So, yesterday I either suddenly became hyper-aware or neurotic about my brake pedal "feel" or there really is something going on..... I'm not sure which.

No brake work of any kind has been performed since last summer, which was just a pad replacement and rotors turned. No leaks that I am aware of. Fluid is not low.

Symptom: While sitting at a stop, say at a red light, the brake pedal will slowly sink down while there is significant pressure on the pedal. It doesn't go to "the floor" (not sure if that is even possible with the pedal geometry of this car). But braking seems fine.

I have diagnosed and replaced master cylinders before, so I realize that the standard symptom of a failed/failing MC is when the pedal does push to the floor, either that or there is a leak elsewhere. I have no leaks.

But then I thought it didn't feel quite like a failing MC as there was resistance and the pedal didn't feel like it was "falling away" from my foot.

And then I went home and tried testing my 1995 Buick Riviera and 2005 Honda Pilot. They both did the same thing, resistance, but under firm pressure on the pedal they both sunk as well and inch or two, then stopped. The only exception was a 2015 Altima of my daughter's which had a 'rock hard' pedal that hardly moved. Of course all cars were tested with the engine running.

So now I'm thinking I just am having some sort of paranoid moment.

With that, can anyone else confirm that when stopped, with foot on the brake, firm pressure, their pedal is not "rock hard" and will sink slowly an inch or two?


As an aside, does anyone know why our MC for these cars are so stratospherically expensive as compared to other cars, especially of the era? New units are $600-900 depending on the source, and most are around $700. What is so special about our MCs?

I had read a post elsewhere on the forum (XK forum I think) that said "they had never seen of our MCs fail".... so is there something hyper durable about ours that justifies this high cost?

Rebuilt units are priced at around $100, which is more typical and akin to similar makes/models.



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Well, now that I've driven again today, I'm pretty convinced I have had some sort of "mental break"

.... as the pedal is I think behaving normally.

I'm going by the shop on Friday morning for some other things, and I'll have the mechanic check, but I suspect all is well.

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I had the same feeling with my XK8 a year ago. I bled the brakes and got a couple of bubbles out, not noticed it since. But I'm glad you brought that up, time for a flush soon.

 

I've noticed this too but I think it's just how the x300 brakes are. Sometimes while sitting at a light I'll press down on the pedal with some force and it'll sink. It happens on both the XJ6 and XJR

 

Yep, losing my mind

Went and had the "old car mechanic" (the one that works on anything X300 and earlier) at Jaguar of Cary drive the car around the block and he says the brakes are A-OK.

He repeated the same advice/observation we've all talked about which was the X300(and XJ40 as well) do feel somewhat "soft" compared to others, and the gradual pedal 'sink' a couple inches is normal too, but the brakes are great. It is just the nature of the design, but he's seen it for decades now that owners come in and think something is wrong. But that's just how the brakes are.

He said that it was humorous that Jaguar moved from the hydraulic assist in the XJ40 to the vacuum assist/boost because people complained that the hydraulic assist was too vague and soft....

Anyway, false alarm. All is well with the car, not so much with the driver apparently


BTW, they quoted me $120 to flush and refill the brake system (I asked, they didn't push it), although they did say they thought it wasn't necessary right now. Given how much I hate dealing with bleeding brakes and brake fluid in general, I thought that was a pretty average price, especially for a dealership. So I've got it on my list of 1-2 year from now maintenance items.

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I went thru some mental issues in my early days of X300 ownership as well

But even setting X300 quirks aside, people get weird about brake pedal feel. I used my own family members as guinea pigs once. I told them I had bled their brakes when I hadn't. But, sure enough....they complained that "the brake pedal feels soft" and "the pedal sinks lower than before"


Cheers
DD

 

You're not alone, Al. It seems like every other week I find myself questioning whether or not the brake pedal has more travel than the previous day.

 

your brake master needs replacement or if the cylinder is still smooth you may purchase a repair kit consist of rubber seals and a piston with spring.