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Duramax First Generation: 2001-2004 (LB7) Discuss the first generation (2001-2004 LB7) of the 6.6L Duramax diesel engine & associated components. Engine related discussion ONLY.

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Old 01-30-2017, 09:19 AM   #1 (permalink)
UncleShank
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Engine temp concerns

Back in November I had an injector go out on me. Before engine temperatures would be 165 in winter driving around home and get up to 186 on highways. This year I started transporting campers, on my way to Florida and in Florida where it was nearing 90 with a camper engine temp reached 195 with a/c blowing. I figured that would be pretty normal. After this injector was replaced truck would reach 150 driving around home and only 177 on the highway and hardly any heat would come out the vents. My first thought was that a thermostat was stuck somewhat open as while towing up hills in West Virginia and Virginia temp would reach 198 at about 30 ambient. I had the thermostats replaced and now, at 25 ambient with any size trailer truck runs 194 and the other day I noticed that around 50 with a heavier trailer it was at 198. To me this seems wrong and I figured it should be like I had before. Is it a possibility that they were installed backwards or do I now have another problem? Could more coolant than water cause it to run warmer? I wouldn't think so but just something I have wondered.

Note: Not the same truck in the signature. Similar but different, don't know how to change it


Thanks

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Old 01-30-2017, 09:35 AM   #2 (permalink)
Rvn4me
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Quote:
Originally Posted by UncleShank View Post
Note: Not the same truck in the signature. Similar but different, don't know how to change it
Thanks
I don't know why this site doesn't have a "How To: Fill out Your Signature"
All other diesel sites do and they always say new members should fill in there signature.
How to:
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Engine temp seems normal.
What's your trans temp at?

I have some links in this thread that might help.
https://www.dieselplace.com/forum/63-...0-degrees.html

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 Rvn4me; 01-30-2017 at 09:49 AM.
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Old 01-30-2017, 09:45 AM   #3 (permalink)
64bawagon
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FWIW, my LLY will run about the same 195-200 while towing heavy at ambient temps around 50. I believe the second stat opens at 195 (oem)
Unless youre getting a digital readout from the ECM the temps are just a guess. Mine are from my scangage.
Nothing you posted sounds out of the ordinary to me. (advice is worth exactly what it cost you)

Last edited by 64bawagon; 01-30-2017 at 09:46 AM. Reason: spellin
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Old 01-30-2017, 09:50 AM   #4 (permalink)
lynn1130
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If you are using the dash gauge, don't depend on what it shows you. In both the LB7 and the current LML my gauges would read 210 and my Edge reads 185.

Pulling a 37' toyhauler the LB7 would stay on 185, even in 105 degree Arizona temps. If I was making a long climb it might go to 230 but cool pretty fast once done with the climb.

There is another thread, below yours with basically the same problem and comments on that one. The rule here is don't trust the temp gauge because it is not accurate.
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Old 01-30-2017, 09:58 AM   #5 (permalink)
UncleShank
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Quote:
Originally Posted by 64bawagon View Post
FWIW, my LLY will run about the same 195-200 while towing heavy at ambient temps around 50. I believe the second stat opens at 195 (oem)
Unless youre getting a digital readout from the ECM the temps are just a guess. Mine are from my scangage.
Nothing you posted sounds out of the ordinary to me. (advice is worth exactly what it cost you)


Temps are read from a Bully Dog Watch Dog
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Picture:
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Old 01-30-2017, 10:04 AM   #6 (permalink)
UncleShank
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Join Date: Jan 2010
Location: Indiana
Posts: 42
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Quote:
Originally Posted by Rvn4me View Post
I don't know why this site doesn't have a "How To: Fill out Your Signature"
All other diesel sites do and they always say new members should fill in there signature.
How to:
Top of page User CP
Edit Signature

Engine temp seems normal.
What's your trans temp at?

I have some links in this thread that might help.
https://www.dieselplace.com/forum/63-...0-degrees.html

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.
Transmission always runs 100 over ambient while towing.
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Old 01-30-2017, 10:06 AM   #7 (permalink)
UncleShank
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I haven't owned this truck but a year and am relatively new to the constant towing world. I believed that the temperatures I was seeing in the fall was what it was supposed to be. I just don't want to melt my engine before I get a change to buy a newer truck.
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Old 01-30-2017, 10:08 AM   #8 (permalink)
64bawagon
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My travel trailer is 36ft long, 12'3" high and over 10K.

Last edited by 64bawagon; 01-30-2017 at 10:09 AM.
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Old 01-30-2017, 12:34 PM   #9 (permalink)
lynn1130
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Coolant temps are only part of it if you are towing. EGT's get to be important with large loads and long climbs. You are more apt to melt it if the EGTs get too high.
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Fumoto Drain Valve
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Sold: 2004 Duramax LB7


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Old 01-30-2017, 02:28 PM   #10 (permalink)
UncleShank
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Quote:
Originally Posted by lynn1130 View Post
Coolant temps are only part of it if you are towing. EGT's get to be important with large loads and long climbs. You are more apt to melt it if the EGTs get too high.
While towing, no matter how long the grade or how steep or how heavy the trailer, I've never seen more than 1200 degrees let alone it ever get that high. Previous owner installed a pyro when he owned it. As far as I know exhaust is completely stock. Although it looks to be around 3.5", can't remember if that is stock size or not as I believe I've seen some smaller. And a question about that, where can I buy a muffler delete kit that some of you would recommend? Wanting to buy online, see many but don't want to buy from the wrong place.

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