In a 2005 S-Type 3.0, how would one tell if there was trouble with the Master Cylinder or the Brake Booster. I know there is a fluid level sensor and a brake booster travel sensor that I assume would throw a warning and a code. I am also guessing that the DCM would not work properly and the ABS would cause an error. However I am not sure. So other than complete brake failure, how would someone know if there was a problem with either?

Thanks

Tom in Dallas
2005 S-Type 3.0 65k

 

If you are sitting at a stop light (for instance) with your foot on the brake and the pedal slowly sinks to the floor, then your master cylinder is bypassing internally and should be replaced. This would not throw a code.

 

+1. Really hard pedal could be a failed booster.

Brakes are really not complex systems if one understand what each components actually does and how it functions.

 

No I do not have that problem. I had changed pads and rotors and got the new dimpled and slotted ones from brake performance / prem- semi-metallic and since then have had a mushy and more of a soft pedal than what is even normal for the S-types. I have another thread on this and if you are familiar with this, I would appreciate your opinion. I am now going one step at a time. Here is the link.

https://www.jaguarforums.com/forum/s...uestion-92205/

Thanks

Tom in Dallas.

 

You mean is it hard to push or just stiffens up like being against a wall and it is just not going any further?

Tom in Dallas

 

Sounds like an issue with the installed material. I would swap the pads out (at least the fronts) with a different brand and see how it feels after that. If you switched from a semi-metallic to a ceramic pad, that can cause a change in pedal feel.

 

No they are the same semi- metallic types. I believe the Brake performance people use Centric. That has been the general consensus. I had brake Best or Raybestos before and did not have the problem. Any ones that you might suggest? I can't imagine that the rotors, being new and despite being dimpled and slotted would cause the problem.

Thanks again. these things can become quite frustrating.

Tom in Dallas

 

With the engine off, press the brake pedal several times with a short rest between each stroke. As the residual vacuum is used up, you'll feel the pedal getting hard. That's what a failed booster feels like.

 

Got it. I have a good working understanding and am very detailed, but am terribly limited by limited vocabulary in the field of car mechanics. Thanks goodness, I do not have that problem.

I am just trying t solve my brake problem one step at a time. The majority of responses I have had, including yours on my other post, point to the pads or pad material. I think that Brake Performance uses centric, which is what I got.

I am going to try different ones on the front and see what happens.

Thanks once again

Tom in Dallas

 

I just changed out my front rotors for upgraded slotted rotors - I use EBC pads - I noticed a difference also, but that difference was greater stopping power - shorter travel time to brake to a dead stop - no issues whatsoever with a soft, hard or traveling brake pedal after swapping out the rotors - look at the pads my friend...

 

Thanks again- I think that makes sense as well. Which EBC did you get?

Tom in Dallas

 

Tom - EBC "Red Stuff" pads - I installed them 15K miles ago on the OEM rotors - was going to change them for new but they still had about 80% life left!

I drive in NJ (Turnpike/GSP) hard braking capital of the US and these pads are awesome and worth every $ spent!