I'm having the dreaded slow shut off and hard brakes. I measured the vacuum at idle and was only getting about 5. When I rev it up, I get 17. Does this mean a bad vacuum pump? I've read it could also be a check valve. How do I test that?
gregp1962
What is expected vacuum reading at idle
Here's a good video illustrating the check valves. You don't have to like or support Mercedessource.
It seems like the FSM has no chapters on the vacuum system.
Before you attempt anything on the pump, have you checked for leaks on the system? The vacuum system uses vacuum from the brake vacuum line. The central locking reservoir continuously pulls vacuum from the system faster than the pump can extract air. If the system is leaking, it will affect the brakes and the shutdown. Those 3-way and 4-way connectors, along with the straight connectors, are easier and cheaper to replace.
Before you attempt anything on the pump, have you checked for leaks on the system? The vacuum system uses vacuum from the brake vacuum line. The central locking reservoir continuously pulls vacuum from the system faster than the pump can extract air. If the system is leaking, it will affect the brakes and the shutdown. Those 3-way and 4-way connectors, along with the straight connectors, are easier and cheaper to replace.
Yes, I have checked the other systems. I'm checking the vacuum directly from the pump. No other leaks are possible during the test. I'm only getting 5 inches at idle. A bit more when revving it up. The check valve seems good. This tells me that the pump is bad.
Sorry, I wish I could help you more. I'll keep my ears to the ground.
I see you're a member of PelicanParts as well. Did you see Stretch's thread on the vacuum pump?
I see you're a member of PelicanParts as well. Did you see Stretch's thread on the vacuum pump?
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