Occasional Hard Brake Pedal

[MrMoots]

Hi.

I am looking for a bit of advice on this.

I have had the 996 almost a year and changed the pads and discs all round about a month ago. The brakes are working fine and I am happy, however is have noted that since doing them under hard acceleration followed by immediate braking and a gear change results in a hard brake and clutch pedal, similar to if the engine wasn't running.

i checked the fluid level and it was way above the max mark, following fitting new pads so if have drained off to just below the max level mark and I would say the issue has improved, however it does still happen when I accelerate hard up steep hills then brake at the top.

The fluid was changed in February as part of the service.

I have done the usual servo checks (pumping pedal when engine off and pedal getting harder, then starting the car with my foot on the brake and it softens) and it is functioning as I would expect.

just gone for a 40min drive around the lanes and it was all fine, got to my usual short hill, accelarated fully in third, got to the top, braked and changed to second and the clutch and brake pedal were hard but still worked then after a split second softened.

From various searches I think I am right in saying that the 996 uses manifold pressure for the servo, as do most cars, but the 997 used a separate pump. From what I have described above, is this an idosicraciy of the 996? I cannot believe it is, because I cannot find any other post on various forms about this and its only started since I changed the discs and pads.

Could it be a loose connection on the abs sensors?

The strange thing is the clutch going hard as well. From the parts diagrams it looks like the clutch and brake share the same spindle. What does the clutch power spring do?

Does the clutch and brakes use the same fluid system?

Its really got me confused.

i am going to call the garage I use tomorrow and get it booked in for a check over, but if they can replicate it is another issue.

Any thoughts grearly appreciated.

Thanks

 

[Motorhead]

Ross,

There was a recent PP article about replacing the vacuum pump on a 997, so I think that your assumption that the 996 uses the old fashioned direct connection between the servo and the inlet manifold is correct. Bearing this in mind, when you go from WOT to throttle off/max braking effort you're going from min to max depression - and therefore max servo action. Maybe there's a fault with the servo itself and it's momentarily over-servoing and I wonder if that's what you're experiencing?

In answer to your other questions, the braking and clutch systems share the same hydraulic reservoir and the clutch assist - or booster - spring is just a device for reducing the cluch pedal force (just Google it for more information). Unless the spring is malfunctioing in some way, I can't really see it being the cause of the problem you describe, but you never know.

Hope you get it sorted.

Jeff