Vacuum loss-partial - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 05-16-2008, 08:49 PM Thread Starter
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Vacuum loss-partial

'75 240D- lost vacuum to brake booster and locks.

Previous symptoms were, locks getting very slow to function and not holding pressure very long after shut down and 1st to 2nd shift very hard if driven right after start up.

On freeway trip home, vacuum loss, no booster under braking on offramp, luckily no traffic or bad conditions.

Actuators function in both direction with hand vac pump, disconnected line to booster, had slight hiss on removal, seems like it held pressure, check valve in booster/lock line functioning properly. Almost no vacuum draw on booster/lock side of vacuum pump.

Car does still shut off and trans seemed the same even after failure.

Will a vacumm pump rebuild be in order and why would it effect only one side.

Last edited by 911s55; 05-16-2008 at 09:10 PM.
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post #2 of 3 (permalink) Old 05-21-2008, 03:05 AM
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Check pump vacuum by either connecting your miteyvac to the pump and seeing if it holds (engine not running) to check the valves OR connect a vacuum gauge to the pump and check that you have any vacuum. If no vacuum the problem is the pump valves. if you have vacuum check the vacuum connections under the hood for leaks on the rubber connector. The plastic lines last for ever unless one has chafed through. The door actuators have rubber diaphrams which perish with age,so you may have to investigate in the doors ,trunk and fuel door for leaks.
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post #3 of 3 (permalink) Old 05-25-2008, 07:27 PM Thread Starter
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Vacuum restored-smooth

Replaced vac pump diaphram, old one was torn at center and a fair bit of oil in front portion of pump, also checked door actuators and lubed internal locking hardware, latches and tightened up door panels.

Transmission and door locks work better than when I got the car 6 years ago.

Thanks for listening and the tips!

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