I just started getting this hard pedal today. The Anti-lock pump is starting to activate as soon as I tap the brake, instead of hard braking.... If I slam the brake the pedal pressure return to normal.

Any of you every experience this problem???

 

I've moved your post to a separate thread so it'll get better exposure.

 

I had a hard pedal situation on my 97 once, turned out to be a vacuum leak so the brake booster was basically useless.

Booster was a 6:1 ratio so if my leg was 18' long I wouldn't have noticed a difference. Car did stop but couldn't press hard enough to lock them up.

Never had the ABS activating concurrently so probably not the same but worth a look.

Jaguar recommends changing the brake fluid every 2 years regardless of mileage so maybe you have a vacuum leak and some air in there somewhere that's tripping out the ABS.

 

Do you get any error messages or lights relating to the brakes, either on startup or use (other than the ABS triggering)?

 

No just the ABS Fault message and the check engine light came on. The next day all was well when I started up and after a couple of miles of driving the ABS Fault light would come on a turn off with had breaking. But now it's on constantly. I just had 1 of the ABS sensor in the rear changed. I did recently have the rear pads brakes changed.

Hopefully...it just has air in the lines that I can get pumped out!

 

Would be worthwhile getting a specialist (dealer or indie) to read the fault codes and see what the car is reporting.

 

My apologies Ngarara...my brain is working a little slow today. I don't know why I was thinking that "indie" was referring to Indian and not Independent repair technician.

I made an appointment to meet up with my mechanic on Thursday.

 

Didn't realize you were getting an abs fault message, just thought when you were braking that the abs was kicking in.

I think you have a few separate issues going on.

I never known an abs fault to throw a check engine light, two separate animals.

If you check the XK8 forum you will find lots of topics on the ABS fault and the pump connector solder connections developing small cracks and require soldering. You will get intermittent faults in the beginning and finally stay on when they go.

My other question is when is the last time you changed your battery. Recommend checking your voltage with the car off. I know some have had weird and multiple codes come up when the battery drops below 12.6 volts.

Hope this helps and good luck.

 

Generally, the battery-related issues show up on startup. They might carry on until the car is restarted (or even until it is locked & restarted), but they don't just appear when driving, because the alternator keeps the voltage up. So the 'check engine' might have been battery, but the 'ABS fault' is probably a real ABS issue.

 

This thing was doing all kinds of weird stuff. When I applied the brake the pedal is HARD. Slam on the brake and it softens up. Apply the brakes again that the right front caliper clamps down and the car pulls hard to the right. Slam the brake again...everything is all good???? Took it to my mechanic and got a left front wheel speed sensor fault.

Who knows. I just got the car....so I expected some ***** stuff to happen. We'll get it all sorted within the next couple of weeks. Getting all of the rotors and pads and sensors replaced to make it 1 and DONE!

 

It might possibly be the ABS Module & Hydraulic Control Unit on the bulkhead just behind the left front wheel. All the brake hydraulics run through it, and if the valves in it are sticking, it would give all sorts of weird braking symptoms.

 

That's interest Ngarara....I was just involved in an accident there the driver's side wheel was impacted. I think the wheel is bent, but unsure if the impact was hard enough to cause damage to the Hydraulic Control Unit. But I never had a problem with it prior to the accident.....

 

If the wheel has been pushed far enough back to hit the HCU, it would be jammed, the suspension would be wrecked and the car wouldn't be drivable. But if the wheel has been hit, it may well have damaged the brake disc or calliper. In fact, if it hasn't already been checked out by a mechanic, I strongly suggest you get it looked at, just from a safety perspective.

 

I'd be leaning towards the ABS module/pump.

Don't thinks pads/rotors and sensors are going to change anything based on your symptoms.

If sensors are good, leave them alone, not cheap. All the sensors do is count lobes and send that feedback to the ABS module base on pulses per wheel rev. If one goes bad you will get an 'abs/trac fault'.

If the pump/abs module is messed up it also gives an 'abs/trac fault' but because of the accident maybe the brake lines going to it got messed up.

Definitely an odd one. I've had experience with the 'abs/trac fault' on my 97 and replaced the ABS module. Found a used one out of Florida for $350 with the module and pump compared to the $5k jag wanted for a new one.

Also had a sensor trip it but that was actually the cable connection and not the sensor.

If the wheel got hit maybe it damaged the lobes on the cog the sensor counts, that might throw it off if only the one wheel is acting up.