Stopping Suddenly Got Harder. Possibly Master Cyclinder or Check Valve?

CaptainXL

Original poster
Member
Dec 4, 2011
2,445
So I replaced the Wagner Thermoquiet pads I put on my truck last November after hearing much hoopla about them. As it turns out they did not work well with my Envoy. They always exhibited a screetching sound like a city bus stopping. The pedal feel was not right either.

I switched to the Wearever Platinum ceramic pads from Advance Auto a few days ago. Immediately after changing to these pads I took the voy for a test drive and it was great. No noise and also the braking was excellent and it only took a little pressure on the brake pedal to come to a stop. Just like it should from the factory.

I then let the truck sit overnight...

I went to the store in the morning and the bad braking problem is back. What I am experiencing is weird. Yesterday I was able to stop the truck with little pressure but today it takes about double the foot pressure to come to a stop. The only immediate thing I can think of is that maybe the check valve is somehow screwy. When I take it off the booster I hear a swoosh sound so the booster is holding vacuum. What else to check?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
I would put a vacuum gauge on it in a place I could see while driving.
 

CaptainXL

Original poster
Member
Dec 4, 2011
2,445
the roadie said:
I would put a vacuum gauge on it in a place I could see while driving.

OK. Monitor engine vacuum before or after booster check valve?
 

CaptainXL

Original poster
Member
Dec 4, 2011
2,445
the roadie said:
At the booster, since that's what affects pedal pressure.

Any particular reason to test the booster with the truck running? I have a vacuum pump and can test it that way. Does that sound satisfactory?
 

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