Loud Engine Fan 2002 TB

Discussion in 'Chevy Trailblazer Forum (GMC Envoy)' started by smithnr, Jul 23, 2008.

  1. smithnr

    smithnr New Member

    I have a 2002 Trailblazer LT, in the year or so, when I first start it up the fan on the engine makes a loud roar. When I drive down the street it sounds like a dump-truck. After about 5 minutes it tends to go away, but on really hot days, it is more frequent.

    There is also a big loss of power when driving. The higher the rpms, the louder the noise.

    Dealership said it is just the way it is and it isn't fixable. This isn't the case as it wasn't like this when the car was new.

    Anybody experience the same thing? Ideas on how to fix it?
  2. GaryL

    GaryL Epic Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    That's the fan clutch doing it's job. When it gets hotter, it tightens up and make the fan spin faster and that makes more noise. If it's constantly doing it, the clutch may be starting to lock up. If it bothers you, you can replace the clutch, but you may still have the same sound when you are done.
  3. smithnr

    smithnr New Member

    Does the fan clutch cause a reduction in power as well?
  4. GaryL

    GaryL Epic Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    Yes, that's part of it's job as well. When the engine doesn't need as much cooling, it slips alot more, but when it heats up, it goes closer to a direct drive (near the same rpm as the fan pulley is turning). There is a spring visible on the front of the clutch that increases/decreases the amount of force on the fan clutch and that determines how fast the fan itself turns. When the clutch engages more, it causes more drag on the motor and therefore a loss of power to the rear wheels.
  5. hockeyham

    hockeyham New Member

    My TB (02 LTZ) is also doing this. It has done it more frequently in the last 2 months. I've owned it for just over a year and only in the last 2 months has it really kicked in more often than normal. It will eventually disengage the clutch but it's annoying, especially when I've just started the car and it has no reason to be overheating.

    I've also noticed the temp gauge on the dash will register off-scale low (as if the temp is below 100) and I've been driving for 5+ mins and it should be at normal temps. Then, it will suddenly "kick in" to mid-scale instantly. I've only noticed it once or twice.

    I mentioned it to a mechanic when I got my oil changed and he had a look of "seen it before", so apparently it's occurring often enough he immediately knew what it was. Can't remember if he mentioned the actual clutch assembly or a sensor that kicks the fan in itself.
  6. hockeyham

    hockeyham New Member

    Update to my fan clutch issue

    Well over the last several days my clutch fan seemed to be getting more and more noticeable. Today it decided it was not going to cut off at all the entire 30 minute trip to work. And on the way back, "Service Engine Soon" appeared on the dash.

    I took it to AutoZone (tm) and had them plug up their handheld computer. OEM Code "PO495" appeared.

    They were nice enough to print out the explanation:

    Definition: Cooling fan circuit error.
    Explanation: Cooling fan clutch RPM too high when the ECM has commanded 0%

    Probable Causes:

    • Open or short circuit condition
    • Cooling fan relay fault
    • Failed cooling fan clutch
    I opened the relay box and swapped the two black relays (I believe they're 43 and 44) in the image below at the suggestion of the AutoZone (tm) tech (they're the same relay) and the clutch fan did not change it's tune and "Service Engine Soon" is still illuminated.

    The two relays are near the center of the box (black, not grey) in the lower left.

    I drove back to "the Zone" (tm) and the fan clutch didn't change it's tune. I even tried gunning the motor since that actually would cut the fan clutch off over the last few weeks.

    I certainly hope it's not the fan clutch. AZ priced it at $199.
  7. hockeyham

    hockeyham New Member

    Update: It is the fan clutch after taking it to repair shop. They quoted me at $620 to fix it!

    The part they're getting is $300+ and the labor is $300.

    Obviously I can find the fan clutch for less at AutoZone. Does the labor sound about right? I'm going to ask around other shops for better deal.
  8. GaryL

    GaryL Epic Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    That's a lot of money to for such an easy job. Autozone will loan you the tool that is needed to remove and install the fan clutch. It's held on to the water pump shaft with a big nut, and has 4 bolts that hold the fan on. You will have to pull the upper portion of the fan shroud off to get everything out, but it shouldn't be too much trouble to do yourself.

  9. hockeyham

    hockeyham New Member

    I got another quote for 1/2 that, and while I'd love to do it myself, I'm not very mechanically inclined when it comes to repairs. The guy who quoted me (the actual mechanic) talked like he knew this problem and it occurred often enough that he could get in and out in no time. He's going to get the part for about $190 new.

    Another mechanic offered $560 without even looking at the part, labor, etc. Raised a flag that all he was doing was beating the competitor and still thought he could take advantage.

    Man it's hard to find good honest auto repair. If this works out I'll promote the heck outta the guy. They've done work for me in the past and had great rates. This is the litmus test... :)
  10. hockeyham

    hockeyham New Member

    Got TB fixed, it was the fan clutch. Only cost $340. Mechanic did great job.

    The Service Engine Soon light stayed on for about 3-4 startups and I was going to pull battery cable to reset computer but it went off as I was on my way to house to do just that.

    SMITHNR: If your engine is doing it more often than you feel comfortable with, it may be the fan clutch. My TB had just over 100k mileage. You can try to swap the relays in the box to see if it's a bad relay, but it's unlikely the cause.

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