When I come to a stop, after several seconds the car will start creeping forward even thought I’ve not released any pressure on the brake peddle. When this occurs I have to press the peddle down further to get the car to stop moving. Is this indicative of a master cylinder problem or something else?
Roger,
When I had that symptom in one of my Series III saloons I first tried bleeding the brakes but that did not fix it. So I removed and replaced the master cylinder and that did fix it. I had a nice firm brake pedal again that held firm and did not have to be pumped when stopped while in Drive.
Paul
Paul,
Thanks for that info. Will have to get some parts and replace it. Do you happen to know of a good one man brake bleeder kit?
TIA,
Roger
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If the pedal ‘sinks’ gradually, Roger - it means a leak…
Which may be internal, in the master cylinder, or external in lines or calipers. An external leak shows up as a drop in brake fluid reservoir - a leaking master cylinder will not cause level drop…
That said; it is the pressure on the pedal that keeps the car stationary by constant system pressure. Ie, a constant pedal pressure(!) will hold the car - a leak will simply cause the pedal to sink under constant pedal pressure. With a leak; holding the pedal position(!) constant will cause pressure to drop - and the car will start to creep…so…?
It is important to find the cause of the leak before getting parts…
Frank
xj6 85 Sov Europe (UK/NZ)
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Frank,
Thanks for that. I found that the level isn’t up to where it should be. Should I top it off? What fluid would you recommend as I have no idea what’s in it now?
Roger
Roger,
Your car should have DOT 3 brake fluid.
Paul
Thanks Paul. I’ll get some today.
Roger
Roger,
There should be a decal located beneath the brake fluid reservoir in your car that stipulates the use of DOT 3 in your brake system. Attached is a picture of the decal that was in my 1984 XJ6 Vanden Plas before I removed it for the engine bay cleanup and engine swap.
Paul
Paul,
Thanks, I’ll check for that. Was focused on the level in the
reservoir and probably didn’t notice it.
Roger
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Loss of brake fluid is one of the diagnostics for detecting an external leak, Roger. Observing levels over time may tell…
The brake fluid reservoir is wilfully divided into two compartments - to ensure that if one circuit is drained the other one will work. However, as brake pads wear, the fluid level will gradually drop in any case…
As long as the level is above ‘min’ there is no ‘need’ to top up - but no harm doing so. Pursuing a possible leak; note the levels for future reference…
Frank
xj6 85 Sov Europe (UK/NZ)
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I would be inclined to go to DOT4 it is backward compatible.
The lower level in the reservoir may just be a result of the general wear in the pads, how are they looking for thickness?
Thanks Frank. I’ll be sure to keep a close eye on it.
Roger
I recall that the last can of BF that I bought at a NAPA store, now closed, was Dot 3/4!!!
Sad, good guys, real know how as to parts not mere software users…
Year make and model helpful, but not an absolute necessary.
But, bringing the old part was always appreciated.
Carl
Carln