Jump to content

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

Brake slips down hill!


Recommended Posts

Here's one that has my dealer perplexed so far...

The brakes on my wife's 997 tip will sometimes slip and then grab at the bottom of our driveway at speeds under about 5 MPH. It's steep, but not extremely steep. Speed doesn't seem to matter. Happens in either first or second gear. The service manager is speculating it might be ABS related, and may come over some time to try to reproduce the problem. It happens on a dry asphalt surface. No skidding or anything, just unnerving to my wife.

Has anyone else seen anything like this? Are there any known issues with ABS programming on the 997? The car is totally stock, and it's happened to me as well as to my wife.

Link to comment
Share on other sites

Brake slip meaning brakes releases? Is this going up the incline? Are you rolling onto the drive way in one continuous motion without coming to a stop?

Heading downhill in my driveway, maybe 5 MPH, and have to stop at the bottom of the driveway for my gate to open. Press on the brakes (not real hard, since going slow), the pedal presses, it feels like the brakes are slipping, then the brakes grab again. It's never been felt in any other car, and my '01 Boxster (manual) does not do it.

At first I thought it might be the transmission, but I've had it happen in tip manual mode in both 1 and 2, and in the automatic mode. I haven't noticed any dash lights coming on when it happens to help pinpoint what's going on.

It's not always repeatable, maybe one out of 5 or 10 times. Driveway surface is dry asphalt, so water / wet is not the issue.

Link to comment
Share on other sites

Any oil, grease or any other slippery substance been sprayed on the wheels & rotors?

Car parked inside our garage - dry. Only happens slowly downhill in our driveway, haven't experienced it anywhere else. So don't think it's oil, etc on wheels, pads, rotors.

Link to comment
Share on other sites

How about one or more warped rotors? This condition would likely be felt every time down the hill or even on the flat.

What happens if you are in neutral coming down the hill?

Wouldn't warped rotors be apparent other times as well?

I haven't tried it in neutral. Good idea. :thumbup: I'll give that a try

Link to comment
Share on other sites

I am guessing the slope of the driveway causes the tire to loose traction and ABS may have kicked in. 997 front end is notorious to lose traction on uneven pavement or slope due to little weight in front. Try stopping the car earlier on the slope or at 2-3 MPH to see if this still causes an issue still. If so, the culprit could be in the ABS, PSM (if equipped), tires. You may also try entering the driveway at an angle to make the car less skid prone.

Link to comment
Share on other sites

I have a 986 Boxster S and an Audi A4. On the A4, the ABS is software version 5.0 and V5.3 on the Boxster.

Now with version 5.0 and 5.3, ABS carries out a self test every time you start. (from ignition on.) So as you move away from rest after starting the engine, the ABS runs the pump for about 0.25 seconds and checks the solenoid valves, when the wheel speed sensors reach about 6kph.

99.9% of the time you'll be on the gas to move off, so won't feel anything. However, in the A4, once I started downhill with my foot on the brake (a rolling start) and felt the self test through my foot. Occasionally I'll perceive the headlamps dim slightly.

I've experienced this in my Boxster too, though where I park I always have to use the gas to move off - being on the level.

I wonder if your experiencing the self test, having a downhill driveway, the cold engine will idle faster so the forward creep will be stronger in your Tiptronic so, as a rule, you'll be moving off with the foot brake applied?

Link to comment
Share on other sites

Have been on a business trip all week, so haven't had a chance to try to reproduce the problem when not in gear.

Normal routine is as follows: back car out of driveway (relatively flat area), stop, put in drive, and head down the driveway. About 100 feet from garage to bottom of driveway. Stop, push clicker, and proceed after gate opens. Stop on other side of gate at street to make sure no cars coming, then proceed. Bottom of driveway at street has enough slope that nose will scrape ever so slightly unless going very slow.

The slip occurs when stopping right before the gate, or when stopping right after the gate before hitting the street. It doesn't feel like any kind of traction problem, and like I said, nothing similar happens on my Boxster, or any other car I've driven down the driveway.

I think PSM is standard on the 997, so the car has that. Not sure if that would affect braking. Tires are original Michelin Pilot Sport

Link to comment
Share on other sites

I suggest that you call PCNA customer service and speak to a technical person. Also get your dealer to involve the regional Porsche technical person. If the problem is reproducible, they should be able to determine the cause and correct it.

Link to comment
Share on other sites

  • 1 month later...

And the answer is :(

They all do it!

Took the car in for an oil change at just under 8K miles and the brake problem. My service advisor was finally able to reproduce the problem on a steep driveway, and on Friday had another 997 in for service, which he took to the same driveway, and it had the same problem ... err, "feature". It's definitely ABS related. He hasn't tried it with a 996, but my Boxster doesn't exhibit the same symptoms in our driveway.

They sent a "P tech" (sp?) in to Porsche, and I asked them to also check with the district service manager when he's around.

I told the salesman this afternoon when I saw him, and he wasn't happy about the problem.

Link to comment
Share on other sites

  • 3 months later...
Geoff, did you ever get a difinitive answer for this? Was my 'ABS Self Test' theory correct?

The car hasn't been back to the dealer since it was in for an oil change in September, and they were able to reproduce the symptoms on another 2005 997. It DOES still do the brake slip thing at the bottom of the driveway.

I'm nor sure about your ABS self test theory. After backing out of the garage, depending on how our other cars are parked, it takes one or two forward and backward turns to point down the driveway, and we have to slow down once or twice before our gate (all downhill and driving forward). After exiting the gate to the street and putting brakes on, that's the only time the brakes slip. It happens whether in gear or neutral, and in either Tip mode or manually in 1st or 2nd. It's still irritating, especially since my '01 Boxster has never done this. Based on the time involved, I think the ABS self test would have probably happened sooner.

The next time the car is in (probably soon since the radio now changes stations at random - I think there's a TSB on this), I'll have it checked again and report back.

Link to comment
Share on other sites

  • 8 months later...

I am new to this forum . While surfing for DIY items, I read your problem of wheel slipping.

I have the same problem since my 2005 997 c2 was 17 miles. It happened only when going down to my basement garage in a steep driveway( 30degree). My guess is that it has something to do with the ABS because it feels like ABS is functioning. Because it never bother me so I ignore it. My car is 9700 miles now and give me no trouble. I will be looking forward to your follow up.

Link to comment
Share on other sites

Since my original posting, several discussions with dealer service personnel. The "feature" is reproducible on other 997s, including the service manager's personal car (or so she says)

I also asked the question to the PCA experts - see https://www.pca.org/tech/tech_qa_question.a...5-4672B8EB5BBC} for the answer from Peter, who I think is Mr. Tool Pants' good buddy. It's also a feature with the 996, but more pronounced with the 997.

It sounds like it's a combination of rear engine, automatic transmission and general vehicle design. Just one of those things you live with. :o Just one more reason why you shouldn't put an automatic in these cars!

A friend just got a new 997 turbo with tiptronic. The next time he's over for dinner, we'll have to experiment with his car and see if the feature also occurs in his car. The turbo is all wheel drive, so it might behave differently.

Link to comment
Share on other sites

Geoff, did you ever get a difinitive answer for this? Was my 'ABS Self Test' theory correct?

The car hasn't been back to the dealer since it was in for an oil change in September, and they were able to reproduce the symptoms on another 2005 997. It DOES still do the brake slip thing at the bottom of the driveway.

I'm nor sure about your ABS self test theory. After backing out of the garage, depending on how our other cars are parked, it takes one or two forward and backward turns to point down the driveway, and we have to slow down once or twice before our gate (all downhill and driving forward). After exiting the gate to the street and putting brakes on, that's the only time the brakes slip. It happens whether in gear or neutral, and in either Tip mode or manually in 1st or 2nd. It's still irritating, especially since my '01 Boxster has never done this. Based on the time involved, I think the ABS self test would have probably happened sooner.

The next time the car is in (probably soon since the radio now changes stations at random - I think there's a TSB on this), I'll have it checked again and report back.

Just drive to the dealer and right through the front windows. Tell them that the brakes slipped again. That should get someone looking into it. Or better yet, wait for the service manager to leave and rearend him in the parking lot.

Edited by 1999Porsche911
Link to comment
Share on other sites

Geoff, did you ever get a difinitive answer for this? Was my 'ABS Self Test' theory correct?

The car hasn't been back to the dealer since it was in for an oil change in September, and they were able to reproduce the symptoms on another 2005 997. It DOES still do the brake slip thing at the bottom of the driveway.

I'm nor sure about your ABS self test theory. After backing out of the garage, depending on how our other cars are parked, it takes one or two forward and backward turns to point down the driveway, and we have to slow down once or twice before our gate (all downhill and driving forward). After exiting the gate to the street and putting brakes on, that's the only time the brakes slip. It happens whether in gear or neutral, and in either Tip mode or manually in 1st or 2nd. It's still irritating, especially since my '01 Boxster has never done this. Based on the time involved, I think the ABS self test would have probably happened sooner.

The next time the car is in (probably soon since the radio now changes stations at random - I think there's a TSB on this), I'll have it checked again and report back.

Just drive to the dealer and right through the front windows. Tell them that the brakes slipped again. That should get someone looking into it. Or better yet, wait for the service manager to leave and rearend him in the parking lot.

Service manager is a 'her', not a 'him' :) Rearending dealer's staff cars probably wouldn't earn me any favors in the future.

What I find most interesting is Peter Smith's (PCA) comment that this also affects the 996 model. I guess high speed stopping power is good, but really slow speed stopping isn't so good!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.