I need some suggestions on a cold heater problem. The heater is not putting out heat like it should. Here is some background: 1965 Mustang 2+2 stock 289, fresh engine rebuild, new heater hoses 5/8", no restrictions in the heater coil, hoses hooked up in the OEM locations, new180 degree thermostat. The radiator hose is the normal hot to the touch butboth heater hoses are much cooler than the radiator hose and do not seem to have the same pressure inside them. The heater blower is workingin both speeds as it should, and the heater doors are opening and closing as they should. I just rebuilt the entire heater box and made sure everything was working. Should there be a control valve between the water pump and the return line to slow the flow down and let the heater coil transfer the heat?
Thanks
David

 

My guess would be a bad heater core. Did you replace that when you did the box?

 

I checked the core and it had a good flow through it and no leaks so it did not get replaced.

Skunk

 

Do you have the factory heater elbow on the intake with the proper extension tube, or one of those crappy generic deals that's basically a pipe thread to ****** hose end?

Do you have the hoses routed properly? The lower hose (on the firewall) should go to the intake and the upper hose should go to the water pump.

What thermostat are you running? Assuming your cooling system is working properly, a 160 or even 180 degree t-stat won't allow the engine to get up to proper operating temp, which will obviously impair heater function.

What condition are the seals in the heater box in? Poor seals are going to leak air, reducing the effectiveness of the heater.

 

The intake connection is the stock 65 289 elbow that isjust behind thethermostat housing, notjust a ****** fittinged as you described.
I am running a 180 degree thermostat. Andnew heater seals were installed when the box was rebuilt. There is good air flow coming from the ducts of the heater so there is very little air bypass if any.
Thanks for the reply
Skunk

 

Sounds like you have some kind of restriction if the heater hoses are not hot to the touch means you are not getting the hot water thru the core as needed.The heater hoses will be cooler than the rad hose but will still be hot if the water is flowing thru them correctly.Are you sure the hoses are installed in the right position? You could also have a thermo in the intake that is just not functioning properly or is the wrong degree.You could try a higher degree thermo and see if that fixes the problem! Good Luck!!

 

And check for an bend that collapses the hoses - check the routing again.

 

sure the radiator is topped off might be low on coolant

 

when the radiator (heater) has good flow and both hoses going to the radiator (for the engine) are hot, then my first guess would be that you might have forgotten to bleed your water system. some air trapped in there ? check that first.

kalli