Radiator Fan Always Engaged...

7milesout · December 6, 2018

I'm agreeing. Fan clutches are cheap and effective (when not busted ). And if I had time for this, I could do this repair myself. I've got to give him his truck back as soon as I can. This weekend is booked with crap to do (sons / wrestling). And it's dark (and cold) out when I get home. So I have to outsource it. One thing I was curious about when I was looking at what it would require to repair, is: It looks like the upper radiator hose would have to come off in order to get the fan shroud off. Am I wrong about that?

And … the emblem on the other side is removed already, courtesy of the same car wash. Lost 'em both at the same time. They were probably not in prime condition prior that car wash, would be my guess.

Those decals were like $50+ from ebay. That's more than I'd prefer to pay … for something that doesn't effect the performance of the truck.

I just dropped the truck off this morning for the new fan clutch. He wanted more than I wanted to pay, for the Intermediate Steering Shaft and bearing. So I rejected that. I will try to tackle that job in the spring.

7milesout

txab · December 6, 2018

Here's one thread on the IS shaft (ISS). Probably videos on Youtube also About a 20-30 minute job max.

https://www.gm-trucks.com/forums/topic/176434-how-to-fix-your-gmt800-steering-shaft-clunk/

Pics are gone in this one, but some good info.

https://www.truckmodcentral.com/threads/how-to-replace-the-gmt800-intermediate-steering-shaft-iss.1652/

7milesout · December 7, 2018

Got the truck back last night. OMG … it is so much WORSE! It sounds like there's a military grade commercial vacuum cleaner attached directly to the crank pulley. But this confirms, it's definitly fan noise, and it is the fan clutch (new one too). I'm in communication with my mechanic. I'm thinking he sourced the wrong part. So, we'll see how he is to deal with, under an issue like this. So far it's been harmonious. But I suspect it may get a bit testy with this.

I could use a part number suggestion from you guys. I can find these on rockauto, and take a stab myself. I'm also going to try to find the original part number. Heck, I've got the original in the truck, I'm going to see if I can find a part number on a 15 year old part.

7milesout · December 7, 2018

Sorry guys, I know I'm blowing you up with this thread. But I saw a video on replacing the fan clutch. It is way easier than I figured (note to self, always watch a repair video). I can and will do this myself. As soon as I can get the part. But I need your help picking out a fan clutch. The truck is this:

2003 GMC 1500 4.8L 2X4 standard cab short bed. It does have the tow package (says my dad). And it does have the tow/haul switch (if that's proof).

When I search rockauto, I get this web page: https://www.rockauto.com/en/catalog/gmc,2003,sierra+1500,4.8l+v8,1415416,cooling+system,radiator+fan+clutch,6812

But here's what I'm thinking. If I get the heavy duty / "with towing package" one, it's likely going to want to cool more / kick on more often at lower temps … which means more fan noise. But this truck, if it ever does tow, it's going to tow little sissy trailers. I have a 2500 Dodge Cummins 4X4 and it tows big. The only thing my dad's truck will ever see (maybe) is a 5 X 10 utility trailer with maybe a couple motorcycles. And I doubt it will ever see that. As I have the Cummins, and it has more cab room and get better mpg (6 speed manual).

I'm so dern gunshy about this fan noise now, I want the most sissy fan clutch I can get.

So, I think I want to get the w/o tow package fan clutch so it will be more quiet.

I think I'll get the cheapest sucker on that linked list. If it's no good, it's a $25 mistake, no big deal.

Is my reasoning sound?

diyer2 · December 7, 2018

I would put AC Delco HD on it.

This is made for this truck IMO.

Keep it like it came from the factory.

If the price is an issue check with NAPA or?

txab · December 7, 2018

What's your axle ratio? By all means find out the part number that was installed. You might also give it some time to see if it "breaks in" so to speak. Depending on axle ratio Delco 20913877 was the original for 3:73 or less. That number is AC Delco 154694 on rockauto. I know I installed a Hayden once and it had different performance from the Delco unit.

As you found out, it's only about a 30 minute job. If you have a pipe wrench you can use it for the large nut, if you have nothing else. Pop with a hammer and it should come right off, If you have an air chisel you can use it on the nut and bump it a few times in the correct direction to get it going. Of course if you use the chisel, it's at a pretty flat angle to the nut

sefiroxx · December 7, 2018

Sounds like a non-thematic fan clutch is installed ( always on at engine speed). Search spec of clutch carefully. For thermal control - door are either off or on, others are viscous controlled and turn at 20% to 90% of engine speed.

I believe the tow/haul button was a stock option and only changes the shift points. The true tow package added additional coolers for the tranny. The rear gearing/tranny upgrades were special upgrades likely only available for larger engines/vehicle sizes. You can confirm exact options using the codes located in the glove box.

7milesout · December 11, 2018

Last night I put a new upper steering shaft in it. No more bumpity-bump sound from the steering. You guys probably know that bumping clunking sound and feel. It was at its worse when the steering was turned and the suspension was undulating. Anyway, an easy fix, and no more annoying sound and feel from that. Took about 30 minutes.

Theoretically the new fan clutch is set to arrive today. So, the truck will go back "out-of-service" tonight. I suspect that will take me about 2 hours. I work slow / methodical / accurately. I hope this new one does the trick.

And lastly, the cluster is on its way back to me. It should be to my house by Thursday. 10 minutes later it will be installed. GM did an awesome job simplifying the gauge cluster installation, as well as the front lights. I replaced the blinker and side marker bulbs in the front last week. If I hadn't watched a video, I would have removed the battery and the airbox (and cussed a lot). But daggone, those locking pins are quick, easy and effective. I'm starting to enjoy driving my dad's truck around, a little too much. I better give it back this coming weekend or I might rather it stay with me! At this point, the only flaw (assuming the new fan clutch is quiet) is the below...

Last thing, I'm going to go do a search for this but … the other day I was driving it and it was wet. There was an airhead on my left that had come flying up beside me to jump in front of me for an upcoming right turn. A traffic light put an end to that temporarily. But I could tell it was going to be a drag race (for her) when the light turned green. When the light turned green, I accelerated enough to prevent such rude driving, and when I did, the rear tires spun when they hit the (wet) painted white (stop) line. Immediately after, the truck pulled right. Not just a little. Hard right. The truck had to be steered about 30° left (steering wheel) to go straight. I drove this way for about another 1/2 mile to see what would happen. Nothing changed. I pulled over, shut the truck of, recranked drove off and it went back to normal. No pulling. My dad had described this phenomenon to me, but this is the first time I experienced myself. I surmise it had something to do with the rear diff, and the anti-lock or anti-spin feature the truck has. Maybe something electronic kicked in when it detected slip. But something in that system is flawed or it wouldn't have gone into the hard right pull it was doing.

I'm not good at searching, so if you guys had any hints for me, that would be great, and much appreciated.

7milesout

txab · December 11, 2018

No electronics in OEM diff. Sounds like it may have locked, as it should when there is enough speed differential between the two rear wheels. Did you hear a clunk? When it locks you can usually hear it. I would think driving in a straight line you would have had no issue. Most people notice it during turns, when the axles need to rotate at different speeds. You might change the diff fluid, if never serviced. Plenty of options out there. 75w-90 synthetic. Mobile 1, Amsoil severe gear, even Wally's synthetic brand will work for you. Whichever one you feel comfortable with. No need for any added friction modifiers for a G80 diff. Look at RPO sheet in glove box for the code.

Only other thing would be a brake suddenly grabbing for some reason.

7milesout · December 11, 2018

I heard no clunk. It seems as if it half-locked or something. It was SPECIFICALLY driving in a straight line that presented the problem … after the tire spin. Generally it is the right rear that would spin, if only one spun (likely). I'm certain it is had no service in 82,000 miles. I'm comfortable with any of them. Instead of opening a can of worms, I wonder if it has been clarified the exact brand of the original fluid. I'd probably just do that. Is it feasible that a fluid change might improve this locking function?

Last year I put an Eaton Detroit TrueTrac in my 1972 Plymouth Scamp (vs an open diff). The TrueTrac is one awesome differential. If it weren't so expensive ($550 or so, plus labor) it would be nice to have one of these in my dad's truck. He likes to stand on it. And if it gripped even better to shoot off the line, it would make him even happier. This little truck does zip around (compared to my 2500 Dodge Ram Cummins 4X4 with a 6 speed manual). Seriously, I'm liking it too much.

7milesout

7milesout · December 14, 2018

More times than not, contributors forget to come back and post up the results of their efforts. I almost did as well.

Result; Fan Clutch: Replaced. The new fan clutch is AWESOME. When the truck cranks cold, the fan is active. After about 0.1 miles (within the neighborhood), the fan deactivates and man … is almost Lexus quiet. The engine (intake) and exhaust sounds really nice in this truck. Mission accomplished.

Result; Steering Shaft: Replaced. The bumpity-bump is gone. However, there's a thump when pulling the steering quickly, left-right-left-right (when sitting still). I don't think that's a condition of what I did, but I'll check the 2 bolts, make sure they haven't backed off. The under hood bolt was tightened to 35 ft-lbs (spec) with a torque wrench. My torque wrench wouldn't fit under the dash so I just hand tightened it. Also, the new steering shaft has a slight squeak while turning inside the rubber boot attached to the firewall. So I'm going to dab some grease on my finger, and push my finger between the new shaft and rubber and grease that up. Should stop the squeak. That same solution worked great on one of my vehicles.

Result; Cluster: The rebuilt cluster is installed. All seems to work great. I noticed that there's an icon for when the cruise control is operating. That icon wasn't working when I drove the truck to my house. Almost every gauge was either acting goofy or not working at all (for my dad). But now, it's all working. Mission accomplished.

A note about working on the fan clutch. I did the steering shaft on Monday evening. I got the fan clutch on Tuesday. I worked on the fan clutch on Tuesday, but couldn't loosen the nut. It was so easy to get to the fan clutch, I can't believe I bothered to outsource it. Note … always search for and watch a video on youtube on how to do repairs not done before. But the smacking of the big adjustable wrench didn't work for me. I tried all kind of stuff to remove that nut (without the proper tool). I aborted working on it any more on Tuesday evening. Wednesday, I got the Lisle tool with the 2 posts that fit the holes in the water pump pulley. It's a partial spanner with a 1/2" square drive hole, made to attach a socket wrench. $30 plus tax. Within 5 minutes of getting home Wednesday, the fan clutch was off. It pays to have the right tool. I then switched the fan clurch (17 ft-lbs on the fan clutch fasteners). I had the truck completely back together in 15 minutes. And took my time. During that 15 minutes, the Fedex truck dropped the cluster at the front door. I slapped that in within 10 minutes. I then returned the spanner because I will not likely ever need it again. For that reason and, "it didn't work!"

New front lights, all the above. And I'm going to febreeze the truck as my dad has stopped smoking (hopefully for the rest of the life he has left), because the doctor said he won't do lung surgery on a smoker. Hopefully the febreeze (for autos) will cover / remove the stankerette smell in the truck, which will curb his cravings. Would be bad if he went to drive his truck and smelled stankerettes, and gave in and started smoking again. My dad has lung cancer and will have sugery about mid-January.

7milesout

txab · December 14, 2018

Congrats on all your successes. I'd use a silicone grease on the rubber boot at the shaft. Which fan clutch did you use? Might post part number for future readers.

Look into OdorXit. They have several products/versions of their product. I've used them in the past for odors in vehicle and in houses as well. Easily available. https://www.odorxit.com/shop-now-odorxit-products?gclid=Cj0KCQiAxs3gBRDGARIsAO4tqq3EWP2yyx8SNYiZZ-fV8AsMwruhHGOuJMY-D_UWwkkf-9HU1FxR6cUaAmQQEALw_wcB

Good luck for your dad!

7milesout · December 14, 2018

I used SKP SK36945. The least expensive fan clutch listed on rockauto for said vehicle. I figured if it was a mistake, it would be the least expensive mistake. I also kind of think that maybe his truck does NOT have the trailer towing package, but does have the trailer tow switch. I wanted the least active fan as is possible. As this truck is likely to have the lightest duty cycle of any truck with a 4.8L (due to the SCSB, 2WD configuration, and the unlikely potential of towing anything substantial).