3.2 litre Puma Overheating Issues.
Posted: Mon Nov 06, 2023 9:40 am
Sould you ever experience overheating issues with a 3.2 Puma 5 cylinder engine there is one possible cause thats not documented.
There is a 10mm dia hose that goes from the top of the header tank to the top of the thermostat housing.
Cast into the housing connection is a brass bush with a 1.5 mm dia orifice. If this orifice becomes blocked ( as mine did ) it prevents the engine block from venting any entrained air and the engine becomes air locked and can very quickly overheat.
The symptoms on mine were very illegular coolant levels and air in the radiator that I could never seen to remove - I tried using a pump to circulate the coolant and to remove all the air, this was successful but only for a week or so and then the problem returned with air again in the radiator.
To test your system disconnect the 10mm hose off the header tank and blow down it, if you can then its not blocked, if you cannot then its blocked and it needs to be resolved.
I tried clearing the blockage with an air hose but 100 psi wouldnt move the blockage so I replaced the housing with a new one complete with a new thermostat and stripped and dismembered the original housing down and found the brass insert. The tiny orifice was blocked by a grain of sand, possibly from when the engine was cast.
Ford tell me that if the orifice is greater than 1.5mm the by-pass rate through it with with the engine running is too great and the thermostat may not be able to fully controll the engine temperature, any less than 1.5mm and its too small for the entrained air to escape, if, when your engine is up to temperature, you can feel the 10mm hose is hot then the orifice is clear, if its cold, you could have a problem.
Finally I could not get a logical answer from Ford as to why the 3.2 engine block does not have a coolant drain point to remove/flush out all debris when a coolant change is being carried out !
When I get around next April to installing a new "short motor" ( mine "grabbed" two pistons 2 & 3 when it overheated badly scoring the bores ) one of the first things that will be done prior to installation is the block will be drilled and tapped and a 3/8" NPT drain plug on the exhaust side on the engine block.
Happy motoring to all.
There is a 10mm dia hose that goes from the top of the header tank to the top of the thermostat housing.
Cast into the housing connection is a brass bush with a 1.5 mm dia orifice. If this orifice becomes blocked ( as mine did ) it prevents the engine block from venting any entrained air and the engine becomes air locked and can very quickly overheat.
The symptoms on mine were very illegular coolant levels and air in the radiator that I could never seen to remove - I tried using a pump to circulate the coolant and to remove all the air, this was successful but only for a week or so and then the problem returned with air again in the radiator.
To test your system disconnect the 10mm hose off the header tank and blow down it, if you can then its not blocked, if you cannot then its blocked and it needs to be resolved.
I tried clearing the blockage with an air hose but 100 psi wouldnt move the blockage so I replaced the housing with a new one complete with a new thermostat and stripped and dismembered the original housing down and found the brass insert. The tiny orifice was blocked by a grain of sand, possibly from when the engine was cast.
Ford tell me that if the orifice is greater than 1.5mm the by-pass rate through it with with the engine running is too great and the thermostat may not be able to fully controll the engine temperature, any less than 1.5mm and its too small for the entrained air to escape, if, when your engine is up to temperature, you can feel the 10mm hose is hot then the orifice is clear, if its cold, you could have a problem.
Finally I could not get a logical answer from Ford as to why the 3.2 engine block does not have a coolant drain point to remove/flush out all debris when a coolant change is being carried out !
When I get around next April to installing a new "short motor" ( mine "grabbed" two pistons 2 & 3 when it overheated badly scoring the bores ) one of the first things that will be done prior to installation is the block will be drilled and tapped and a 3/8" NPT drain plug on the exhaust side on the engine block.
Happy motoring to all.