Some aircraft actually havd done away with the lockwire on brakes and such
Fasteners “backing out”
- Thread starter JHZR2
- Start date
JHZR2
Staff member
I don’t think it would be straightforward to do here given space and access. It’s a delicate tightening scenario, don’t want to ruin the WP threads, don’t want to strip the Allen. FSM says 45nm…
JHZR2
Staff member
No, but the coolant level warning light sure did.
Could be part of the issue. Has this clutch fan been worked on by anyone, or has it been untouched from the factory?
JHZR2
Staff member
Untouched from the factory.
Maybe I missed it ... how many miles are on the vehicle? Any other owner's having a similar issue - ie, is this a rare issue that struck you, or are others also having it happen? Any TSB about this ... have you checked with a dealership on their take yet or if they have a TSB or similar on this issue?
JHZR2
Staff member
209k, I haven’t heard of this before. And I’ve been tinkering on these cars for 20 years now. Dealerships are less knowledgeable than me for the most part. The good diesel guys retired as shop foremen a decade ago.
Back to the semi-seized bearing. If the bearing is starting to seize up, and the bolt is contacting the center race of the bearing, then as the bearing starts to seize up there will be a turning force on the bolt. Check to see if that turning force would be in the direction to loosen the bolt. At 209K miles, I'd expect the bearing not to last forever, and you did say it turns hard.
JHZR2
Staff member
This clutch has somewhere between 500-1000 miles on it. It is a Chinese model I bought from RA somewhat in error (thought it was a repackaged OE on close out).
The bolt holds the center of the race of the bearing to the water pump pulley, indeed.
I think if I visualize it, looking at the front of the engine from the front of the car:
- the engine turns cw (right)
- the fan turns cw
- the aerodynamic force against the fan blades is ccw (left)
It seems to me that regular operation the bearing allows for takeup of speed differences. With a seized bearing, there’s a significant opposing force when the engine slows down but the fan is at speed. Once the bolt loosens a bit from enough of those “impacts”, then the long bolt can wobble a bit in the female threads (I felt that to be the case, and then the mild friction/interference fit can ultimately back out far enough to make the fan wobble and then fall off.
I think that’s what I noticed. Maybe 25 miles earlier I had come off the interstate and I felt that the engine was idling low. I couldn’t tell but I thought I heard a new vibration. In hindsight it was probably the fan working loose due to the seized bearing. It just took a while for the bolt to back out far enough, and then the rest is history…
So it has been worked on. I asked earlier if the clutch fan had been worked on by anyone or was it factory original and the response was it was factory. If it's not the factory part, and it's been worked on then there may be other factors involved. Was the bolt torqued to spec? Was loc-tite suppose to be used per the manual or not? ... stuff like that. And of course it being a non factory part doesn't help. The bearing not feeling/turning right looks suspect to me.
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JHZR2
Staff member
Yeah untouched from the factory that makes it. I didn’t tinker on it in any way. Just bolted it in. Can only go on in one direction. This was a Chinese part that I bought on Rockauto thinking it was a relabeled OEM based upon the picture. I had wrote that someplace.
FSM doesn’t specify loctite. @The Critic recommended to look at photos of the OE part, and pics don’t show pre-applied. I torqued to 45nm.
If you removed the factory part and installed a new part then it was tinkered with from the original factory configuration. That's what I was trying to verify when I first ask that question back in post 25 (shown below
).
JHZR2
Staff member
I’m not splitting hairs here. I have a few threads on this. The question of this specific thread is really how fasteners back out. The physics of it not the specific scenario at hand….If you removed the factory part and installed a new part then it was tinkered with from the original factory configuration. That's what I was trying to verify when I first ask that question back in post 25 (shown below
I guarantee they still have some locking method.
Safety wire, cotter pins, diaper clips, nylon locking nuts, friction locking nuts or nut plates, nordlock washers, etc...
I was trying to find out what went on with it before the failure happened as part of looking for a root cause. Not ever being disturbed since it was factory installed vs putting on a different part could have a bearing on why it failed. Part of a failure analysis. Not every bolt backs out for the same reason.
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Forgot to ask ... is the hole the bolt threads into a blind hole, or a through hole? If it's blind, is there any sign that the bolt was trying to bottom out some before torquing up tight? Since the new part is not OEM, maybe the stack-up when assembled isn't exactly the same.
JHZR2
Staff member
Yeah I understand. The fan clutch on those cars gets removed to access a variety of things. Very easy if the Allen doesn’t strip…
I meant it was a “factory” part that I hadn’t done anything to. Thought it was reasonably known that o had put a Chinesium part in my car
There’s a flange that’s pressed onto a shaft. I’d suspect that makes it a blind hole.
It is a fair theory that if the front to back thickness of the bearing was different, the bolt could bottom out with inadequate binding to hold the fan clutch in place. A few mm could just reduce the thing by a thread or two.
That said, it was on for almost a thousand miles, so I’d have thought such a thing would be the cause of infant mortality instead.
Guess I didn't equate that Chinesium statement to it being swapped out, thought it could be a China made OEM part from the factory. Anyway, on the same page now.I meant it was a “factory” part that I hadn’t done anything to. Thought it was reasonably known that o had put a Chinesium part in my car
Hard to say when a fastener is going to loosen up for whatever reason. Anyway, I'm pretty sure it came loose because the bearing was basically seizing up. If both the water pump and the fan are spinning the same CW direction (when looking at the front of the engine), any time the engine RPM increases there will be a counter CCW torque from the inertia of the fan going through the inner race of the bearing and therefore on the bolt, which would try to unscrew the bolt. Having that counter torque applied over and over enough times is probably caused the failure. When the bearing is working as it should, the counter torque isn't much (just the internal drag of a normal working bearing), but with the bearing seized up that counter torque would be much higher. It was essentially was like a "mini impact" gun on the bolt, and took some time to loosen the bolt.
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