coolant flush question
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Mountain Pass
Joined: May 2015
Posts: 221
Likes: 3
From: Northeast Ohio
coolant flush question
So I'm still in the process of this coolant flush on the 1992 7.3 idi, and I have circulated and drained 2 batches of distilled water, with the first batch having the flush/cleaner in it. So tonight I just pulled both of the block drain plugs and got an additional gallon or so out. But I went ahead and put more water in because its still coming out dark brown, and the system only took 4.5 gallons of the roughly 7.5 that it needs. So my question is, do I HAVE TO take off the thermostat housing now in order to get the water down into the engine block? Or will the thermostat open even with the lack of water in the block? I think I could leave the radiator cap off while its running and add water as needed but I am afraid to start this thing because I don't want it to overheat.
Fleet Owner
Joined: Jan 2004
Posts: 26,007
Likes: 575
From: Brentwood,CA
The thermostat stay only opens when at temp, without water you will obviously never open the t stat and overheat. Remove the heater hoses and start flushing with a garden hose connected and the lower radiator hose removed.
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Mountain Pass
Joined: May 2015
Posts: 221
Likes: 3
From: Northeast Ohio
<br />I thought the heater hoses were after the thermostat? I'll have to go look at it again tomorrow.
Cargo Master
Joined: Oct 2012
Posts: 3,072
Likes: 48
From: California
The heater core circuit is basically just an output from the head and return to the pump. Until your t-stat opens, you are not circulating all your coolant thru the entire circuit.
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Mountain Pass
Joined: May 2015
Posts: 221
Likes: 3
From: Northeast Ohio
Thanks! That helps a lot, makes sense now I'll just pour the water down the heater hose.
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Mountain Pass
Joined: May 2015
Posts: 221
Likes: 3
From: Northeast Ohio
Genscripter, I have another question, or for anyone that wants to answer... Are these radiator tubes too plugged up to cool properly? About 1/3 of all the tubes I could see from shining a flashlight into the hole there looked to be plugged solid. Do I need a new radiator to be able to cool properly or do i just need to do a second or even a third flush to get all this crap out of the tubes?
Fleet Owner
Joined: Jan 2004
Posts: 26,007
Likes: 575
From: Brentwood,CA
That is solder bloom, very hard to remove if not impossible. I suggest a muriatic acid flush or a heavy duty acid engine flush. Ford sells one and so does international.
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Cargo Master
Joined: Oct 2012
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From: California
Unless you are hauling 8 tons regularly up and down the mountain grades, it would take a lot of grime to make a stock IDI radiator malfunction.
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Mountain Pass
Joined: May 2015
Posts: 221
Likes: 3
From: Northeast Ohio
that's good to know, this truck will occasionally haul firewood and a couple times a year haul maybe 8,000 pounds..not in the mountains, on smaller hills. This thing is retired now. I'm leaning towards just finishing the flush with water a couple more times and putting the DCA coolant in there. I'm about at my wits end with this trucks quirks and issues. Been working on this steadily since February, about to shut it down for the year and pick back up next year. I do like the idea of the acid flush that would be a good idea at some point to do. And btw..I do not think my thermostat is working I think it is stuck open, i was able to pour water down the upper radiator hose, about a gallons worth. And it all disappeared. I'll have to replace that next year.
Cargo Master
Joined: Oct 2012
Posts: 3,072
Likes: 48
From: California
There is a ball bearing that resides in that t-stat housing. Someone might have removed it, allowing the flow of coolant to occur faster than normal. I removed my ball a few years ago, because I was sick of waiting 20 minutes for my t-stat to open when refilling the radiator with coolant.
You won't know until you take off that t-stat housing. If it is a bad t-stat, make sure to buy a motorcraft one. aftermarket t-stats are terrible.
You won't know until you take off that t-stat housing. If it is a bad t-stat, make sure to buy a motorcraft one. aftermarket t-stats are terrible.
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