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Engine temperature when towing heavy on a hot day, how hot is to hot?

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Engine temperature when towing heavy on a hot day, how hot is to hot?

Old 09-02-2019, 12:52 PM
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Originally Posted by dawgsfish View Post
are you going off the gauge in the dash? because they are notoriously inaccurate.
Nope, using the gauge on the tuner's gauges display screen. The factory gauge only moves slightly from about 200 to 220 during all of the temp fluctuations.

Next week when I get back, I'm planning on replacing the thermostats with a Mishimoto low temperature set (174F & a 180), a new coolant temperature sensor and a fan clutch. Depending on my motivation, I may blow out as much of the stack as I can reach while the upper fan shroud is off.
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Old 09-02-2019, 12:55 PM
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there is no need to use low temp thermostats. I'd replace with Delco's and allow the system to run as intended at the intended temperatures personally. cleaning the coolant stack first, seeing what difference it makes, if not acceptable, replace t stats with delco's, if that doesn't provide necessary solution, try the fan clutch/temp sensor. I wouldn't do it all at once, you won't ever know that the issue was to start with.
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Old 09-05-2019, 12:39 PM
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You can pull the radiator and clean the fins with AC coil cleaner and a water hose. My LLY was packed pretty good with dirt, bugs, etc. and was causing it to run warmer than usual. Back to normal after the cleaning. LBZs are getting pretty old too so I am guessing you probably have enough miles to warrant a good cleaning.
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Old 09-05-2019, 04:10 PM
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Had a 2015 Duramax before my 2017 Powerstroke and neither one of them got anywhere near that hot when towing.
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Old 09-06-2019, 03:58 AM
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if you are running that warm, a lower temp thermostat isn't going to help at all. At those temps any thermostat is already wide open and at full flow, and if that still isn't cooling the motor you have other issues. figure out what those are, and stick with the OEM temps on thermostat.
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Old 09-08-2019, 04:28 PM
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Update, I pulled my dad's old boat (2000 Targa 17 with a 50HP Merc on the back...appx 2200 lbs on the trailer) from Roanoke, VA to Elkton, Md via 460, 29, 15, 70 & 95. I left at about 4:30 AM to take advantage of the cool temps back in the mountains (about 55 degrees). Coming out of Lynchburg VA to Charlottesville VA there are some pretty long grades where the engine got up to about 210 to 220 pretty quickly during the pull, however once over the mountain (hill) the engine would cool back down to the upper 170s (closed thermostats) about halfway down. While I'm sure that the cooling stack needs cleaning no matter what else I find wrong, it appears that the 195 degree temp thermostat isn't opening or isn't opening completely due to the temps that I saw climbing the mountains with only a 2200lb load. That truck shouldn't even have known the boat was behind it, much less start running a little warm in those cool ambient temps. That tells me that the engine is producing more BTUs than the cooling system can remove under those conditions; and the fact that the engine IS cooling back down after any load has been removed tells me that the cooling system is working...somewhat!

Dropped the truck off at the shop Friday and they said that there is an intermittent MAF error code that is causing a "no power" condition before clearing up and taking off that they want to chase down before they tackle the cooling issue and stack so they can have a solid baseline to work from. They think that it could be stemming from a leaking EGR or "up" pipe from the exhaust (boost leak). I'm gonna have to wait until Monday or Tuesday to see. Also the mechanic and manager strongly suggested new thermostats (just one step cooler...a 174 & a 185 degree and a radiator block off tarp for the winter) since the housing appears to have never been taken off. That's an easy job that I can do that to save a few $$ once I get the truck back.

Stay tuned as I try to figure this one out.

Last edited by Wingnutt; 09-08-2019 at 04:38 PM.
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Old 09-08-2019, 04:41 PM
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Something to consider is that the water pump is likely on borrowed time and is not something you will change in a parking lot somewhere. Buddy is a GM mechanic and told me that at 160k you are either replacing the water pump or it is staring you in the face. If you stay local its not a big deal but if you go long distances I would replace as a preventative measure.

My lbz reached 215 a couple of times but normally hovered around 200.

I would start with t-stats and coolant flush.
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Old 09-08-2019, 04:51 PM
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Yea, that water pump on a LBZ is a bieotch!

Almost everything has to come off the front of the engine! I've helped some friends with two, and when (now? ) that time comes I've decided that it will go to the shop! The book calls for 6 to 8 hours of labor depending on the individual configuration, so that one is going to sting! Also I've discovered that there is a semi-major problem with the water pump manufacturers (there are only two and surprise, surprise they are both in China!) recently; it appears that under very heavy loading, the impellers are spinning on the input shafts! As of now the only solution is a US made one that isn't cheap!

Last edited by Wingnutt; 09-08-2019 at 06:08 PM.
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Old 09-08-2019, 06:03 PM
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Originally Posted by Wingnutt View Post
Yea, that water pump on a LBZ is a bieotch!

Almost everything has to come off the front of the engine! I've helped some friends with two, and when (now? ) that time comes I've decided that it will go to the shop! The book calls for 6 to 8 hours of labor depending on the individual configuration, so that one is going to sting! Also I've discovered that there is a semi-major problem with manufacturers (there are only two and surprise, surprise they are both in China!) recently; it appears that under very heavy loading, the impellers are spinning on the input shafts! As of now the only solution is a US made one that isn't cheap!
I charge about $1000 with parts and labor
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Old 09-08-2019, 06:09 PM
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Originally Posted by suzuki140 View Post


I charge about $1000 with parts and labor
That's about what I am thinking. Plus if I have to use that US made pump, add another $500

EDIT:
Just had a friend stop by who is a Duramax mechanic. He got on his computer and according to the specs the stock thermostats are not full open until 230 according to the OEM manual. The 180 degree thermostat just starts to open at 180 and is fully open by 212 degrees. This is where the bypass gets blocked, but 230 is where both are supposed to be full open according to GM. And again, according to the factory manual, it says 240 coolant temp is just fine to run at when pulling heavy loads in high ambient temperatures.

Crap, now I'm totally confused. But still, I know it should normally run much cooler. Research says the same thing people here are saying...200 to 210 in hot weather because of the size of the cooling system.



Anyway, FYI here is how the whole system is supposed to work:


Cooling Cycle (6.6L Diesel Engine)

Coolant is drawn from the radiator outlet and into the water pump inlet by the water pump. The coolant flows to the heater core while the engine is running. This provides the passenger compartment with heat and defrost.
Coolant is then pumped through the water pump outlet and through the coolant pipe to the engine oil cooler. The coolant flows around the oil cooler element and to the rear engine cover. The rear engine cover distributes the coolant flow to both banks of the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders where it absorbs heat.
The coolant is then forced through the cylinder head gasket openings and into the cylinder heads. In the cylinder heads, the coolant flows through the water jackets surrounding the combustion chambers and valve seats, where it absorbs additional heat.
Coolant is also directed to the turbocharger. There it circulates through passages in the center housing. During engine warm-up cycle the bypass valve located in the turbocharger inlet hose at the outlet pipe prevents coolant flow. During normal operating temperatures, the coolant assists in keeping the turbocharger cool.
From the cylinder heads, the coolant flows to the thermostats. The coolant flows from the thermostat housing to the water pump through the bypass pipe until the enginereaches 85C (185F).
Operation of the cooling system requires proper functioning of all cooling system components. The cooling system consists of the following components:

Thermostats (6.6L Diesel Engine)

The thermostats are coolant flow control components. The purpose of the thermostats are to regulate the correct operating temperature of the engine. The thermostats utilizes a temperature sensitive wax-pellet element. The element connects to a valve through a piston. When the element is heated, it expands and exerts pressure against a rubber piston. This pressure forces the valve to open. As the element is cooled, it contracts. This contraction allows a spring to push the valve closed.
The 6.6L diesel engine requires two thermostats for correct coolant flow. The front thermostat is a dual purpose thermostat. The front thermostat controls the coolant flow to the bypass port and to the water outlet. The rear thermostat only controls the coolant flow to the water outlet.
When the coolant temperature is below the rated thermostat opening temperature, the front thermostat valve remains closed to the water outlet and is opened to the bypass port. The bottom portion of the thermostat is raised off of the bypass port while at the same time the top portion closes the coolant flow to the water outlet. The rear thermostat also is closed to the water outlet during engine warm-up. This prevents circulation of the coolant to the radiator and allows the engine to warm up quickly. After the coolant temperature reaches 82C (180F) the front thermostat primary valve opening temperature, the front thermostat primary valve will start to open. The coolant is then allowed to circulate through the thermostat to the radiator where the engine heat is dissipated to the atmosphere. As the engine coolant reaches 85C (185F) and more coolant demand is required the front thermostat secondary valve begins to close the bypass port and the rear thermostat begins to open coolant flow to the water outlet. The thermostats will continue to control the coolant flow by opening and closing. The front thermostat will be fully open when the coolant temperature reaches 95C (203F) the rear thermostat will be fully open when the coolant temperature reaches 100C (212F). The thermostat also provides a restriction in the cooling system, even after the it has opened. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block

Engine Oil Cooler (6.6L Diesel Engine)

The engine oil cooler is a heat exchanger. The engine oil cooler is mounted to the left lower corner of the engine. The oil filter is attached to the oil cooler housing. The engine coolant flows around the oil cooler element. The oil cooler element is a series of plates. The engine oil temperature is regulated by the temperature of the engine coolant that surrounds the oil cooler as the engine oil passes through the cooler.
The engine oil pump, pumps the oil through the engine oil feed line to the oil cooler. The oil then flows down through the cooler while the engine coolant absorbs heat from the oil. The oil is then pumped through the oil return line, to the oil filter, then to the main engine oil passage.

Turbocharger Bypass Valve (6.6L Diesel Engine)

The turbocharger bypass valve is a temperature control valve. The valve is located in the turbocharger coolant inlet hose at the water outlet tube.
The purpose of the valve is to close the coolant flow through the turbocharger. Closing off the coolant flow through the turbocharger avoids turbocharger overcooling.

Last edited by Wingnutt; 09-08-2019 at 07:14 PM.
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Old 09-08-2019, 07:32 PM
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When my buddy changed my water pump it took about 2.5 hours with a coolant flush. He is super fast. It would have taken me 2.5 days.
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Old 09-09-2019, 06:27 AM
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Originally Posted by R Days View Post
Something to consider is that the water pump is likely on borrowed time and is not something you will change in a parking lot somewhere. Buddy is a GM mechanic and told me that at 160k you are either replacing the water pump or it is staring you in the face. If you stay local its not a big deal but if you go long distances I would replace as a preventative measure.

My lbz reached 215 a couple of times but normally hovered around 200.

I would start with t-stats and coolant flush.
I was always told to expect about 200k out of the factory water pump. I got a low coolant warning at 201k miles and coolant coming out of the weep hole lol
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Old 09-11-2019, 10:54 AM
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Here's the first update. Turns out that the no power issue was cause by the old ('08) Edge piggy-back tuner. Something must have said *uck it and stopped working. This resulted in a condition where the computer saw a 0% airflow through the MAF. Unhooked the tuner and the truck is happy again.

On to the cooling issue, a partial disassembly of the fan shroud showed a ton of crap in the cooling stack. The shop didn't fully dissemble it to clean it out because they said that the area that they could reach to clean was packed full and the crud was as hard as concrete. Additionally they said that there was a lot of internal corrosion build up as well, so it looks like I will need, at a minimum new thermostats and a new radiator. Since I'll be into that far into it, I'm giving some serious thought to throwing a new fan clutch as well.
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Old 09-13-2019, 07:12 PM
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holy crap definitely ditch the edge juice with attitude, they are notoriously, distinctly nothing but bad news on a duramax. Do yourself and your truck a huge favor and get some decent EFI tuning
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Old 09-14-2019, 01:42 PM
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Throw that edge away. That's how you tear shit up. I have a CTS2 Insight on mine, but the Insight does nothing but a monitor. If you WANT a tune, go Kory Willis PPEI.

The LBZ has plenty of power stock anyway. I just wouldn't get too close to 100hp over stock cause then you'll start asking for the Allison to be a disapproving sister
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Old 09-14-2019, 01:43 PM
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mine has been running a 120hp ATP tune for about 7 years now, only limped it twice, but I also did do a transgo jr. kit to increase line pressures. I think around 100 is a safe bet on a lbz, as long as you aren't a moron and/or trying to tow heavy on the big tune.
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Old 09-14-2019, 02:39 PM
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Originally Posted by Manoverboard123 View Post
Throw that edge away. That's how you tear shit up. I have a CTS2 Insight on mine, but the Insight does nothing but a monitor. If you WANT a tune, go Kory Willis PPEI.

The LBZ has plenty of power stock anyway. I just wouldn't get too close to 100hp over stock cause then you'll start asking for the Allison to be a disapproving sister
The EPA is coming down on all diesel aftermarket companies PPEI will no longer due offroad tuning anything with emissions they will not do.They will do LB7 but they won't do offroad tuning they are doing emissions complaint tuning now.After 9/16 they are not doing offroad tuning anymore it's all over there facebook and Instagram paige.
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Old 09-14-2019, 03:02 PM
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Originally Posted by suzuki140 View Post
The EPA is coming down on all diesel aftermarket companies PPEI will no longer due offroad tuning anything with emissions they will not do.They will do LB7 but they won't do offroad tuning they are doing emissions complaint tuning now.After 9/16 they are not doing offroad tuning anymore it's all over there facebook and Instagram paige.
yep. all the stateside stuff is coming down hard. everything is going to be happening through canadian shell companies or canadian companies for the forseeable future
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Old 09-14-2019, 03:21 PM
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Originally Posted by dawgsfish View Post
mine has been running a 120hp ATP tune for about 7 years now, only limped it twice, but I also did do a transgo jr. kit to increase line pressures. I think around 100 is a safe bet on a lbz, as long as you aren't a moron and/or trying to tow heavy on the big tune.
I have a Kory Willis PPEI 100hp in my truck. Have had it for about 30,000 miles now and haven't limped once. The allison still shifts like butter and is the one thing I've yet to have any issue with. But then again, I'm rarely over 2500rpm. I dont drive mine like a race car. Only time I'll step on it is about once a week to blow out all the gunk, but I get on it for a short time and dont let it go into 5th or the torque converter to lock.

I remember someone on here (not gonna name any names lol) sweared up and down I'd blow that thing up within a month lol.
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Old 09-14-2019, 03:44 PM
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Originally Posted by Manoverboard123 View Post
I have a Kory Willis PPEI 100hp in my truck. Have had it for about 30,000 miles now and haven't limped once. The allison still shifts like butter and is the one thing I've yet to have any issue with. But then again, I'm rarely over 2500rpm. I dont drive mine like a race car. Only time I'll step on it is about once a week to blow out all the gunk, but I get on it for a short time and dont let it go into 5th or the torque converter to lock.

I remember someone on here (not gonna name any names lol) sweared up and down I'd blow that thing up within a month lol.
can't imagine someone on THT being extremely opinionated about something and having very little actual knowledge... lol. keep current on ATF changes and filter changes and you'll be fine for a long time. mine has 240k on it now and still shifts as well as it did when i got it with 110k. The two times it limped were my own fault, I was just starting to come up a hill and got on it too hard trying to pass someone, i'm thankful the allison has those self protect features.

It all depends on how you treat it/drive it. I could ruin a transmission in less than 100 miles if you really set out to.
PPEI as of tuesday is no longer offering any sort of delete tuning. value of LB7's may be about to go up for anyone that wants a tuned truck
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