Chevy Trailblazer fan wobbling
05-19-2008, 09:20 AM
#1
Tough Mudder
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Chevy Trailblazer fan wobbling A co-worker of mine has a regular V6 Trailblazer. It was making a knocking sound this morning and she asked that I look at it.
The Trailblazer has a belt driven cooling fan. The fan seems to be held in place by 4 bolts toward the engine. Those bolts are not loose.
With the engine off, when I spin the fan blade, it turns around 3 or 4 times. It doesn't stop after 1/2 to 1 rotation.
Fan clutch? How much should she pay someone to fix it, and what is the part called? I'm moving and I have a lot of things going on. Plus, I don't want to fix it.
Thanks,
Hilton
The Trailblazer has a belt driven cooling fan. The fan seems to be held in place by 4 bolts toward the engine. Those bolts are not loose.
With the engine off, when I spin the fan blade, it turns around 3 or 4 times. It doesn't stop after 1/2 to 1 rotation.
Fan clutch? How much should she pay someone to fix it, and what is the part called? I'm moving and I have a lot of things going on. Plus, I don't want to fix it.
Thanks,
Hilton
05-19-2008, 07:24 PM
#2
That should have an electro-viscous clutch on it. Basically, it's a PCM controlled fan clutch. They're expensive, and a PITA to replace. The PCM calibration will need to be updated as well. Make sure the clutch is the problem! Parts, labor, and PCM reprogram from a dealer is in the $600-$700 area.
05-19-2008, 08:02 PM
#3
Tough Mudder
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Jesus. How sure are you of this. I knew about the viscous fluid part of it, but I didn't see any wires going to it. I'm pretty sure it's just a manual, belt driven fan.
05-19-2008, 08:49 PM
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Is the fan wobbling like it would with a bad water pump, or just freewheeling? Marc85Z28 is right about that clutch. Heres some info:
Cooling Fan Control
The purpose of the Electro-Viscous (EV) fan clutch is to maintain powertrain cooling requirements. The Powertrain Control Module (PCM) monitors the following sensors to regulate the fan speed;
Engine coolant temperature sensor
A/C refrigerant pressure sensor
Vehicle speed sensor
Intake air temperature sensor
Transmission fluid temperature sensor
Ambient air temperature sensor
The PCM controls the electro-viscous fan clutch engagement. The PCM regulates a 12-volt pulse width modulated signal (PWM) to the cooling fan relay. The PWM signal determines the ON time of the relay. As the commanded state of the fan clutch increases, so does the ON time of the relay. This ON time directly effects the amount of time the solenoid, which is internal to the fan clutch, is energized. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, increasing the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and blocks the path of the fluid to the fluid coupling of the fan clutch, reducing fan speed.
The fan has the ability to create a feedback signal, so the PCM has an actual fan speed input. This is done with a hall effect sensor internal to the fan clutch.
The PCM supplies a 5-volt reference and a low reference to the hall effect sensor. The hall effect sensor returns a signal pulse through the cooling fan speed signal circuit in response to the reluctor track passing by the magnetic field of the hall effect sensor.
The PCM commands the cooling fan to 100% under the following conditions:
Engine coolant temperature exceeds approximately 129°C (264°F).
The transmission oil temperature exceeds approximately 151°C (304°F).
A/C refrigerant pressure exceeds 1655 kPa (240 psi).
When certain DTC's set. These include P0116, P0117, P0118, P0125, P1481, P1482, and P1484.
The scan tool can engage the cooling fan clutch. This is done with the engine controls special function menu screen. To engage the cooling fan, It can take up to 2 minutes for a 100% command with the engine at 2000 RPM. The lower the engine speed, the longer it will take the fan to engage. To disengage the cooling fan, it can take up to 2 minutes with the engine at 2000 RPM . The lower the engine speed, the longer it will take to disengage. In lower ambient air temperatures the cooling fan will engage in less time, however, it will take longer to disengage due to the properties of the fluid vs. temperature.
Under certain conditions the cooling fan may be engaged at engine restart. They are as follows;
The cooling fan was engaged at the time the engine was turned off
The fluid may bleed from the storage chamber into the fluid coupling of the cooling fan
Although the fan is commanded off at this time due to a cold start condition. This is the most likely time a vehicle driver will notice that the fan noise is excessive compared to normal engine starts with out cooling fan engaged. As the engine speed is increased the fan noise will be louder than before. These are normal conditions that can be very intermittent.
Cooling Fan Control
The purpose of the Electro-Viscous (EV) fan clutch is to maintain powertrain cooling requirements. The Powertrain Control Module (PCM) monitors the following sensors to regulate the fan speed;
Engine coolant temperature sensor
A/C refrigerant pressure sensor
Vehicle speed sensor
Intake air temperature sensor
Transmission fluid temperature sensor
Ambient air temperature sensor
The PCM controls the electro-viscous fan clutch engagement. The PCM regulates a 12-volt pulse width modulated signal (PWM) to the cooling fan relay. The PWM signal determines the ON time of the relay. As the commanded state of the fan clutch increases, so does the ON time of the relay. This ON time directly effects the amount of time the solenoid, which is internal to the fan clutch, is energized. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, increasing the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and blocks the path of the fluid to the fluid coupling of the fan clutch, reducing fan speed.
The fan has the ability to create a feedback signal, so the PCM has an actual fan speed input. This is done with a hall effect sensor internal to the fan clutch.
The PCM supplies a 5-volt reference and a low reference to the hall effect sensor. The hall effect sensor returns a signal pulse through the cooling fan speed signal circuit in response to the reluctor track passing by the magnetic field of the hall effect sensor.
The PCM commands the cooling fan to 100% under the following conditions:
Engine coolant temperature exceeds approximately 129°C (264°F).
The transmission oil temperature exceeds approximately 151°C (304°F).
A/C refrigerant pressure exceeds 1655 kPa (240 psi).
When certain DTC's set. These include P0116, P0117, P0118, P0125, P1481, P1482, and P1484.
The scan tool can engage the cooling fan clutch. This is done with the engine controls special function menu screen. To engage the cooling fan, It can take up to 2 minutes for a 100% command with the engine at 2000 RPM. The lower the engine speed, the longer it will take the fan to engage. To disengage the cooling fan, it can take up to 2 minutes with the engine at 2000 RPM . The lower the engine speed, the longer it will take to disengage. In lower ambient air temperatures the cooling fan will engage in less time, however, it will take longer to disengage due to the properties of the fluid vs. temperature.
Under certain conditions the cooling fan may be engaged at engine restart. They are as follows;
The cooling fan was engaged at the time the engine was turned off
The fluid may bleed from the storage chamber into the fluid coupling of the cooling fan
Although the fan is commanded off at this time due to a cold start condition. This is the most likely time a vehicle driver will notice that the fan noise is excessive compared to normal engine starts with out cooling fan engaged. As the engine speed is increased the fan noise will be louder than before. These are normal conditions that can be very intermittent.
06-26-2008, 06:18 PM
#6
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Its a known problem with the I6 (no V6 offered, ever) TrailBlazer. Usually the fan clutch locks up making an airplane noise (think F16 taking off), but it sounds like the water pump is failing. Thats when the fan and clutch assembly start to wobble. Mine moves a little bit but not too badly, Im just going to yank it for a set of efans.
