Crankshaft center bolt
02-14-2011, 12:25 PM
#1
AudiWorld Newcomer
Thread Starter
Join Date: Feb 2011
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Crankshaft center bolt
I am replacing the front crankshaft seal on my 99 A6 2.8L 30-valve. Does anyone know if I need to get a new crankshaft center bolt, and what would the tightening torque be? Do I need to oil the bolt slightly before installing?
The info I found for the 2.7 and 4.2 engines says yes to new bolt and torque to 200 NM plus half turn. Any insight is much appreciated.
The info I found for the 2.7 and 4.2 engines says yes to new bolt and torque to 200 NM plus half turn. Any insight is much appreciated.
02-14-2011, 02:02 PM
#2
AudiWorld Super User
Yes to new bolt. No oil.
You can stack the old bolt next to the new bolt and see that the old bolt has been stretched.
That's 'torque-to-yield'.
If you reuse the old bolt and torque it the same way it will stretch further and may break.
This TTY is purely for assembly, cost, and audi's convenience...a stronger material and perhaps a 250NM torque would have enabled multiple uses of the crankshaft bolt.
You can stack the old bolt next to the new bolt and see that the old bolt has been stretched.
That's 'torque-to-yield'.
If you reuse the old bolt and torque it the same way it will stretch further and may break.
This TTY is purely for assembly, cost, and audi's convenience...a stronger material and perhaps a 250NM torque would have enabled multiple uses of the crankshaft bolt.
02-15-2011, 03:56 AM
#4
AudiWorld Senior Member
New bolt is like $10 at the dealer. It's also for assembly safety - while the bolt is stretching, you get quite a bit less clamping done per turn, it takes quite a bit more turning to do any damage when the bolt is in its plastic stress range (when it's stretching), and you're more likely to break the bolt somewhere along its threads than you are to pull the threads out of whatever it is you're torquing.
As for the oil, don't fill the hole up with oil, but certainly lubricate it. Dry torque specs are much higher than oiled torque specs, so if the book gives you an oiled torque spec and you torque it dry, it won't be torqued sufficiently.
As for the oil, don't fill the hole up with oil, but certainly lubricate it. Dry torque specs are much higher than oiled torque specs, so if the book gives you an oiled torque spec and you torque it dry, it won't be torqued sufficiently.
02-15-2011, 10:18 AM
#5
AudiWorld Super User
Disagree. Do not oil the center bolt when reassembling.
Only reason to remove that center bolt is to replace the front seal. Incidentally, you're supposed to rotate (reverse in North American English) the thrust washer behind the toothed pulley (timing belt pulley) so the new seal has a new face to run on. So you can use the thrust washer ONCE. Mark it with a felt pen on the front before you remove it, then reverse it when you put it back on with the marked side toward the engine. If you pull the thrust washer and it has a mark on the back, you need a new thrust washer. BTW, you may not have a thrust washer...one of the belts used doesn't have a thrust washer, probably seals against the back of the toothed sprocket...my bentley ebahn has a note on this.
Anyways, I Disagree on oiling. My Bentley says "Do not oil the bolt for crankshaft toothed belt sprocket." I just looked it up.
This was for the 200NM +180 degree tightening specification on the 4.2V8.
The tightening specification for the crankshaft center bolt on the 2.8 is also 200NM+180 degrees.
My hardcopy Bentley says nada about removing or installing the center bolt. Of course, it also says nothing about r&r the front seal too. Inadequate. At least the ebahn Bentley manual shows how.
Only reason to remove that center bolt is to replace the front seal. Incidentally, you're supposed to rotate (reverse in North American English) the thrust washer behind the toothed pulley (timing belt pulley) so the new seal has a new face to run on. So you can use the thrust washer ONCE. Mark it with a felt pen on the front before you remove it, then reverse it when you put it back on with the marked side toward the engine. If you pull the thrust washer and it has a mark on the back, you need a new thrust washer. BTW, you may not have a thrust washer...one of the belts used doesn't have a thrust washer, probably seals against the back of the toothed sprocket...my bentley ebahn has a note on this.
Anyways, I Disagree on oiling. My Bentley says "Do not oil the bolt for crankshaft toothed belt sprocket." I just looked it up.
This was for the 200NM +180 degree tightening specification on the 4.2V8.
The tightening specification for the crankshaft center bolt on the 2.8 is also 200NM+180 degrees.
My hardcopy Bentley says nada about removing or installing the center bolt. Of course, it also says nothing about r&r the front seal too. Inadequate. At least the ebahn Bentley manual shows how.
02-15-2011, 01:39 PM
#6
AudiWorld Super User
Join Date: May 2009
Posts: 2,467
Likes: 0
Received 0 Likes
on
0 Posts
wouldnt even bother replacing unless it was leaking... too many guys ive seen break the bolt... rather put it in service position when it starts to leak then changing it while doing the timing belt, "just cause its there" and end up having to drill and tap the broken bolt out to replace a perfectly fine seal...
my 2 cents
my 2 cents
02-15-2011, 01:59 PM
#7
AudiWorld Senior Member
I got mine out of my spare motor with a 22mm wrench stacked on the 24mm wrench, while pulling and hammering. 1/2 turn worth of hammering before I could turn the stacked wrenches by hand.
The front and rear seals on my 2001 with 140k seal just fine. Don't see why you'd replace it just for fun. What if you buy a defective one or screw up the installation and it leaks after you're done?
The front and rear seals on my 2001 with 140k seal just fine. Don't see why you'd replace it just for fun. What if you buy a defective one or screw up the installation and it leaks after you're done?
Trending Topics
02-15-2011, 10:52 PM
#8
AudiWorld Super User
The Bentley Manual for the 2.8L 12V V6 engine used in the C4 platform does state to lubricate the crank bolt, and has the same tightening torque spec. I replaced that bolt on my '96 A6 Avant 6 or 7 times chasing an oil leak, and oiled the new bolt each time before tigthening. I also checked the service manual for the 1.8L T 4-cyl engine, and the 2.8L 30V V6 (years VW Passat 1998 - 2002) and it also states to oil the new crank bolt. But the crank bolt for the 4.0L W8 engine (VW engine) does not state to oil the bolt. So, maybe the V8s are the only engine that doesn't have oil requirement for the crank bolts.
02-16-2011, 06:59 AM
#9
AudiWorld Super User
Interesting. The guy who started this thread had a C5 and I looked in my CD/online eBahn manual for his engine.
Perhaps all the guys who posted re broken CCBs having to be drilled and extracted had that problem as a result of oiled CCBs and Audi changed the spec for the C5.
Perhaps all the guys who posted re broken CCBs having to be drilled and extracted had that problem as a result of oiled CCBs and Audi changed the spec for the C5.
02-18-2011, 05:00 PM
#10
AudiWorld Newcomer
Thread Starter
Join Date: Feb 2011
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Thanks everyone for your input, left up to the Bentley manual I'd be riding my bicycle year round. Today I got a new bolt from the dealer ($13.50). They told me to torque it to 200 NM plus 1/2 turn. I forgot to ask them about oiling, will do on monday. The bolt is coated with some red stuff, and as it stands now, I will follow the advise of not oiling.
The parts guy at the delaer said I needed something called a diamond washer, a paper-thin notched washer which looks like it goes between the sprocket and the seal and costs 29 bucks. I bought it, but when I took my sprocket off there was nothing behind it. Maybe it was lost during a previous job? My Bentley ebahn has no mention of it for the 2.8, but shows it for the 3.0.
I compared the new bolt with the old one: I lined up the treads at one end, and they did not mesh at the other end, I suppose that is enough evidence of stretching. Again, thanks SloopJohnB for the tip.
The crankshaft seal is leaking quite a bit, the front and bottom of the engine are covered in a lot of oil and gunk. I cannot 100 percent be sure that it is the seal and not the front cover gasket so I am thinking to replace that one as well, with removing just the lower oil pan and the four bolts holding the front cover to the upper pan. Is that a bad idea? Thanks.
The parts guy at the delaer said I needed something called a diamond washer, a paper-thin notched washer which looks like it goes between the sprocket and the seal and costs 29 bucks. I bought it, but when I took my sprocket off there was nothing behind it. Maybe it was lost during a previous job? My Bentley ebahn has no mention of it for the 2.8, but shows it for the 3.0.
I compared the new bolt with the old one: I lined up the treads at one end, and they did not mesh at the other end, I suppose that is enough evidence of stretching. Again, thanks SloopJohnB for the tip.
The crankshaft seal is leaking quite a bit, the front and bottom of the engine are covered in a lot of oil and gunk. I cannot 100 percent be sure that it is the seal and not the front cover gasket so I am thinking to replace that one as well, with removing just the lower oil pan and the four bolts holding the front cover to the upper pan. Is that a bad idea? Thanks.