Glad you got the problem fixed. :thumbs: :thumbs: :thumbs:
Just to clarify,
The early production 08 had the "improved" design that eliminated the electric vacuum pump. After the first few months of production, they went back to the electric vacuum pump design.
We have an early 08 Sky without the vacuum pump and have occasionally experienced the low vacuum braking condition but never had a brake failure.
http://www.solsticeforum.com/forum/f43/brake-issues-41801/
http://www.solsticeforum.com/forum/...ost-ohb-feature-information-34000/#post522248
Subject: Information on Optimized Hydraulic Boost Characteristics 2008 Pontiac Solstice GXP
The Optimized Hydraulic Boost (OHB) is a standard feature, included with all 2008 vehicles equipped with the 2.0L (RPO LNF) engine) and Electronic Stability Control (ESC) or known as StabiliTrak. OHB assists / supplements brake operation under low engine / low brake booster vacuum conditions using the ABS system.
Important: Increased brake pedal effort due to low brake booster vacuum conditions may exist during;
• The initial cold engine start up and the first few brake applies.
• When the vehicle has been parked for extended periods and/or at higher altitudes and restarted.
• Any time the vehicle is started up after a brake booster has been completely bled down (no stored vacuum).
The OHB functions are controlled by the Electronic Stability Control (ESC) Module. The ESC module determines when to activate the OHB.
The following OHB characteristics are considered to be normal:
• Increased brake pedal effort under low brake booster vacuum.
• Change in brake pedal effort when OHB is active.
• Ratchet sound coming from the brake system during OHB activation.
• Frequent brake stops may result in OHB activation.
• High altitude driving may result in OHB activation.
• Brake pedal movement or pulsation when the OHB is active.
Some customers may bring their vehicle back to the dealership commenting on any or all of the above characteristics . The customer may experience brake pedal movement or pulsation accompanied by a change in brake pedal effort when the OHB is active.
Important: Do not attempt to repair or replace any parts for what is considered normal operation of the OHB.
If a condition should exist in which you might not be receiving the intended brake boost, the SVC BRAKE SYSTEM message may be displayed on the DIC.
Hydraulic Brake Boost System
If your vehicle is equipped with Electronic Stability Control (ESC) and the optional 2.0L turbocharged engine, it also has a hydraulic brake boost feature which supplements the power brake system to maintain consistent brake performance under conditions of low brake booster vacuum. Low brake booster vacuum conditions can include initial start up after the vehicle has been parked for several hours, very frequent brake stops, or high altitude driving. When hydraulic brake boost is active, you might feel minor brake pulsation or movement in the pedal but this is normal.
The Hydraulic Brake Boost system activates (only) during a brake apply when the brake module detects low vacuum from the vacuum sensor mounted in the booster. The boost function in this case will be provided by the ESC system to provide metered brake pressure to the wheels. When the system activates to build pressure, the ECU will run the pump motor, opens the Electronic Shuttle Valve (ESV), and closes the Isolation Valves (NO TCS Valves) at the same time. The ECU runs the pump in pulsed cycles and builds pressure in the wheels that exceeds the TMC (with low vacuum in the booster). As the brake fluid is drained from the TMC, the brakes pedal will move accordingly (pulsing feel in pedal). Pump speed and duration are controlled by computed volume models in the ECU (information includes low vacuum sensed, TMC pressure, and pedal travel through the BAS sensor). If the pressure is reduced or vacuum restored while a Low Hydraulic Boost is required the wheel pressure can thus be continuously adjusted to the TMC pressure by selectively lowering the current on the Isolation Valve (NO TCS Valve).