M104 issue but relevant - Lean condition from Brakes!

[195910]

Hello Everyone,

I have documented a lean running condition caused by the brake system. Got the car to run %20 lean with misfires on 3 cylinders (brake vacuum connector side) just by pumping the brakes a few times!
Any tips on checking the brake booster or vacuum reservoir ?

Thanks in Advance

 

[TerryA]

I’ve had a similar experience on a long gone 67 230 Finny. Turned out to be a vacuum leak on the check valve to the brake booster. In my case the check valve was allowing brake fluid to be sucked into the engine. When I stepped on the brakes I had huge clouds of white smoke behind the car.

Inspect the check valve.

 

[gerryvz]

As a starting point, I would check closely the vacuum line between the intake manifold and the brake booster (which contains the check valve). These (both the line itself, and check valve, as said) can and do get brittle and crack with heat cycles and age.

 

[195910]

I’ve had a similar experience on a long gone 67 230 Finny. Turned out to be a vacuum leak on the check valve to the brake booster. In my case the check valve was allowing brake fluid to be sucked into the engine. When I stepped on the brakes I had huge clouds of white smoke behind the car.

Inspect the check valve.

Interesting case Terry

@gerryvz @TerryA I will have a look at the check valve tomorrow as I don't remember there was anything with the hose itself.

I don't feel any issues with the brakes such as loss of servo.