Just bought new insulation and carpets for my xj40, remove the previous ones and the cover behind the brake and accelerator pedals is all yellow! Anyone have any ideas of what It could be?!

 

Hi Brahlinski,

The only three fluids I can think could be possible are:

1. Brake fluid leaking down the brake pedal arm from the master cylinder;

2. Hydraulic System Mineral Oil (HSMO) from the anti-lock brake system or Self-Leveling Suspension (I can't recall if any of those hoses or pipes are routed near your pedals, or even how the ABS/SLS works on the early XJ40s);

3. Engine coolant leaking from the heater core in the Climate Control Unit in the center of your dash.

Can you identify the fluid as any of these?

Perhaps one of our early-XJ40 experts will have some better ideas.

Cheers,

Don

 

Hi,
I believe pre 1990 xj40's have the abs/brake system and the self levelling system linked using the yellow mineral oil. From 1990 on the abs/braking system was separated from the self levelling system.
I'm pretty sure however they both still used the same fluid. I know my '91 Daimler still uses the yellow fluid in the braking system and it is all original though fully rebuilt, the self levelling system in mine is linked to the power steering. Though I need to check to be sure.
If the seals are leaking around the pedal rod into your brake system then it will get inside to the floor.
You'd need to find the residue of the trail and trace it back.
Troy

 

Thanks heaps for the replies! Yeah the fluid is leaking into the cabin and it's pissing me off! Ive traced it to brake master cylinder. What are the possible solutions to this? Very clueless in this matter

 

Would this solve the problem?? $400

Jaguar XJ6 XJ40 Vacuum Brake Servo Conversion | eBay

 

Hi Brahlinski,

Sounds like you have a leaking seal. If it's just an end seal, you may be able to find replacements. For example, Jagbits lists some of the seals for an '88-'89:

Jaguar Master Cylinder, XJ6, XJ8, XJS, XK8, S-TYPE, X-TYPE, XJ40, X300, X308, jaguar parts, new and used Jaguar auto parts, technical information, Jaguar XJ6 parts, Jaguar XJS

You might search this forum for "XJ40 master cylinder" or "master cylinder rebuild" to see if anyone here has replaced seals or rebuilt their master cylinder. It would be worth searching the archives at the Jag-Lovers XJ40 forum also because there are several long-time owners there who collectively have done just about everything that can be done to an XJ40. Also search the Jag-Lovers XJ40 forum for recent threads from members who have done the vacuum servo conversion. It will eliminate the mineral oil boost system (so if it's HSMO that's leaking in your car rather than brake fluid, it might solve your problem), but it won't eliminate the standard master cylinder and brake fluid.

There is some additional helpful info about the Jaguar brake systems here:

http://coventrywest.com/jaguar-tech-tip-4

Cheers,

Don

 

The master cylinder is not the problem but the BOOSTER is.
The hydraulic power booster is the unit that is leaking.
The master cylinder will leak BRAKE FLUID into the engine compartment (clear type fluid).
The pedal is attached to the BOOSTER.

bob gauff

 

Bob,

So if I understand what you're saying, it is not brake fluid leaking down Brahlinski's brake pedal, it is hydraulic system mineral oil (HSMO), and if he does the vacuum servo conversion, he will eliminate the leaking hydraulic booster?

Thanks,

Don

 

Correct Don B.

The hydraulic booster is the 'spacer-tube' with the 2 hydraulic lines between the pedal tower and the master cylinder.

The vacuum conversion will eliminate the need for the 3 piston pump on the front of the engine IF the Self Leveling rear suspension has also been converted.

The pump is only required on the 3.6 liter (88/89) for the brake system once the rear SL suspension is replaced with conventional springs/dampers. The 1990MY> has the electric/hydraulic brakes so it can be removed with NO affect on the brakes.

The pedal pushes the booster and the booster pushes the brake master.
A leaking master cannot leak brake fluid through the hydraulic booster (too many seals and pressure differences).

bob gauff