Just recently I've noticed that right after i start the car the brake pedal goes almost all the way to the floor. However, if I then press the pedal a couple of times it "pumps up" and seems to work correctly.
Unfortunately, the situation will repeat after driving for a few minutes (i.e., press to the floor, press the pedal to "pump"it back up).
I'll clearly need to call my shop, but wanted to see if anyone on the list had ideas about what may be going wrong.
Thanks
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Current Hers: '13 Lexus ES350
Current Mine: '15 Jaguar XF (X250) Portfolio AWD
Jaguar - making mechanics out of customers since 1935

 

sounds like a vacuum leak somewhere

 

There should be a check valve on the brake booster right where the hose goes in. It’s supposed to keep the vacuum inside the brake booster after there is no longer a vacuum on that line if that check valve leaks, or if the gasket that seals that check valve to the brake booster body is leaky or if the brake booster itself is leaky internally, you’ll lose all the vacuum once you shut the car off and the vacuum from the engine is gone.

so pull the hose. check the check valve. check the grommet that it goes into it. maybe get a vacuum pump put it on the line for the vacuum, pull a vacuum and see if it decreases over time. If the check valve is good and the grommet is good and you have a tight seal there and it’s still lose a vacuum your brake boosters bad.

 

A lose of brake boost (vacuum) will give a hard pedal. A lose of brake pressure (hydraulic) will give a soft pedal. I suspect a bad master cylinder.

 

>A lose of brake pressure (hydraulic) will give a soft pedal. I suspect a bad master cylinder.

Thanks, I thought it might be a brake-fluid problem, too... I made an appointment to take it in.

In January I had a major service done (yes, that would be the $1000 spark plug replacement job, that had me taking it back a month later, 'cuz it started throwing O2 sensors errors on both sides), and it had developed a vacuum leak.
Well, guess what, why yes, yes indeed, I did have a total brake fluid flush done at the same time! We'll see what they have to say ...

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Angle parked in a parallel universe

 

Jaguar has O2 sensor extended warranty. includes labor to replace.

https://www.fpaceforum.com/threads/o...-letter.48078/

 

Just heard from the dealer ...
They drove the car and felt the quickly softening brake pedal confirming my description ... :-)
They then did a visual inspection and on finding nothing did a complete brake fluid replacement (note: I just had that done, with them, last December) ... :-(
They have concluded that the problem is with either the brake booster or the master cylinder and recommend both their replacement ... :-|
They estimated the job will be ~$3K USD ... =8-\

But it's actually what I expected, as far as the failure is concerned.
So, I know I may have gotten a less expensive price with a non-dealer shop, but probably not really that much less.
Plus I would have taken it somewhere else if it wasn't for the fact that I just had that big service done by them, that included replacing the brake fluid ... :-p

So there we are, I told them to go ahead. Hopefully the fact that I bought the car there will prompt them to give me some price flexibility.
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You dreamed of a big star -
He played a mean guitar -
He loved to drive his Jaguar...

So welcome to the machine

 

Just got it back w a new brake booster, a new master cylinder. Plus they did a overall check and found the rear differential pinion seal leaking, and leak in the vacuum pump seal. Both of which they fixed.
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You dreamed of a big star -
He played a mean guitar -
He loved to drive his Jaguar...

So welcome to the machine


Total $4720USD

 

Didn't the US have a recall or TSB on the rear differential seal, Canada did?
We had our seal replaced on the 2014 3.0 AWD unfortunately they forgot to top it off, needless to say a couple of weeks later they replaced the rear differential for free too.

Kevin

 

>Didn't the US have a recall or TSB

Don't know, will try to look it up
Thanks
Oh, my dad grew up in a farming town in Saskatchewan ...

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My karma just ran over your dogma
Current Hers: '13 Lexus ES350
Current Mine: '15 Jaguar XF

 

Hopefully you might be able to recover some cost with the seal replacement. We are waiting on the O2 replacement as they have been deemed covered by Jaguar as well, getting them in is a different story though as according to the dealership, we have more backorder issues.

Just out of curiosity do you know which town?

Kevin

 

Marshall, right on the road to Edmonton where my mom was from.
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Angle parked in a parallel universe

 

LOL, beside Lloydminster, I drive by it every week to and from work.