Question: Dual Mass Flywheel

[gboone]

I recently purchased a S15 SR20DET, which has a dual mass flywheel. This engine supposedly has less than 50,000 miles but there was a significant amount of water inside the bell housing when I got it. Obviously this caused some signicant rust on all the steel surfaces inside, including the flywheel. I've removed the flywheel and bead blasted it thoroughly, but since the assembly is riveted together, it's impossible to inspect and clean the hidden areas between the 2 plates. After blasting it, I remounted it and performed the rotational tolerance check and it's 23 mm (well within the allowable limit of 29 mm). But I expected there to be some resistance from the springs as I rotate the rear plate relative to the front plate. And it doesn't tend to center itself anywhere, it just stays where ever you let go of it. It seems to rotate very freely within the 23 mm range of motion. Is this normal? Also, I fear some hidden rust may cause problems with the operation. I'd like to have high confidence this flywheel is OK before re-installing. Any ideas? TIA.

[riaazfr1]

It would probably be better to buy a brand new flywheel altogether to save you the trouble later on no?

[gboone]

It would probably be better to buy a brand new flywheel altogether to save you the trouble later on no?

Yes, this is the easy answer, but is it justified to spend $1000 for a new one if it's likely that this one will work fine?

[riaazfr1]

I guess that depends on how you look at it. You can try and inspect it, but then later on, may still have to spend the $1000 to get another one, plus take the time to get back into the bell housing to get to the flywheel again.

I personally don't know how to take it apart and inspect the flywheel. I had to replace my clutch on my 2010 sentra. I only had the flywheel resurfaced. I know of the rivets you are speaking of, probably would be best to take it to a transmission shop and get a quote. Would more than likely be cheaper than $1000 as well as be safer.

[Hijacker]

I did a quick google search on resurfacing dual mass flywheels. One of the good responses to doing it was this:

Following a seperate post on a 'E28' to E34 M30 flywheel swap, I thought to share this tidbid from the Master Machinest of a reputed local facility. He asked me why I was thinking of dropping the dual mass unit: one of the 'facts' I quoted was that they could not be resurfaced if required.
With a knowing smile, he reassured me that he had resurfaced numerous BMW dual mass units.
He brass shims the inner 'mass' such that they can be clamped down in the same plane. Them, brass wedges are used to force the two discs concentric. The resurfacing grind then proceeds as for a normal flywheel .. "A breeze" he said, with excellent results!
Interresting, or so I thought: not bad for <$50 if one wants a dual mass unit restored. Yes, I know that a preferred route is to 'downgrade' to the E28 M30 assembly; however, that may not be the route for everyone - and this may be a viable option.

The last time I manhandled an S15 flywheel's been about 6-7 years ago, so I don't remember too much about their construction. If they're riveted, you can drill the rivets out and then try to rivet it back together yourself, but if it were me, I would let a reputable machine shop handle that job. TBH, the flywheel might be FUBARed if it's not self centering. That makes me think something is causing drag inside the spring channels to keep the springs from doing their jobs. It only takes 87 in/lbs of torque to move it, so that's not a lot to move it. Which means it wouldn't take much to keep it from moving back to where it needs to be.

I will also say, Nissan says to replace the flywheel and not to disassemble it. But they do say that about quite a few things that are rebuildable. If you decide to have the flywheel taken apart, instead of riveting them back together, you could try having countersink seats machined into the surface and tapping the lower section to accept countersunk machine screws, kind of like the friction surface screws on Fidanza flywheels.

[gboone]

Thanks Hijacker. That's the most useful information I've gotten so far. I fear if I attempt to disassemble the flywheel and find some bad parts, that I'll never find replacement parts, like springs. But then what do I have to lose but time, right?

[Hijacker]

That's about all you have to lose. You can probably try to replace the springs IF you had the specs on them, but Nissan doesn't list them in the FSM obviously. You'll have the length and OD/ID of the spring, so all you would need is the spring rate to replace them. Getting spring rates for it shouldn't be hard, just gotta do some testing on a spring that's in good shape.

http://www.newcombspring.com/article_spring_rate.html