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Discussion Starter · #1 ·
I understand that there are a ton of threads about lly's overheating but I am looking for suggestions. Our 2004.5 lly silverado duramax started overheating while towing. It carries about 2000 lbs all the time because it is my dads work truck. Semi-regularly we use it to tow an enclosed trailer (roughly 8-10,000 lbs). We never had any problems until there were about 200,000 miles (about a year ago) on the truck, and at first it was only while towing. The local chevy garage thought that it may have been the water pump, so that was replaced. That seemed to help, but we were still having problems, but only while towing the trailer.
Recently (about 250000 miles) it began to overheat during everyday driving. As I said there is about a ton in the bed 100%, but this was never an issue before. Since the problem has become more serious (my dad depends on this truck for his livelihood), we took it back to the chevy garage and they told us that the fan clutch was going out. Instead of replacing the fan clutch we opted to upgrade to electric fans. This still did not solve the problem. Next we replaced the thermostats, and still no luck. After that (thanks to some info dug up on this forum) we replaced the turbo MP with and AFE bladerunner and that still did not solve the problem. The coolant has recently been flushed and replaced and that also did not help. All radiator hoses appear to be in good condition and not collapsed.

It has gotten to the point now where it is almost always running at 235 or more, no matter what kind of driving you're doing.

:help I'm starting to run out of guesses for the cause. Could this be a plugged catalytic converter? The exhaust is still stock and is the next thing we were planning on upgrading to attempt to fix the problem. If it would be a plugged cat, most turbo-back kits eliminate the cat, correct? Any thoughts on the likelihood of this being the problem? When we do replace the exhaust what are your thoughts on what is the best? Whatever goes on will be stainless because I have had bad luck with non stainless exhausts in the past. I apologize for the long winded post, but I wanted to make the circumstance as clear as possible. Any input of advice will be very much appreciated! Thanks in advance!
 

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Goog luck wit dat...
same trouble here
 

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Cat was my first thought. If you're thinking about changing the exhaust anyway, why not try gutting the cat first, doesn't cost anything and it's easy to do, you can do it without removing the cat. Just unbolt the front flange, pop off the two front rubber exhaust hangers (brake fluid helps lube them up), and drop the exhaust pipe out of the way. Get a large spade bit and ream out as much "stuff" as you can, then use a crowbar, pry bar, big screwdriver or chunk of rebar to hack a hole at least the size of the pipe diameter through the center. Vacuum out as much as you can, then rebolt the flange, pry the hangers back on and see if that helped. Takes about an hour or so. When you start it back up, it will blow a bunch of whitish powder for a couple of miles til it all gets blown out the exhaust. I would also try disconnecting the Superchips and clean the MAF, probably don't have anything to do with overheating but never know....
 

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i have no cat no egr no nothing and mine overheats on a real hard run up hill with a coolant leak other than that mine dont.
 

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Also check for dirt & debris in front of the radiator, between the rad and intercooler. That's a common problem with trucks that spend a lot of time around hay and dust, etc.
 

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Discussion Starter · #6 ·
Everyone has offered good advice... but unfortunately we have already tried most of it. We did remove the superchips tune the last time we towed with it and it was no help. The K&N filter has recently been removed, cleaned and re-oiled, during which the MAF sensor was cleaned. (Also, we removed the metallic tape stuff on the inside of the fender in an attempt to draw more cool air from outside the engine compartment). When it began to overheat regularly we took the entire front end apart and cleaned the front of the radiator/intercooler because it does spend a lot of time around dust and hay. There is no coolant leak, and it is to the point where it overheats on flat ground while babying it.

I appreciate all the suggestions! Any other ideas? Any suggestions for exhaust systems. This truck is driven about 50k miles a year so fuel mileage is important.
 

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Elec fans were the wrong direction. You made your issue worse.

With your miles, a radiator replacement is probably necessary.
I agree. After 200k on a radiator I consider them junk.
 

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Discussion Starter · #10 ·
killerbee-after a little more research i see what you mean about the electric fans. I guess i should have looked into a little more first, whoops. I just (stupidly) assumed that because i've had positive results with them on my gasser that similar results would be obtainable on the diesel. In any case, this truck does not tow heavily too often, so if I pick up a little MPG these fans may not be a total wash.

Anyhow, any recomendations for radiators. Is it worth the extra money for dual row setups? What in particular should i be paying attention to when choosing one of another. A quick search at summit has radiators that range from 200 bucks to over a thousand and I guess I don't really know what i should be looking for.
 

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Bump for ya. Curious myself.
 

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Discussion Starter · #12 ·
I think we are going to end up replacing the radiator as soon as I have a chance. Once again does anyone that has replaced their radiator have any suggestions? I will update after we replace to radiator with results.
 

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Water pump gears have been known to come loose. Merchant Auto sells there WP's with the gear tig welded on. I wish I would have known about this when I changed mine out. Duramax Water Pump 01-05 LB7/LLY Fan clutch, turbo MP and water pump are the ones come to mind. What is the trans temp running at?
 

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Discussion Starter · #14 ·
trans temp is running a little higher than normal as well. I don't know exactly what it has been running out. I'll check this afternoon and have a more precise number.
 

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So did the radiator fix the over heating issue ?? And if so Wt and where did u get it
 

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I had that problem with my truck and it was the rad was right plugged with bugs and shit could not even see between the rad and intercooler. But took rad out to clean crap out betwenn it and cooler so I thought I would wash the rad out while it was out. OMG the bugs and crap that game out of the rad. It looked clean but was far from. Once washed out and with fresh coolant in it no more heating problem at all. Just recently cut muffler off aswell and just put in a chunk of pipe and it runs even cooler now
 

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Discussion Starter · #17 ·
Haven't replaced the radiator yet. Like Hunter we cleaned the radiator more thoroughly yesterday. As he said, it looked clean but it really wasn't. We pushed as much of the crud out of it with the air compressor as possible then washed it several times with an industrial cleaning solution, and it was much dirtier than it appeared. On the test run afterwards it did not show any signs of building heat and it did not overheat on a 100+ mile drive this morning. Its supposed to be close to 100 degrees the rest of the week and I will be towing a 10000lb trailer on Friday, so I should know for sure by the end of the week and I will post the results on here.
 

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2004.5 gmc sierra 3500 hd lly engine .same truck. same overheating issue. on a hot day ,towing going uphill it overheats very quickly. have new rad, new thermostats , fresh coolant change. no coolant leaks and holds pressure in coolant sytem. help please!!!
 
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