Forums69
Topics113,597
Posts1,341,077
Members1,801
|
Most Online731 Jan 14th, 2020
|
|
|
Grande Punto scary brake issue. Help?!
#1632057
28/04/2019 16:27
28/04/2019 16:27
|
Joined: Dec 2005
Posts: 16,603 Corridor of Uncertainty
Jim_Clennell
OP
Forum veteran
|
OP
Forum veteran
Joined: Dec 2005
Posts: 16,603
Corridor of Uncertainty
|
Hi everyone.
We bought our 2008 Grande Punto 1.9 M-Jet Sporting a few months ago when we probably should have walked away (see key post, etc...). However, we are where we are, and the latest - pretty troubling - issue concerns the brakes.
When you brake (at any speed - it's happened to me at around 50mph and to my wife at under 10), the nearside rear wheel locks with very light pressure on the pedal and before the ABS cuts in. This has the effect of sending the car sliding across to the left, which is quite unnerving. Not to say potentially lethal.
No warning lights are coming up on the dash and no codes on the diagnostics.
With the help of our local garage, we have so far tried changing all discs and pads (they needed it anyway), purging / bleeding the circuit, swapping tyres front to rear and side to side to see if wear was a factor. It's not, still always the nsr wheel locking. And the latest thing we've tried is a new ABS pump to see if it was sending the wrong pressures to the different wheels. No joy.
We are reaching the end of our patience; the car was bought to be a courtesy car for our business and until this is definitively sorted, we can't allow customers to drive it.
Our next step is to change the nsr caliper to see if that helps, but it's a slim hope.
Does anyone have any bright ideas as to what might be causing the issue?
I feared a bent/cracked chassis, but apparently that's unlikely.
All constructive thoughts welcome!
|
|
|
Re: Grande Punto scary brake issue. Help?!
[Re: Jim_Clennell]
#1632064
28/04/2019 21:13
28/04/2019 21:13
|
Joined: Mar 2019
Posts: 251 North Macedonia
386ka
Club member 1814
|
Club member 1814
Making a profit
Joined: Mar 2019
Posts: 251
North Macedonia
|
It could well be a problem with the caliper itself, as I know of a similar experience with a Grande Punto, albeit the wheel didn't lock-up instantly, but only while braking more aggressively. As @szkom said, you may check how the rear brakes feel via the handbrake, but it's not definitive.
Regarding the mechanical valves, I don't think that the Grande Punto had one, since it has an electronic brakeforce distribution. The lines should go directly from ABS to the wheels, without any valves in between.
If you have an OBD reader, there's a software called MultiECUScan, and you can hook it and see the wheel speed sensors, as well as what the ABS control unit is doing. But, be aware that when you go into the ABS control unit, it will temporarily disable the EBD, so be VERY LIGHT on the brakes, as they will feel even more agressive.
TL;DR, check the caliper first, as you might be surprised to see that the problem is actually there.
Last edited by 386ka; 28/04/2019 21:18.
|
|
|
Re: Grande Punto scary brake issue. Help?!
[Re: Jim_Clennell]
#1632084
30/04/2019 00:17
30/04/2019 00:17
|
Joined: Dec 2005
Posts: 8,410 Lightwater, Surrey
DaveG
Club Treasurer Member 311
|
Club Treasurer Member 311
Je suis un Coupé
Joined: Dec 2005
Posts: 8,410
Lightwater, Surrey
|
Also check the condition of the rear brake hoses, sometimes they can collapse internally and give problems (eg: if a hose has been clamped in the past...)
1996 Portofino 20vt & 2000 Pearl White Plus 1985½ & 2016 2017 Fiat 124 Spider + XF Sportbrake
|
|
|
Re: Grande Punto scary brake issue. Help?!
[Re: Jim_Clennell]
#1632090
30/04/2019 12:28
30/04/2019 12:28
|
Joined: Sep 2009
Posts: 5,012 ation
szkom
Club member 2000
|
Club member 2000
Forum is my life
Joined: Sep 2009
Posts: 5,012
ation
|
Not sure it's related, but the handbrake is dreadful... Which is surprising if you've had new discs and pads.
|
|
|
Re: Grande Punto scary brake issue. Help?!
[Re: szkom]
#1632093
30/04/2019 12:52
30/04/2019 12:52
|
Joined: Dec 2005
Posts: 8,410 Lightwater, Surrey
DaveG
Club Treasurer Member 311
|
Club Treasurer Member 311
Je suis un Coupé
Joined: Dec 2005
Posts: 8,410
Lightwater, Surrey
|
Not sure it's related, but the handbrake is dreadful... Which is surprising if you've had new discs and pads. Eh? Aren't we forgetting that the design is similar to the Coupe, with a mechanical handbrake acting on a lever that pushes in a piston, the same piston that's likely stuck in the "just about to lock up" position? Changing discs and pads is no guarantee to "fix" weak rear brakes/handbrake...
1996 Portofino 20vt & 2000 Pearl White Plus 1985½ & 2016 2017 Fiat 124 Spider + XF Sportbrake
|
|
|
Re: Grande Punto scary brake issue. Help?!
[Re: Jim_Clennell]
#1632126
30/04/2019 20:54
30/04/2019 20:54
|
Joined: Sep 2009
Posts: 5,012 ation
szkom
Club member 2000
|
Club member 2000
Forum is my life
Joined: Sep 2009
Posts: 5,012
ation
|
I should have specified that it was the front discs and pads that were changed, not the rears. Definitely I'd get them sorted next. Dave probably has hit it on the head; sticky piston.
|
|
|
|