Alright, I cleaned the radiator, replaced the clogged small hose, replaced the thermostat, took every hose off and cleaned out, replaced filter, replaced crossover pipe, flushed the engine, replaced temp sensor,checked the water pump,added new coolant and distilled water,rebuilt actuator,replaced trans coolant filter, blew out trans cooler, and yet this SOB is still overheating!!!!!! Any ideas? I'm at my wits end with this dag gum truck!!!!
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Yet More coolant issues! 84' M923
- Thread starter tbar123
- Start date
- 737
- 14
- 18
- Location
- Bothell, WA
I see where it was recommended, but I have to ask since I didn't see the results...
Did you check the temp with a separate indicator just to be sure?
Did you check the temp with a separate indicator just to be sure?
I am NO EXPERT, at all, but after reading this, if that were
my truck, while the radiator is out, I would disassemble
the balance of the cooling system and CLEAN / FLUSH IT ALL.
Even if you had it open before, open it again and FLUSH IT ALL,
forwards and backwards AND THEN DO IT AGAIN.
The very first thing I did to my M925A1 / NHC250 was to service the cooling system.
Here is what I learned about my NHC250.
You HAVE to flush the heater core FORWARDS AND BACKWARDS several times to get the yuck out
with a high volumn hose and proper adaptors, not just a rag wrapped around things.
Replace cap.
You HAVE to make sure the long small diameter hoses across the top of the engine are CLEAR AND
IN GOOD SHAPE. I simply replaced, easy to do.
I think you said you replaced the thermostat. Still pull it again and FLUSH ALL
forwards and backwards and left and right and do it again!
I do not remember reading you saying you flushed the block as I would.
You HAVE to pull the inspection plates on the side of the engine and flush till
you are blue in the face! Up, down left right and do it ALL OVER AGAIN!
You HAVE to add drain down petcocks and flush forwards and backwards at
both sides at the bottom of the radiator!
You have to disassemble EVERY LAST THING COOLANT RELATED then clean
and flush EVERYTHING all at one time, not one section at a time and put
it back together and hope for the best.
You HAVE to make sure fan components work as advertised.
When you reassemble I think I filled w/ water first and tested for leaks
then I drained down for the last time using my 2 new radiator butterfly
petcocks an filled w/ antifreeze.
All is well...when the fan engages it still scares the begesus out of me
but it tells me its working!
You should listen HARD to Will Wagner FIRST, IMO.
my truck, while the radiator is out, I would disassemble
the balance of the cooling system and CLEAN / FLUSH IT ALL.
Even if you had it open before, open it again and FLUSH IT ALL,
forwards and backwards AND THEN DO IT AGAIN.
The very first thing I did to my M925A1 / NHC250 was to service the cooling system.
Here is what I learned about my NHC250.
You HAVE to flush the heater core FORWARDS AND BACKWARDS several times to get the yuck out
with a high volumn hose and proper adaptors, not just a rag wrapped around things.
Replace cap.
You HAVE to make sure the long small diameter hoses across the top of the engine are CLEAR AND
IN GOOD SHAPE. I simply replaced, easy to do.
I think you said you replaced the thermostat. Still pull it again and FLUSH ALL
forwards and backwards and left and right and do it again!
I do not remember reading you saying you flushed the block as I would.
You HAVE to pull the inspection plates on the side of the engine and flush till
you are blue in the face! Up, down left right and do it ALL OVER AGAIN!
You HAVE to add drain down petcocks and flush forwards and backwards at
both sides at the bottom of the radiator!
You have to disassemble EVERY LAST THING COOLANT RELATED then clean
and flush EVERYTHING all at one time, not one section at a time and put
it back together and hope for the best.
You HAVE to make sure fan components work as advertised.
When you reassemble I think I filled w/ water first and tested for leaks
then I drained down for the last time using my 2 new radiator butterfly
petcocks an filled w/ antifreeze.
All is well...when the fan engages it still scares the begesus out of me
but it tells me its working!
You should listen HARD to Will Wagner FIRST, IMO.
rhurey; I have not checked the engine temp with a seperate source. I think I need to do that!
Artisan; I have not removed the inspection plates! I will do that tomorrow since I've already taken everything apart again.Just to make sure there is 3 correct on the passenger side of the motor? I will remove the block heater as well and wash that "REAL" good as well. Other than that once I put everything back together and it still overheats there will be a M923 up for sale!
Artisan; I have not removed the inspection plates! I will do that tomorrow since I've already taken everything apart again.Just to make sure there is 3 correct on the passenger side of the motor? I will remove the block heater as well and wash that "REAL" good as well. Other than that once I put everything back together and it still overheats there will be a M923 up for sale!
Csm Davis
Well-known member
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Okay so how hot is it getting up to before the fan comes on? Then how high before you shut it down?
- 737
- 14
- 18
- Location
- Bothell, WA
As a quick check, does the trans oil temp go up as quick? I'd expect the two to be fairly in sync... I know they're not super accurate, but the $15 IR guns on Amazon will likely get you in the ballpark.
And yeah, you're gonna get a ton of junk out of the inspection plates, I recall what all poured out when I installed the block heater. Convinced me to get a coolant filter installed asap. (Which reminds me, time to change that filter now that it's had a chance to get the initial yuck out.)
And yeah, you're gonna get a ton of junk out of the inspection plates, I recall what all poured out when I installed the block heater. Convinced me to get a coolant filter installed asap. (Which reminds me, time to change that filter now that it's had a chance to get the initial yuck out.)
In a sad way I hope those plates show all kinds of crap, but when I removed the middle plate for the block heater it was picture perfect inside, as well when I removed the water pump.I must have re-rebuilt the actuator wrong because the temp reached 240 and the fan never came on. SO I shut it down then.The trans temp was fine never got over 90 I believe. I was looking at it but since it wasn't bad I never really paid to much attention!
Csm Davis
Well-known member
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- Hattiesburg, Mississippi
Okay double check that temperature and if it's accurate fix that fan!
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You can force the fan on. Put the locking bolts in, and see what happens. If that cools you back down, then you have it narrowed down. Interesting though that the oil and tranny temps are not rising with the coolant. Are you driving the truck to get it hot, or is it running up static?
Still not sold that this reading is real. Need an independent temp sensor of some sort. I have left the overflow tank open and shot with an IR gun before.
I have had a hard time getting any of my trucks hot enough for the fan to even come on. Both the 14L and the 8.3L engines.
Edit: One of my trucks, the air lines were switched on the shutter stat. I rebuilt it, played with it, did everything, and then swapping air lines fixed everything. Make absolutely sure they are correct, not just how they were when you got it.
Still not sold that this reading is real. Need an independent temp sensor of some sort. I have left the overflow tank open and shot with an IR gun before.
I have had a hard time getting any of my trucks hot enough for the fan to even come on. Both the 14L and the 8.3L engines.
Edit: One of my trucks, the air lines were switched on the shutter stat. I rebuilt it, played with it, did everything, and then swapping air lines fixed everything. Make absolutely sure they are correct, not just how they were when you got it.
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162tcat
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- Washington
How does it run (other than possibly hot)? How much smoke out of the stack at idle, cruise and wot? Any odd colors or smells?
Wheelspinner;I have caged the fan before and it did absolutely nothing. In fact after I drove the truck to turn in some cans. The actuator got stuck in the open position and no decrease in temp.Side note: When rebuilding the actuator make sure you get the right size high heat o rings. The ones I bought were just over sized and that caused the actuator to stick in the open position. The airlines to the actuator are correct according to the TM's.
162tcat;It runs really good, There is a small amount of white smoke during normal running. I have changed the fuel filter less than 50 miles ago.The only smell I can tell ( my nose doesn't work Dr approved)is the scent of coolant at/around the 230 mark.
Well I took the garden hose out and flushed and back flushed and noticed that the trans cooler had a few blocked ports, So I ran a rod down all 2.5 million of them and then took the power washer and blew it out backwards. I then continued on blowing the entire engine with the power washer. ( Every one I could get to at least). I also noticed that when I shot water forward into the forward inspection plate it seemed that more water ran out of the rear plate than out of the oil cooler. So I hit it really good and didn't notice any color difference in the water but it appeared to run better after a few minutes.Other than that everything appeared to be good. I do want to thank the community for helping with this. I feel like I'm not contributing any since all I do is pose my problems as of lately, but once again thank you for the help and advice all of it is very much appreciated!
162tcat;It runs really good, There is a small amount of white smoke during normal running. I have changed the fuel filter less than 50 miles ago.The only smell I can tell ( my nose doesn't work Dr approved)is the scent of coolant at/around the 230 mark.
Well I took the garden hose out and flushed and back flushed and noticed that the trans cooler had a few blocked ports, So I ran a rod down all 2.5 million of them and then took the power washer and blew it out backwards. I then continued on blowing the entire engine with the power washer. ( Every one I could get to at least). I also noticed that when I shot water forward into the forward inspection plate it seemed that more water ran out of the rear plate than out of the oil cooler. So I hit it really good and didn't notice any color difference in the water but it appeared to run better after a few minutes.Other than that everything appeared to be good. I do want to thank the community for helping with this. I feel like I'm not contributing any since all I do is pose my problems as of lately, but once again thank you for the help and advice all of it is very much appreciated!
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I've read through this thread twice now and also find all the help offered to be great! So where are you on temperature now? Still hitting 230? I didn't see that you replaced your temp guage or checked it with another gauge.
I took mine for a spin and noticed it ran a little hotter than usual (225 indicated) hitting 230 driving around town today. That concerned me so I stopped and took out my IR temp gun. I shot many places on the engine, thermostat housing, radiator and hoses and found the max temp on my gun to show 190. I know my gun to be pretty accurate. So that means my guage is probably reading about 40 degrees high. I'm assuming an external temp measurement is going to be pretty close to actual coolant temperature. If your issue still exists this might be your problem.
I took mine for a spin and noticed it ran a little hotter than usual (225 indicated) hitting 230 driving around town today. That concerned me so I stopped and took out my IR temp gun. I shot many places on the engine, thermostat housing, radiator and hoses and found the max temp on my gun to show 190. I know my gun to be pretty accurate. So that means my guage is probably reading about 40 degrees high. I'm assuming an external temp measurement is going to be pretty close to actual coolant temperature. If your issue still exists this might be your problem.
Csm Davis
Well-known member
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- Hattiesburg, Mississippi
Easy take an IR gun in the house and check it against a pot of boiling water and an ice cube if it is within a few degrees it can be considered a good gun. Then use it to verify the trucks reading.
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- 737
- 14
- 18
- Location
- Bothell, WA
Yup. This thread convinced me to buy an IR gun. Got over the measure the temperature of everything quicker than I thought I would.
- 737
- 14
- 18
- Location
- Bothell, WA
You're trying to calibrate against a military gauge... Realistically if you assume everything lies and the max deviation from truth for any one unit is 5%, the 10% the two will be off in the OP's case would more than alarm for real problem or bad gauge.
I finally broke down and bought a temp gun....I know, I know. Well let me start from the beginning. I went out this morning and after letting the truck run up to 240 on the gauge yesterday, I removed the rad cap, and a huge rush of air came out. That really surprised me since I vented the system a lot yesterday.So I reopened the vent valve on the heater core and fluid ran out fine, SO I then took the cap nut off the top passenger side rad and had the nut off completely for around 5 seconds then fluid shot out of that hole like a coolant fountain! So I quickly replaced it.I then went and spent a few hours with Momason. Came home and got back at it.I started a pot of boiling water to see the temp variance. I put a food thermometer in the water at 180 degrees, the temp gun hit 177. SO close enough. I simply started the truck and let it run at 1000 rpm. It took about 45 minutes for the truck to get to 177 on the temp gun. I was expecting the thermostat to open when the fan turned on and it scared the **** outta me.So I let it run for another 10 minutes to see if the fan would turn back on and it did! You know what this means! I actually did not 1 but 2 things right! I still however feel that the temp sensor was accurate until, I drove the truck to return those cans when it did overheat something fierce. But now it's onto moving the bed! I do want to sincerely thank everyone for their input,advice, and help with this problem! So Thank You!