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Cooling System Service
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  Cooling System Preparation and Inspection

  Ideally, if your Pontiac has been restored, than by definition, the entire vehicle was returned to “as new” condition.  Unfortunately the term “restored” is used indiscriminately and all too often the results are less then thorough or satisfactory.
  We are going to assume for the purposes of this section, that your Pontiac was adequately restored at some time in the past, or is a reasonably well maintained survivor.  That is to say; you are not aware of any persistent problem with your car.
  You should be using a 50-50 mixture of ethylene glycol (conventional green) anti-freeze and plain water.  This is essential to inhibit rust and corrosion, in addition to raising the boiling point above that of plain water.  Since “anti-freeze” has many desirable qualities and we should use it year around, lets call it coolant.  Coolant, like motor oil, has an “additive package” blended in when it is made; these additives included anti-foaming agents, corrosion inhibitors, acid neutralizers and a “wetting” agent to break down the surface tension of water.  These additives are designed to last for the recommended life of the coolant; which is almost universally 2 years.  You can not see these additives when new, nor can you see when they have become depleted; you simply have to flush out the cooling system and install fresh coolant.
  I mentioned the “wetting” agent added to coolant; this is also available as a stand alone additive under the brand name Water Wetter, among others.  I have tried it in my own car without any appreciable change in the operating temperature; but I know of people who have used it and experienced lower temperatures.  It is not unduly expensive and I do not believe its use can cause any problems; it is entirely up to you whether you want to use it or not.
  A product I do use and recommend is Bar’s Leaks.  Pontiac, among many manufacturers’ world wide, installed this product on the assembly line for years.  The active ingredient is granulated Turmeric root and it stops minor leaks by simply plugging them.  These granules have a scrubbing action as they flow through the system and actually serve to remove or prevent the formation of rust and scale.  This unique property does cause the granules to break down into a fine powder which no longer has any “stop-leak” capability.   This is why Bar’s Leaks will not clog your cooling system like other “stop-leak” additives can, as a fine powder it simply drains out when you replace the coolant.  I add a fresh dose of Bar’s Leaks every time I drain and flush the cooling system.  I prefer to use the dry tablet form, but if I owned a ’38 or older Pontiac, I would use the bottled product.  In the bottle, the Turmeric is combined with water-soluble oil, a good lubricant for the early water pump shaft seals.
  I personally replace the hoses on my cars at least every 5 years, unless you have installed the heavy duty silicone jacketed “fleet” hoses, this is my recommendation to you as well.  The hose to watch is the upper radiator hose; it is subjected to the highest heat and also to some amount of contact with air when the engine is cold and the coolant level drops.
  Pontiac installed a thermostat as original equipment and I recommend you run one.  The majority of wear on an engine occurs during the warm-up from cold, the less time an engine operates at low temperature, the less wear.  This is one of the reasons that modern cars have used 195 degree thermostats for the past 30 plus years.  The higher the operating temperature, the minimum wear combined with the best efficiency.  If you are adamant against running a thermostat, you need to install a flow restrictor in its place.  If the coolant flow is completely unrestricted, at highway speeds it does not spend enough time inside the engine to absorb sufficient heat.  The other benefit of restricting the flow is that the water pump actually pressurizes the coolant inside the engine, forcing the coolant molecules into the porous surfaces of the cast iron and improving the cooling action significantly.
  All of the straight eights, and the six cylinder engines beginning in 1935, have a water distribution tube running the length of the cooling system.  It is essential to cool running.  The water pump must be removed to access this tube, but unless you know beyond doubt that your engine still has one, and it is in good condition, it will have to be inspected if you are experiencing any overheating issues.
  Be sure to inspect the fan belt for excessive wear or cracking of the rubber.  The belt needs to be tight enough so that it does not slip, but if too tight, you could damage the bearings in the water pump or generator.
  The final inspection of your cooling system would be to insure that your car has all of its bodywork intact.  See the 1941 Pontiac Radiator Air Trap  For the most part, every piece of sheet metal baffling serves its purpose to guide and/or contain air flow through the radiator and engine compartment.  Your cooling system could be in perfect condition and you could still experience over-heating issue due to missing close-out panels, baffles, shrouds, etc.  You may not even be aware that pieces are missing from you car, but it will be worth the effort to check.
  I have come across some unusual problems during my years working on cars; a relatively common cooling system issue is a missing reinforcement spring in the lower radiator hose.  This keeps the hose from being sucked shut by the water pump at higher engine speeds; you can squeeze the hose with your hand to determine if it has one.
  I have also seen water pump impellers with reversed fins; these are commonly used in twin engine marine applications on the counter-rotating engine.  It is unlikely you would find a reversed impeller in an assembled Pontiac water pump, but if you bought a box of parts at a swap meet, you never know what may have found its way into the box.

Other Items to Check

  Nearly all of our Pontiacs were fitted with a “heat riser” system in the exhaust manifold to aid in bringing the engine to operating temperature, it is also essential for proper operation of the automatic choke which most of our cars feature.  Unfortunately the heat-riser valve is prone to sticking due to lack of proper lubrication over the years; and since the valve usually sticks in the heat position, if it is stuck on your car, you will experience abnormally high operating temperatures.  It can be difficult to free a stuck heat-riser valve, but it needs to work properly if you expect to have a good running car from cold starting to highway driving.
  It is also essential that the distributor be in good working order, especially the mechanical and vacuum advance mechanisms.  Retarded spark timing will result in poor fuel economy, high operating temperature and sluggish performance.  Tuning your Pontiac to peak efficiency not only nets you the best gas mileage but also the lowest operating temperature.  The vacuum advance unit is the most important with regard to cool running under part-throttle (cruising) speeds, where the carburetor is set to lean the mixture for peak economy.  A lean mixture requires more time to burn efficiently, so the spark timing needs to be advanced; since engine vacuum is directly proportional to throttle opening, a vacuum advance unit is employed.  The leaner the mixture, the higher the vacuum and the more degrees of advance provided.  If the advance unit fails, the timing will be retarded and the operating temperature can climb dramatically.
  A stretched and worn-out timing chain will cause late valve timing and higher than normal operating temperatures, along with sluggish performance.  Valves that are adjusted with too little clearance are also cause for high temperature in the short term, and eventually burned valves if the adjustment is not corrected.

Summary

  Pontiac earned its reputation for reliability, due in no small part to the fact, that their cars were fitted with a host of features that functioned automatically to quickly bring the engine to a safe operating temperature and keep it there.  All of these items are covered in either the owner’s guide, the shop manual, or in the appropriate training booklet.  If you are experiencing actual overheating issues, it is essential to thoroughly check all possible causes; but even if you are not, spending the winter months inspecting your Pontiac will be great for your piece of mind next summer when you are out on the road.

   Pete
This cut-away shows the water distribution tube running adjacent to the valve guides through the block.  Note the jets of coolant being directed toward guides and seats of the valves.  Keeping these areas cool essential for long valve life and overall engine durability.  All cylinders were surrounded by coolant, another important feature for maximum engine life.
1941 Pontiac Radiator Air Trap