Loctite on Flywheel Bolts?

[dukeofchen]

Hey all, in the middle of a clutch job right now, and my old torque wrench went kaput last night while tightening the flywheel bolts to 77 ft-lbs. The store was closed already so I never finished torqueing them down all the way.

I was using a new set of bolts, which come with what appears to be a yellow threadlocker on them. Given that they've already been torqued down and I'll be taking them back out, my thought was to use a thread chaser to clean out the threads and re-install them with some blue loctite applied. Possibly clean the existing yellow compound off the bolts as well to provide clean metal on metal contact.

Is this correct? Only reason I ask is that the torque spec PDF on here specifies not to use loctite and thread them slightly oiled, and I don't understand why given the bolts seem to come with threadlocker pre-applied. Definitely don't want to have them back out down the line and re-do this job over some stupid bolts.

[Slideways]

The yellow stuff might not be threadlocker, but a yellow threadlocker does exist. Usually, the common threadlockers are blue and red. TIS states the same thing about the bolts:

[dukeofchen]

Interesting, hard to argue with TIS here. I wonder exactly what the yellow substance that comes on the bolts is, given the standard threadlocker on all the BMW bolts I've seen is blue.

In that case, oiled and torqued to spec looks like the recommended route. Hopefully it's G2G with the correct torque spec in a star pattern, but one can't help but worry.

[cobra]

All I know is my buddy had that little dowel come loose on his (item #2) and wreaked some havoc. That should definitely get some loctite! Haha

[jbfrancis3]

My read of it all is with new OEM/OE replacement bolts, they all come with the thread sealant already pre-applied. The sealant prevents oil creeping up the spiral of the thread, as the other side of the bore is exposed to the crankcase. Per the spec, use only oil for installing to achieve the torque spec. I recall having to clean out white residue (the sealant) from the threads of the crank on a flywheel that had never been removed.

With the aftermarket setups, and removal of the DMF’s, many spec to use a threadlocker as extra security. A threadlocker will be sufficient to seal in this application.

[sapote]

Yeah, the yellow stuff on the new bolts is not threadlocker, but threads sealer to prevent oil leaking.
OP, why do you want to remove the new bolts?

[dukeofchen]

I had incorrectly assumed that the yellow substance on the flywheel bolts was threadlocker, as I've seen it referred to in relation to flywheel bolts before (FCP's listing for the bolts even refers to it as loctite).

So that led me down an incorrect train of thought, thinking that since I had only partially tightened the bolts that night, this mythical "threadlocker" began its reaction at the incorrect tightness, and tightening to the final spec the next day would break the seal and negate its effectiveness. Classic case of thinking a little too hard here 🙄.

The yellow stuff being thread sealant makes a lot more sense. I hadn't seen the last two replies here before going ahead and torqueing them down with a hefty amount of loctite – hopefully that combined with the high torque on the bolts is enough to seal it off. The entire gearbox is already back in, so it'd be hard to turn back at this point.

[Mr.wReckless]

Following curiously as I'm having my gearbox out for the 2nd time this summer after I developed a leak from the RMS area when I did a SMG -> manual conversion with new LWFW + clutch and new RMS. After I disassembled it the 2nd time around, due to my engine oil being fairly fresh, I couldn't see a clear culprit, but will definitely look into using thread sealer on the FW bolts as well as the RMS housing bolts.

Regards

[George Hill]

I've been using thread sealant on the original bolts for years without any issues.

[dukeofchen]

Following curiously as I'm having my gearbox out for the 2nd time this summer after I developed a leak from the RMS area when I did a SMG -> manual conversion with new LWFW + clutch and new RMS. After I disassembled it the 2nd time around, due to my engine oil being fairly fresh, I couldn't see a clear culprit, but will definitely look into using thread sealer on the FW bolts as well as the RMS housing bolts.

Regards

Second time this summer - I sincerely hope you aren't doing this on jack stands like I am 😂

In addition to the flywheel bolts, RMS bolts, and the RMS itself, there's also the RTV needed when installing the RMS housing.

Based on what I've seen you want a bead along both of the 90 degree corners where the oil pan / engine block / RMS housing meet before placing in the RMS housing. I referred to FCP's DIY video when I did this, and also spread a thin layer along the bottom of the RMS housing as extra insurance.

[dukeofchen]

I've been using thread sealant on the original bolts for years without any issues.

This is reassuring, thank you!

[Mr.wReckless]

Second time this summer - I sincerely hope you aren't doing this on jack stands like I am 😂

In addition to the flywheel bolts, RMS bolts, and the RMS itself, there's also the RTV needed when installing the RMS housing.

Based on what I've seen you want a bead along both of the 90 degree corners where the oil pan / engine block / RMS housing meet before placing in the RMS housing. I referred to FCP's DIY video when I did this, and also spread a thin layer along the bottom of the RMS housing as extra insurance.

Jackstands indeed🙈 Kinda sucks but I got myself a 2nd low profile (but higher lifting) jack so at least the jacking part of the job isn't such a time consuming event anymore. And I got it 1 notch higher on the stands so I can now (just about) sit upright in the trans-tunnel which makes doing this job ever so slightly less cumbersome. Last time I sort of had to do the ultimate core strength workout whilst adopting a banana shape on my body sitting on my ass.. It was a real workout!

Yeah did all the RTV stuff. The worst part about this job was that when I got the FW off I couldn't see a clear culprit to where the leak came from. But I've ordered the RMS pre-installed in the housing this time. Will chase the threads in the block and crank with a tap to get the old gunk out, drained the oil pan and will use thread sealant on the bolts as well as RTV to hopefully get this right the 2nd time around. Also been advised to run 3000 grit sandpaper wet/gently around the hub and lube it up before installing the RMS and housing and I think the pre-installed RMS will also come with a storage collar around the inside lip which also doubles as an installation tool.

Fingers crossed I won't have to do this again.

Regards

[tnord]

if the factory bolts come with some sort of sealer already applied I can understand not mixing it with loctite. however, I don't know how many dozens of times I took flywheels off of miatas and hondas back in my racing days, and put red loctite on every single one of them. never a problem.

loctite isn't used to make sure something never comes out. it's used to make sure the torque applied during installation is retained at that spec, and bolts won't loosen due to vibration or heat.

[Mr.wReckless]

I ended up polishing the crank before using the plastic storage item as a tool to fit the RMS. Also bought thread sealant and applied this to every bolt used for the housing, flywheel and pressure plate. I don't see the harm in this, and torqued things to spec.


Regards

[dukeofchen]

I ended up polishing the crank before using the plastic storage item as a tool to fit the RMS. Also bought thread sealant and applied this to every bolt used for the housing, flywheel and pressure plate. I don't see the harm in this, and torqued things to spec.

Best of luck sir – so far so good on mine. Haven't seen any drip or smelled burning oil, but my exhaust is definitely smellier after I put everything back together. The header to sec 1 gaskets were totally shot when I pulled it off so those are up next.