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To start, this is my first ever post on M5 board and i just purchased my first ever M5 two weeks ago from my pops. Though I'm new to the 5 series world I've previously owned a 85' 325, 89 325is and my last car sold back in June a 99' M3. So I'm not new to the BMW world. I'm a heavy equipment tech for a John Deere dealership so my mechanical abilities are pretty extensive.

Now onto the issue at hand. Driving home from a cruise Saturday night, I started smelling oil and was flagged down by another driver that my car was smoking. Pulled off the highway opened the hood and saw quite the oil leak coming from the drivers side rear valve cover grommet. Got the car towed home so I didn't burn it to the ground.

The next morning pulled the intake manifold off and began to pull the drivers side valve cover. When I removed the rear corner valve cover bolt I noticed the stud it threads onto was loose and moving around. I could pull up on the stud and it would physically pull outward. Thinking the stud was coming undone, I continued and pulled the valve cover. What I saw next nearly made me pass out. The drivers side, rear exhaust cam bearing cap had one nut missing and the other stud was completely broken off in the head. AHHHHHHH! The cam bearing cap was just bouncing around in there completely free besides the stud holding it to the valve cover. The nut that came off one stud is nowhere to be found. I can see that it was smacked between the head and the cam at the rear of the engine and I'm assuming it fell through an oil galley and into the oil pan. Hopefully! Thankfully the cam lobe was not damaged! I don't believe the cam cap came loose during my ownership because the damage on the inside of the head would have been noticeable when it happened. (see attached photo for damaged area and stud) So I decided to dig around and found 5 other cam cap nuts completely loose and not even snug. I decided to pull the passenger side cover and check the other cam cap nuts and found 6 other cap nuts not even hand tight :(


cam cap.JPG


For some back ground on the engine. Back when my pops owned the car around 2 years back and maybe 10k miles ago, the car was at Ryan G. MotorWorks in auburn, California to have both vanos units rebuilt. When they put the top end back together they timed it incorrectly and the valves contacted the pistons and bent the valves. ****. At this point my dad decided to have the engine completely gone through. Bottom end bearings, new timing chains, new tensioners, heads rebuilt. Basically everything minus the piston rings. My thinking is, that once they ****ed up the engine the first time around they rushed to get the engine back together and forgot to tighten the bolts or something of that matter since the cams had to be removed to replace the bent valves.

Sorry for the long story but I'm almost to the end. If you've made it this far, Thank you! So my main question here is, Are the cam cap studs supposed to be screwed into the head with loctite? The reason I ask is that the stud I was able to thread out had no loctite on it and I'm wondering if that's why all the nuts are starting to back off. I know they take very little torque for the nuts, but could the problem be that the studs were backing out? What is the correct procedure and torque spec for the cam cap hardware? Has anyone else experience the cam cap hardware coming loose? Was the just a case of carelessness reassembling the engine? Granted it has gone 10K miles and countless redlines since the repair.

Really could use some input as this is my first M5 and I'd like to make sure this doesn't become a problem down the road. Thanks for sticking it out through this novel!
 

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they probably removed them to do the head work. it would make me scared of anything else they touched and it being a possible ticking time bomb. I would plastiguage the clearance to check
 

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The TIS will list the need for loctite in the notes section (tightening specifications), if it was not included in the directions for the cams (11 31 1AZ) then loctite is not required per BMW.

see for reference examples:


I see what you mean that it will be noted in the TIS, but what I'm trying to find is how to install the studs that the cam caps slide over the top of. I cant find it listed anywhere in TIS but maybe it is just worded different than what I'm expecting.
 

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they probably removed them to do the head work. it would make me scared of anything else they touched and it being a possible ticking time bomb. I would plastiguage the clearance to check
That is what I was thinking as well. What exactly should i be checking with plastic gauge? Cam cap oil clearance? I haven't tore any of the bottom end apart, this is all in the top end. But, if I cannot get the broken cam cap stud removed from the head I will have to pull the engine and at that point I will be checking all of the bottom end hardware. Also the engine has ran fine for over 10K miles since it was torn down so I feel like if the bottom end was going to let go it may have already happened. Either way this loose hardware is giving me anxiety!!
 

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Thanks for the quick response! I've been scouring TIS trying to find the correct way to install the studs with no success. I was able to find the cam cap nut torque though. Still unsure if the studs should be installed dry or with some type of loctite.
I gotcha, unfortunately if those details are available somewhere you're gonna have to dig through the TIS page by page. In some cases you might have to search though the instructions for non-M or non-E39 models.

The part you are referring to is 07129908191

all chassis that share that part:

usually BMW will include the loctite from the manufacturer if it is necessary:
 

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I see what you mean that it will be noted in the TIS, but what I'm trying to find is how to install the studs that the cam caps slide over the top of. I cant find it listed anywhere in TIS but maybe it is just worded different than what I'm expecting.
I imagine you can just use the double nut technique to get them in. And even if loctite isn't required, it probably wouldn't hurt.
 

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I imagine you can just use the double nut technique to get them in. And even if loctite isn't required, it probably wouldn't hurt.
+1 on adding a locking agent if you chose, just be mindful of the operating temperature of the cylinder head vs the heat range of the locking agent

there are lots of tools that you can find to make installation easier:

Hazet

Amazon
 

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I imagine you can just use the double nut technique to get them in. And even if loctite isn't required, it probably wouldn't hurt.
Thanks for the tip! Planning on using medium strength loctite and hoping these things don't back out again!
 

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+1 on adding a locking agent if you chose, just be mindful of the operating temperature of the cylinder head vs the heat range of the locking agent

there are lots of tools that you can find to make installation easier:

Hazet

Amazon
Thanks! I've got the stud installation tools!
 
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