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Vacuum brake servo unit replacement / retrofitting - Volvo P1800

Volvo P1800

01.12.2021

Tutorial for exchange or retrofit of a brake servo unit in the Volvo P1800 with single circuit brake.


At first the brake fluid must be evacuated from the master cylinder, the brake hoses until the hose distributor and the old vacuum servo unit if it exists. In our example in an early Jensen model there wasn`t any brake servo unit before. In this case you have to order or produce two additional brake lines and the screws for fixing the brake servo. For pumping down the old brake fluid it is good to use a simple venturi brake bleeder.

To absorb the remaining fluid while we opened the brake lines we used paper rags and a measuring cup.


At last unscrew the brake line at the small distributor with the brake light switch.


Dismantle the cap, hose and pump of the windscreen washer tank.


Set the lower screws in the original console from the bottom side, the upper screw through the hole under the pump setting. You also have to fix the screws in the console through this hole with a cardan joint and an extension.


Pass the choke cables under the negative pressure line, therefore pull the hose beside or dismantle the choke cables and mount them again after threading.


If there was`t any brake servo before, screw out the hexagon or square socket worm screw and attach the connection stud for the vacuum hose.
The square version can be carefully removed using the 1/4" square end of a wrench even it it does not fit for 100%.


Bend the brake line and set the fittings. Set and bend the brake lines careful. They must not rub at another parts. The smallest bending radius has to be bigger than three times the diameter of the lines. Don`t bend down the brake lines!
The line from the master cylinder leads to the brake servo on the vacuum side, the other line leads to the distributor with the brake light switch.

Now set the negative pressure hose and clamp it with brackets. This hose also should not rub at another part. Mount the washer pump, cap and hose again.
Now fill in the brake fluid and bleed the brake system. Then you are ready with the retrofit or exchange of the brake servo. The brakes of your care are much easier to handle now!
  • All notes serve only as an example and do not replace the workshop instructions of the automobile manufacturers! All information is supplied without guarantee!

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