XJ-S V12 brake problem
Discussion
I have an intermittent problem with the brakes on my 1991 XJ-S. Basically, a couple of times, the brake pedal has gone hard and I've lost pretty much all braking performance. This is accompanied by the ABS warning light clicking on. I took the car around the block last night and the light stayed off and the brakes behaved, but I'm loathe to venture further/faster just in case.
I did a bit of research which suggests that it could be the brake accumulator that has gone, but I don't understand why the brakes work ok sometimes? It's a pricey part, so before I start buying things willy nilly, does anyone know of a good testing procedure for it?
Thanks in advance.
I did a bit of research which suggests that it could be the brake accumulator that has gone, but I don't understand why the brakes work ok sometimes? It's a pricey part, so before I start buying things willy nilly, does anyone know of a good testing procedure for it?
Thanks in advance.
Could be the accumlator. Turn the ignition on, dont start the engine. Leave the ignition on for about 1 minute, all lights should go and and the brake acc should be fully charged. Now pump the pedal quickly and see how many pumps you get until you hear the brake pump cut in. It might be easier to open the bonnet so you can hear it. From memory you should have a good 15-20 pumps before the pump cuts in. The pump/ acc work like an old fashioned servo storing and providing braking assistance.
If you only get a few pumps before the pump cuts in the the pressure inside is low. This could be due to a couple of reasons 1: Accumlator diaphram weak and now holding pressure. 2: Pressure switch faulty therefore cutting out to soon and the brake system not reaching rewuired pressure.
We used to change loads of accumlators on the older/original XJ40's. We did change a few on later models.
You will need someone to diagnose it properly but hopefully it points you in the right direction.
Then you will have to decide whether or not you spend the money on the parts. In theory its still safe to drive, but should you lose electircs you will only have 3-4 braking operations before you have no assistance.
Hope this helps, i will try to answer any other questions if i can remember my apprenticeship on these old beasts !!!
If you only get a few pumps before the pump cuts in the the pressure inside is low. This could be due to a couple of reasons 1: Accumlator diaphram weak and now holding pressure. 2: Pressure switch faulty therefore cutting out to soon and the brake system not reaching rewuired pressure.
We used to change loads of accumlators on the older/original XJ40's. We did change a few on later models.
You will need someone to diagnose it properly but hopefully it points you in the right direction.
Then you will have to decide whether or not you spend the money on the parts. In theory its still safe to drive, but should you lose electircs you will only have 3-4 braking operations before you have no assistance.
Hope this helps, i will try to answer any other questions if i can remember my apprenticeship on these old beasts !!!
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