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With all the hubbub lately regarding the different styles of water pumps and heater coolant flow, I decided to take an old water pump that I had and do a little research.

Here's what I've been able to confirm;

The heater port at the top of the water pump IS connected into the inlet side of the pump and as such would be the return for the heater. This is what I suspected, but I didn't want to stick my nose into that argument until I had proof.

PB050359.jpg

Also, in regards to the by-pass setups. The pump pictured is the one that came on my engine and has been replaced because it leaked. There was no core charge so I kept it. Anyway, the small hole just above the "D" shaped port (which goes into the water distribution tube) is the by-pass port. It is lined up with a port in the block which goes directly up into the water jacket in the head. (I remember checking that out when I had the engine apart) This port, in the pump, is also connected into the inlet side of the pump. This also confirms theories that the bypass allows some coolant to 'by-pass' the thermostat back to the inlet of the pump to help eliminate hot spots before the thermostat opens by allowing some coolant to flow.

PB050362.jpg

What still confuses me is why some engines have an external setup and some are internal. I was under the assumption that it was a change in a given year of manufacture. However, my 1950 B2C T172 engine has the internal by-pass as does the the engine in my '50 B2C parts truck. Now, recently I acquired an engine from a '51 B3C (T306 engine). It has the external by-pass setup. :confused:

PB050365.jpg

And my B2 Series shop manual only references the external by-pass in any pictures I can find. Here is a scan from my manual showing a cutaway drawing. If you look closely at the thermostat area, you can see that the by-pass is ported in below the actual thermostat and goes over into the inlet side of the water pump. Also, in the previous picture, you can see the heater return connection is connected into the by-pass elbow.

SDOC37072.jpg

Take this for what you will. I just needed to do this to appease my curious mind and thought I'd share it with the rest of you.

Merle

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Merle I think the earlier external water pumps do not have the hole in your second picture. Now my question is there is one water pump that napa sells that has both sets on top to put either an external or internal heater hose piece on it. So how does that one work?

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That I don't know. I got my new pump from Checker. It was exactly like the one pictured. I did have to go to a '51 or newer listing to find it. The ones pictured, in their catalog, for a '50 appeared to have the external porting. When we looked up a pump for a '51 it looked like mine, so that's the one I ordered.

This is what had always confirmed my theory about a model year change in manufacturing. Also with dealings with our good friend, Mr. Bernbaum, he made it very clear to me that my engine couldn't be a 1950 and have internal bypass. Apparently I didn't know what I was looking at, according to him. He was addament that the internal by-pass didn't start until 1951. But I have 2 1950 engines with internal by-pass and now a 1951 engine with external bypass. Go figure...

I suppose if you could connect the by-pass elbow into the heater port on my pump, and the gasket would block the small port on the back, it could be made to work on an external by-pass engine.

Merle

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I did a little research on Napaonline. It looks like their water pump may dual purpose. The same pump is listed from '48 - 53. (I didn't go beyond that) From the pictures it looks like it has the right top flange for the external setup. It also looks like it has a heater return port below the radiator hose inlet. Interesting...

112603.jpg

112604.jpg

This is water part # NWP55713 which lists at $71.49

They also show a part # TFW42554 for $59.29 but there's no pictures for that one.

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--snip--

This also confirms theories that the bypass allows some coolant to 'by-pass' the thermostat back to the inlet of the pump to help eliminate hot spots before the thermostat opens by allowing some coolant to flow.

--Snip--

Merle

If there is no bypass then there will be no coolant flow at all until the thermostat opens.

The thermostat is located at a point on the block that is relatively cool. So without a bypass to move coolant through (external bypass) or near (internal bypass) the thermostat will be cooler than the rest of the engine and it will not open until the back of the block is warmer than desired.

For what it is worth, the Plymouth L-6 engine originally came with an internal bypass system. The external bypass was introduced 1934 on the DeLuxe models. I believe that for a number of years the DeLuxe had the external bypass and the Standard or Road King had internal bypass.

One advantage of the external bypass is that the bypass is shut off when the engine warms up so all water goes through the radiator. On an internal bypass setup some water is always recirculated without being cooled. Based on the fact that they dropped the external bypass, I'd guess that the difference in cooling was not all that great while the slight increase in complexity and the failure modes if a clueless mechanic left out the thermostat dictated against the external bypass.

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Merle thats the one I was talking about. Pretty sure thats the one I have on both of my externally bypassed engines. So no bypass is bad-what about dual?

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I'd still like to hear Tod's opinion, but I would think the plug wasn't tight enough in the first place if water jacket pressure was able to push it out. Although I have no idea what kind of pressure one would find inside the block.

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Just to add my 2¢...I've had a few folks ask me about the differences between the internal & external bypass blocks/heads and water pump applications, specifically when installing the newer NAPA water pump which can work with either setup.  While going through some boxes of parts I've acquired recently, I found an external bypass water pump with an internal bypass backing plate, as well as a newer NAPA water pump (pictured on the right).  The external bypass pump casting does not allow coolant flow through the internal bypass backing plate, and drilling through this area of the casting can be difficult without cracking the rest of the casting.  Also shown in this pic is a '50 218 without internal bypass; the location of the internal bypass port would be in the area pointed to in this pic, and a sharp eye may notice that an internal bypass water pump & head gasket have been mounted to this external bypass block.

post-2888-0-70464600-1377370461_thumb.jpgpost-2888-0-63274500-1377371728_thumb.jpg

 

The red block pictured is a '54 230 with the internal bypass.  The bypass passage is pointed out in the block & the head; the 'hump' in the head can be seen as well.

post-2888-0-99968800-1377370496_thumb.jpgpost-2888-0-34353900-1377370524_thumb.jpgpost-2888-0-73625600-1377370546_thumb.jpg

 

The assembled engine is a '52 218 with the internal bypass head and thermostat housing (water neck).  The fewer parts required made for a more economical assembly; with one less hose to leak, it also is a more reliable assembly.

post-2888-0-21390700-1377370570_thumb.jpg

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To muddy up the water a li'l bit, confusion as to how to assemble these flatheads has been going on for awhile...when I rebuilt the 218 in the '48, I assumed it was the original engine, as the truck had been in the family since new & no one recalled it ever being worked on.  After rebuilding the motor, the internet told me otherwise:  I was able to locate the casting date, and the 'original' motor turned out to be from a '55 Plymouth.  This 218 has the internal bypass, a NAPA water pump, and an external bypass thermostat housing.  I snagged a '50 Plymouth 218 with the external bypass block, but it has an internal bypass thermostat housing.  When I rebuilt the '49 230, the gasket set I used had all the internal bypass gaskets, which fit & don't leak (the rear main seals are different, but that's another story).  So the internal bypass gaskets supplied with the NAPA water pump will work on external bypass engine blocks because the openings in the gaskets for the internal bypass are sealed over with solid metal on the block.

post-2888-0-05424400-1377373227_thumb.jpgpost-2888-0-63147100-1377373244_thumb.jpgpost-2888-0-25527000-1377373264_thumb.jpg

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All that having been said I have a question: does it take special tools to rebuild a water pump. I have two cores, would like to rebuild both of them.

 

My engine has an external water pump. I didn't catch that until the gasket leaked, then I had to get a different head, so now I have two internal heads, both squared and hardly used.  DETAILS are in the DEVIL.

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pumps are precision machines, and once they start to wear, their efficiency drops, they become less effective, and eventually they just wear out to the point where replacing seals, pump impellers, bearings etc. are ineffective because the casting and/or the backing plate are out of tolerance for the pump impeller to work properly.  They sold water pump rebuild kits in the past because the seals would blow out, the impellers would corrode from non-glycol based coolant, and bearings would wear out.  But eventually water pump designs changed to where they were more precise castings & machined parts, so rebuilding the pump from a kit might not improve the effectiveness of the pump.  That's when they started to just replace the water pump as a unit, because the special tools required were for measurement; if certain areas were out of tolerance, the casting and/or impeller were to be replaced, and then it was just cheaper to recycle the old pump & replace it with new.  I reckon some places rebuild water pumps, but they know what to measure and how to take those measurements.  Rebuilding those core units might not yield the results ya want if them castings are corroded enough.


 


When I first heard about the NAPA dual application pump, I was interested because they had eliminated the grease fitting and routed coolant through the casting to be used as a lubricant.  This meant the bearings would be lubricated as long as there was coolant going through the water pump, so ya never had to worry about them drying up & shelling out or being over-greased & blowing out a seal.  The integral heater port is nice, too.


 


I have seen what a failing water pump can do to the radiator & sheet metal of a truck, and back in '88, had to walk 15 miles through ranch country to town for help because of a bad one.  The water pump had been leaking in the Suburban, eventually the bearings failed on a lightly trafficked highway one evening, causing the fan to vibrate wildly & eventually fly apart, spinning shrapnel through hoses, radiator cores & tanks, and sheet metal...very expensive repair.  And that was on a truck that was less than 5 yrs old at the time...I wouldn't trust an old water pump, even if it was rebuilt, because of the mess it might make.  The NAPA water pumps might cost more, but it's like buying peace-of-mind :cool: 


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DETAILS are VERY IMPORTANT! No such thing as an external  or internal water pump. You may have an external or internal coolant by-pass system. But the water pump is still just a water pump. Pay attention to details and use the correct termonology. Your mentor Plymouthy need to give you more training. 

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I stand corrected. The head did not match the block, that corrected, I put the water pump I had removed back on. 

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PB050359.jpg

.

Merle

 

 

DETAILS are VERY IMPORTANT! No such thing as an external  or internal water pump. You may have an external or internal coolant by-pass system. But the water pump is still just a water pump. Pay attention to details and use the correct termonology. Your mentor Plymouthy need to give you more training. 

 

Not 100% true. See the picture posted by Merle. This is internal bypass only. However just to simplify production all modern replacements will do either.

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DETAILS are VERY IMPORTANT! No such thing as an external  or internal water pump. You may have an external or internal coolant by-pass system. But the water pump is still just a water pump. Pay attention to details and use the correct termonology. Your mentor Plymouthy need to give you more training. 

 

 

gee Don...just when did I become responsible for everything....lol   Left up to me I would be confiscating some car keys...

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gee Don...just when did I become responsible for everything....lol   Left up to me I would be confiscating some car keys...

 

Quess I'll be seeing Tim soon to get my keys,! :eek:

Let me know when Tim.

Make sure to get both sets! ;)

 

Doug

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I'm glad I stumbled onto this thread.  I pulled my water pump a couple days ago and was planning to have it rebuilt.  I didn't know about the internal vs. external bypass issue.  My existing pump must be a Napa-type replacement as it is set up for both, even though the block does not allow the internal bypass.  I'm just going to get a Napa replacement now.  It's a little cheaper than rebuilding, more convenient to pick up, and I don't have an original one in any event.

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WOW, this is an old thread. Good to see it's still interesting to everyone.

 

Regarding rebuilding vrs. buying new... The pump pictured in post #1 was on my engine when I overhauled it. I got a water pump rebuilt kit from Bernbaum and rebuilt the pump. It didn't really take any special tools, but I did have a problem with the bushing. I didn't notice the roll pin that held it in place. When I drove the bushing out of the housing, it broke the housing where the roll pin went through. It wasn't that big of a problem. I just drilled another hole, in another place, for the new roll pin. As I recall, the kit came with a new impeller shaft, bushings, and seals. Once completed it all seemed to work fine, but it leaked out of the shaft seal once the system built up a little bit of pressure. Then it started to drip all of the time. So I ended up buying a new pump and it's been leak free ever since. In retrospect, the pump rebuild was a waste of time and money. The only value I got out of it was the learning experience. ;)

 

Merle

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Finding old threads has not been easy for me......seems I have to stumble across it them in a search. 

 

This really is a great thread Merle. And great pics JBN. ^_^

 

 

I mean without this thread...the water pump that was laying in the oil pan of a motor I bought....I would have thought in was an internal water pump, and just left it there..... :rolleyes:

 

48D

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I just tried to get a new NAPA water pump (TFW 42554) but they are no longer available.  They were able to order me a remanufactured one.

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Availability has been an ongoing issue with the NAPA water pump.  I had found out about these water pumps from the article written on Moparforum and I reckon Airtex has a run of new pumps every few years or so when they feel they can maximize profit on them.  I'm just glad they are still available :cool:

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I once read an article on rebuilder of this type stuff.  They wait till they get X cores stock piled and run them through in a batch.  This would also support Merle point that they would do this as the market allows.  Returned cores mean x products have moved from the shelves indicating that the market is now ready for new units.  To change over a production line form one model to the next to rebuild these take time and of course source of rebuild parts on hand to produce X amount up front.  This even holds true for companies that remanufacture larger items like engines and transmissions

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