Ever since I changed my master cylinder, the brakes are too soft. They're drivable but quick stops have me standing on the pedal. On very, very cold days the brakes are REALLY soft for the first couple stops.

Two different shops have tried bleeding and one checked to make sure the master cylinder is good. Suspect something with the ABS pump, which I know very little about.

Is there something unique that has to be done to bleed the brakes? Is there a way to bleed the ABS pump in case there's air in it?

Last mechanic suggested vacuum exchanging the brake fluid, which should clear out any air throughout the system.

Any help or ideas much appreciated ... thanks!

 

Please provide vehicle details.

Yes, regardless of MY I believe you need a scanner capable of enacting/disabling the ABS motor to allow full bleeding of the ABS circuitry.

You still have trapped air in system.

 

Have you considered the vacuum assist power booster system?

Perhaps the rod that goes from the vacuum assist unit to the master cylinder out of place, the engine vacuum line leaking, the rubber diaphragm broken, etc?

Or horror of horrors, the new master cylinder connections are reversed. I don't even know if such a thing is possible on these cars. Your double damn sure the correct master cylinder has been supplied?

 

Thanks, guys. I believe my vehicle info is in my signature line, but it's Jaguar/VDP/2004/4.2L V8. I have over 235k miles. I'm sure the master cylinder is functioning and put on correctly, but the other areas could be issues. I just may have to have the Jaguar shop take a look at it. I have an ABS scanner, but unfortunately it doesn't read Jaguar.

 

When I changed my rt rear caliper I had the same issue. I have been bleeding brakes for 35 years, but couldn't get all the air out of this Jag. I tried everything. Went thru 2 LT of fluid with using a vac pump. Called my friend at the dealer. He said I still had air in the line, and one of the only sure fire ways to bleed it all out of that system is a pressure bleed. I dont know if he disabled the abs pump, in 10 minutes it was done. Cost me about $30.00, and was well worth it.
Old SER III land rover slave/clutches were the same. The piston throw was not long enough to push the air over a high bend in the line. But a Vac bleeder could pull it thru.
The vac bleeder cannot pull enough air thru fast enough to bleed some of the lines on a SV8, as 5" extra in that right rear line can make it very hard to bleed.

 

Good tip! Mine brembos also seems too soft after I changed all lines corroded underneath. Sometimes I can't even freeze the car by pedal kick on walking speeds in traffic.. really scary. Always justified that its a comfort feature not to nod by passengers Will go and ask for force bleeding by pump.

 

235k miles? Impressive!

 

After disconnecting both rear calipers, to put new bushings in my rear control arms, my brake pressure seems lower than it was prior to doing the work.

I have pressure bled the rear calipers three times now and still same feel at the brake pedal.

I have not touched the front calipers.

No error codes at all.

I tried using my JLR SDD to use the brake system maintenance routine but it comes up with a "mantab" error.

Has anyone had success with the JLR SDD brake system routine?

My ABS module should not have been affected as it is quite difficult to get air in the ABS module with a simple caliper bleed. If there was air in the master hydraulic cylinder that would be a different story and there was not.

 

Hi, I also have a 2003 super V8 with corroded brake lines. I've been told it would cost $lots to replace them as it needs the petrol tanks removed, rear axle dropped etc. How did you do it? I wondered if threading through flexible braided line would mean less dismantling?

 

Exactly the way you've been told. I made it during all rear suspension arms and swaybar bushes replacement.. yes, they dropped rear axle. You just have to find affordable place for this job.

Concernig soft pedal and scary feels, the reason was just in stuck pistons in all calipers. Changed all damaged pistons and seals. Now i'm scared of brake power really!

 

Have never replaced the lines on a Jaguar, but they make an alloy of about 95% copper, 5% nickel. It's stronger than steel, yet still bends like copper, have used it more than once. No need to run the lines in exactly the same route as stock in my experience. As long as your flairs on each end are made right, its long enough to reach the calipers, & tie out of the way, everything should be fine.

 

I ended up re pressure bleeding starting with the calipers at the front as per Jaguar instructions.

Braking noticeably better and safe for sure however NOT what I remember it being like before I did all the rear bushing work.

The car brakes in a strait line no problem.

 

Thanks, I also had to have several of the pistons in the brake calipers replaced last year due to corrosion. About 7 of 16 from memory. New seals all round.

Latest idea from the garage: Give the lines a good going over with a wire brush. If a leak develops, cut out that section and splice in a replacement. If not, the inner wall is sound, just coat with stone chip protective coating. Implicit in this scheme is "don't worry about any bits you can't see". Thoughts? How fragile were the bits of brake line you removed? Was there any bad corrosion on bits you can't see e.g. above the fuel tank?

 

Jag had a recall for corroding brake lines for early year X350's. I don't know if it was for all markets or not, but I know it definitely included all Canadian 2004 XJ's - mine included. The US dealer who replaced my brake lines had to drop the rear end, tank and exhaust system. It sounded like the Canadian dealer from whom I bought my car found a way of performing the replacement with slightly less dismantling, as they had to do quite a lot of XJ's. Given corroding brake lines has been a known issue with our older X350's, I'm not sure how prudent it would be to ignore what you can't see.