Wondering if anyone has experience replacing the fan clutch on the 2002+ 4.2 I6 Chevy Trailblazer?(GMC Envoy, Olds Bravada, Isuzu Ascender are others that are the same.) I have a new design clutch in the box that's supposed to fix a poor a/c performance issue, and I need to get'er done, but have read several ways to go about it including the GM SI that has you just about take the whole front-end apart! Also any advice busting the clutch nut loose from the water pump shaft? THANKS!
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Fan clutch replacement 2002 Trailblazer
- Thread starter tblazed
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How does the fan clutch affect the poor AC performance?
I had a bad one on my 2004 GMC. It made noise and caused slight overheating. It had no bearing on my A/C performance. The fan cools the engine and should not have anything to do with A/C performance.
btw-I watched the tech change my fan clutch and noticed he had a special tool to remove the bolt, took him less than a hour.
I had a bad one on my 2004 GMC. It made noise and caused slight overheating. It had no bearing on my A/C performance. The fan cools the engine and should not have anything to do with A/C performance.
btw-I watched the tech change my fan clutch and noticed he had a special tool to remove the bolt, took him less than a hour.
No airflow over the condenser core equals higher condenser pressures and temps, hence reduced cooling. Many times a bad fan clutch can cause the high pressure switch to stop the compressor to prevent compressor damage.
Don't know about GM fan clutches specifically but we usually used a drift and a hammer to knock the clutch loose from the water pump shaft (worked on numerous FoMoCo vehicles}. Any doubt, get the right tools and pay attention to the thread direction. Many screw on clutches have left hand threads. Have fun.
Don't know about GM fan clutches specifically but we usually used a drift and a hammer to knock the clutch loose from the water pump shaft (worked on numerous FoMoCo vehicles}. Any doubt, get the right tools and pay attention to the thread direction. Many screw on clutches have left hand threads. Have fun.
Not enough air flow though the A/C condenser is exactly the problem. High side pressure exceeds the limit, and the compressor shuts off. The original design fan clutch, "electro viscous" or EV as it's called, at startup freewheels, to almost a stall. You can see the individual fan blades turning it's so slow. The EV clutch can take several minutes to respond to commands from the PCM. The new design clutch that was released in June 2005 solves the problem by having a faster response time and higher minimum operating speed. This applies to all vehicles built before June 2005. GM released a TSB on the problem:
TSB 04-01-38-019A - (Jun 7, 2005 )Intermittent Slow to Cool HVAC Performance Concerns in High Ambient Temperatures and/or High Humidity Conditions After Start Up, Especially at Low Engine Speeds (Install New Engine Cooling Fan Clutch).
TSB 04-01-38-019A - (Jun 7, 2005 )Intermittent Slow to Cool HVAC Performance Concerns in High Ambient Temperatures and/or High Humidity Conditions After Start Up, Especially at Low Engine Speeds (Install New Engine Cooling Fan Clutch).
Find either a Chiltons or a Haynes repair manual,they may give the info you need.
Advance Auto carries the Haynes manuals at a descent price.
The clutch nut may be left hand threads,find this out before you do something really bad.
Advance Auto carries the Haynes manuals at a descent price.
The clutch nut may be left hand threads,find this out before you do something really bad.
Thanks... The "GM SI" I refer to in my first post above is the official GM Service Information manual which I have, I've got a copy of the "Haynes" method, was inquiring here if anyone had actually done this, and if they had any tips. I already have the new clutch, and it unscrews counter clockwise, that I do know.
I grab a piece of 40 grit sandpaper, fold it so that the grit is sticking out. I then turn the big nut on the fan clutch and pull the sandpaper in between the belt and pully.
Get a buddy to add pressure to the automatic belt tensioner with the appropriate wrench.
Then smack the wrench on the big fan clutch nut with a hammer.
Get a buddy to add pressure to the automatic belt tensioner with the appropriate wrench.
Then smack the wrench on the big fan clutch nut with a hammer.
In the shop, speed rules.quote:
Originally posted by tblazed:
punisher... I am still trying to visualize using a drift and hammer to loosen a 36mm nut from the water pump shaft. Please explain!
We would use a long drift, lay it against the edge of one of the flats and tap the clutch loose. Think of the way your grandma used to knock stubborn lids on jars loose and that is pretty much the way it works. I eventually got a long pointed chisel point for my air hammer and gently used that to knock the clutches loose. There were all kinds of special wrenches to use to get them loose but it was a pain to keep the pulley from turning. Thank god for older experienced techs to help the (then) noob guy out.
This is not covered by warranty (2002)?
THANKS for the additional info punisher. Wonder if you ever tried an air hammer to drive the nut loose?
Out of warranty- a 2002, bought in Jan 2002. Had it in for poor A/C performance twice while in warranty, but GM didn't have the actual fix figured out until I was 6 months out of warranty. If GM was nice they would fix it for me free since the problem had been addressed twice before, but the answer was, go ahead and pay the dealer for the repair and ask for reimbursement. We are talking $600 total repair, vs a $170 clutch. So I am doing it myself. I don't have that much faith that I would ever get any $$ reimbursed.
Out of warranty- a 2002, bought in Jan 2002. Had it in for poor A/C performance twice while in warranty, but GM didn't have the actual fix figured out until I was 6 months out of warranty. If GM was nice they would fix it for me free since the problem had been addressed twice before, but the answer was, go ahead and pay the dealer for the repair and ask for reimbursement. We are talking $600 total repair, vs a $170 clutch. So I am doing it myself. I don't have that much faith that I would ever get any $$ reimbursed.
My brother owns a 2002 Trailblazer as well, we haven't had any air conditioning problems, blows colder than most other cars I have been in, it doesn't seem to spin very slow at all. The only problem it seems we have had is the clutch would be fully engaged when starting it and wouldn't turn off until the first time the truck would go over about 4000 rpm. Hasn't done it in over a year though.
Up there in Minnesota you probably don't have the same conditions outlined in the TSB... " High Ambient Temperatures and/or High Humidity Conditions". Drive that TB down here to D-FW and try it when the "Temperature Humidity Index" is pushing 110°!
tblazed - you might be surprised at just how warm it can get up here! Now that doesn't apply to every day, but certainly there are some 'fun' days each summer.
A TB in the family had a similar AC issue to the one you are describing. That TB was out of warranty in less than a year and was never properly diagnosed by dealer techs. It ended up just being lived with until the TB was sold off...
A TB in the family had a similar AC issue to the one you are describing. That TB was out of warranty in less than a year and was never properly diagnosed by dealer techs. It ended up just being lived with until the TB was sold off...
Yep the fan clutch-A/C problem seems to vary with individual clutches- some apparently have more minimum speed than others. Mine freewheels so slow at idle you could stop the fan by hand. A friend in Phoenix has a 2003 Envoy that does not exhibit the problem. Mine will overshoot the A/C high pressure limit and start blowing warm air in my face as I back out of the driveway, after running less than a minute! Once the fan responds and starts moving air, it easily blows 45° out the vents with 100° ambient temp. Works great once the fan starts running properly. Have never seen the engine coolant temp gage exceed 210° so the clutch does keep up with engine heat fine.
I just replaced my second water pump on my K1500.
I had to buy a special tool to hold the water pump pulley the first time I replaced the water pump.
It's just a big vice-grip tool with about a foot and a half of bicycle chain attached to the end. You wrap the loose end of the chain around the pump pulley, hook it to the other end of the vice grip and then clamp it tight. This makes a nice, damage free connection to the water pump pulley and then allows you to get a big crescent wrench onto the fan-clutch nut.
That nut should brake loose relatively easily. When you re-install, use anti-sieze. Don't tighten it too tight. The resistance of the fan-clutch/fan to the rotation of the crankshaft will ensure that this nut will never get loose.
I had to buy a special tool to hold the water pump pulley the first time I replaced the water pump.
It's just a big vice-grip tool with about a foot and a half of bicycle chain attached to the end. You wrap the loose end of the chain around the pump pulley, hook it to the other end of the vice grip and then clamp it tight. This makes a nice, damage free connection to the water pump pulley and then allows you to get a big crescent wrench onto the fan-clutch nut.
That nut should brake loose relatively easily. When you re-install, use anti-sieze. Don't tighten it too tight. The resistance of the fan-clutch/fan to the rotation of the crankshaft will ensure that this nut will never get loose.
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