S M110'd models there is an access hole in the dampener which allows you to remove the lower pump bolts. Beats me why, only Mother Benz knows.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

If the front seal is not leaking, only the damper disc need be removed (six socket head bolts). The front crank hub/balancing disc can stay on the crank.

Use new bolts and torque them to spec. Otherwise they can crack.

And... I once had a Mercedes dealer mechanic tell me that Mercedes of that vintage could run about 300 miles on a leaking water pump. This is because in some parts of the world you might be that far away from a shop.

OK, that's great. But I am guessing you are not that far away from a parts source. I would fix it asap or it might tear up the water pump housing. (I am just guessing that the M110 has a housing. It seems like all Mercedes engine from that time do.)

OK, I listened to the wisdom of the listers and I bought the seal just in case.

Thank all of you for all the input.

__________________

1976 280C
SLOWER DRIVERS KEEP TO THE RIGHT.
DRIVE RIGHT PASS LEFT

I've seen fans go through radiators when the pump shaft breaks, makes a real mess, don't drive it.

She's been sitting. I am tackling it this morning Saturday 6/2

__________________

1976 280C
SLOWER DRIVERS KEEP TO THE RIGHT.
DRIVE RIGHT PASS LEFT

The pump was toast, it wobbled all over the place and even outside the car it made a scrubbing sound.
Do yourself a favor, order the small engine shock and while you're in there replace it. It is so visible and easy. The upper bolt on mine was gone so the shock was loose. I already had mine from when I had the engine mounts (which I haven't tackled yet).
The hardest part for me was getting the radiator off, it just wouldn't budge. Many sprays of lubricant later it finally slid from one side and then the other.
Upon tightening the WP, the uppermost bolt broke. I was using the small 1/4 inch drive and wasn't torquing that hard.
I think that ordering the five bolts and replacing them on a 42 year old WP wouldn't be a bad idea. I am running it without that bolt to see what happens; if it leaks, I'll have to dismantle and get that bolt out. If not, I'm letting it ride.

Thank you all for the input.

__________________

1976 280C
SLOWER DRIVERS KEEP TO THE RIGHT.
DRIVE RIGHT PASS LEFT

Just pop over to the nearest Ace Hardware. They have the bolts. Yup, if one broke then they are all suspect. Ain't that fan clutch fun! The sadistic bastid who came up with THAT configuration has a special place in my version of Hell.

Might be a good idea to pick up a tap and clean the threads whilst you are this far into it. Use a Never-Seez type of product on the threads NOT a Teflon tape or a thread locker sealant.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

How do I get the bolt out of the motor?
The head broke off and the remainder stayed in there. I would have to disassemble all of it again. After I do that then there's the broken bolt.

__________________

1976 280C
SLOWER DRIVERS KEEP TO THE RIGHT.
DRIVE RIGHT PASS LEFT

You MIGHT get lucky and enough of the bolt is protruding to grab with a pair of small needle nosed pliers. If not, then yes, disassembly is the option.

At least not only are you experienced in the process but all the bolts have been loosened. Replace ALL the water pump mounting bolts. I prefer using an Allen head bolt/screw in these areas. Personal preference but I think it gives me a better "feel" as to the amount of torque I am applying.

If the bolt is broken flush with the housing, it's a bit trickier. If this is the case, considering your skill level (no offense), remove the housing (now is a good time to replace the short bit of hose between the housing and the lower hose inlet) and take it to a machine shop if you don't feel confident with using an Easy-Out.

As my old Grand-pop used to tell me, "If it were easy, ANYBODY could do it".

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now