Hi I have a 89 f250 351ci. with no heat. I've replaced the t-stat and have plenty of coolant.I have also checked the control pannel and the controls appear to work correctly.Should I assume the core is no good?,Or are there any other options? Is the core change difficult to do? Please help Thanks John

 

Don't assume!! Trace out the heater pipes to the core, carefully remove both pipes. Hook up the garden hose to one side and a drain pipe to the other. Gently turn on the faucet and check the water flow. Should be clear and even flow, if just a trickle then the core is blocked. Any way reverse the hoses and try again. If you are lucky this will clear the core of any blocks. You also might have had an air block and this will clear it. Hook up the engine hoses and check it out. From what I remember the heater is supplied from an outlet on the side of the water pump you should also check to see if this is also clear.

 

Before discionnecting the hoses and backflushing the core, run a simple test to see if a clogged core is actually the problem.

With a warm engine, feel the temperature of both heater hoses.

If both are hot, the core is flowing coolant and your problem is most likely in the HVAC system in the dash.

If one is significantly hotter than the other, then proceed with the core flushing.

Steve