Hi Guys,

Help! I drove to the grocery and my brakes got hard to press and then the engine wouldn't shut down. I looked under the hood and all my lines looked ok. I limped it home.

Mityvac at the ip vacuum T showed 3 in Hg. I measured 20 in Hg at the metal line directly to the pump. I disconnected the booster and plugged up the T's with golf T's and I could measure 3 in at the hose end at the booster with the vacuum reservoir connected. Then I plugged off the reservoir and the vacuum at the booster fitting went up to 20 in Hg. I mityvac'd the reservoir and it holds...dang near got tendonitis but it does hold.

Checked the seal between the booster and master cylinder. Squished up but I greased it with vacuum grease and put it all together. Still couldn't shut down or get brake action. No hissing anyway.

So naively I said, well it's the booster. Big leak in there. Pump is working. But in the back of my mind I'm wondering why the pump needed the reservoir blocked off to work? I couldn't get the engine to shut down with only the booster blocked off, the reservoir connected and the shutdown line connected.

Weird. So given the nice 20 in Hg number on the pump I ordered a new booster. I figured heck, toss in a rebuilt master cylinder while I'm at it. They're on their way from the big cheap place on every corner.

But I started reading threads here about boosters and I started wondering about the check valve. No way I thought. I have 20"Hg at the pump. No way I have a bad check valve. However the fact I had to plug off both the booster and the reservoir to get the shutdown to work was still burning in my head. Didn't compute.

So for grins I pulled the check valve. I should have done this first.

I got this much out of the hole.



Dangit!!! Did I get everything out? Would this explain my wonky vacuum behavior? The pump was sucking but maybe that's because there are multiple check valves in it.

I have a couple of days for the booster and master cylinder to come in.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles