Replacing the heater hose bypass fitting will depend on how the fitting was installed. It could be screwed or bolted in. Try searching for your specific vehicle for a detailed description of the install.
loosen the clamp holding the hose on to a fitting and pull the hose free.
How to replace a heater hose on a 2001 Oldsmobile silloute
The Chevy heater hose removal tool is a plastic piece that clamps around the hose. The tool slides into the fitting to release the hose.
Quick disconnect. You can get the replacement part that is in the intake at Autozone. If you dont want to do that you cat replace the fitting with a old style one and cut the end of the hose of and slide it on.
Heater core? Inlet or outlet hose fitting at heater core?
Cut off the crimp connectors, pull the old hose off and replace with conventional heater hose and conventional hose clamps
you may have to remove the intake from the block and then use an extractor tool to remove the rest. then replace the connector.
Remove both heater hoses from the engine, then fabricate a fitting to attach a garden hose to one of the heater hoses. Direct the remaining hose into a bucket then slowly turn on the water until the water runs clean. Then reverse the flow by switching the garden hose over to the other heater hose and repeat until the water runs clean. Then replace the hoses to the engine and refill the coolant reservoir.
What you have to do, is replace the heater core itself
There are two ways to fix this problem. 1 get the factor oem fitting that has the plastic clip. 2 go to the hardware store and get a pipe fitting that fits the hole on one end and the heater hose on the other end.
one large hose from bottom of radiator to side of water pump. other large hose from thermostat housing to top of radiator. one heater hose from water pump to heater core, I think this one has a Y in it if there is a rear heater other heater hose from heater core to somewhere on top the engine. If there is a rear heater, its return hose goes to a fitting on the radiator.