Brakes soft after start up??

[jweaversf]

I have a bit of a headache that maybe you guys have seen before- My brakes get softer after the start up phase on my 89 sub. During the first five minutes of start up from cold my brakes a excellent. After warm up and when the idle drops is when they get a bit softer- not dangerous by any means- but softer. I know that there is a cold start valve/mechanism that regulates vaccum and I am thinking it might be the problem. I have checked the hoses and they are tight and solid. Wondering if you guys have seen this one before and know of any common areas where vaccum hoses or a component might fail??? thanks guys

[Twisted Whipz]

not sure but check this out
http://coloradok5.com/forums/showthread.php?t=130488

[k5LS2]

Measure your vac at the booster with a tee, run the gauge up under a wiper blade so you can see it thru the windshield, Note cold start vac and hot vac, if the #"s (hopfully 12inches or better) are consistant I would suspect the 90degree one way valve at the booster, or the booster itself.

You can try this,,, take a propane torch and turn the gas on (do not light) run the torch around the booster and valve, even under the dash where the brake rod comes thru the firewall, If there is a leak the engine RPM should increase as it sucks the gas in .,,,, good luck :thumb:

[jweaversf]

not sure but check this out
http://coloradok5.com/forums/showthread.php?t=130488

shucks..not a member

[jweaversf]

Measure your vac at the booster with a tee, run the gauge up under a wiper blade so you can see it thru the windshield, Note cold start vac and hot vac, if the #"s (hopfully 12inches or better) are consistant I would suspect the 90degree one way valve at the booster, or the booster itself.

You can try this,,, take a propane torch and turn the gas on (do not light) run the torch around the booster and valve, even under the dash where the brake rod comes thru the firewall, If there is a leak the engine RPM should increase as it sucks the gas in .,,,, good luck :thumb:

sounds flamable! ha. actually wouldn't propane sucked in through a leak lower engine rpms since it is a less volitile fuel than gas?