BlueGT pulls right harshly under heavy braking

[cenkay]

Right, this is a bit of an odd one... I've owned my polo for 3 weeks now, and it has been doing this since the first day.

At around national speed limit, on a straight, flat stretch of road, if i brake hard the car will dip its nose as it breaks (obviously) then harshly pull to the right lifting the back end almost as if the front right wheel is applying a hell of a lot more braking force than the left. This happens on dry roads where ABS isn't kicking in too much, more noticeably than in wet conditions, but nevertheless both conditions have similar results. No traction control light flashes, so the computers do not try and correct this mistake, which the computers may actually be causing


What i wrote there is on a flat straight stretch of road with me testing the brakes, when it first happened to me on the first day of ownership, i was going round a right hand bend when i had to apply the brakes, now i know braking around a bend can cause oversteer anyway, but with the conditions of this particular event, around this road that i know well, in any other car including my mums bluemotion that i drove for months, i would not have had the same results, the back end tried to kick out to the point that i was properly tackling to keep the car inline with the road... all i can think is if this was for example, my mum driving, who wouldnt have a clue how to control a car in these situations, i know the car probably would have ended up on the otherside of the road. This result was obviously worse as it was a righthand bend, and as ive already said it pulls to the right when braking hard (i didnt know this at this point) anyway, so both those factors multiplied the effects that i otherwise should have felt.


Has anybody had anything remotely similar sounding to what im experiencing in my polo? Its really only noticeable at speeds of 50 and above, when applying the brake relatively hard. I am going through vw, i just dont want my polo to be used as a guinea pig for this problem and taken apart and major parts be fiddled with so early on in ownership

[daveb73]

In my view the car is too new for this to be a binding caliper (though it sounds symptomatic of one) - it's more likely to be the braking system/computer over compensating? Either way you need to get this looked at as it sounds potentially dangerous.

Keep us updated as to what VW say.

[AntonDelin]

How old is your car? I would bet on either Daves binding caliper idea or wheel alignment.

[jeepster]

Hi Cenkay,

Did you ever get to the bottom of this issue, as I have just started having the same problem? I replaced all the brake fluid last night because it hadn't been done for a while and the brakes were feeling a bit weak and spongy. Now the brakes are a lot firmer and stronger, but this issue (which might have been there before but would be less noticeable with weaker brakes) has come up. It basically feels like the left side is trying to keep going while the right brakes normally.

One thing I did notice was that the pressure bleeding kit I was using wasn't man enough to bleed the rears properly, but even with the bleed screws loose it was fairly hard work to push the pedal to the floor (so much so that I unscrewed the driver side rear banjo bolt and tried bleeding straight from the hose to the used fluid container - which helped a bit), so I think maybe the rear flexible hoses have perished inside, making the hydraulic pressure at the caliper(s) less.

Any thoughts would be much appreciated - before I start spending money on hoses / calipers / slider pins / repair kits, etc, etc!!!!!

[RUM4MO]

I've never had any real issues using a pressure bleeder on cars, including the rear cylinders/callipers - unless, the dust cover has/had hardened over time and had let moisture in and had rusted up the hole in the bleed nipple. I've also tended to replace the brake nipples after maybe 3 or 4 brake bleedings as you usually end up forming/forcing ridge/ledge to form on the bleed nipple which can make sealing it up afterwards a bit tricky - these bleed nipples are designed to have a point sealing surface on them and so only low torque is normally needed to seal them - well for the initial and first and second fluid change!

[Ricmondo]

BGT has a trick electronic diff that uses the brakes rather than a limited slip device. If it malfunctions it will cause the car to act as you describe.

This is a safety related defect that could invalidate your insurance should you decide to use the car and have an accident.

I think you might have to take a deep breath and take the car to an authorized dealer, something I hate doing but it could be cheaper in the long run.

[jeepster]

I must admit it is the first time I've used a pressure bleeding kit, I normally use pedal pressure and an assistant or a one-way valve. A mechanic friend of mine suggested it was because my car has the ABS unit, which causes extra restriction and would make it harder, which makes sense. That's an interesting idea about replacing the bleed nipples, hadn't occurred to me before, although the one I took out (after unscrewing banjo bolt) looked ok and they don't appear to be leaking now.

I'm still unsure about the best way to proceed in terms of resolving the 'pulling to the right' issue. Does anyone know of a reliable sequence to try, as being quite an old car now I don't want to throw lots of money at it to start replacing major components if I don't have to? Just wondering if this is a known issue on 6N2 Polos?

On a possibly unrelated matter, are the rear calipers are supposed to have a handbrake lever return spring fitted? The ones on my car do not and when the car is jacked up, with the hand brake off, it is still difficult to turn the road wheel - unless you manually push the caliper lever back to its "fully off" position, which a return spring would do automatically. If one isn't meant to be fitted that is a really bad design - is there a DIY improvement to install a spring somehow? By the way, the cables are newish, so will not need to be replaced and the number of clicks at the in car lever is the recommended 6 or 7 clicks.

[RUM4MO]

No, I don't think that any of these "short" cars got external return springs fitted to the rear callipers, some people including me fitted them to 9N > Polos with rear discs, in fact I fitted them to my wife's new August 2015 6C Polo 12TSI SEL as soon as we took delivery of it, but I think that VW group have improved the internal return springs.

ELD, if this function is faulty and causing this issue, can you not disable it using VCDS, ie "untick" that function as being present, if it is possible to do that then that might let you move forward on finding out what is causing your problem? My wife's last Polo had ESP which has ELD included with it/in it, it was very handy in snow/ice as long as you trusted it and kept the throttle pressed down as far as normal, I failed a couple of times in extreme conditions by backing off the throttle (position) while ESP was controlling/limiting the actual throttle demand - so, car got back in control with EDL regaining wheel grip on the road - and because I had backed off the throttle (position) the engine stalled!

ABS and brake bleeding, I've always found that the only issue with ABS is when you accidentally run the brake fluid reservoir dry and air gets into the region of the ABS block, there are ways, including VCDS or running the ABS pump to resolve that though.

Maybe Google Fabia and/or Ibiza fitting external brake return spring and I'd hope that you will find enough to work on - it is the VW Sharan/SEAT Alhambra/Ford Galaxy springs that I've tended to fit as they offer just enough "return" action, but do clean things up as much as possible before fitting them as trying to overcome a stick lever action is not the best plan.

[jeepster]

Thanks RUM4MO; I have fitted the caliper return springs and I have not had the binding issue when releasing the handbrake since fitting them. I manually bled the brakes with an assistant and there was some air still in one of the rear lines (driver side I think), now the brakes are still firm but it doesn't pull to one side anymore.