VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Water Pump Rebuild

I currently have an aftermarket water pump on my '37 Master coupe. It is starting to drip some water especially just after starting the engine. My plan is to have a rebuilt one ready to install when the leakage gets worse. There are no cooling problems.

I have an original GM water pump with part number 598309 on the casting so I am assuming it is a 598308 pump. Based on my research this pump was introduced sometime during the 1938 model year and replaced both of the pump designs used in 1937. The early '38 pump was the second design '37 pump.

Rebuild kits are available through eBay and I already have the correct offset fan 838936.

-Are there any tricks or "gothca's" to consider when rebuilding the pump? It seems to be a pretty simply process.

-How perfect does the inside surface of the back plate need to be? I was able to remove the 2 countersunk screws and the remove the baffle plate. There is some minor pitting and corrosion on the impeller side of the plate.

-What is different between this pump and the 41-52 pump?

Thanks for the information!

You've asked the perfect question word for word that I've thought about for awhile as I have a couple kits but lucky enough to have some NOS and rebuilt pumps but I just want to know how to rebuild them!

I did read about some people breaking the pump body when pressing the old pieces out as the pump wasn't properly supported. I recently took a bunch of tired 1938 water pumps to Chevs40's as they paid me $75 each for the cores. They will also rebuild your pump, so seeing they sell rebuilt pumps with warranty for $150ish - your time and a rebuild kit eat up that $75 difference quickly. If you have a few old GM pumps you could also "trade" a couple cores for one rebuilt for a spare too and then rebuild one since like me, you like to work on projects like this.

I've also wondered about the 41-52 pumps as they seem very, very common...

Did you ever get any feedback on your waterpump questions?

I keep seeing tons of the 41-52 pumps on ebay and makes me wonder if they could be modified to fit the earlier blocks. I've never had one of the newer ones but suspect there's an obvious difference when sitting in front of you...

I am probably wrong but I think the early pump has only 1 hole towards the block while the later has 2. I have no idea when the change took place.
Tony

Ya, the water holes are different in the backing plate but it looks like the backing plates could simply be switched.

Of course if it was EASILY done, I think we'd have heard about it by now...

I am still trying to identify all the differences between the late 30's sealed bearing water pump and the one that fits all the 40's and into the 50's. I knew that the back plate was difference (one hole versus two holes).

There must be somethings else because the rebuild kits I see (mainly on eBay) are different. And those do not include the backing plate. There might be a difference in the pulleys or shaft diameter. Based on what I see in the Master Parts list they use the same pump body casting.

By the way, my approach might not work as well as I would like. I received the original aftermarket rebuild kit I bought on eBay. All the parts look like they will fit just fine. However the sealed bearings feel "dry" when you spin the shaft. My guess is that the seals have dried up and let the lubricant evaporate/drain out.

The orininal 1937 and 1938 water pumps were different and had an oil cup and bushings. They gave a lot of problems so Chevrolet made a sealed bal bearing pump for replaement. I have never seen a 1937 with an original water pump.


the 1937 and early 1938 pumps were differentt. Shaft length housing and depth of pulley. The seal parts were the same but bushing different.

How have you made out with your waterpump rebuild?

Just for information,

I compared the back of the 37-40 to the 41 and later water pumps. The bolt pattern is narrower on the 37-40.

Best,

Charlie

Thanks for bumping this thread. I have not completed the pump rebuild yet for 2 reasons. Lots of competing projects and the current pump is barely dripping. I do need to get back this so I have a spare.

Dens41 and I talked at our VCCA meeting in July. We agreed to share pictures so we can post some that show the differences between '40 and '41. Charlie is already helping us with that information.

I agree with Gene that the first and second design '37 pumps had oil cups and bushings. The difference between those designs was mainly a 1/2" longer housing and shaft to get more distance between the bushings and allow longer bushings to help reduce the load on the bushings. That also required an offset fan to keep the fan away from the radiator. They were not very reliable. That is the reason Chevy introduced the sealed bearing design in mid-'38.

I cannot find the pump that was on my car when I got it. I know it was a shorter shaft design because it still used the 2 piece flat fan. I do not know if it was a Chevy pump or something aftermarket. There was an aftermarket longer shaft pump with the car and I installed it. That required me to get the offset fan. It does have a grease fitting on it so I expect it is a bushing style pump. That is the pump that is dripping slightly.

Since I had to disassemble my pump because it was leaking, I would like to share the repair with you and thought this would be the right thread, because it is a 1940 Pump. From a Military Car Shop in the Netherlands I got the Bearing (GM-954214) and the Seal (GM-838967).
Enclosed are a few pictures of the disassembly. On one picture you can see the new, shorter bearing shaft, next to the old one. But this should fit anyway, because it looked beyond the pulley anyway. The shafts are from New Departure and have the number 885159 (new) and 885155 (old). Unfortunately I have no new thrust washer and the old one is quite worn out (picture with impeller). But it should work, if I turn the thrust washer around, the surface seems to be still good. What do you think?

Tim,
I don't know whether you have noticed this but the Canadian 216s still had domed pistons in 1940 and 41. It would make sense to me that the change to the newer flat top pistons and the waterpump probably happened at the same time. Therefore I would think that the waterpump changed to the 2 hole version in 1946 for the Canadian engines.