E60I

Either that or disconnecting the intake manifold once too often?. Obviously, the cheap Harbor Freight torque wrench didn't work! Comparing to the Craftsman digitial torque wrench, I can obviously hear and feel and difference.

twh

There are several types of torque wrench. The beam type needs no special treatment except to note were the pointer is at the start. The click type needs to be stored unwound and it needs to be unwound every so often. While I am using it, I unwind it every few bolts or every 15 minutes, which even comes first. The other thing to note is that torque wrench is best used in the middle of the range. You need two wrench's to cover the most common torque ranges.

twh

I had a feeling you were looking at the stripped threads all in a nice little coil. I've been there before, unfortunately.

The good news is that the stripped threads are in the all aluminum cylinder head and it is all relatively accessible. The bad news is that the threads are not at the surface of the bolt hole, but down deep. This bolt is 50mm long, by its description. Looking at your picture, the Internal threads you stripped out are 15mm or so. The Helicoil you show is only 10mm long. I haven't done one of these where the bolt had a long shoulder. You need to do some surfing for how to handle this. In the least, I don't think the kit at O'Reilly has a long enough thread. The general process is drill out the hole bigger using the bit size specified on the package. Then, you need to tap the new hole with the special tap provided. Then you insert the Heliciol with the tool provided. But, your situation is different and poses some issues. How deep is the original hole and will the tap get sufficiently down the hole to clear the entire bolt length? Sometimes you need a special tap that is less "pointy" if the hole isn't a lot deeper than the bolt. Then, you need a longer threaded insert. Then, you need a way to get the threaded insert all the way down the hole to where the bolt's threads actually are (past the smooth shoulder). I'm not a professional mechanic and there may be a standard way of dealing with this. Or, maybe they would decide to use a different bolt than the original one. Or, maybe they would replace this with a stud. Not sure, but I'd do some surfing. Also important is how much "spare" material is there in the cylinder head if you drill a larger hole. Also wondering why BMW didn't just use a stud here like all the other 6 ones?

Just as aside...for the N52 engine, you can only use the special Helicoils when you are dealing with the magnesium parts. BMW says this:

"Special aluminum HELICOIL Plus threaded inserts have been developed for professional thread repairs on the N52 magnesium crankcase. Only this aluminum HELICOIL Plus threaded insert is to be used when repairing threads on the magnesium crankcase. For reliable identification, the aluminum HELICOIL Plus threaded insert are colored blue, like the aluminum screws."

twh

Here is the Helicoil catalog:
http://www.stanleyengineeredfastenin...c2000-rev9.pdf

Timesert his is an alternative, but similar repair. I have used their oil drain plug repair kit on my wife's X5. You'd need the 20mm long M7 insert, but have to cut the shoulder off in order to get it all the way down the bolt hole.
++ TIME-SERT Metric Kits ++ thread repair kits and inserts repair stripped threads damaged threads repaired threads threaded inserts for metal thread inserts for metal aluminum inserts threaded inserts for aluminum

twh

Looking at some more online posts, it seems like some people have had success stacking multiple helicoil inserts. Haven't done it myself. Please let us know what you end up doing and how it works out.

turboawd

Can you just tap the hole for a size bigger and use a bigger bolt?

twh

You could do that also, but you may have to make the hole bigger in the intake manifold as well. Not sure you can just move to an M8 bolt if you stripped out an M7. You'd need to use M10 probably. I think timesert or stacking two 10mm long helicoil is the best option and retain the original bolt.

E60I

Twh,

Thanks for all the info.

I went and bought the Heli-coil set, 9/32" drill bit and tap wrench today. I forgot a couple cases of beer, so the work will have to be postponed until this weekend. ;-)

I am going to use the 10mm insert only because I think it will be strong enough to withstand 9 ft-lb of torque.

Do you have any idea what can happen if I use the Heli-coil stainless steel insert on our aluminum engine? I hope nothing serious!

twh

Stainless Helicoil in the all aluminum cylinder head is fine. Yea, 9 ft-lb seems like it should be fine. It isn't the bolt threads you need to be worried about now, but the threads that bit into the newly tapped hole. Even so, 9 ft-lb is pretty low.

E60I

"Aluminum" should be easy to drill and tap. The current hole (outer most, further away from the firewall) is not what I am worried about, it's the other two (harder to work on locations) that have 70% chance of stripping also. I think I really got myself in a mess this time.