No Heat after Radiator Replacement with Two Core - Ford Bronco Forum
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post #1 of 14 (permalink) Old 03-05-2017, 06:10 PM Thread Starter
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No Heat after Radiator Replacement with Two Core

85 302 EFI
Replaced single core with double core.
Everything working fine before swap other that radiator leaking.

After swap I have no heat and little if any pressure in system when hot.

Engine not overheating.

I've been burping and filling but only able to add a cup of coolant or so at a time.

I think I still have air in the system or the two core is providing too much cooling.

Ideas? Thanks!

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post #2 of 14 (permalink) Old 03-05-2017, 07:03 PM
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It sounds like your thermostat is not opening. I just started mine today after draining my coolant enough to hook up my heater core. I also didn't have heat until I let it run for several minutes, shut it off for a few minutes, then repeating a couple times. I did open the cap and relieve the pressure once, which wasn't much, during the process. The thermostat then opened, I had heat and then was able to add more coolant.
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post #3 of 14 (permalink) Old 03-05-2017, 07:16 PM
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Yo Big,
After running engine to normal operating temperature; BEWARE OF FAN, BELTS, PULLEYS, HOT HOSES AND ENGINE COMPONENTS;
FEEL heater water hoses. If the heater water hoses are too hot to hold, the thermostat is OK. If the heater water hoses do not get too hot to hold, REPLACE the thermostat. If only one heater water hose gets hot while the other remains cool, a plugged heater water hose or heater core is indicated.

Heater water hoses.
CHECK condition and routing of hoses . Visually inspect condition of heater water hoses for pinched or collapsed conditions

Start vehicle and allow to reach normal operating temperature.
Place temperature control knob in the full warm position.
Grasp inlet and outlet heater water hoses. Both heater water hoses should be warm to the touch due to coolant flowing through them.

Fill the radiator with a 50/50 mixture of the specified engine coolant concentrate and water. Allow several minutes for trapped air to escape (bubble out) and for engine coolant to flow through the radiator.
2. Replace the radiator cap to its fully installed position, then back off to the first stop. This will prevent high pressure from building up in the cooling system during this part of the fill procedure.
3. Start and idle the engine until the thermostat opens and the radiator upper hose becomes warm.
4. Shut off the engine and allow the engine to cool. Cover the radiator cap with a thick cloth and cautiously remove it. Step back while the pressure releases.
5. Finally, check the radiator and add more engine coolant if needed, following the procedures noted above. Reinstall the radiator cap securely, when finished.
6. If more engine coolant is necessary, fill the overflow reservoir to the appropriate level marked on the bottle..."
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post #4 of 14 (permalink) Old 03-06-2017, 05:35 PM Thread Starter
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Thanks guys. Again, everything worked before the swap so I'm leaning air trapped. However, the single core may have been able to heat even with a stuck open thermostat so I'm going to try a new 195 and see what happens.

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post #5 of 14 (permalink) Old 03-09-2017, 07:50 AM
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Sounds to me thermostat is stuck wide open. Not regulating the water temp.


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post #6 of 14 (permalink) Old 03-09-2017, 08:25 AM
on KIK as same
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Also agree with the above.
I have replaced a bunch of radiators in these trucks and they seem not prone to getting air stuck in them. I have never had to do anything other then just fill them up, and check the level once its ran a cycle and top off. Not saying that you do not have that problem, only that I have not seen it happen very often.

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post #7 of 14 (permalink) Old 03-09-2017, 09:03 AM
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My first inclination is when the radiator was changed a bunch of crud was broken loose and plugged the heater core. In this case I would disconnect the hoses to the heater core after recovering the antifreeze. Use a garden hose fitting on the return side of the core to backflush the core and throughly flush the engine also to remove setement in the water jackets.
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post #8 of 14 (permalink) Old 03-09-2017, 04:08 PM
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I did a three core in mine. When burping mine I let it get up to operating temp and gave the upper rad hose a good squeeze and I could hear quite the burp. Been working great ever since.
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post #9 of 14 (permalink) Old 03-10-2017, 12:58 AM
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Make sure the "inline and return" line heater hoses are hooked up correctly at the firewall, on my 86 XLT EFI 5.0 the inline goes underneath the FI plenum to a tube which goes into a HEX riser threaded into the intake manifold and the return line goes to the water pump.......just saying!

Thermostat could an issue so get a new one if need be and a "STAT" radiator cap....

Good Luck ~
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post #10 of 14 (permalink) Old 03-10-2017, 03:03 PM
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I second the votes for thermostat or heater core.

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post #11 of 14 (permalink) Old 03-10-2017, 10:19 PM
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My heater core was stopped up. I had no real heat. I replaced the heater core (a very easy job in these vehicles by the way) and voila, great heat again.

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post #12 of 14 (permalink) Old 03-14-2017, 12:44 PM
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So, biggum, did you get the Bronco throwing heat again?? And what was the cause?
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post #13 of 14 (permalink) Old 03-15-2017, 01:36 AM
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It's not the radiator either heater core or tstat or both. FYI get a premium stant t-stat off rockauto (better than mc imo). that or a motorcraft. The cheap ones are like a paperclip. junk.
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post #14 of 14 (permalink) Old 03-20-2017, 05:47 PM Thread Starter
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The thermostat was in fact stuck open. With the single core radiator it still ran hot enough to generate heat in the cab but with the two it could not. Put in a new stant therm and it's doing great. Thanks for the help folks.

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