# 2004 2500HD 8.1 running hot



## secret_weapon (Jan 24, 2007)

When I bought the truck 3 years ago I put a 180 deg. t-stat in it and would hold that temp. 180-185 no matter what, now just cruising around town 25-40mph empty and even on 60 deg days the temp will go up to 210-220 then the fan clutch locks up and coolant temp will slowly drop, but not to 180, only drops to 195ish. Having the heater on full does help a little. Temps are at normal when cruising on highway. Trans temps are higher too because of this. 

I've recently replaced the thermostat with another 180 deg. but no change. New heavy duty fan clutch, no change. Truck has 112k miles on it, so I replaced the water pump too. Still no change. Old coolant that was drained was still very clean looking.

I have blown out the fins of the radiator also. 
My last thought is that the radiator has somehow become partially clogged. This being pretty pricey I was holding off, but now I am thinking this may be my cooling problem. 

Has anyone else had an issue like this or is this something common?


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## dieselss (Jan 3, 2008)

Have you back flushed the system? Take the hoses off the rad and just run water through it? And the same with the heater core?


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## secret_weapon (Jan 24, 2007)

Haven't tried back flushing yet. Think I will do that after I run some cooling system flush through it. Unless someone advises not to use the flush.


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## dieselss (Jan 3, 2008)

I see no need for the flush. Just garden hose in the radiator, heater core and block


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## CARDOCTOR (Nov 29, 2002)

take the radiator to a radiator shop and have it flow checked to see if it is blocked


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## leolkfrm (Mar 11, 2010)

run your finger over the fins, may be soft and not cooling correctly


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## secret_weapon (Jan 24, 2007)

When I get a chance this week, I'll pull the radiator out and take it to a radiator shop and have flow tested/cleaned. If they can clean it, Awesome! If not, radiator is already out and ready for new one.


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## secret_weapon (Jan 24, 2007)

Went to local radiator shop and they recommended replacing/upgrading my radiator instead of trying to clean out. Apparently mine was too small and not efficient with only a 1 row core,. Leaves me wondering why GM put in single row radiator on such a large engine that normally runs hotter. So for $240, I bought a 2 row. The original radiator has 1 1/4" thick core, the new one is 2" thick. 
New radiator installed, almost 4 gallons of fresh coolant, top up engine and trans fluids, run up to temp... Perfect! 
Now I'm ready for snow!


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## dieselss (Jan 3, 2008)

That's a big upgrade. Glad you decided to go that route.....happy plowing


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## plowflowmaster (Oct 18, 2016)

We have been helping people solve this problem for over a decade . www.plowflowmaster.com When you havetime, check it out.


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## dieselss (Jan 3, 2008)

plowflowmaster said:


> We have been helping people solve this problem for over a decade . www.plowflowmaster.com When you havetime, check it out.


 . . Then why haven't we heard about this before? And what happens when you go right into a pile, is it going to bend, break, or twist? If it brings air into the radiator, won't it also bring snow? And if that's the case won't it actually plug the grill counter act it's purpose?


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## plowflowmaster (Oct 18, 2016)

We haven't advertised in the traditional sense until recently and relied on word of mouth from satisfied customers. Our product is strong. Our manufacturing process includes the highest quality steel and is fabricated by certified welders. We haven't had a warranty issue in over a decade of sales. As far as your air flow question. The science works like this. Plowflowmaster doesn't 're-direct' or 'force' air to your radiator. What it actually does, is break the vacuum of air directly behind the plow and allow free air to move around the radiator. Thus, it doesn't bring snow into the radiator and block it. If you go to our website at https://www.plowflowmaster.com/how-it-works you can watch a wind tunnel simulation with our product as well as diagrams that explain.

Hope that answers your questions!


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## secret_weapon (Jan 24, 2007)

plowflowmaster said:


> We have been helping people solve this problem for over a decade . www.plowflowmaster.com When you havetime, check it out.


That's kinda of neat, but getting air to the radiator wasn't my problem. Getting coolant to flow through the radiator was my issue. 
Thanks for advertising.


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## plowflowmaster (Oct 18, 2016)

secret_weapon said:


> That's kinda of neat, but getting air to the radiator wasn't my problem. Getting coolant to flow through the radiator was my issue.
> Thanks for advertising.


Thanks! Glad to hear your back up and running!


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## bootstrap (Apr 29, 2016)

Hey secret, I see your dyno numbers in your signature. Is that at the wheels? Because the 8.1 had more power than that stock. I assume that's at the wheels.


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## secret_weapon (Jan 24, 2007)

bootstrap said:


> Hey secret, I see your dyno numbers in your signature. Is that at the wheels? Because the 8.1 had more power than that stock. I assume that's at the wheels.


Yes, my numbers are at the wheels. Stock ratings are at the crank.


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## secret_weapon (Jan 24, 2007)

Upgraded cooling fan (I think), Lots of research and I found that using Hayden severe duty fan clutch 2851 has the same thread, which is 30mm x 1.5 and fan bolt/mount hole same size as Duramax cooling fan. Same diameter of 21", no clearance issue. 
Very good so far, although I haven't driven any where with plow on yet.


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## leolkfrm (Mar 11, 2010)

ive never known gm to use a single core on a bb...usually a double with electric assist fans in front


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