2008 GMC W4500 Forward Crew Cab

eash66

New Recruit
Driver
Hi Kinda New here,

I have a 2008 GMC W4500 Forward Crew Cab 6.0 lts, gas (basically is an NPR HD), with overheating problems, Water Pump, Thermostart, Fan clutch and even the head job has been done since it was overheated, but as I got the truck back, it runs fine cruising at 60 MPH, but if you go 70 MPH the truck's temperature starts rising,only thing i have left to replace is the radiator so, here are my questions:

has anyone had this problem before?
Since is a crew cab, do i need to lift the whole cab to do it?
 
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Hino123

Expert Expediter
Researching
Not sure if you have to remove the cab. I would just remove the rear cab mounts and jack it up enough to do my work. I never had to remove the entire cab, and i even put a radiator in the Peanutmobile that Planters drives around once. I would not overlook the radiator cap as a culprit. Make 100 percent there is no air trapped in the system. We had issues with the egr coolers trapping air pockets. Look the two attached documents and visually inspect the charge air cooler for leaks, this could cause an overhear condition. Make sure the radiator itself in nor restricted with dirt and debris. Make sure the coolant is a 50/50 mix and the protection level is at or near -32 degrees.
 

Attachments

  • Isuzu Electronic Service Information System (1).pdf
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Hino123

Expert Expediter
Researching
TSB
 

Attachments

  • Isuzu Electronic Service Information System.pdf
    101.6 KB · Views: 1

Hino123

Expert Expediter
Researching
Forget it,:sweat: I just noticed you have the 6.0 gas job. I saw "HEAD" done and assumed you meant the 4 cylinder diesel.
 

Hino123

Expert Expediter
Researching
Step​
Action​
Values​
Yes​
No​
1​
Inspect for a loss of system pressure and/or coolant.
Is there a loss of system pressure and/or coolant?​
—​
Go to Step 2​
Go to Step 3​
2​
Inspect and repair any faulty hose connections or radiator cap. Fill the system to the proper level, then retest.
Does the engine still overheat beyond the specified value?​
125°C (257°F)​
Go to Step 3​
System OK​
3​
Inspect the coolant concentration for low temperature protection below the specified value.
Is the proper low temperature protection present?​
−37°C (−34°F)​
Go to Step 5​
Go to Step 4​
4​
Replace the coolant. Refer to Draining and Filling Cooling System.
Does the engine still overheat?​
—​
Go to Step 5​
System OK​
5​
Inspect the drive belt for excessive wear or low tension.
Is the drive belt worn or is the tension too low?​
—​
Go to Step 6​
Go to Step 7​
6​
Replace the drive belt.
Does the engine still overheat?​
—​
Go to Step 7​
System OK​
7​
Inspect the radiator fins for obstruction.
Are the radiator fins obstructed?​
—​
Go to Step 8​
Go to Step 9​
8​
Inspect and clean the radiator. Refer to Radiator Cleaning .
Does the engine still overheat?​
—​
Go to Step 9​
System OK​
9​
Inspect the water pump for physical damage.
Is the water pump damaged or inoperative?​
—​
Go to Step 10​
Go to Step 11​
10​
Replace the water pump. Refer to Water Pump Replacement.
Does the engine still overheat?​
—​
Go to Step 11​
System OK​
11​
Inspect the cooling system passages for obstruction.
Is the cooling system passage blocked?​
—​
Go to Step 12​
Go to Step 13​
12​
Inspect and flush the system. Refer to Flushing .
Does the engine still overheat?​
—​
Go to Step 15​
System OK​
15​
Inspect for a stuck thermostat. Refer to Thermostat Diagnosis .
Is the thermostat stuck in the closed position?​
—​
Go to Step 16​
Go to Step 17​
16​
Replace the thermostat. Refer to Thermostat Replacement.
Does the engine still overheat?​
—​
Go to Step 17​
System OK​
17​
The following factors may cause the engine to overheat:
• A heavy vehicle payload
• The A/C system
• Excess engine oil
• Restricted air flow through the radiator
• Extreme air temperature
Correct or repair as necessary.
Does the engine still overheat?​
 
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