Over heating 97 12v

I went through this problem on my '97 very recently.

I cannot go over ANY mountain west of Denver on I-70. Even if I drop her in 2Lo (4x4 low with front end disengaged), I still cannot go more than a half mile without running too hot!!! I was grossing 20k.

I gave up and turned back down and went to a nearest auto parts store that had parts for my truck and when I torn my truck down in their parklot, I found there's bunch of curds INSIDE my radiator. Even the coolant looked CLEAN! After that, I can go up the mountain, including the Vail Pass (I got to the summit before I knew it, it wasn't bad at all) going 50+ mph with 1200*F EGT.

Take your truck apart and really inspect it to see where it's in need of attention.
 
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Like others have said, the fan is very loud and you will know it is on. I had on flexlite dual fans and mine got very hot towing, had to pull over and run fans on full on warm days towing. got tired of that put back on stock fan and have had 0 issues while towing. my setup is very aggressive as far as towing is concerned. I run 5x..020 injectors with 29* timing, turned up 215 pump and twins. I tow up hills at 50 psi so my power level is way over stock and still have no issues with temps.
 
I agree with others, check you fan clutch, then I'd say move onto replacing coolant, pulling the radiator and cleaning it out.

Inspect your Tstat while replacing coolant. Check it in a pot of water on the stove.
 
Well I sprayed the radiator out with water the best I could without removing it. The truck was past normal operating temperature and when the water barely hit the fan it spun very free. Seemed like there was no resistance at all.

Should I even worry about checking to see if my temp gauge is reading incorrectly? On a 20 minute drive today it went from cold all the way to the last line before over heating. I slowed down to 65mph and the temp dropped down to normal. I went back up to 70mph and it dropped below the middle line. It was sitting on top of the 1 in 190.

Missing my 6.4.
 
For all you know that thing could have a junk gasser oriellly stat that fit the hole. Seen it before. I ran no fan from October until 2 months ago. That faster you go the more it should cool. Replace the stat and get it over with op.
 
95cummins5.9 said:
For all you know that thing could have a junk gasser oriellly stat that fit the hole. Seen it before. I ran no fan from October until 2 months ago. That faster you go the more it should cool. Replace the stat and get it over with op.
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Roger that

Missing my 6.4.
 
I am not an "OE only" guy, but the Cummins thermostat is the only choice there. I have seen aftermarket ones not fit, have crappy gaskets, and at best fluctuate 20-30* after things are warmed up.

My truck has the stock radiator, about 500RWHP, and I can beat on it on 100* days and the gauge never moves.

Change that thermostat and flush out the cooling system/block/heater core with a garden hose forward and backward, use some flush chemical according to the bottle, and I bet that fixes it.

For the record, I don't ever notice my fan coming on. *shrug* When I check the clutch on it if feels a little loose actually, but again, almost 4x the power on stock cooling system with AC, never any issues.

Hope that helps


Owner @ Power Automotive. ASE Master, L1, T2. Pretty much a Cummins fan, but I fix them all 50+ hours a week.
 
Thekid760 said:
......pulling the radiator and cleaning it out.
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^^^^^This. You will never be able to adequately clean the fins with the radiator in the truck. I just finished cleaning mine a couple days ago. Only 110k miles since it was cleaned last, it was full of dirt and bugs (a dust storm in N. TX and a bug storm in ID, plus a winter of sand and salt driving). While it is out you can access the intercooler and clean it also. I pour a gallon (or two) of Simple Green into a garden sprayer, spray the fins, let it soak, wash, repeat. Don't use harsh cleaners like Super Clean, Purple Power, etc. They contain chemicals that can attack the solder joints. Also, take the time to straighten the fins if they are bent over. A small flat screwdriver and patience. Spend the $$ for new hoses while you are at it if the ones you have are 4 years old or older.
 
GAmes said:
^^^^^This. You will never be able to adequately clean the fins with the radiator in the truck. I just finished cleaning mine a couple days ago. Only 110k miles since it was cleaned last, it was full of dirt and bugs (a dust storm in N. TX and a bug storm in ID, plus a winter of sand and salt driving). While it is out you can access the intercooler and clean it also. I pour a gallon (or two) of Simple Green into a garden sprayer, spray the fins, let it soak, wash, repeat. Don't use harsh cleaners like Super Clean, Purple Power, etc. They contain chemicals that can attack the solder joints. Also, take the time to straighten the fins if they are bent over. A small flat screwdriver and patience. Spend the $$ for new hoses while you are at it if the ones you have are 4 years old or older.
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I'm with ya there , :Cheer:.

Thinking clogged and a posssible t-stat issue all combining together to create a real annoying issue .
 
GAmes said:
^^^^^This. You will never be able to adequately clean the fins with the radiator in the truck. I just finished cleaning mine a couple days ago. Only 110k miles since it was cleaned last, it was full of dirt and bugs (a dust storm in N. TX and a bug storm in ID, plus a winter of sand and salt driving). While it is out you can access the intercooler and clean it also. I pour a gallon (or two) of Simple Green into a garden sprayer, spray the fins, let it soak, wash, repeat. Don't use harsh cleaners like Super Clean, Purple Power, etc. They contain chemicals that can attack the solder joints. Also, take the time to straighten the fins if they are bent over. A small flat screwdriver and patience. Spend the $$ for new hoses while you are at it if the ones you have are 4 years old or older.
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Going with this ^^^^^ Then take it to a car wash spend couple bucks and use degreaser and then wash! use common sense and don't fold your fins over!!!! The guys are right about the cummins thermostat.
 
You said you don't know what all might have been done to the truck. I have seen some heads that were fine at stock power, but won't stay cool when the fuel was turned up. My truck always stayed cool as a cucumber till we had to change heads, and that's all that changed, now it won't stay cool for nuttin'
 
Cowchaser said:
You said you don't know what all might have been done to the truck. I have seen some heads that were fine at stock power, but won't stay cool when the fuel was turned up. My truck always stayed cool as a cucumber till we had to change heads, and that's all that changed, now it won't stay cool for nuttin'
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When you changed heads did you swap your old T stat into the new head?


I like to go fast
 
Yes, same CUMMINS t-stat. The engine this head came off of had a problem with heat and we never could figure out why. When mine cracked, I had this one worked over and put it on and now my engine runs hot.
 
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Might also try installing a Coolant Bypass , might help with the heat being more evenly distributed in the Cylinder head, and the T-stat changed or at a minimum , Verify that it is infact opening @ the correct temp.
 
I replaced the thermostat with a Cummins t stat and it quit over heating but now it fluctuates. Seen a lot of guys say this is normal but others say it's not when using a Cummins t stat. What do yall think?
 
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