Went to change my motor mounts today on my S4. I was using Pirtle's procedures and everything was going smooth until I got to the point where you take off the 13mm and 17mm bolts on the motor mount housing. There is a 13mm and 17 mm on each side of the mount. These bolts thread into the engine block. The 17s came out with no problem. I then started on the 13s. Major problems. The bolts that Porsche used on my car were longer than the engagement in the block, so the few mm that stuck out past the block are rusted up. I soaked them down and they are locked up. One has even broken off in the block. What am I supposed to do now? Why did Porsche use two different size fasteners here? Is it alright to only use the 17mm bolts? I got one 13mm out, one is broke off, and the other two feel like they can break any second. Any suggestions besides pulling the motor? I cannot hardly get to these bolts to drill them out due to their location. Is there anything out there to drive them forward instead of trying to back them out? There is space above the engine block to drive the bolt forward. HELP!

Thanks

 

Mike,
Do you have air and a 1/2" impact gun? - and did the other 3 bolts begin to move? If yes to both, I'd set the gun on medium - and carefully work the bolts in/out/in/out ....., otherwise, just slowly impact them out. The 'shock' value far outweighs the torque applied with a long ratchet.
On the broken stud, can you see or feel above what clearance is available: I can't recall, but if there is enough, I'd try to center punch the broken bolt. Then, with a 1/4" drill, begin drilling for an EZ -out: The act of drilling ( right hand twist) may actually drive the bolt piece out through the top.

 

Okay, I've seen a similar situation with another car recently. Garth has a good idea with the impact gun. Just back and forth gently, will destroy the threads in the block, but should get the fastener out. Once the bolt is out, drill the hole clean and use a through bolt and nut on the top.

As for the broken one, remove the nut holding the MM to the crossmember, and pull the crossmember out. Once you have the crossmember out, you'll have room to work up there with a drill. Start with a center punch! This is important because we don't want the drill to wander off the steel bolt, and into the Al. Start with a small bit! Less wandering. Work up to a 4-5mm bit, then clean up with a bit slightly bigger than the shank of the bolt that broke. Use a longer 13mm bolt and nut on the top.

 

I'm in the same boat. I snapped one of the 13mm bolts when it was nearly out. There's about 1/3 of the bolt still in the hole. I'll be tackling it with the engine out and on a stand.

 

That was mine. The threads in the block were stripped. The weird thing is that someone had installed a long bolt and nut before I was in there. The bolt seized and stripped when I removed it. Replaced it with a new bolt and nut. I don't think the motor mounts had ever been changed. What other reason would someone have to remove the bolt other than to replace the mounts? When pulling the engine perhaps?

 

Whatever happens, just make sure you don't forget the anti-seize when you put it back together!

 

Jim:

 

Well, The impact wrench trick worked! Thanks Garth!

I went to center punch the broken bolt, but the bolt did not break off flush. There is no way to start the drill centered on the bolt? Does anyone have any ideas? Does anyone know where to buy a drill bushing to fit the hole?

Thanks

 

That's good news! You may have to run a tap up through the holes to clean up the threads, for I suspect they are still in reasonably good shape.
A couple of thoughts re. the snapped bolt; it may be possible to use a small dental burr in a dremel tool to score a center hole in the bolt to guide the drill - obviously, the trick is to keep it from waltzing all over the place.
My preferred method , if the bolt broke off well inside the hole, would be to make a guide from a piece of plastic/teflon/aluminium rod stock that just fits the bore. Run a 1/16" drill through the center , insert, and use as the centering guide.
Failing that, look in your junk box - for example, I have a collection of various small diameter soft copper tubings: a piece of something like this dropped over a drill bit can also work.

 

The same thing happened to me, and I drilled a 1/8" pilot hole through the broken bolt, then larger and larger drill bits and was able to get the rest out with an easy out. Then took a tap of the same thread and cleaned it out.
The most important part is drilling the beginning of the pilot hole. Has to be centered and in line. Take your time there.

 

Just a thought on rigging a guide to keep the bit from wandering on the initial drilling (haven't used this but wonder if it would work). For bolts broken off above the surface, could you take an appropriately sized nut, turn it 1/2 way on, fill w JBWeld, remove and drill a pilot hole and have this act as a guide? Any chance this might work ? I've had to deal w this in the past and ended up trying to file/grind the surface flat first and then try to get a center punch on it.

Jim

 

You probably thought of all this already, but...
Use a mirror if you can't see the broken stub -try a dental mirror Wal-Mart, Walgreens, drugstores-
and look at the broken stud. Sometimes -rarely- when the bolt breaks it will cup giving you something to work with. Eyeball the broken -bolthead side- and estimate from a good bolt how much length is remaining on the broken shank side. Then ... give yourself at least a 1/8th inch leeway so
you don't overdrill, use a piece of 1/4" masking tape to use as a max depth gage.
Use all the penetrant you want to, and take your time.
Also there is a 'T' handle you can use on the easy-out as well as just the wrench or socket method. Examine your space and your options the easy-out can go in a tiny bit crooked but if you apply an of center wrenching force and break the easy-out things get ugly ...fast.
I buy most of my tools at the cheapo endcaps or after X'mas sales with the understanding that if they work, just once, they paid for themselves. BUT, drill bits, clamping pliers, cutting disc's, and above all easy-outs are all purchased from aircraft maintenance tool suppliers or outlets.
Don't go cheap here! Believe in anti sieze.
Good luck.

 

Drill bushings are available from http://www.mcmaster.com/ keywords for search are drill bushing