Power brakes not working right.
 

Hello,

I have a 2002 X-Type 2.5. After the first or second push of the brakes they will become hard to press but still function although you may stop quicker than intended or need a little more pressure to do the job.

I had a vacuum leak on the manifold and thought it could be the culprit but I changed the upper and lower intake manifold gaskets and although my limp mode 3000 rpm limiter is a thing of the past, the brakes are still wonky.

I can only think of 2 things, a restriction in the master cylinder/ABS related issue (No ABS lights though)

Or

the vacuum booster.

But, it does not act like other vehicles with a bad booster, I do not have to stand on the brakes and I do not hear air hissing when pressing on the brakes.

I suppose it could be a small leak in a diaphragm but I am not really certain.

Has anyone else had issues like this?

Thanks

Check the brake booster line for leaks. SEARCH will tell and show you how.

I purchased a new line for it a while back and it is good at both ends, no leaks check valve is good. I even RTV the part to the manifold to be sure. PCV valve line is in great condition, replaced IOT oil Rings, Replaced Upper and lower manifold gaskets as I was getting P0420 code. All those codes cleared up only Dirty Cat code now :( but, that doesn't involve vacuum so I am still kind of stumped and hate to randomly throw parts at it.

You have not bled the brakes, correct? Automatic or manual?

A sticking rear caliper can cause this also. As member Thermo says, take it out for a good drive. When done, get out and place palm towards each wheel (don't touch them). If one is SUBSTANTIALLY hotter than the others, that's the culprit.

Correct, I have not, I was thinking about this also but they are not spongy more like a bottle jack that pumps easily until it hits the load. But, Jag could be a bit different from regular cars but it is the same basic systems so I am a bit stumped not having coming across it before.

It is an Automatic, sorry, missed that bit.

Just a thought on a manual they share system with the slave cylinder

I have been having the exact the same problem. Mine was/is a split brake booster vacuum grommet. (Rubber part that the vacuum line elbow pushes into.)
See this thread: https://www.jaguarforums.com/forum/x...5/#post2086546

My car would start out without vacuum to the brakes, then when I rev'd the engine, I would get partial brake vacuum. I moved the elbow around on the booster grommet and I would get brakes again.
The leak is close enough to the vacuum booster that the leak is drawn into the vac line and you don't get a brake error.

Perhaps you have a different problem than I did, but at least it is worth looking into.


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