water pump question.........

[Chris in Jax]

thanks for the photos, Jim, especially the service manual page. it clears everything up.

my Napa pump has all 3 holes. seems like I'll be OK with it, especially if I keep the by-pass type thermostat housing on this engine, which I need to do anyhow for a more authenitic appearance......

next time I drive the car I'll double check with my infrared imaging camera for hot spots on block & head but I don't expect to find any......

[Ed_Ungerman]

I've got a '50 (P20) engine in my '37. I had to replace the water pump when I first got the car. I got a '51 pump from NAPA and all I had to do (actually the repair shop) was take a plate off the '50 pump and put it on the '51 pump. Think this is from the site you mentioned.

You can use the NON by-pass pumps backing plate on a by-pass type to eliminate the internal by-pass. This is recommended if you replace a NON bypass pump with a by-pass type and you develop a leak between the block and the pump. I have never had that happen, but it is described that way in repair manuals.

[JimCno]

Here is a picture of a water pump with an internal bypass. If it did not have an internal bypass, it would not have that 1/4" hole that lines up with the large round hole in the block.

This shows the difference between the two systems. As I said before, you need to have one bypass system working, I'm not sure if it is a problem to be running both systems. Don't forget to match your thermostat to your thermostat housing (by-pass or choke).

Hope this clears things up.

[JimCno]

Chris,

I'm sorry, I think I have it all mixed up. Let me go get my spare water pump, take a picture and try to get it all straight. The 1/4" hole in the back of your pump, where the large hole is in the block IS the internal bypass hole. I had a brain freeze.

"you can use an INTERNAL by-pass type water pump on an EXTERNAL type engine, but you CANNOT use a NON by-pass (or EXTERNAL by-pass) pump on an INTERNAL by-pass type engine."

If that is not what I said, it is what I meant to say.

The deal is, as I understand it, if you put an internal bypass pump on a block without the internal bypass, as long as you have the external bypass thermostat housing, everything is fine. The hole in the back of the pump is not doing anything. The problem is if you put an older pump, with no internal bypass on a block with an internal bypass and no external bypass. There needs to be some type of bypass, one way or another. There is also the question of choke or non choke thermostat.

Tell you what, until I can get some pictures and get things straight in my own mind, check out these old tech manuals: http://www.imperialclub.com/Repair/Lit/Master/013/Page01.htm
http://www.imperialclub.com/Repair/Lit/Master/040/Page24.htm

They can expalin things better than I can. BTW, that picture is of a '57 - 230 ci Plymouth engine. I'll try to take those pictures and get them posted sometime this weekend.

[Chris in Jax]

what year is the engine in your photo?

[Chris in Jax]

You can use either pump on your engine.

Dave-? according to Wojciechowski,? ?"you can use an INTERNAL by-pass type water pump on an EXTERNAL type engine, but you CANNOT use a NON by-pass (or EXTERNAL by-pass) pump on an INTERNAL by-pass type engine."? he claims it will spot overheat & burn valves.? ?why the difference of opinion?? not trying to be a wiseguy, just trying to sort this out accurately..... I wonder if I have a external bypass pump on the internal bypass engine??  -Chris

[Chris in Jax]

do not know what my block looks like- have not needed to remove the water pump yet.

my spare water pump has holes #2 & 3 but not the big hole. there is a small (1/4") hole in that general location. what exactly do I have here?

since it is a '53 engine, it must be internal bypass, but there is a small hose from the thermostat housing to the little casting atop the water pump. did they retain the '37 thermostat housing & water pump when swapping to the '53 engine?? is this a problem?

trying to determine the source of borderline overheating- it runs about 200+ degrees in summer (without thermostat) but has never boiled over.? an infrared scan of the radiator shows very uniform temperature, no cool spots to indicate clogging.?

[JimCno]

As you are looking at the block,the large circle on the right is the inlet, the elongated hole to the left is the outlet to the water distribution tube, and the small round hole to the upper left is the internal bypass hole. If your water pump has that third hole it is an internal bypass pump. You can use the internal bypass pump on the non internal bypass block, but you can't use the non internal bypass pump on the internal bypass block.

My engine has the internal bypass block and pump but has an external bypass thermostat housing so I put a rubber stopper in the external bypass hose and use a choke thermostat. Seems to be working fine, though I haven't driven it in hot weather yet.

[David Pollock]

You can use either pump on your engine.

[Chris in Jax]

my eternal quest for knowledge led me to the MoPar forum, where Neil Wojciechowski has information regarding by-pass vs. non-by-pass water pumps.? unfortunately the photos he downloaded to show the difference do not open up (just the little red X in a square).? anyone out there have photos of the 2 types of pumps or is there another way to determine which is which?
since my '37 P4 has a '53 Dodge engine, I wonder if my spare water pump (NAPA 55-713) is the correct one.......