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No Brakes When Cold, Volvo V70 Vacuum Pump

No Brakes Vacuum Pump/Switch Replacement with Pics V70 P2

dan777 writes: 

No Brakes Symptoms

I know there were some other posts dealing with this issue but I thought that would be very helpful to write a detailed tutorial with pictures about how to diagnose and eventually fix the problem. This should point people in the right direction and prevent them wasting time checking the whole brake system when the issue is somewhere else.

Symptoms: After a startup when engine is cold there is no brake assist, the brake pedal feels very hard, braking efficiency is very low and for some reason it feels worse when driving in reverse.

Normal operation: The brake assist needs vacuum and after the engine was stopped for a while there is not enough vacuum left in the system. After a minute or so the engine produces enough vacuum for the brake booster. To compensate this there is an electrical vacuum pump that it activated by a vacuum switch when the vacuum is too low. When the vacuum is back to normal the switch disconnects the pump, which is not designed to run for an extended period of time.
Issues: If the switch contacts get sticky then the pump runs for too long and eventually it will fail or burn the fuse. If the switch contacts are not closing properly then the pump will not start.

Tools needed for diagnose and pump replacement:
T25 torx screwdriver, 10 wrench and rachet, voltmeter, pliers

After a startup when engine is cold there is no brake assist, the brake pedal feels very hard, braking efficiency is very low and for some reason it feels worse when driving in reverse.

No Brakes Solution

Vacuum pump and/or switch replacement

I bought the parts from FCP:
$179.55 for the Pump – 31317445
$8.99 for the Snap-on Coupling – 30744403
$59.95 for the Vacuum Switch – 31265825

No Brakes When Cold – Vacuum Pump/Switch Replacement with Pics

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