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Exploding Fans

7K views 86 replies 38 participants last post by  Kirk's67SS 
#1 · (Edited)
Has any of you guys seen a fan explode? Like totally disintegrate? I had never seen it until yesterday.

Took my truck to get it weighed, turned onto a state highway off of a county road and goosed it a bit. It was spinning a little on the 2-3 shift but the governor is set to shift at 5,500 and the rev limiter is set at 6,000. It didn't hit the limiter. Loudest bang I've ever heard, shrapnel and smoke everywhere. I thought at first the engine had let go but that wouldn't explain the holes in the hood. Plus it was idling just fine and the oil pressure was good.

I couldn't pull to the side of the road because there's no shoulder and a ditch at the edge of the road. It's a really busy two-lane so blocking it isn't an option but there's a spot I can get across the ditch about a half mile up the road. The smoke trail is unbelievable and I knew there's was no water in it because the windshield was covered in it so I shut it off and coasted. I had plenty of momentum to make it to where I needed to be, though. Too much momentum it turns out because when I got there I hit the brakes and nothing happened. No brakes. I made the turn but before I could get on the parking brake I ran through a fence. Punched a hole through the passenger fender and left a pretty good scrape down the side.

What a freaking ride.

I get myself composed and check the damage. The fan is gone. Not a trace. The clutch is there and seemingly unhurt, as are the bolts that attached the fan. All four of them. But not any proof that a fan had been bolted there....WTF???

When the fan came apart it of course took out the shroud and hoses but it also took out the transmission cooler lines, explaining all the smoke. The brake proportioning valve sits on a crossmember directly under the radiator and it wiped that out too. I guess I should feel lucky it didn't take out a front tire.

The only proof I have that the fan ever existed is the damage it left behind. I've never seen anything like it.

It was a brand new Derale fan. 18” reverse rotation, rated to 8,000 RPM. I'll be calling them in the morning. It caused an easy couple thousand dollars damage and damn near killed me. I know it was tight and the clutch was fine because I had checked them right before I left because the water pump is seeping a little out of the weep hole and I grabbed the fan to check the bearings. All good at that point. 5 miles later...not so much.

Less than a thousand miles on the engine, fan, GM serpentine setup.

Dammit.
 
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#4 ·
I'm trying to post pics but can't figure out how on my phone. I need to find a teenager to do it for me.
 
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#6 ·
Six blade steel on this one. I'm a "mechanical fan only" guy but this shook me pretty bad. Someone could've been killed. If I had a 'glass hood, who knows where it would've gone. It went right through the steel hood.

Does Lakewood make an explosion proof shroud?
 
#9 ·
I'm trying. I'll get them sooner or later.

Tom, what is the truck?

Glad this didn't turn into an accident.

Although it's unlikely, if something on the road got kicked up into the fan, it's damage could have caused it's destruction in a instant at that RPM.
The truck is the '76 C20 in my signature. The road was clean and clear. Beautiful Colorado fall day, gone awry. It would be really difficult for anything to get into the fan from the bottom with the crossmember under the radiator.
 
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#8 ·
Tom, what is the truck?

Glad this didn't turn into an accident.

Although it's unlikely, if something on the road got kicked up into the fan, it's damage could have caused it's destruction in a instant at that RPM.
 
#11 ·
That scares the crap out of me. If a fan can cause that much damage imagine what flywheel and clutch could do. I will definitely have an explosion proof bellhousing on any stick cars going forward.
 
#12 ·
I have had clutch fans exit the engine compartment but usually the clutch was at fault and it happened at less than 40 MPH not getting into it.
3 failed clutch fans that exited the vehicle and multiple repairs from failed electric fans all original equipment on stock vehicles. and multiple failed clutches.. which is not such a big deal if you catch it soon enough.
Middle of the desert in Arizona is not a good place..Had that happen also. Hate clutch fans.

I run nothing but Ford Flex fans on my engines. And I have personally tested them to sustained 6500rpm engine RPM with the fan being over driven.

Shifted one of my small blocks at 7600 on a daily basis with Ford Flex fans.
Blades are offset and are not noisy like evenly spaced fan blades.

I hate to hear your story of the fail as it does suck and will probably make you gun shy of that setup.

I am gun shy of all clutch fans. I was left stranded too many times.
Not really stranded but forced to take the Nike Express.
 
#13 ·
Pics...
 

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#15 ·
I had a Six Blade Stainless Steel one let got in my Blazer going up a freeway on ramp. Doubt it was anything close to 4k, took out the Radiator, Belts, Cracked the Fan Shroud. When I change the engine, I'm going to Electric Fans.....SC had an article in the November Issue that looked very promising. I need to upgrade the Alternator anyway.....
 
#34 ·
Sorry guys, I worked until 11:00 last night and back at it at 5:00 this morning.



I'm pretty confident but I'll give it a hard look in the next couple days. I checked it right before I left and the bearings and clutch felt fine. The clutch looks perfect and the bolts threaded out by hand after the fact. They were tight when I left the house. The pump wasn't "leaking”, I just happened to notice the weep hole was damp so I gave the fan a wiggle just for peace of mind. All seemed well. The pump came with the GM serpentine kit and everything was brand new but had sat on a shelf for a few years. I think the seal was just a little dry.

Interesting. Did you retrieve any of the shrapnel that you say went all over the place? I'd be curious which of the company's fans https://derale.com/product-footer/belt-driven-fans you had installed? I don't know about aftermarket fans, but just looking at the elongated holes in the flex fans and the race fans and the fan spacers, that I take to be for mounting to whatever is the hub, looks half-fast to me. But I'm not an engineer. Wonder why the holes for the clutch fans are not like that? As far as liability goes...I'll bet that any installation that is not "stock" or "OEM replacement" absolves the company of liability. See any fine print that might pertain. Good thing that you or someone else wasn't injured. I'll bet that lives have been lost to fan failures like this.
https://derale.com/product-footer/b...everse-rotation-fan-clutch-fan-black-1-detail

That's the fan. There were no pieces left in the engine compartment. And none in the road when I went back. I'll search the side of the road and when I get a chance. The holes for this fan were not elongated and it fit the clutch nice and snug. Seemed like a well built fan...

Hows the power on that truck?
No problem with power, Mark. But everything I bolt to the darn thing takes leave in spectacular fashion. First was the transmission, then the carrier bearing, now the fan. Not to mention the right rear tire. It might be pretty darn quick when I get the spool in and get some tires on the back. Or I might scrap the truck and put the engine and trans in the 'Camino. I don't know. I'm a little disheartened right now.

I've also had a fan and clutch make contact with the shroud and destroy the shroud and fan assembly, due to bad rubber engine mounts. A close check there would be good.
The mounts are new poly and the clam shell design but I'll double check. The fan had a full inch of clearance from the factory shroud that was well secured.

Inspect the hub piece of the fan to see if there was any evidence of a crack prior to the carnage, there will be some rust (if steel) at any one of the fan blade mating surfaces.
The clutch is still on the engine but looks like it just came straight out of the box. No rust, no wear marks. I'll get it off and post pictures.

wow that sucks Tom.
If you need any parts to get it back together let me know I have a reverse clutch fan on the blazer sitting in my drive way. I also have a stock BBC water pump and a heavy duty diesel clutch fan that came off the malibu but they are regular rotation and V-belt but I have all the pulley's you need to convert it if you want. I am going all electric fans, aluminum brackets, and pulley's when I get it back together next summer, I was always a mechanical fan guy too till one did this same thing on my vega at the track. Plus that is how my 174 super charger got damaged flex fan came apart and went through the super charger belt and upper pulley that took out front snout bearing and is why I am rebuilding it and going through the whole thing before I run it.
I kept all the V belt parts when I converted but I'll get in touch with you if I need something. Thank you. Luckily, I don't really need the truck. In fact, since I have a company truck I don't need any personal vehicles which really confounds my wife since I keep 5 not including her car. And they're all hoopties.

I remember in the 70's a guy got killed at the track in the pits. Story said he was revving the engine while checking timing. Fan let go and hit him in the chest. Also know of a very nice '69 Chevelle SS convertible that a metal flex fan let go and pieces went through the stock steel hood.
I have the inner fenders out right now because I've been fiddling with the suspension and I have a habit of standing in the engine compartment while it's running to adjust carb and timing. I have a nice scab on my elbow from the alternator fan... Maybe I should go buy a lottery ticket because my whole body was inline with the fan and I was revving it up to check mechanical advance. Holy crap did I luck out.
 
#17 ·
Happened to me on a 66 k20- 250 ci , a blade broke off upon acceleration in granny gear to get going. I was passing a school bus and I thought a kid had thrown something out the window as the hood had a mark on it. The mark was where a blade had come through the hood. The motor was out of balance but still runnable but can you imagine having your head in there doing a tune up and ........ It was a stock steel fan with rivets and all. I gained a ton of respect that day.
 
#19 ·
The one in my S-10 came apart last summer but it was plastic, 35 years old and had 290K miles on it. Tore up my recently replaced radiator :(

As far as your goes I would have to try and find all of the parts and pieces and take a real good look at them to try and find a cause. Kind of scary if it just came apart on its own.
 
#20 ·
Interesting. Did you retrieve any of the shrapnel that you say went all over the place? I'd be curious which of the company's fans https://derale.com/product-footer/belt-driven-fans you had installed? I don't know about aftermarket fans, but just looking at the elongated holes in the flex fans and the race fans and the fan spacers, that I take to be for mounting to whatever is the hub, looks half-fast to me. But I'm not an engineer. Wonder why the holes for the clutch fans are not like that? As far as liability goes...I'll bet that any installation that is not "stock" or "OEM replacement" absolves the company of liability. See any fine print that might pertain. Good thing that you or someone else wasn't injured. I'll bet that lives have been lost to fan failures like this.
 
#22 ·
Good advice above regarding the water pump bearings. Any significant wobble would've led to your carnage.
 
#23 ·
I had my first dealership job around 1976 and was working on a Granada.One of the older mechanics told me to be careful as there was a recall on some of the Ford flex fans around that time.He warned me they could break off and go through the hood or the fender.
 
#36 ·
And when would you like me to bring the Dart block and parts down for you to finish? I still haven't got to it.
 
#25 ·
I've also had a fan and clutch make contact with the shroud and destroy the shroud and fan assembly, due to bad rubber engine mounts. A close check there would be good.
 
#26 ·
Inspect the hub piece of the fan to see if there was any evidence of a crack prior to the carnage, there will be some rust (if steel) at any one of the fan blade mating surfaces.
 
#28 ·
wow that sucks Tom.
If you need any parts to get it back together let me know I have a reverse clutch fan on the blazer sitting in my drive way. I also have a stock BBC water pump and a heavy duty diesel clutch fan that came off the malibu but they are regular rotation and V-belt but I have all the pulley's you need to convert it if you want. I am going all electric fans, aluminum brackets, and pulley's when I get it back together next summer, I was always a mechanical fan guy too till one did this same thing on my vega at the track. Plus that is how my 174 super charger got damaged flex fan came apart and went through the super charger belt and upper pulley that took out front snout bearing and is why I am rebuilding it and going through the whole thing before I run it.
 
#29 ·
I remember in the 70's a guy got killed at the track in the pits. Story said he was revving the engine while checking timing. Fan let go and hit him in the chest. Also know of a very nice '69 Chevelle SS convertible that a metal flex fan let go and pieces went through the stock steel hood.
 
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