E brake and PIWIS

[Laurence Gibbs]

Have recently learned that with the introduction of the electronic handbrake on the new models , when the shoes or discs need changing on the rear, the system tester is required to set them up ! i am assuming this functionality is only available via PIWIS 2 ? Which i guess might be a little out of many smaller indi's price league(rental wise)?
Will be interesting to see how things pan out. I wonder how many other things will be PIWIS 2 only?

 

[Richard_Hamilton]

Looks like the Durametric will handle the 9x1 to a certain degree, and I expect they will improve functions as time goes by. I can't see many indies getting PIWIS2 due to the immense cost. Even if you could afford to buy one, there is a large monthly fee to allow access to the Porsche PIWIS server, without which useage is quite restrictive. Aftermarmet testers such as Durametric, Autologic, etc, will be the only wat to go for most independents.

Not an issue for most owners now, but once they come out of warranty it will be a different story.

 

[BartyB]

It makes you feel smug being a 986 owner and knowing you can change your pads yourself or get an indy to do it for you without needing any technology other than a jack, a socket set and caliper retractors.

 

[fbr]

Dear Laurence,

Any details where & why a 'system tester' is required following rear pads or disc changes on newer models? On other modern cars, problems with sensors and brake pressure monitoring systems can sometimes be circumvented by disconnecting the battery before starting working on the brakes. How for this may apply to Porsche models is difficult to assess without any further insight into the problem.

Worried but smug-free 981 owner!

FBR

 

[Laurence Gibbs]

I am unsure of all the technical aspects but the problem is that the new Boxster and 991 models are fitted with an electronic handbrake. The software for this I assume needs to know when pads are changed to operate the calpers without over pressuring the system and keep it within tolerance. You can't simply fit a 10mm pad where a 3 mm one once sat and expect the system to know this has happened. On a regular cable handbrake you can adjust the cable this obviously can't be done on a software based system.
Even on a 986 I would not advise that you disconnect the battery to reset anything, unless it's absolutely needed. There are an awful lot of things that need to be re-calibrated when so doing. There are set procedures to follow. Tiptronic equipped cars for instance need to re-learn the basic shift map, which must ideally be done within a given temperature range to get the ideal settings. Throttle position is re learnt within a set time on restarting the engine after battery disconnection , rados need codes re input, window limits reset etc etc.

 

[fbr]

Dear Laurence

Thanks for your reply. Difficult to know how best to respond.

Disconnecting the battery is a normal procedure, even in a Porsche. The owners handbook suggests it for any work on the the electrical system and gives guidance for its re-connection. How else might you change the battery? See for example the 981 BS owners handbook pp 195-97. I promise you it is not difficult procedure and the effects are not as alarming as you make out. Odd statements re 'Re-learning shift maps' are not very helpful. Similarly radio codes are not a problem in the current models.

You do appreciate that the 981/991 handbrake is a simple electro-mechanical system that operates through a separate small drum and shoe brake system built into the rear hub
and is independent of the hydraulically operated disk based brakes? You can even operate it as an emergency brake on the move, aka "J" turns, simply PUSH and let go! (it doesn't appear to lock on) - don't try this home folks. Disbelievers see owners handbook p118 and associated warning messages.

Back to the initial question re electric (NB not electronic) handbrake, disc/pad changes and PIWIS intervention - we appear to be no further forward.

I was however not suggesting disconnecting the battery to 'reset' the system but rather to obviate it throwing a fault when changing/moving pads by disconnecting the battery before you start. Which might be a good idea anyway to reduce the risk that the electric handbrake is not activated during the process. I suspect that a locked-on handbrake is more of a problem in this style of brake.

Does anyone else have a deeper/more helpful insights into this putative problem?

best wishes

FBR

PS see the ever helpful Richard Hamilton's guide to battery removal in the Cayman (why different forum is a mystery!) technical articles section (01/06/2013 http://www.porscheclubgbforum.com/tm.asp?m=770011 ). Is Richard Hamilton a secret Porsche mechanic/dealer hiding under the guise of an extremely helpful agricultural engineer?

Also note that there is another comfort for owners of older vehicles - the more recent Porsche models seem to require a new replacement battery (AGM) to be 'initialised in the control unit' by your friendly 'Porsche Partner' Its good to spread a little smugness to cheer up the greybeards now that winter is drawing in!!

It's not been the same since set of points, a spare condenser and a screw driver in the glovebox could get you from Manchester to Buxton and back and still have time for a tea dance at t'Winter Gardens! Provided that you remembered to kick over the reserve fuel valve when you topped up with five bobs worth of fuel at Macclesfield on the way back...

PPS

First tinkered with combined handbrake/disc on my DB 123 and it's still a fairly common car feature. Look on the rear disc of your Porsche and you can identify the mechanism, if you search about you'll find a small hole that gives access to the brake shoe adjuster.

Hope this helps...

posted this previously : http://www.porsche911.lt/files/981/E_981_KATALOG.pdf

 

[Laurence Gibbs]

I was informed of the need to use the PIWIS whilst chatting to an OPC Porsche Technician. So i took it he knew what he was talking about ! Perhaps i misunderstood the reason for using the tester but i am sure he mentioned E-Brake. Perhaps it's some other issue with the braking system? I did do a little search to gleen more information and the only thing i could find mentioned something about e-brake "calibration".
You might well think that disconnecting the battery is a straight forward enough thing to do(after all, it's in the manual). But i'd suggest you do a search on "Boxster issues after disconnecting battery" to get a feel for what can happen and the systems involved. That said perhaps 987 onwards does'nt have so many battery related issues? I did specifically mention 986. And i did add the words "unless absolutely needed". I think a dead battery comes firmly under that heading! I didn't think it odd to mention the issues around the learning function of the tiptronic map when you disconnect the battery, as we were talking about disconnecting the battery and it's another part of the system that loses it's memory after a battery disconnect on a 986 ! I wasn't trying to be "alarming" just making the point that disconnecting the battery on a 986 and possibly later cars requires care when reinstating and can be troublesome.
Where did you find the information about E brake? I could find no decent technical info apart from the bit about using it as an emergency brake. Short of looking it up on PIWIS.
P.S Richard's post was very much what i was trying to point out !

 

[Laurence Gibbs]

Thanks for the edited post. That picture helps make things a little clearer. I hadn't realised there was a PET catalogue for the 981 given it's not yet listed even on the US Porsche site ! There certainly appears to be adjusters. I can only guess at what the Porsche tech was trying to put across. Perhaps the handbrake fails to on when the battery is disconnected, otherwise the brake would release causing obvious safety issues if this happened accidently on a hill ! So perhaps that's the reason for having to use the tester? Though that would cause towing issues so maybe not ? I stick to the idea that the E brake is electronically controlled as i can't see why durametric would list a controller otherwise? Or there be mention of calibration? I would also guess that the motor (6) is possibly a stepper motor to get the level of functionality required. However without paying to look at PIWIS I can only guess.
I "tinker" a little myself[]. Here is a pic of the rear shoes from my RS taken a while ago.

 

[Motorhead]

Gents,

Just to say that (from the Gen 2 9X7 cars?) the hill hold function requires electric handbrake actuation which requires footbrake/gear selection sensing incorporated into the control circuitry and therefore available presumably for PIWIS interrogation.

Jeff

 

[BartyB]

ORIGINAL: Laurence Gibbs

Even on a 986 I would not advise that you disconnect the battery to reset anything, unless it's absolutely needed. There are an awful lot of things that need to be re-calibrated when so doing. There are set procedures to follow. Tiptronic equipped cars for instance need to re-learn the basic shift map, which must ideally be done within a given temperature range to get the ideal settings. Throttle position is re learnt within a set time on restarting the engine after battery disconnection , rados need codes re input, window limits reset etc etc.

I don't think that is the case Laurence. I've never had to reset anything after disconnecting the battery on my 2004 3.2S 986 which I've done several times. I believe it's necessary to re-enter a code for the radio on a pre-facelift 986 but that's all you need to do on a 986 as far as I'm aware.

 

[Laurence Gibbs]

Please take a look at a factory workshop manual or do a websearch. A lot of what Richard H has posted on the Cayman also applies to 986.
I can assure you it applies. People discconnect their batteries often blissfully ignorant of what it resets. Often they are lucky or don't notice any change. Sometimes it causes issues ! I should add there are changes to some of this with introduction of MOST bus so some of it no longer applies.

 

[fbr]

Dear Laurence

Thanks once again for your replies. Re your original post I had the opportunity to raise your question at a Porsche garage during a local PCGB open day, where they put your car on a hoist and you get to ask the staff about any technical or safety issues that may be of concern.

The current procedure for the brake pad replacement in the 981 is largely the same as the conventionally handbrake equipped 988/987 variants and normally requires no intervention by a 'system tester'.

To remove the rear disc and replace internally expanding brake shoes on a 981 currently requires the intervention of the PIWIS. This backs off the electric motor and isolates the system. This allows for easy removal of the disc/combined drum and brake shoes and isolation prevents unexpected operation of the system during maintenance (for obvious reasons). The simple mechanical adjuster, as is conventional, fine tunes the position of the brake shoes to minimise drag.

Interestingly, it was suggested that in the future a simplified 'in car' procedure may be unveiled that did not require the intervention of a 'system tester'. The simplified operation would also be of use, for example, during roadside recovery. In the event of failure of the handbrake motor release system there is a simple mechanical procedure for the removal of the motor unit. This releases the brake and enables repair/replacement of the system.

Thanks for raising an interesting topic.

best wishes

FBR

 

[Motorhead]

ORIGINAL: fbr

...Interestingly, it was suggested that in the future a simplified 'in car' procedure may be unveiled that did not require the intervention of a 'system tester'. The simplified operation would also be of use, for example, during roadside recovery. In the event of failure of the handbrake motor release system there is a simple mechanical procedure for the removal of the motor unit...

In a recent Motorway Cops episode on the Beeb, some poor woman was stranded in the outside lane of the Motorway when the electric handbrake activated for no reason on her RR Evoque. Even the Traffic Officer was unable to drive the car on to the hard shoulder and it had to be dragged on to the back of the recovery vehicle.

Scary..!

Jeff

 

[fbr]

Dear Jeff

Fortunately in our part of the world we don't have to suffer the ill effects of televisions & motorways.

...but that's progress for you!

FBR

 

[BartyB]

But is it progress? Using technology for technology's sake and to boost service revenues is not good design. Visiting Audi and VW forums reveal the excessive cost of maintaining e-Brakes once the car's out of warranty.

 

[BartyB]

ORIGINAL: Laurence Gibbs

Please take a look at a factory workshop manual or do a websearch. A lot of what Richard H has posted on the Cayman also applies to 986.
I can assure you it applies. People discconnect their batteries often blissfully ignorant of what it resets. Often they are lucky or don't notice any change. Sometimes it causes issues ! I should add there are changes to some of this with introduction of MOST bus so some of it no longer applies.

Fair point Laurence. Being aware that a battery disconnection will erase any previously stored control module faults and may cause 'supply voltage' faults to be stored on re-connection in some control modules is of course worth noting. Trip, odometer and clock settings are usually lost and power windows need normalisation on re-connection. Idle speed fluctuations and altered Tiptronic shifting characteristics can be experienced after re-connection but these should be restored after driving a few minutes of driving. If a PCM is fitted then this appears to need a few minutes to sort itself out.

I've changed batteries a few times, mostly caused by the failure of the rubbish Moll units that Porsche will insist on fitting, and never experienced any real issues other than having to re-set the trip and clock. Later 986 Boxsters (MY2003 and MY2004) were fitted with the MOST-bus and the PCM codes are stored in the control unit so no radio re-coding is needed for these cars.

 

[Richard_Hamilton]

Curiosity got the better of me again, so I looked up the adjustment procedure on PIWIS TSI. These are the basic steps for adjustment:

1. Raise the vehicle.

2. Release the EPB so that the wheels and brake discs can turn freely.

3. Move the brake shoes into installation position using PIWIS Tester II 9818. Select >>Parking brake<< in the control unit overview. Select >>Drive links/checks>>All<<>>Move to installation position<<.

4. Adjust brake shoes (on both wheels). To do this, turn the relevant rear wheel with the opening to the adjustment device position. Using a screwdriver, adjust the adjustment device until the wheel can no longer be turned. The subsequent torque of the wheel must be greater than 100 Nm (74 ftlb.). Then loosen 17 (+/- 1) clicks of the adjustment device (wheels must be able to turn freely).

5. Using PIWIS Tester II, select >>Parking brake<< in the control unit overview. Select >>Maintenance/repairs<<>>Check parking brake basic setting<<.

It may be necessary to fine-tune the adjustment device after selecting >>Check parking brake basic setting<<.

No hope for a DIYer then.......

 

[Motorhead]

Thank goodness my 987.2 has a proper (manual) handbrake..!

Drove one of the latest generation of Morgan 3-wheelers a few weeks ago (what a hoot.!). It had a fly-off handbrake.......for those of you who are old enough to remember such devices.

Jeff

 

[Chris_in_the_UK]

ORIGINAL: Richard Hamilton

No hope for a DIYer then.......

Not good news then....

 

[Laurence Gibbs]

Richard , thanks i nearly cracked and looked myself [] I think that info basically covers what i said in the original post[8D] I think the Durametric has this functionality so all is not lost for the diy'er.
BartyB, Yes i think i was basically saying that you should exercise caution and be aware that systems do reset and need to be recalibrated (often this recalibration happens automatically without it being apparent, but it's important to be aware of, and know in what sequence things happen !) . The majority of times nothing untoward happens if you diss the battery. But it can occasionally. Worth noting that Richards post in the Cayman section covers 2005 on cars which would have MOST bus.