[P38HSE46]

I have put over 1000KM on my newly resurrected 4.6 P38 and I am really starting to enjoy it.

I do feel that the brakes are a bit weak, meaning they don't "bite" and require more pedal force to slow it down (I have new pads and discs front and rear).

Could it be due to a weakened brake accumulator?

Is there anyway to test it, for example with the Bentley/Rolls Royce where you pump the pedal with the engine off and the warning light comes on?

 

[P38HSE46]

Wait until it is up to pressure and the pump stops, then press the brake pedal and see how many times you can press it before the pump cuts in again. If you can press 3 or 4 times before it cuts in, then the accumulator is fine, if it cuts in on every press or only after 2, it needs replacing. The brake pedal does need more pressure than you might be used to on other cars but if the brakes seem weak, they might need bleeding. Air in the pressure circuit will give a slight delay between hitting the pedal and the brakes coming on.

Should I do this with the engine off, easier to hear the pump running perhaps?

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[P38HSE46]

Affirmative, after 2 pumps on the brake the brake pump goes in immediately.

I suggest everyone do this test as well.

Any special precautions with replacing the accumulator, I assume it needs to be completely depressurized prior to removal - which fuse do I need to remove to deactivate the pump?

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[P38HSE46]

Tip: much easier to do with the engine off, sound from the pump is more audiable.

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[P38HSE46]

Ordered from 4x4 Island, 129 GBP.

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[P38HSE46]

I've replaced the accumulator and bleed the brakes as per the manual, the difference is incredible!

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[P38HSE46]

The "pump the brake" test is the easiest way to determine the health of the accumulator. I found it easier with the engine off and the ignition ON.