I am rebuilding the water pump on my D2. 4U 6123 d311 engine. I replaced the bearings and seals in the front and installed a new ceramic type seal for the coolant. I got a new impeller for it because I broke it when I was pulling it off the shaft. The original set up has the seal riding on the impeller. The seal I have now has a polished washer and rubber sleeve that would go in front of the impeller. Question is, is there enough room to install the washer or should the seal run on the impeller like original?

The new impeller should have a ceramic washer on it which the the new seal should ride on. Also make sure there is a relief valve 6U1989 [4B4550 former#] in the pump housing, NOT two grease fittings.

Just an F.Y.I, when I rebuilt the one on my D2 5U I tapped the fan blade back on the shaft using an oversize socket and a hammer. Not a good choice because I ruined the new seal. So I just worked it back on the shaft by putting the proper size socket and ratchet on it and turned it. I was so proud of myself....... until I put coolant back in the radiator and watched it hit the ground. Just trying to save somebody some time and $

It takes a real person to admit they boo booed. Glad you chimed in, and I am glad you shared, as it is better to learn from others most of the time!
Yes, hopefully others can learn from your unfortunate incident. JM

NOT two grease fittings? Mine came with two grease fittings installed and is still that way. I had wondered about that. Which hole is supposed to be used for a grease fitting and which is supposed to be open? (D2 5U engine made up of pieces from salvage yard.)

The relief valve looks like a grease fitting that is short, or has been cut or broken off, and is commonly mistakenly replaced with a grease fitting. The relief valve is the top fitting.

I received my new impeller finally. It had a hardened washer made onto the front of the impeller just like original. Thanks for the heads up on the relief valve, when I tore it down I figured it out, mine don't look like it could have done much reliving though. The port was full of hard black grease. Here is a good one for you, make sure yo dig that washer out that is in the impeller or it will come out in about three pieces! mine had so much crud in there that looked like it was part of the impeller.

Thats what happens when it gets over greased and doesn't have a relief valve, it pushes past the seal and fills the hub with grease.