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Flywheel micro cracks

tomasss

former PRVert
Joined
Oct 13, 2008
Location
Sydney, Australia
Flywheel hairline cracks

I have unmounted the pressure plate and clutch from my 740T and found out there are harline cracks in the flywheel surface...now I am wondering if I should worry about it or if it is normal.

What do you guys think? (click the pic for full res)

<a href="https://imgur.com/q26z8n9"><img src="https://i.imgur.com/q26z8n9l.jpg" title="source: imgur.com" /></a>

<a href="https://imgur.com/zNMeuRj"><img src="https://i.imgur.com/zNMeuRjl.jpg" title="source: imgur.com" /></a>

<a href="https://imgur.com/chMFQ2k"><img src="https://i.imgur.com/chMFQ2kl.jpg" title="source: imgur.com" /></a>

<a href="https://imgur.com/7qBNLcB"><img src="https://i.imgur.com/7qBNLcBl.jpg" title="source: imgur.com" /></a>
 
As jack said, it's totally normal, but you should get it resurfaced. Any machine shop that does car stuff will handle it, shouldn't cost much over $100.

I can't speak to what will happen if you don't get it done, but it's easy enough to handle.
 
Resurface it. It looks like a lot of clutch slippage to get it so hot to burn the surface.
 
It looks like that car was driven by a clutch slipper, or had a poorly adjusted one. Before you took it out, did the clutch squeel or chirp on engagement?
 
I drove the car like 20 meters...from the tow truck to my garage :-D but those two or three clutch engagements were ok, without any weird sounds.
Ok, going for resurfacing.
 
Depending on how severe The blueing is, that flywheel might be scrap, as the metal has been compromised. Resurfacing will only clean up the surface, not core(if you will) of the flywheel.
 
If your just putting a stock stuff back in and not racing it should be fine if it cleans up with resurfacing. Problems happen when you try and use ceramic discs and go racing. Make sure you get the top of the dog dish ground down so the gap is within spec between the pressure plate mounting surface and the surface of where the disc rides.
 
Agreed that with resurfacing that FW should work fine for daily street use.


Make sure you get the top of the dog dish ground down so the gap is within spec between the pressure plate mounting surface and the surface of where the disc rides.

Where is that spec to be found?
 
We'll my machinist in Creswel Oregon, Drummond automotive machine, he had a book or he just knew it. I never asked, but he did do both surfaces. Also only charged me 25 buxs. Bro deal. Others like big time shop in Portland say Bearing services would probably charge at least 100 maybe more. Bearing services charged me 550 buxs to lighten my dog dish flywheel that exploded at the track with a ceramic disc after it got way to hot doing 10 runs in a row 100 degree day. Nowdays I only run billet steel flywheels, cheaper then other BS..
 
Hmmmm... somebody must know that. What if it has been previously ground incorrectly? If I know the proper depth of the step I can check for that beforehand, and check my machinist's work afterward. It is hard for me to believe that any random machinist would know it.

Will search greenbooks...
 
Some more pics just to justify myself why do I need to spend more money on it :)

<a href="https://imgur.com/raR2184"><img src="https://i.imgur.com/raR2184l.jpg" title="source: imgur.com" /></a>

<a href="https://imgur.com/teIj1Ue"><img src="https://i.imgur.com/teIj1Uel.jpg" title="source: imgur.com" /></a>

<a href="https://imgur.com/1J0zGyg"><img src="https://i.imgur.com/1J0zGygl.jpg?1" title="source: imgur.com" /></a>

It is indeed little bit blueish on the daylight, so I am preferably replacing it with a different one rather than resurfacing the current one.
 
Guys...it's damn tough to find a good flywheel! :roll: Most of them is cracked even worse than mine...
The only one I have found not worse it >this< one but still I see that it has some heat spots and the surface is rough...any opinions about this one?
 
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