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I replaced the cacuum shutoff unit on my '85 300D Turbo yesterday morning. Well now the engine shuts off, but only if its cold. When the engine is at normal opertating temperature, it just keeps on running. I'm able to shut if off by applying suction to the vacuum hose. <br> Question:<br> 1. What should the vacuum be coming out of the vacuum switch?<br> <br> 2. (unrelated to #1) Where's the electric window relay?
 

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1- There is a brown (?) vacuum line from the multi-way 'T' by the brake booster that goes to the ignition switch. A second brown (?) line leads back to the vac shutoff can on the I/P. When you turn the key off, the switch should send vacuum to the pod and kill the motor.<br> <br> It sounds to me like you have a vacuum leak somewhere else - door locks, climate control actuators, etc. A leak in any of these will prevent the engine from shutting off. Mercedes realized this problem and in later years made the source for the ignition shutoff totally separate, through a check valve off the main brake booster vacuum line - so a leak elsewhere won't keep the engine from shutting off!<br> <br> <br> Good luck tracking it down...<br> <br> <br> 2- Don't know, sorry.
 

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Dave M: Thanks for the info! 'made the source for the ignition shutoff totally separate, through a check valve off the main brake booster vacuum line' was the key! I put a 'T' fitting at the brake booster line and capped off the 3-way fitting where the brown vacuum line goes through the fire wall, and now the ignition shutoff is the first in line for vacuum. AND, everything works fine, now.
 
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