Hi... A simple enough question. I have checked the threads but cannot find a definetive answer. I have read several sources of info' but get conficting views. There are 2 size hoses on the heater core... 5/8 and 3/4, Which is which? i.e: Should the inlet be 3/4 and outlet 5/8 to give some kind of pressure in the core or should it be the other way 'round so there is NO pressure in the core? Someone out there must know the truth.... If so, PLEASE tell me and preferably the reason for the 2 different sizes. My system is the simple setup with a single hose from the inlet manifild and another single hose to the water pump top. This might be a good entry for the FAQ section if we can actually find the TRUE answer! All input welcome... Thanks and kind regards...
Geoff (86trNZam).

 

big goes from intake to heater core. small goes from heater core to water pump. There's only one size hose that will fit onto each "nipple" fitting on the water pump and intake....this should be relatively easy to figure out.

 

Thanks for the reply, appreciate that... It's not that 'Easy to figure out' when you dont have the original motor/intake or fittings and never saw the thing factory original. So... If the 3/4 is the input and the 5/8 is the output, the heater core is probably slightly pressurised? If no other replies then I can assume this is correct? Thanks for the help. Regards...
Geoff.

 

all coolant is pressurized by the pressure rating of the cap regardless of the size of hose used, the pressure would be the same. typically people use 16 pound caps, so there would be 16 pounds per square inch of pressure throughout the cooling system.

 

Of coarse.... Miss the Bleading obvious sometimes! Thanks again.... regards... Geoff.