27 series 80 radiator losing water

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    I am new to my 27 series 80 roadster and now that the hot weather is here, it is giving me trouble!  On hot days, temp over 95, and at speeds over 45 mph,  the motometer will read in the middle of the gauge and then shoot up to the top.  When checking the radiator, I find that the water level is very low when only a few minutes earlier the level was just fine.  In trying to determine where the water went, it appears that it is being pumped out of the radiator via the overflow pipe.  When I rev the engine, I see a large discharge of water from the overflow pipe.  How do I keep the water in the radiator?

    Rod Smith

    Reno NV



    On my Pierces the overflow is a couple of inches below the top of the radiator neck.  I found that when driving at speed I was pumping a lot of water out the overflow.  I took an appropriate size piece of fuel hose and slid it over the over flow so that the open end is just below the radiator cap up inside the radiator neck.  It made a big difference.

    Also, if you are running anti-freeze, in non pressurized systems it tends to foam and go out the overflow. I use water with and anti-corrosive (Pencool 3000).  NAPA has something similar.

    It also may be time for a radiator flush. There is an article in the PASB sometime in the last couple of years about using Evapo-Rust to clean the cooling system, as well as reverse flushing the radiator.



    Hello Rod.  This is a common problem with the Pierce cooling systems, actually with non-pressurized cooling systems.

    The water pump in a Series 80 can pump about 100-120 gallons per minute.  Think about that: two 55 gallon drums of water per minute!  That’s a lot of water flow..

    BUT a fresh, clean Series 80 radiator can only flow about 50-60 gallons per minute.. So, the radiator is a ‘choke-point’ in the flow to water through the cooling system..

    This also means that the water pump is trying to SUCK or DRAW water from the radiator, and cannot draw enough fast enough so the lower radiator hoses and pipe and the suction side of the water pump are under a significant suction.  So much so, that if the water pump packing is just slightly loose, and the water pump grease is thin and has washed away,  then AIR is sucked into the water pump.  Also the lower radiator hose clamps need to be tight.  Don’t assume if they are not leaking/dripping that they are tight.. Put a screwdriver on them and make sure they are tight. A hose can NOT drip, but be loose enough to let air be drawn in.

    The Series 80 engines originally had a thermostat in the lower part of the aluminum neck bolted to the cylinder head, going up to the radiator upper tank inlet pipe.  This thermostat was bronze.  So with an aluminum water neck, copper radiator, and iron cylinder block, just the slightest bit of acidic water in the cooling system resulted in the aluminum radiator neck being eaten away by electrolysis.  So, very few original Series 80 thermostats exist.  The thermostat created a flow-restriction for the coolant flowing up into the radiator.   You can add a modern thermostat to the system, but you must drill two 1/8″ diameter holes in the thermostat’s flange to allow a slight bit of circulation when the engine is cold.

    Also a restrictor plate can be added to the top hose at the radiator inlet pipe..  Get a ‘freeze-plug’ or core plug from your local auto parts store that will fit into the upper radiator hose.. but not fit through the radiator inlet pipe..  Drill a 5/8″ or up to 3/4″ hole in the core plug.. Insert in the hose so that the plug is up agains the edge of the radiator inlet pipe..  This restrictor will slow the flow and help keep the upper tank from over-filling faster than the water pump can suction the water down through the radiator core..

    Reverse flushing the radiator is a must.. The very thin openings for each water passageway in the upper radiator tank get plugged up with old blobs of water pump grease, chips of rust from inside the cylinder block and head.  You can use a stiff wire, wrap it around a magnet and fish the magnet down each side of the radiator tank, it will pick up an amazing amount of rust flakes..  Just think about how much of this debris is not magnetic and is clogging the entrance to the cooling tubes in the radiator core.. This is why it’s important to reverse flush the radiator with hot water..  The hot water will help soften the congealed water pump grease and let it get washed out, along with rust and crud..

    When installing a thermostat, or an upper hose flow restrictor,  get a ‘footy’ sock, and stuff it into the upper radiator inlet pipe, wrap the last 1″ of the sock around the outside of the inlet pipe, then slide the radiator hose over the sock and inlet pipe.  Sometimes a bit of Permatex Ultra Black worked into the fabric of the footy-sock around the pipe will lubricate it for the hose installation and also seal it against slow drips/leaks..  The footy sock is  very effective coolant filter. It will accumulate a golf-ball sized collection of rust flakes and crud every season.. Even a brand new, fresh engine will have a significant amount of debris get caught in the footy-sock filter.  Unfortunately and ‘Gano’ filter does not work well in a Series 80 water neck, there is no room to install one, the connecting hose is only a few inches long..

    And: a huge caution: if you remove the aluminum water outlet, DO NOT use a thick gasket under it when you reinstall it.. Use only a coating of Permatex ultra-black on each surface or if you ‘must’ have a gasket, use a cut out from a thin cardboard 3×5 file card NOTHING thicker..  The water neck is held on by two cylinder head studs/nuts. they should be torqued to about 40-45 ftlbs.  if you put a thick gasket under the water neck the tight head fasteners WILL break the ears off the water neck..  [don’t ask HOW I know this!]

    Pure water with Napa-Cool, or Penn-Cool 2000, or ‘Water-Wetter’ or your favorite anti-corrosive additive is far better at reducing foaming of the coolant and also conducts heat better than the typical 5050 antifreeze mix..


    Greg Long



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