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1942 heater hot water plumbing

Started by gary griffin, June 01, 2015, 11:48:19 PM

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gary griffin


I recently found a picture of a 1942-6719 Cadillac engine compartment and there appears to be a cross over pipe for the heater water to cross the engine block ahead of the exhaust crossover pipe. In my parts boxes I have an approximately 20 inch piece of brass tubing with two mounting brackets. I have been told this is for the heater crossover from the boss in the drivers side head to the heater on the passenger side. I know my car has had an engine change and is not original and I have been studying diagrams of the water flow. It appears that the heater water supply comes from the tap at the rear of the drivers side head. If this is so where does the sensor for the temperature gauge go? Also I have seen diagrams showing the heater water going down through the defroster. This is against everything I know about hot water heating as the air would be trying to go down through the defroster. Are there any accurate drawings of this area to clarify this?
Gary Griffin

1940 LaSalle 5029 4 door convertible sedan
1942 Cadillac 6719 restoration almost complete?
1957 Cadillac 60-special (Needs a little TLC)
2013 Cadillac XTS daily driver

Jeff Hansen

Gary,

The only place I know of that you would find a factory drawing of the heater hose routing for the Automatic Heating System (AHS) would be with the installation instructions that come with it when it was ordered from the factory via the Parts Department. 

Your description of the water routing seems correct to me.  The takeoff is to the rear of the driver's side head.  There is a bung above and between cylinders 6 and 8.  A short section of heater hose will connect from the bung to one end of the brass pipe (the temp gauge sensor is on the driver's side head above and to the right of cylinder 8 - see attached photo).  The pipe runs between the exhaust manifold crossover and the distributor to the other side of the engine.  The pipe is held in place by the brackets (sheet metal loops) which are connected to the rear bolt on each end of the exhaust crossover.  Another section of heater hose will then connect the other end of the brass pipe to the LOWER connection on the defroster.  More heater hose takes the water from the UPPER defroster connection down under the car to the underseat heaters in series and finally forward to a connection on the side of the water pump.

After typing all of that, I found a section in the January 1947 issue of The Serviceman which talks about the path of water circulation in the AHS.  See other attached photo.

Hope this helps you!
Jeff
Jeff Hansen
1941 6019S Sixty Special
1942 7533 Imperial Sedan

Bill Ingler #7799

#2
Gary: In addition to what Jeff has said,here are three pictures which might  also help you in the routing of the hot water heating. The pictures are from my 47 but I believe they also apply to the automated system used in the 42-47. Hot water leaves the rear of the left head by rubber hose,then connects to a pipe that crosses over the back of the engine. The cross over pipe is held by two clips attached under the rear exhaust bolts for the cross over exhaust pipe. That 1st picture also shows the temp sender in the left head just back of the outlet for the hot water. 2nd picture shows the hot water entering the defroster through the lower inlet connection of the defroster. The hot water then comes out the top connection of the defroster and goes down and back on the frame, crosses over to the left heater, then across to the right heater and back on top of the right frame rail to the water pump as shown in picture 3.  Hope this helps    Bill

gary griffin

#3
A hearty thank you is due to both Jeff and Bill.  Now I know the problem. I have a 2006 letter from the GM Heritage center, handwritten by  Mr, Matt Larson (who is lifetime member number 202 of this club) stating that my engine was originally in a 1941 -  6219.   I am guessing that the crossover pipe was a new development for 1942 because the drivers side head in my car has no second bung. I will go forward using a tee to install the piping and temperature sensor and try to find a correct head with a second bung as shown in the drawings you gentlemen provided.  A small item but hopefully something I can correct prior to Las Vegas 2016.  My car was owned by the military during the war and I had (Can not find now) a document that said the 1941 engine came from the east coast.; I doubt a later owner would buy an engine form the east coast and send it to Utah so my guess is that the military did the swap?

I just checked and the pipe that I found is straight and has the brackets along with a sort of flare on each end so the hose will be secure. The brass pipe I found was in a crate with numerous other old parts, mostly worthless.  I am guessing that the straight crossover pipe was an early version and was later replaced with the pipe with curves on both ends as shown in the pictures above?
Gary Griffin

1940 LaSalle 5029 4 door convertible sedan
1942 Cadillac 6719 restoration almost complete?
1957 Cadillac 60-special (Needs a little TLC)
2013 Cadillac XTS daily driver

TMoore - NTCLC

The crossover on mine is straight - no curve - with a slight nipple at each end for the hose.  I think you have found the right piece.

And, both Jeff an Bill have concurred your previous mention that the inlet to the defroster core should be at the BOTTOM, and the outlet on top (as you say, to prevent any air trap).

Finding a late model head should be no problem, but if I were you, I would really be disappointed about having to open up a freshly rebuilt engine!

Jeff Hansen

From what I've been able to tell, the straight brass crossover tube was a '42 only thing.  The curved pipe in Bill's photos was used starting in '46 I believe.  If anyone has an original '46 with the Automatic Heating System, I would like to know which style of pipe you have.

Gary and Todd, from the way you both describe the pipe with the sort of flare at both ends, that tells me you have the correct piece in hand.

Thanks,
Jeff
Jeff Hansen
1941 6019S Sixty Special
1942 7533 Imperial Sedan

gary griffin

#6
I talked to Eddie Jones today and he figures he has a head that will work. I do not like opening up my engine and will probably jury rig the crossover by using a tee on the drivers side for the heater pipe and the heat sensor.  I will have it machined and cleaned and painted and change it out before Las Vegas next year. No hurry.

I wish I could add pictures with my camera phone like I can on other websites. Maybe somebody should look into this?

I can post a picture on facebook or eBay in seconds  but not this site?
Gary Griffin

1940 LaSalle 5029 4 door convertible sedan
1942 Cadillac 6719 restoration almost complete?
1957 Cadillac 60-special (Needs a little TLC)
2013 Cadillac XTS daily driver