I'm Bummin, 450SL Water Pump - I think

[rzrob]

We'll, it just keeps getting better and better. My beautiful old '76 450SL I recently purchased began puddlin yesterday . Although I don't see anything leaking from the weep hole (if it's on the top of the water pump), I felt under it and it appears to be wet . This is consistent with water I can see on the front of the oil pan and the dripping is coming from the back of the oilpan (when parked in driveway). I didn't seem to feel any leaks at the hoses and when I squeeze the top hose it feels empty if that makes a difference .

So can anyone give me advice? Can I rebuild something here? I can change the Water Pump myself I think. Does anyone suspect I might have misdiagnosed?

Anyone have any insight into changing the water pump? Also, any suggestions on where to get one cheap?

RZ Rob

Replacing the water pump usually requires that you remove the radiator so you will have room to access the pump body bolted to the head and block.

I haven't done this on my SL, so I cant give details. Haines manuals are available from places like AutoZone, etc, and give a detailed how-to.

Yes, it sounds like a water pump leaking. Only other possibility may be hoses, or head gaskets! .......BB

[Chaosmosis]

I just changed my pump on a 1973 450SL, you need to remove the distributer to get at one of the bolts but it only took about an hour and a half. The indy wanted $500 but I did it for around $120.00.

Good Luck!!

[DanielG]

In my 560sl I had a leaky situation that turned out to be the monovalve -- next to the firewall on the passenger side.

[Mr. Elbe]

Replacing the water pump is a fairly easy job. No need to remove radiator or A/C condenser. Just carefully remove the plastic fan shroud after removing belts from water pump.
I got my replacement water pump at CarQuest. They shipped it overnight from Philadelphia and it was about CAD$ 130.00

[rzrob]

It was the water pump on my '76 450SL. I didn't have to remove the dizzy or the rad, but I did end up needing a new fan clutch. And, who wouldn't change the belts and hoses (and let's not forget the distilled water and antifreeze) Geez. It wasn't a fun job, but possible.

Although there's a weep hole on the top of the WP, there's another on the bottom. The culprit.

I pressure washed the motor before I started and made sure the car ran fine.

I flushed the system, then drained it all and cleaned it good.

I covered the fenders with pieces of shag carpet upside down. Not the best choice, but available and better than nothing.

I took the upper and lower hoses off, undid the 4 fan bolts, and the shroud and removed both. It was at this time that I noticed that the fan clutch, while basically working, the seal was hanging free around it, and the bearing had serious play.

I removed all the belts by loosening the adjustment clamps on each assembly (2 minutes total) except for the matched set which came off with the fanclutch

Using a 7mm small wrench, I painstakingly loosened the bypass [factory] hose clamps. Good light helps.

Using a 13mm socket and a 6" extension I removed the bolts around the perimiter and the one on top holding the dipstick. There's like 7 of them (most not easily visible and very close together). I had to rotate the flywheel to get the bottom 2.

I changed the thermostat over to the new waterpump while it was out, and using a 10mm wrench I took off the other water outlet.

Then I put it all back together using some GE Hightemp along the way.

I drove the car for 2 days to make sure all was tight. Then, I drained everything and replaced with distilled water (~2 gallons) and antifreeze (1 gal).

GMB Water pump - $100
BEHR Fanclutch - $192
Belts - ~$55 Dayco TopCog
Hoses - ~$65 All German repro's except the larger bypass which is Gates off the shelf (it's in the Gates catalog) like 42mm or so, cut to fit (less than 3").

I have the satisfaction of knowing I did it myself.