the flyin' scotsman

Good for you; I did same except the water pump...........our cars are of an age where its a crapt call; replace whats worn or replace all beacause its 20 yrs old?

In my case the pump was changed, from PO's records, not too long ago (in Kms) but I wanted to go wit a new belt with the Porkentensioner; so far excellent............the OEM tensioner still sits on the bench despite offers to buy.

tomcat

?????


I have the torque wrench in my car. Let me know when you want to meet.

jon928se

SWAG - That sounds like too much to me although sitting in the office I can't go have a look see. The hole in the washer is the same size as the bolt ? not big enough to go over the crank nub ? So that however much you tighten the bolt the washer will never clamp the pulley group.

JPTL

Jon, keep in mind that the 5mm measurement was taken at the face of the A/C pulley before the pulley group is set onto the crank nub. With the pulley being 2mm +/- thick, I'm guessing the protrusion is somewhere about 3mm inside the pulley group.
The bevel inside the crank bolt washer is deeper than 5mm, so the shoulder of the bevel will press against/clamp down on the pulley group.....assuming that the bolt isn't bottoming at the threads (as if there were a missing washer or spacer somewhere).
John,
Thanks, I'll give you a call tomorrow. I'd like to grab that wrench @ your convenience.

Mrmerlin

the crank nub should be sticking out from the face of the pulley and the recessed washer should make up for the difference and then some, the Keyway in the crank must also be in alignment (it is tapped into the side of the crank).
So if things are loose they you didnt fit every part back together correctly look at the WSM it gives a good picture of the crank snout and the fitting of the pulleys and washers, did you refit both of the thrust washers to the drive belt pulley? this might make up for some lost clamping distance, did you have any leftover parts from you TB/WP job

Bill Ball

Measure the bolt. The shank should be 45mm. I'd get a new bolt. It sounds like you had the thrust washer oriented correctly (recess facing the engine). If it had been the other way around, the pulley wouldn't tighten at all due to the protruding crackshaft snout.

marton

I replaced my TB & WP about 1 year ago, after I read this I tried the crankshaft bolt. Got about 1/8 to 1/4 of a turn on it

Now I know why some people do them up so tight

Marton

Garth S

JP,
I suspect that the crank bolt needs to be replaced.

By your description, it was correctly assembled and torqued ( loctite should not be necessary) .... so, if it came loose, it is highly likely that something in the contact mating surfaces is not absolutely square. That something is possibly a miniscule bend in that very stout bolt: such a bolt will torque up to spec when installed, but only be making point contact at the mating surfaces. Inherent vibrations will quickly back out such a fastner in service.

If the same bolt was used, drive around with a breaker bar and 27mm socket in the car for the next few days ... just in case.

JPTL

Bill, you're absolutely right re: the orientation of the washer. I'd be conceding that I had it on backwards had I not looked at it on the bolt when I took off the bolt this last time. I'm 100% sure it was on correctly. In fact, there isn't as much as a scratch inside the recess of the washer. The bolt head would have quickly carved a circle inside the recess had it been on backward. Also, I'm guessing that the pulley group, AC pulley and vib. damp. would have been loose from the get-go. I got several miles with those things being quiet & I assume tight. FWIW, the bolt head appears to have been turning on the washer, as that's got fresh grooves in it as well....that would be expected with a loose bolt.
I guess I've exhausted this topic. The only reason that I'm belaboring this with tireless details to the extent that I have, is that I don't think I did anything wrong - at least in the re-assembly.
Something caused this to happen....be it an unseated vib. damper & A/C pulley, a bent bolt....whatever.
I now feel strongly that although it won't lead to catastrophic engine damage like a loose t-belt, this bolt loosening up will leave the car stranded where ever it may be, until the right tools are located to get it tightened back up.
I think a subsequent check of this bolt torque after 100 miles is probably worth mention in any manual or how-to as a follow-up as part of a t-belt job.
I know that I'll be doing it.
Another great suggestion that I'll take.

JPTL

Two questions - kind of physics-related:

• Could an overtight power steering belt cause the loosening of this bolt? If the crank pulley is getting an uneven pull to the driver's side, could that create a loosening effect?
• Does the flywheel lock need to be installed in order to get the correct torque at the crank bolt (it was when I did the reassembly, but I'm wondering if I need to do it again)?
  Isn't the resistance that the bolt puts out (torque) the same, regardless of whether there's a slight give at the bolt-down point (in gear w/ebrake on), or it's rigid/unmoving (flywheel lock)?

Vilhuer

Washer wrong way round would have been easy explanation. Since its not the cause it could be anything really. I would check threads inside crank nose really carefully and replace the bolt just in case even if it looks like new.

SteveG

Technically, Yes.

dprantl

I haven't messed with those Physics equations in years, but I think that if you do not have the flywheel lock in place, when you put torque on the bolt the driveline will flex. Usually this flexion is negible but in the case of the crank bolt without the flywheel lock tool it can be quite large (you can flex up to 90 degrees or more on the crank). This flexion stores potential energy like a spring, which must then be subtracted from the torque the wrench is reading. But since you used a flywheel lock tool, you don't have to worry about this.

Dan
'91 928GT S/C

tomcat

I need to make sure I understand what some are saying.

JP torqued his crank bolt on w/o the flywheel lock. There was some play/movement of the crank even with the tranny in gear.

So as you torque the bolt subtract the torque from the slipping crank? I would say if the torque wrench says 225#, then the bolt is torqued at 225#. Maybe the force on the torque wrench (JP's arm) is more than 225# because of the slippage, but the torque wrench isn't going to click until it reads 225#.

dr bob

I think one needs to rethink their 'physics equations'.

It takes a certain amount of torque on the bolt head to get the wrench to click or the beam to bend a certain amount, regardless of why the crank isn't turning. Everything is relative. No need to subtract the earth's rotation or add in the air temp divided by the time of day.

Of course, there's the inertia of the crank and part of the driveshaft moving when the torque wrench is used at one end but the driveline is twisted at the other; eliminate that component from your calculation by turning the wrench really slowly just before you reach your target torque on the wrench.