Hi all

I've got a new problem that's just cropped up... The brake pedal has a constant hissing sound when I push it, it gets louder the harder I press it. I'm assuming a vacuum leak... But brake systems are new to me... Also, when shes been on the freeway and all nice and warm, her brakes go a little spongy... Any ideas of what to start with? I don't fancy losing them...

Many thanks.

 

My first thought is that your power brake booster has sprung a leak.


Cheers
DD

 

Crumbs... How do I check and fix the problem?

 

So I gather it's definitely the brake booster... Are the XJ6 and XJ12 and XJS boosters interchangeable? Any tips on year models to watch out for?

Also, was this booster used on any other cars? as you can imagine, I wanna replace it.

I've also heard of rebuilds... Any good? Anyone ever done this?

Any help is much appreciated.

 

Right so I tackled the job myself, took the booster apart, fixed the problem (slit in the second diaphragm, unknown cause) and put everything back together. Learnt a lot too.

If anyone wants to attempt stripping one of these boosters themselves, feel free to send me a message, email or whatever. Not as hard as it looked.

Cheers.

 

I'm having the same problem on my 85 xj6. Hearing the constant hiss and the break pedal is very hard and the car is barely stopping.. I am interested in tearing it down and fixing if possible. I would also like to know if you know of any other cars that have the same booster in them..

 

Very nice! Pics?

 

I'm thinking I want to attempt this. How would you recommend I go about it..?

 

Greetings goodgame, first off I am wondering if you have a workshop manual for removing the booster? If not I'll guide you through the removal, pretty simple, just got to know what to do.

Then is to take it apart, I used a 13mm spanner to pry the dents/lugs out, you will notice that they are in 4 sets of 3, loosen 3 of those sets, then, with the master cylinder off, use a length of wood or whatever you have, and twist it off, careful now, there's a fairly strong spring in there, you wont want it jumping up at you, keep clear of its path, keeping the wood ontop will assure it wont go flying, relax, it isn't super strong, can be compressed with 2 hands.

I'll go further if need be, maybe a word doco is in order? Thoughts?

 

Word doco is complete, reply here, PM me or email me, whatever works, I'll be glad to help.

 

As per your request Lagonia.

 

Very nice! Thank you!

 

OK I think I'm going to try tackling this today or tomorrow due to the rain.. I'm not quite sure about what you mean when you say to use a piece of wood to twist it off but maybe once I actually get it back in my hands I'll understand a little better.. And what type of sealant did you use when repairing the slit in the rubber.. Will a plain ol innertube repair kit suffice..?

 

I used a sealant from Liqui Moly, don't know what you have in your part of the world. Yes it should work, depends if it has to flex or not.

This is where I wish I'd paid attention in maths class... The best I can explain is "square section" or maybe a suitable sized (ruler length) "beam" of wood.

Do you have a workshop manual? If you'd like my word doco please email me, Don't know if i can attach it here.

 

No manual but I'm sure I'll be able to wing it once I get to that point. Thnx and I'll keep you posted..