i've got a problem with my '83 300td turbo diesel. sometimes when i start the car, i will notice that the power brakes are not working and it will be extremely hard for me to stop the car. when i manage to start the car, it will not stop even after turning the key. i have to get out and push the red stop button to get it to turn off. this usually seems to happen when first starting the car. i have yet to have the power brakes go on me while driving which would be extremely dangerous. anyone know why this is happening?

steve

Your Vacuum pump is not working.
Try to re-build the vac pump or get someone else to fix it. Unless you dont need to stop much.

Just check to make sure there are no obviously loose open vacuum lines. You can still stop without power brakes, just takes some effort from your leg.

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1985 CA 300D Turbo , 213K mi

Take the large hose off of the vacuum pump, the one that leads to the power brake unit. See if there is alot of black engine oil inside the fitting. If there is alot of oil then good chances the vac pump has a hole on the diaphram. Ck also the milk white ehxaust hose from the vac pump that leads to the air filter. If it shows oil in it then the vac pump needs a rebuild. CAREFULLY....CAREFULLY, start the car and see if you feel suction from the pump by putting a short length of hose back on the pump and with your thumb over the other end of the hose, you feel suction.
I have successfully replaced the diaphram without removing the pump from the engine. I believe I removed the engine cooling fan.....(It was awhile ago!)
I had diesel VWs and they went through the pumps faster than mercedes do.

Let us know what you find

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.