Jaguar Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
808 Posts
Discussion Starter #1
I recently have noticed that when I want to start the car in the morning, brake pedal is firm that I have to push hard to be able to start the car. This only happens when I leave the car for several hours.
by firm I mean like when you press the pedal several time with engine off. Very similar.
Is there anyone else having this issue.
if not does it mean there is a leak in vacuum line? Or problem with brake master cylinder?
This won’t happen if engine is warm or I come back to car after few hours.
 

·
Administrator
Joined
·
27,849 Posts
yes - leak in the vacuum side of the brake servo.
 
  • Like
Reactions: hamedhbb

·
Registered
Joined
·
808 Posts
Discussion Starter #3
yes - leak in the vacuum side of the brake servo.
Thanks
That is my guess as well because it started about the time that I replaced my intake manifolds and and I had to disconnect the vacuum lines from the vacuum pump. However they are one of those snap on connectors. How can I check the seal?
 

·
Registered
Joined
·
2,840 Posts
Hi, mine's been doing this on and off for years, never bothered about it, just pressed the pedal harder. Phil
 
  • Like
Reactions: hamedhbb

·
Registered
Joined
·
808 Posts
Discussion Starter #5
I will just check the vacuum tubes that I touched see if there is any improvement
 

·
Registered
Joined
·
5,814 Posts
Mine does it on occasions too.. no logic or pattern to it that I have been able to determine though..
 

·
Registered
Joined
·
808 Posts
Discussion Starter #7
From the symptoms I have two theories. One is a smallest leak in vacuum system. Second is that before leaving the car I press the pedal one or two time without noticing.

or a combination of both!
 

·
Registered
Joined
·
10,182 Posts
My x250 done this, never fixed it. Is it temp related since the dropping temp?
 

·
Registered
Joined
·
18,452 Posts
Mine was hard yesterday morning. Back to squishy this morning.
 
  • Like
Reactions: hamedhbb

·
Registered
Joined
·
808 Posts
Discussion Starter #10
Not sure yet. I think time is the key point. I will try a quick start to top up the vacuum and then leave the car for few hours see that would help. When car is warm I don’t have issues after few hours.
 

·
Registered
Joined
·
18,452 Posts
Dirty boy
I wondered who would be the first to bite. ;)
But actually, I WAS talking about the brake pedal.
 
  • Like
Reactions: hamedhbb

·
Registered
Joined
·
808 Posts
Discussion Starter #13
I wondered who would be the first to bite. ;)
But actually, I WAS talking about the brake pedal.
It seems it’s not that abnormal then but I don’t know why I have noticed this only recently. Could be the brake pedal switch that is on the way out and less sensitive to pedal travel which reminds me that I have push further to start the car. The the pedal travels enough it works fine.
 

·
Super Moderator
Joined
·
11,362 Posts
Loss of vavuum when standing is common to all vehicles with vacuum servos.
 
  • Like
Reactions: hamedhbb

·
Registered
Joined
·
10,182 Posts

·
Registered
Joined
·
3,414 Posts
Yep vacuum leak.

Mines mostly been sorted when I had my coolant valley pipes replaced. Only real way to check it through fully is a smoke test.

Mine will hold a vacuum overnight, to the point of getting an audible hiss if I pull off the pipe to the vacuum accumulator. But over a few days, you'll almost certainly lose it as there's that many joints.
 
  • Like
Reactions: hamedhbb

·
Super Moderator
Joined
·
11,362 Posts
This leakage only becomes apparent on auto cars because on manual ones you have to press the clutch to start it. The engine fires up and the vacuum you didn't know you hadn't got is swiftly replenished.
 

·
Registered
Joined
·
3,414 Posts
This leakage only becomes apparent on auto cars because on manual ones you have to press the clutch to start it. The engine fires up and the vacuum you didn't know you hadn't got is swiftly replenished.
And quite a lot of manuals you aren't required to depress the clutch.

In fact the only modern manual I've driven that needs it is my works Merc van. Oh and my Sv650, but that's a different thing entirely.
 

·
Registered
Joined
·
18,452 Posts
Just as an aside, my muscle memory makes me depress the clutch pedal when I start a manual car, something I've done since my driving instructor taught me to. Two reasons; firstly it means the starter motor isn't also having to turn over the gearbox, small as that extra load may be, and second, if you've forgotten to check for neutral it stops the car lurching forward.
 
  • Like
Reactions: tellmah and Gav
1 - 20 of 26 Posts
Top