M923a2 Coolant System Drain and Flush:

[Defcon-1]

This is just a followup, probably the last post here from my end. Been running the coolant (post-drain and flushes) for months now and this is the sample I took the other day after removing 2+ gallons to work on my fan-clutch actuator / shutter-stat.

Note: This was taken from the drivers-side lower radiator port (the portion where it (probably) gets the least amount of flow / most amount of build-up and accumulation of sediment). It's like a night and day difference between what I started with and what it currently is.

Thanks to all for the help and advice you gave

 

[Lantzj22]

Morning gents, I'm about to start this flush process and I read the TM as well as all 5 pages of this thread. I just want to verify my process is correct before i jump into this project. I have an 87' M923A2. After draining from both sides of the radiator, use distilled water/garden hose to flush from the surge tank (please verify that is correct) till water is clear. Fill from surge tank after everything is closed up (besides the aftercooler) with coolant/dis water mix. Also, Defcon-1 how have you liked your NAPA coolant thus far? 5 pages of different opinions makes deciding tough. Thanks for any advice or info you can give me!

 

[Defcon-1]

Morning gents, I'm about to start this flush process and I read the TM as well as all 5 pages of this thread. I just want to verify my process is correct before i jump into this project. I have an 87' M923A2. After draining from both sides of the radiator, use distilled water/garden hose to flush from the surge tank (please verify that is correct) till water is clear. Fill from surge tank after everything is closed up (besides the aftercooler) with coolant/dis water mix. Also, Defcon-1 how have you liked your NAPA coolant thus far? 5 pages of different opinions makes deciding tough. Thanks for any advice or info you can give me!

Good Day Sir,

For all intents and purposes, the TM has the correct process step-by-step, I was being a little OCD in the process lol. There were a lot of extra steps I did in between, like draining from the block and drivers-side radiator port, adding a coolant-filter, adding cleaning agents to some of the fills and flushes, etc. My goal in this was (because it was so dirty when I bought it) to evacuate any and all areas where water would flow to, so that's why I took a lot of parts off to clean them (or) gain access for better cleaning. I think the level of dirtiness would determine how in-depth you would need to go (or) how many times it would need to be filled and flushed. I started with garden-hose water in the beginning because it was so dirty, but then eventually switched over to distilled water for the flushes when it got cleaner and was running it up hot (including taking it on the road to get fully hot). The main thing (which I don't see mentioned above in your breakdown) is to get the truck up to running temperature each time so that the T-stat opens and allows flow into the radiator post water-pump. Just filling it up, idling, and draining won't cut it, it has to get past the point where the T-stat opens so the entire coolant system is moving around the block. So be prepared to sit and stare at that temp gauge each time lol. So far with the Napa mix it's been good, never overheated and even in the summer the fan-clutch didn't kick on, so it appears to be keeping the system cool and more importantly clean, but that also could be with the assistance of the filter. Lots of coolant options, I honestly went with Napa bc it was cheap and already had the SCA's added, super lazy right? lol. Maybe @DampLemonade can chime in as well on the coolant status in his truck since we were doing the same thing around the same time.

 

[Lantzj22]

Copy that, did you need any special tools etc? I live 2 hours from my 5 ton so I have to plan accordingly! Oh, one thing I forgot to ask about was burping the system. Did you leave the surge tank cap off to burp or what process did you use? Thanks for the quick reply!

 

[Defcon-1]

Copy that, did you need any special tools etc? I live 2 hours from my 5 ton so I have to plan accordingly! Oh, one thing I forgot to ask about was burping the system. Did you leave the surge tank cap off to burp or what process did you use? Thanks for the quick reply!

Hmm special tools... trying to think Nothing outside of my normal tooling I don't believe I needed, maybe my 1/2" breaker bar and torch to get that one block-plug out lol. Everything else was pretty straight forward, other than garden-hose adapters / elbows / swivels to get that 1/4" water-line down into the bottom of the radiator, to snake it down far as possible to blast any sediment out the drain ports.

To burp the system, I used a combination of opening the surge-cap / opening the after-cooler to get the air out, then I would add more water (or coolant in the final fill-up) while it was running / warm. Basically, I would add as much water as possible, run the truck up to idle / T-stat opening, then check the water level (add if needed) then take the truck out for a spin (or) rev up the RPM's to build more pressure, then, re-check the water level (adding more if needed). Sometimes I would wind up getting a whole 1 or 2 gallons of extra water / coolant in there, it's amazing how much fluid these systems carry lol. One time I tried cheating and taking the truck out before shutting down and checking the water again, shutter-stat opened up and fan-kicked on because I didn't have enough in there and it got hot, just take your time and make sure you're topped off and carry water / coolant with you wherever you go.

Hopefully... wherever your 5-ton is, there is no local-restriction on dumping fluid on the ground, it's not parked in a HOA neighborhood is it?

 

[Lantzj22]

Copy that! Thank you sir! I guess lastly, did you follow the TM in regards to coolant/water mix rates? Looks like you said in the first post 16qts for 0 degrees (that’ll be a record where my 5 ton is so I’d say that’s a good gauge for me as well) or did you go 50/50?

ha no HOA where she’s at. Mostly dirt lots and mobile homes around the lake! We use these toys for pulling boats/campers through the sand so we don’t get stuck.

 

[Defcon-1]

Copy that! Thank you sir! I guess lastly, did you follow the TM in regards to coolant/water mix rates? Looks like you said in the first post 16qts for 0 degrees (that’ll be a record where my 5 ton is so I’d say that’s a good gauge for me as well) or did you go 50/50?

ha no HOA where she’s at. Mostly dirt lots and mobile homes around the lake! We use these toys for pulling boats/campers through the sand so we don’t get stuck.

Anytime Sir, happy to help. I did the 50/50 mix because I figured "I have a block heater now" and I would be plugged in for any incoming temperature to single-digits, so doing 50/50 made more sense. Point of order: Now would be the time to do a block-heater if that was on the "to-do" list for you haha, since you would lose (mostly) all your coolant doing it down the road. A coolant-filter can be added later with minimum loss because you can shut the heater-core off from the remainder of the system.

On the final fill-up, added 1 gallon of distilled water to every 1 gallon of NAPA-HD-SCA, alternating until full. Then, made a bunch of 50/50 jugs with the empty containers for the top-offs and burp-offs, adding to the resevoir after the warm-up and burp procedure. Also carrying a few as backup in my tool-box. Good luck with the task, and welcome to SS btw too.

 

[Lantzj22]

Copy that! No block heater for us. Typically we only get as low as 25 at night and that usually follows 50 during the day. We also only use these in the summer. I really appreciate all the info and help! I’ll update you this weekend on how it went.

 

[Lantzj22]

Morning sir! I noticed you pulled your shutter stat in your last picture. I've been trying to remember if my fan has ever kicked on and i don't think it has. Could you point me in the right direction of the location of the shutter stat? Did you end up cleaning/rebuilding yours by chance? I can't find rebuilding in the TM anywhere. Everything i have found on them is for a NHC250. Thanks again for all your help!

 

[Defcon-1]

Morning sir! I noticed you pulled your shutter stat in your last picture. I've been trying to remember if my fan has ever kicked on and i don't think it has. Could you point me in the right direction of the location of the shutter stat? Did you end up cleaning/rebuilding yours by chance? I can't find rebuilding in the TM anywhere. Everything i have found on them is for a NHC250. Thanks again for all your help!

Good Day Sir,

The S-Stat kicks on as the last-attempt to cool the engine down, T-stat opens around 180' (allowing additional cooling via the radiator) and S-stat opens around 195' (provides additional cooling by means of forced-airflow across the radiator and block). Also to note, the removable fender-wells direct the airflow across the block when the fan is on, having them removed will actually stop the engine from cooling down, so if you ever go into an overheat condition, don't open the hood and remove the fenders to allow for more air lol. Somewhere in the TM I remember reading that warning.

On the S-Stat, the position of the plunger inside is normally closed, receives pressure from air system to open when it reaches a certain temp, provides air to fan clutch, fan-clutch spins fan, more cooling air is provided, etc. It's possible that you haven't had it come on because you never reached the higher temp ranges? Or, it could be stuck in the closed position. When I mentioned the fan coming on in the previous reply, that was because I didn't have enough coolant in the system and it started to overheat. This was the only time my fan came on owning the truck, it never got to those higher-range temps needing for additional cooling since then. Eventually, my S-stat started leaking air from the weep-hole on the back of the unit, so I bought an o-ring rebuild-kit from Big Mikes Motor Pool and he has a step-by-step breakdown on how to rebuild it on YouTube. It wound up being a $25 fix instead of a $300+ part replacement.

I'm not sure how you could test the S-Stat function without intentionally going into an overheat, since the thermo-coupler inside detects that condition and activates the plunger to allow air through to the fan-clutch. Providing air to just the out-let side would engage the fan-clutch, bypassing the detection-function of the S-Stat, but that would only check to see if your fan-clutch is operating. Have you gone into an overheat condition and confirmed your fan wasn't spinning?

 

[Lantzj22]

Im thinking possibly my t stat is out then or my coolant is the issue, the other day running down to the lake (1-2 miles) i was running 200+ pretty easily on both engine and trans. fan wasnt on so im thinking I have both the S stat is out, coolant needs flushed, and possibly a tstat all at the same time. Happen to have part numbers for that Tstat and gasket/s you did? Makes it a big PITA that im 2 hours from the truck all the time. Ill end up just buying everything and keeping whats not needed ha.

 

[Defcon-1]

Im thinking possibly my t stat is out then or my coolant is the issue, the other day running down to the lake (1-2 miles) i was running 200+ pretty easily on both engine and trans. fan wasnt on so im thinking I have both the S stat is out, coolant needs flushed, and possibly a tstat all at the same time. Happen to have part numbers for that Tstat and gasket/s you did? Makes it a big PITA that im 2 hours from the truck all the time. Ill end up just buying everything and keeping whats not needed ha.

Yeah it sounds like it could be one or multiple issues, you'll have to eliminate them one by one. That upper tube going across the block is the inlet-line right past the T-Stat, if that is not hot 180' and above, the T-Stat is not opening (no water-flow into the radiator). It could also be opening, but running hotter than normal because it's dirty and not providing good cooling. You'll know soon enough when you dump that coolant out lol.

Here are the part numbers I ordered from Memphis Equipment. Also to note... I wound up not using the gaskets because I got a way *way* better seal from using Permatex water-pump and thermostat-housing sealant. The OEM seals did not like the torque and eventually it started weeping water past the housing, which I noticed during my fill-and-flushes with water only, no coolant at that time. That whole housing-unit is not designed very well IMO, too much mass in one spot and too many connections to get a nice even compression on the gasket because it's a triangle-pattern of bolts instead of a square, so RTV fixed that leak for me, used RTV in-between the metal-to-metal contacts. You'll know what I mean if you have to take out the T-Stat lol.

 

[Lantzj22]

Just doing quick research is there anyway to tell if I have the single thermo or double? I see yours is the single.

 

[Defcon-1]

Just doing quick research is there anyway to tell if I have the single thermo or double? I see yours is the single.

If I remember correctly, A2's have the single, there is a second port in the housing, but there is a giant rubber-plug installed to block that water-flow. I think in the TM under "thermostat removal / installation" it will clarify.

 

[Lantzj22]

Good morning again sir! sorry to bug you with all these easy questions ha, if my tstat is bad and not opening would that cause my shutter stat to not open? I was curious if that may be the case because I see the shutter stat is on that upper radiator hose and if that t stat doesnt open maybe its not getting hot enough to flip on? Im just trying to figure out my order of diagnosis for why shes getting hot and the fans not flipping on. Thanks again for all your help!

 

[Defcon-1]

Good morning again sir! sorry to bug you with all these easy questions ha, if my tstat is bad and not opening would that cause my shutter stat to not open? I was curious if that may be the case because I see the shutter stat is on that upper radiator hose and if that t stat doesnt open maybe its not getting hot enough to flip on? Im just trying to figure out my order of diagnosis for why shes getting hot and the fans not flipping on. Thanks again for all your help!

No worries Sir, you have the theory correct. The t-stat allows the coolant around the block to be pushed up and over (past the S-stat) and then into and through the radiator, back to the block and all other junctions thereafter. So if the t-stat is stuck closed, no water flow past the s-stat, and therefore will not be reading the correct temperature (actual temperature) of the coolant around the block. Trust your coolant temp sensor, since that is basically on the block. Without the t-stat opening up, you have “idle coolant” sitting in the radiator. Even having the fan turn on wouldn’t do anything at that point because it would just cool the water inside the radiator (but coolant is not moving and transferring the heat of the block bc it’s stuck in the radiator lol).

Changing out the t-stat requires a complete coolant drain and fill anyway, start with those two first. The s-stat can be changed out or worked on down the road with losing very little coolant. Keep us posted on your progress and feel free to ask any questions, it’s all still fresh in my head so get it now before that data becomes fragmented or overwritten lol. If you get to the point where you know your s-stat is bad, there are mods to bypass it and you can manually turn the fan on and off, but you aren’t at the point yet or in need of that bc if you really have a bad t-stat that is priority 1.

 

[WillWagner]

Good morning again sir! sorry to bug you with all these easy questions ha, if my tstat is bad and not opening would that cause my shutter stat to not open? I was curious if that may be the case because I see the shutter stat is on that upper radiator hose and if that t stat doesnt open maybe its not getting hot enough to flip on? Im just trying to figure out my order of diagnosis for why shes getting hot and the fans not flipping on. Thanks again for all your help!

If when the gauge says it is hot, see if the upper pipe is hot. I don't understand why the s-stat sender was put in the upper pipe. tehe pipe is never full.

 

[Lantzj22]

Good morning! I got my coolant flush done this weekend. I thought my truck was getting hot (it wasnt) I actually had bad grounding at both the trans gauge and the engine gauge. (verified with thermal gun) When i would push them against the mounting surface it would drop to normal temps. I ended up not rebuilding my S stat or replacing the t stat. My coolant was fairly dirty maybe like jug number 3 from your post. flushed it 5-6x and got it clear. filled it and burped, took it to the beach and ran it for 45 mins and had no issues. I appreciate the help!