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Low brake pressure warning light

HI can you help me with the above problem for a 88 jag cheers

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A vacuum conversion kit is available for your XJ6- look here:

Posted on Jun 09, 2009

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The "low brake pressure" problem is one that plagued XJ40s for years. Unlike almost every other power brake system (vacuum), XJ40 brake boosters used a hydraulic system, which also controlled the self leveling system. The system was prone to problems, leakage not being least among them. While Jaguar offered a conversion kit for the self leveling system, it never did so for the brake booster. The most common cause of failure is a leak in the brake accumulator, caused by a faulty o-ring. The issue is, while an o-ring is relatively cheap, replacing it will often not fix the problem. Often the accumulator will have to be replaced, which is (ahem) outrageously expensive. However, I have seen a vacuum brake booster conversion system in a few XJ40s. I have yet to find a kit, though I believe I have a strong lead. If you can track one down, it would doubtlessly be your best choice.

As for the air conditioner, I have very little advice to offer. I never could figure out the problems I had with mine. I've heard of bills in the thousands of dollars for these repairs. The problem is that the system is needlessly complicated, and the replacement parts can be extremely expensive. My advice to you is to live with any problems you have, unless you have a clear idea of where the problem is originating.

Posted on Mar 13, 2009

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Based on personal experience (another brand/model), low brake pressure ( ! ) warning light would come on if and when:
1. The brake fluid level is low (barely reaching the level sensor), refill to specified level/capacity;
2. Worn brake pads, replace;
3. Weak pressure from ABS pump, check for leakage, replace;
4. Defective sensor/switch, replace.

Only # 1 would be relatively easy to perform. All others would perhaps require the professional services of a qualified mechanic or familiarity with automotive mechanics.

I also did a Google for your particular problem/model. These may be of interest/information to you:
a. David Marks Garage;
b. 1988 Jaguar XJ40 review; and
c: Brake parts & electrical/switches/sensors.

Hope that this be of some help/idea. Pls post back how things turned out or should you need additional information.

Good luck and kind regards.

Posted on Jan 10, 2008

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