basilr Posted August 1, 2012 Posted August 1, 2012 I have to replace the left plastic cylinder head cover because the existing one broke on a "campsite drop". It looks like it is bolted on using the same bolts as the cylinder head. Does anyone know the torque setting for those bolts and how critical/uncritical it is to set them right seeing as I don't have a torque wrench? Thanks, Basil.
lkraus Posted August 1, 2012 Posted August 1, 2012 Sounds like you broke a valve cover guard, if it is plastic. The magnesium valve cover is held by four bolts torqued to 10Nm. It is very easy to feel when these are sufficiently tight - there is a rapid increase in resistance when they snug up. Tighten all four bolts gradually in a diagonal sequence and STOP when you feel the resistance. They do not require much torque to seal the cover and I understand they are expensive to replace. Larry
basilr Posted August 1, 2012 Author Posted August 1, 2012 You are right, that's what I am replacing. Thanks for the help.
spdyjr Posted August 4, 2012 Posted August 4, 2012 Oh yeah, while I'm at it, I've never torqued those bolts, but just stopped tightening when I feel them "bottom out". They never loosen up because there is so much friction resulting the large surface area on the bolt head. I learned that from some one else on this forum.
lkchris Posted August 4, 2012 Posted August 4, 2012 Oh yeah, while I'm at it, I've never torqued those bolts, but just stopped tightening when I feel them "bottom out". They never loosen up because there is so much friction resulting the large surface area on the bolt head. Because the rubber washer works just like a lock washer.
CurtRTGS Posted September 1, 2012 Posted September 1, 2012 I realize this is an older thread, but want to provide an expensive lesson learned about replacing cylinder heads. I recently replaced (actually, I should say 'tried to replace my cylinder head covers, the magnesium ones). I figured it would be simple, just remove the four bolts, put new gaskets on, put pretty new covers on, and replace 4 bolts. Everything was going smoothly when it came time to torque in the cover screws (9NM per the Clymer manual). The first two went to 9 on stopped. The next one went to about 5 and then just kept on turning with no resistance. Uh Oh, aluminum cylinder head threaded hole was stripped. The last one did the same. Took off all the bolts and 2 bolt holes were shot, one stripped, the other actually cracked down the side. Not sure I did that or not. I didn't just keep turning the torque wrench when I failed to feel tightness. Whatever. Bottum line: new cylinder head and lecture from the BMW Service Manager on why not to torque these bolts. Total cost in the end: $1,500+. Lesson learned: forget the torque wrench on this operation, just screw the bolts snug, check for leaks, snug a little more where leak appears, just don't try to torque these particular bolt. Just FYI. Cutt
Meromorph Posted September 1, 2012 Posted September 1, 2012 The 1100, 1150, and 1200 valve covers, are all mounted with thick rubber gaskets. The mounting bolts are designed to put just the right pressure on these gaskets when they are 'snugged up'. It is the design of the bolts that they do not apply increasing pressure to the gaskets, after the bolt bottoms out, only the lightest 'tweak' is required to hold the bolt in place. The valve cover is then 'fully floating' on the rubber gaskets. If a leak appears, remove the gaskets and replace with new ones, and thoroughly clean the head and valve-cover mating sufaces.
Ponch Posted September 1, 2012 Posted September 1, 2012 I did it by hand and they leaked. When I used my torque wrench, it didn't leak. I will say it's a good idea to make sure everything is real clean. I'd rather see studs than bolts on something like this.
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