W126 Vacuum Pump

[KenHeimbuch]

Hi, despite searching this site for a while, I have yet to figure out what the engine/brake vacuum pump looks like and where it is....I've a 1985 500sel w126....thank you in advance and Happy Thanksgiving. Ken Heimbuch.

[stevebfl]

The only vacuum pump on a gas 126 is the one for the door locks and it is next to the spare tire.

The engine vacuum pump for brakes is used on diesels and some older 4 and 6 cylinders. The diesels have no manifold vacuum as they have no throttle. The early 114 280 had a pump that we usually removed when in failure as MB did in 75 or 76. It just wasn't needed. Manifold vacuum was entirely sufficient.

[KenHeimbuch]

Thanks for your reply. I am now more confused than ever, perhaps you could give me your opinion. The power assist is gone from my brakes, and my engine acts as if there is a huge vacuum leak, my economy gauge is always reading half or more. It's hard to keep the engine running. As an aside, what then does supply the vacuum, if not a pump? Anyway, thanks. Ken Heimbuch.

[stevebfl]

Your cars motor is one huge air pump. A small portion of that pumping capability is used for powering vacuum assist on the power brakes.

Sounds like the hose to your booster is broken, probably at the check valve. Look at the booster to one side of the master cylinder. There is a hose as big as your finger in diameter. Grab it, it should be rather firmly positioned. Follow it. It should be solid to the back of the intake manifold.

[KenHeimbuch]

Thanks very much, I'll investigate this morning. Ken Heimbuch.

[KenHeimbuch]

Hello and thank you. Your diagnosis was completely accurate. I'm very grateful. Ken Heimbuch.