dr bob

A local lister here in SoCal opened this same discussion a week or so ago.

I want to remind folks that using the 1/2"-drive torque wrench for these is dangerous! I cringe when I hear that somebody forgot to reset the wrench from doing head bolts or some similar high-torque application. For the 6mm bolts on the water pump and the low torque required, find a torque wrench in the 3/8"-drive size at maximum (~100 lb/ft range) or better, find a 1/4"-drive unit. In the ideal, you'd like the rangeyou are measuring to be in the middle third of the range of the tool you are using. Expecting to be able to get an accurate, repeatable 6 lb/ft torque setting from a 200 lb/ft 1/2"-drive wrench is, well, a stretch. Use the 1/4"-drive wrench, and convert lbs/ft to lbs/inches by multiplying by twelve.

This might save a few broken WP bolts, and the tears that follow.


HTH!

atb

Wasn't it recently posted here that torque wrenches are not reliable for the first twenty percent of their scale? i.e. a 100 ft./lb. torque wrench will be too inaccurate for use below 20 ft. lbs.? I read this somewhere just recently.

GlenL

That's why you need multiple wrenchs. The bending beam model is good for this range. And plenty affordable.

Jim bailey - 928 International

Glen at first glance I thought I read ; multiple wenches..........

SharkSkin

What's wrong with that?

Thaddeus

Multiple wenches?

Let me tell you younger rennlist guys something (old fart mode ON):

One good woman is plenty!

(old fart mode OFF)

Thom1

Torque Specifications per FSM:

Page 10 - 06
…Other, Torque Nm (ftlb):
M6, 6+2 (4.3 + 1.4)
M8, 20+2 (14 + 1.4)
M10, 40+5 (29 + 3.6)
Note: That above precision torques require 2 sequential torques. E.g. M6 (4.3 + 1.4) means to torque to 4.3 ftlb, then to 5.7 ftlb.

Also refer to the FSM and WallyP’s advice. Size is not all that matters!
Page 42 – 02
Location, Threads, Torque Nm(ft lb):
Cross member… M10, 46(33) – most bolts
C.V. joints… M10, 81(59)
Toe-in adjusting bolt, VNM 12X1.5, 120(87)
Brake caliper, VNM 12X1.5, 85(61)
Camber adjusting bolt, VNM 14X1.5, 200(145)
Lower control arm…, VNM 14X1.5, 140(101)

Moral of the story: Buy the FSM and/or Tech. Spec. book before you tackle any big job.

GlenL

Of course that's what I meant. Confounded spell check failed me again!

Is that 6+2 approach meaning torque it twice in the manuals? I thought that was the same as 7 +/- 1 or 6 to 8 Nm.

Thom1

Torque Specifications per FSM:

Page 10 - 06
…Other, Torque Nm (ftlb):
M6, 6+2 (4.3 + 1.4)
M8, 20+2 (14 + 1.4)
M10, 40+5 (29 + 3.6)
Note: That above precision torques require 2 sequential torques. E.g. M6 (4.3 + 1.4) means to torque to 4.3 ftlb, then to 5.7 ftlb.

Also refer to the FSM and WallyP’s advice. Size is not all that matters!
Page 42 – 02
Location, Threads, Torque Nm(ft lb):
Cross member… M10, 46(33) – most bolts
C.V. joints… M10, 81(59)
Toe-in adjusting bolt, VNM 12X1.5, 120(87)
Brake caliper, VNM 12X1.5, 85(61)
Camber adjusting bolt, VNM 14X1.5, 200(145)
Lower control arm…, VNM 14X1.5, 140(101)

Moral of the story: Buy the FSM and/or Tech. Spec. book before you tackle any big job.

Tech Spec. book 1985-89:
Page 22
Location, Torque Nm
M6, 8+2
M8, 20+2
M10, 40+5
Note: No water pump bolt torques were found above.

GlenL

I checked my manuals and there's no mention of a two step torque being defined by the "6+2" nomenclature.

I did find a number of torque specs given explicitly in steps where the second ,or third, step has the "x+y" rating.

If you've got the page that states two levels for "x+y", please post it. I think it's just a range for a single torque.

Thom1

OK, I give up on finding specific explanations of + and – signs. Does – mean through? Does + mean plus or minus, additional torque step, or to a maximum value of additional next torque figure,…? See references below:

Tech. Spec. book 1985-89:
Page 23
Location, Tightening Method, Tightening Torque Nm
Remote thermometer…, , 25 – 30
Thermostat housing…, 2 stages: 1st stage, 10
, 2nd stage, 20 + 2

25 – 30 specifies torque somewhere between 25 and 30 does it not?

1. 20 + 2 could mean somewhere between 18 and 22. But why does it not just say 18 – 22?
2. 20 + 2 could mean torque to 20, then to 22.
3. 20 + 2 could mean torque somewhere between 20 and 22. But do not exceed 22. But why does it not just say 20 – 22?

Maybe I’ll change my opinion to number 3.

Anyone want to vote for your favorite opinion, or propose a new one?

SharkSkin

In general, the way tolerances work, if you have a specification like 20 + 2, that means that you want a minimum of 20, but 22 is OK. Really, it's very similar to saying 21 ±1 but here the emphasis is that it must be AT LEAST 20.

I could be wrong... but that's what was taught in mechanical drawing/engineering classes 20-odd years ago... I suppose it's possible that Porsche means something else by this, and I simply haven't uncovered the reference that says so.

heinrich

Dave A is correct. I know I saw it in the manual.

H2

You're right. I have 5 torque wrenches (don't comment) and I just sent a MAC T-wrench back to teh company for recalibration and talked to their head nerd. He told me that the lower end of a 0-140lb wrench was not accurate and they do their recalibration settings starting at 25 lbs....so I bought a really small dial type torque wrench that's accurate in the lower ranges. So far, no more broken bolts.

Harvey
'85S w/Experienced Bolts (as Jim of 928 Intl. says....as he replaces my broken ones).

Quote" Wasn't it recently posted here that torque wrenches are not reliable for the first twenty percent of their scale? i.e. a 100 ft./lb. torque wrench will be too inaccurate for use below 20 ft. lbs.?"