Very odd heat question - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 6 (permalink) Old 12-04-2018, 10:49 PM Thread Starter
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Very odd heat question

Long time reader, first time poster.

My buddy has an 05 excursion with a 6.0.

About a year ago his water pump blew and coolant dumped all over his driveway. He had the water pump replaced and the cooling system flushed and filled.

A few weeks after this he started to have heating issues in the rear of the excursion, lukewarm, then cold air. Then the front started to go out.

That was at the end of last winter. Now he is getting intermittent heat from the front and from the rear again this winter. I noticed that the thermostat was not opening so I replaced it. And now it opens.

After further diagnosis I noticed that the hoses going into the heater core were cold most of the time. I checked the heater control valve and it seems to be working properly.

I did notice today that the engine fan was running all the time and never shut off no matter what the engine temp was. I checked it out with the engine off and cold and found that it would not spin.

So I ordered a fan clutch.

My question is could the fan clutch be causing the intermittent heat issue throughout the coach? And is there anything else I have missed?

Sorry for the long post and thank you so much for your time.
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post #2 of 6 (permalink) Old 12-04-2018, 10:52 PM
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Re: Very odd heat question

Sounds like air is getting in the system somewhere. Does it have a EGR cooler still ?

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post #3 of 6 (permalink) Old 12-04-2018, 11:17 PM Thread Starter
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It does still have one, it was replaced though about a year and a half ago.
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post #4 of 6 (permalink) Old 12-05-2018, 12:48 AM
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Does the truck use coolant or have excessive cooling system pressure?

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post #5 of 6 (permalink) Old 01-06-2019, 02:28 AM
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How did the coolant look, was there any debris in the system. It's easy to clogg heater cores. My mentor Master Ford technician would disconnect both lines from a heater core and slowly pour Coca-Cola into the core the foam from the carbonated drink was slowly push out some of the debris from the system. You can use a water hose on one side backflushing the core. Keep in mind, the debris could be almost solid and heater cores aren't meant to be pressurized at higher pressures than the system normally operates. If this was your problem I would definitely add a coolant filtration system to the vehicle. They do work to cut down on debris circulating around in the system that they will not clean out the system by themselves you'll have to flush the system manually.
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post #6 of 6 (permalink) Old 01-08-2019, 02:44 PM
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Re: Very odd heat question

I had a similar problem with my Excursion.

First, the fan can run 24/7 and it will have a minimal impact on actual engine reaching operating temp so long as the thermostat is working properly. Since you said you swapped thermostats, let's assume it is ok. Next possibility is the wrong size water pump may have been installed. I know it doesn't sound likely, but it's possible. After that, air/gas getting into the system from somewhere is the next likely culprit.

To diagnose, revving the engine to see if you get heat won't work because that might give you heat no matter what the issue is. I would recommend attaching a pressure gauge into the cooling system (lots and lots of threads on that here) and seeing what the pressure is like. Get it up to temp, carefully release pressure on the degas bottle, now run it some more and watch what the gauge does. Also, watch it while doing a couple WOT runs. If it gets anywhere near 16 PSI, or if it jumps up quickly when going WOT, he has either a head gasket issue or EGR cooler issue. If the pressure remains and there are no fluctuations, I would suspect he may have installed a 90mm pump in a 100mm housing. Those are the only things which come to mind based on the symptoms you're describing.

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