Pontiac Water Pumps
Arn Landvoigt and I have been working on this article for the past 3 months, and I believe we have learned enough to publish it and get feedback from you on anything that does not ring true. We have had water pump questions in the past and thought it would be helpful to do a comprehensive outline on the subject. We relied heavily on several Pontiac parts books and service bulletins for the information needed, which we cross checked as much as possible. There is conflicting information from factory sources, so our goal is to provide you with as much information as possible and let you apply it to your specific application or situation.
The subject of water pumps is confusing for a number of reasons; not surprising considering the Early Times era covers so many years. We have to contend with the fact that both the factory and aftermarket suppliers provided water pumps for Pontiac automobiles. There is the issue of advancing technology and improved manufacturing techniques, and also the variable of factory service procedures versus how an independent garage would make repairs. A final factor which is often overlooked is the cost in parts and labor of repairing / rebuilding an original unit versus replacing it with a complete new or factory rebuilt assembly.
Basic Designs during the Early Times era
Pontiac water pumps from 1926 through 1936 varied in many aspects but all shared 2 basic features; the shaft ran on bushings and was sealed with packing material retained by an adjustable packing (gland) nut. In 1937 a hybrid water pump was released, it was fitted with a front roller bearing instead of a bushing, but the rear bushing was retained and so was the use of the “packed” seal. In 1938 the water pump was a totally new design using a double ball-bearing assembly to support the shaft, plus a new seal assembly which utilized a spring-loaded carbon seal and secondary rubber shield. This type of pump remained in service through the end of the Early Times era for both six and eight cylinder engines. We have broken down the subject into groups which appear to make the most sense to us, hopefully it will to you too.
First generation pumps
For 1932 and older split-head six models and also the ’32 V-8, Pontiac offered service parts to repair the original water pump as needed. Labor cost was low in relation to parts prices, so naturally repair would be preferred to replacement. Every part of the water pump assembly was available individually, so only those parts needing replacement could be changed. According to the parts information included with this article, there were 5 pump body castings for the split-head six, but only 1 pump to block gasket and 1 each, front and rear bushings; so the differences must have been very subtle. These early “packed” type water pumps are readily identifiable by the packing nut threaded into the end of the housing, through which the shaft protrudes. The other visible clue is the oilers by which the front and rear bushings are lubricated.
Second generation pumps
The straight eight debuted in 1933, the new engine’s water pump retained a packed-type seal and a bushed shaft. The new six cylinder engine was released in 1935 and used the same water pump as the eight cylinder job, a savings for everyone concerned. These early six and eight cylinder engines are visually identifiable by the location of the water pump body, which is even with the top of the cylinder head. This basic water pump design continued through the end of 1936. Pontiac offered individual service parts, just as they had for the first generation pumps; but by 1940 at the latest, they also offered an updated service replacement pump. This complete assembly featured the sealed ball-bearing and carbon seal. The other implication of this service replacement unit was that the O.E. style pump body would no longer be serviced; if it was damaged beyond use the service replacement was to be installed. This obviously means that ’33 to ’36 Pontiac six and eight cylinder cars can now be fitted with either the original equipment “packed” pump or the replacement “packless” one.
In 1937 Pontiac cast a new pump body and relocated it on the front of the engine, visually the pump now stood above the cylinder head nearly 2 inches. This was the roller bearing pump I mentioned under Basic Designs. What we have not found yet, is information indicating how long it remained in production. Service parts were available for the roller bearing pump and a quick check shows most of them fit the ’33-’36 pump as well.
The bulletins that follow are both dated October 28th, 1936, fairly early in the ‘37 model year. I checked the engine numbers, over 28,000 sixes and just 1,300 eights were built prior to the problem discussed in the second bulletin.
PS 112, No. 13, October 28, 1936
Leaking Water Pump – 1937 pg.91
“When a leak past the water pump packing on 1937 cars cannot be stopped by tightening the packing nut or replacing the water pump packing, a new Water Pump Assembly Part 499881 should be installed. This part should be ordered direct from your Zone Service Manager.”
PS 112, No. 13, October 28, 1936
Notching Rear Oiler on Water Pump pg.92
“It has been found that the cap on the rear oiler of the water pump, under some conditions, seals the oiler air tight which prevents the oil from entering the bushing. Starting with engine 6-228874 and 8-84301 a small notch is being cut in the rim of the cup which breaks the air tight seal. All 1936 cars having the large oiler at the rear bushing and all 1937 cars bearing an engine number lower than the about should have a small notch cut in the rim of the cup as these cars come in for service.”
The first bulletin states “a new Water Pump Assembly Part 499881” but does not describe any of its features. Presumably any new water pump design underwent a period of extensive testing prior to being approved for production; this bulletin implies to me that one of these new pumps could be made available due to the extenuating circumstance listed. The second bulletin confirms what we already knew; the early ’37 pump was the old fashioned packed-type unit.
In addition to the service parts for the original equipment 1937 pump, there was a service replacement listed under part number 500804 for the 1937 model year only. This was actually a “package” which also included a new fan. I suspect there was probably a new pulley as well, but I cannot prove that. The 500804 package remained available under its original part number through 1954 at least. Playing the part number game, you will notice that the service bulletin water pump is #499881 and the service replacement package is #500804. This helps us date the second pump package, part numbers were assigned in numerical order and only 923 separate them.
Third generation pumps
In 1938 the location remained the same, but the pump was redesigned as already described with a sealed ball-bearing and carbon seal assembly. Although there were numerous subtle changes and various service parts listed for use; it remained essentially unchanged through 1948 with 1 notable exception. The 1939/40 six cylinder engines used a unique water pump. This was due to the fact that either engine was available in the Deluxe Series 26 or 28 models riding on the same 120” wheelbase. Prior to this, the six cylinder models were always shorter from the cowl forward, maintaining the relationship between fan and radiator with the shorter six cylinder engine.
In 1941, with the advent of the “engine option”, Pontiac mated fan shrouds with the six and eight cylinder engines, thus eliminating the fan clearance issue regardless of which Series car the engine was installed in. CLICK TO CONTINUE