Brake pedal

[harley440]

My 18 Silverado I just started noticing a weird brake pedal issue......At cold start I put my foot on the brake pedal when I start my truck I feel their weird pedal pulse and almost feels like a broken spring then after the truck starts the pedal feels and works fine.....it’s happened couple times I’m just wondering if anyone else had heard of this? 

[Jsdirt]

Sounds like that's probably normal, especially if you've got a Hydroboost system. That system uses power steering hydraulic pressure to provide the mechanical advantage to the brake booster. These days with everything having electric power steering, you probably have a regular vacuum operated brake booster - that setup uses engine vacuum instead of hydraulic pressure to create the same mechanical advantage. If there are any leaks in the system - even microscopic ones - the vacuum will bleed off over time. When you first fire up the vehicle, there's a surge of vacuum through that system, and might feel strange. Back in the day, the pedal would feel stiff, then fall to the floor in a mushy fashion when the engine was fired up.

 

Not sure what GM is doing these days for these systems. I've heard they're using vacuum pumps now to create vacuum for the booster. I have zero experience with those, aside from repairing them in 14 year old VW models. That might be a perfectly normal feeling in the brake with that system. Only way to know would be to visit a couple dealers and test drive the exact model you have on that's on the lot, and compare. If 3 of them do the same thing, it's probably normal.

[tlaw91]

You probably need a vacuum pump if it’s a 1500 truck


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