Technical What is the effect of a missing screw fitting clutch-kit to flywheel?

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Technical What is the effect of a missing screw fitting clutch-kit to flywheel?

Navin Talati

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What is the effect of a missing screw fitting clutch-kit to flywheel?
Actually in my Linea T-Jet, I had to change (replace) it's clutch kit and actuator (I.e. a single unit consisting clutch bearing and slave cylinder). On refitting every thing and remounting the gearbox as usual, it was found that the technician fitted only 8 screws and missed 1 while mounting and fixing clutch kit cover on the flywheel! To fit this 1 screw again the whole labour of removing the gearbox and refitting it is required which is very straineous and painstaking job again.
The car is running normal and seems no issue at present.
If I let go that 1 screw, then What is the effect of a missing screw fitting clutch-kit to flywheel?
Please guide me.
Navin Talati
 
Last edited:
Well if the "technician" failed to spot a missing screw while assembling the clutch, you can be 95% sure he definitely didn't torque them down to spec either. I would pull it apart, reassemble with all new screws + locktite, and torque to spec.
It is a critical part and clutches take a beating with all the vibration and hot/cold cycles.
 
Well if the "technician" failed to spot a missing screw while assembling the clutch, you can be 95% sure he definitely didn't torque them down to spec either. I would pull it apart, reassemble with all new screws + locktite,
and torque to spec.
It is a critical part and clutches take a beating with all the vibration and hot/cold cycles.

Dear Sir,
Thanks for the quick response.
It would be nice if you can elaborate a bit more for my better understanding.
The mass of the missing screw is just 7.0 mg.
This is for your your kind information.
Regards.
Navin Talati/09-02-2020
 
Agree with DD, the bolts should have been torqued in a cross patern, so if the "technician" did not noticed the missing bolt, he probably did NOT torque them at all !
Since there is a missing bolt, the two adjacent ones have to sustain the charge (the diaphragm pressure) that the missing bolt isn't, so they might get overstressed and eventually elongate, get loose, transmit the efforts to the next adjacent, etc.

Finally, not doing a simple GB removal (actually you might be able to "slide" the GB just enough to install the missing bolt) could potentially lead to HUGE damages ...

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)
 
Hi,
Firstly as it was the technians mistake they should rectify it at their expense, regardless of possible outcomes.
As for possible problems, by "screw" I think you mean the fasteners holding the the clutch pressure plate assembly to the flywheel. This will weigh several grams not milligarms. This is a significant imblnce and will cause some vibration. Think about how small the weights they use to balance wheels. The missing fastener may also cause the pressed steel assembly to distort under load. The remaining 8 fastners will lso be carrying a higher load than the design allowed for.
Most importantly, as Detroitdiesel has said, it is possible that the technian also failed to correctly tighten one or more of the bolts they did fit.
Looking at it another way, if the clutch assembly fails it could destroy the gear box and even damage the engine. Is the technian going to pay to repair that if it happens? maybe if it happens next week, but what about next year or the year after? You should not take that chance, get them to fix it now.

Robert G8RPI.
 
Hi,
This is a significant imbalance and will cause some vibration. Think about how small the weights they use to balance wheels.
Robert G8RPI.

@ 120km/h, a 15" 185/55 wheel rotates 1089(ish) turns per minute and would already induce HUGE vibrations in the steering wheel if unbalanced.
@ 120km/h, the engine (and so the flywheel/clutch assy) would rotate about 3 time faster (3000 tr/min).
That need to be squared (E=MC²), let's compensate this for the different Ø (15" for the wheel, 12ish for the clutch) and we got [9/(12/15)] which means unbalance effect 7,2 time bigger @ the flywheel !

That + the potential mechanical issues (blown gearbox/engine) SERIOUSLY require the missing screw/bolt to get fixed immediately, at "technician" expenses of course !!

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)
 
Dear Sir,
Thanks for the quick response.
It would be nice if you can elaborate a bit more for my better understanding.
The mass of the missing screw is just 7.0 mg.
This is for your your kind information.
Regards.
Navin Talati/09-02-2020


Does your car still have the
'Timing port'
on top of gearbox: bell housing?

A view of a missing bolt should be possible through there ;)
 
Agreeing with all that has been said, but to be honest, I do not recall applying any particular torquing procedure (though I am 99% sure I did it in the cross pattern out of pure habbit) when I did my clutch 80k km ago, and all is still fine. Nevertheless, forgetting a bolt (any bolt) by a "pro" is unforgivable.

Yes, and I wonder if an acrobat with an endoscope could fit the missing bolt through the inspection hole (really difficult because the stiff clutch cyiinder pipe goes through there too).
 
Navin Talati

Might be able to update

Whether a view of the clutch was possible

Still nothing has been done for the same. the car is running well without ONE missed screw!
However, I am thinking that the screw can be placed and tighten on its position on the flywheel through the timing window or say the window(square hole) linking fluid line going IN. This may require a specially lengthen screw drive having its appropriate tip and be guided through a small diameter ( say 10-12 mm) pipe and could be carefully fixed the forgotten screw. An endoscope may be of special use if becomes available.

Regards.
 
Hi,
Firstly as it was the technians mistake they should rectify it at their expense, regardless of possible outcomes.
As for possible problems, by "screw" I think you mean the fasteners holding the the clutch pressure plate assembly to the flywheel. This will weigh several grams not milligarms. This is a significant imblnce and will cause some vibration. Think about how small the weights they use to balance wheels. The missing fastener may also cause the pressed steel assembly to distort under load. The remaining 8 fastners will lso be carrying a higher load than the design allowed for.
Most importantly, as Detroitdiesel has said, it is possible that the technian also failed to correctly tighten one or more of the bolts they did fit.
Looking at it another way, if the clutch assembly fails it could destroy the gear box and even damage the engine. Is the technian going to pay to repair that if it happens? maybe if it happens next week, but what about next year or the year after? You should not take that chance, get them to fix it now.

Robert G8RPI.

I totally agree with you. Mistakes happen, and I am sure the bolt was not missed on purpose, but it is the fitters job to do things properly and a requirement under the law to provide service of a standard reasonably expected of a competent trades person. Any reasonable tradesperson would sort this out straight away however painful.
 
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