1999 Isuzu Rodeo Brake Problems! My wife had a problem with not enough brake power. It seemed like the brakes were just getting toward the end of their life. So, replaced rotors with cross drilled and slotted rotors, new brake shoes in the rear. Racing brake fluid, completely bleed the system. Rebuilt the front calipers, and replaced the rear wheel cylinders. Rear brakes are adjusted properly, and E-Brake works better than it ever has. The system has no leaks. Had a Isuzu recall on the algorythm for the ABS, got it changed and saw no difference. Yesterday I noticed the gasket between the master cylinder and the brake booster seemed to be rotton and coming out. I popped off the master cylinder and RTV'ed a new gasket in. The only thing I could think next to check was the vacuum line coming off the intake manifold. I pulled the hose off the brake booster, and a hiss of air came out of the brake booster! I started the truck and pumped, and held and waited and pumped and held and I did a test drive. I thought the brakes seemed fine. My wife drove it later and she didn't know I had worked on the truck and asked why the brakes suddenly seemed alot worse! I drove it again and I could tell the brakes were not getting the pressure they did before. Did I ruin the booster by taken off the vacuum line? Do I just need to let it build pressure back up? HELP!
I figured out that the booster is under a constant vacuum, even when the engine is not running. On my Honda, the check valve is installed in the hose from the intake to the booster. On this Isuzu Rodeo, it's just a hose. I took the hose off the intake, but it seems it's just a hose barb. The hose is just a hose. Rethinking this whole project leads me to believe the check-valve could be faulty, leaking air and degrading brake performance. BUT WHERE IS THE CHECK VALVE?
AH HA! The check valve is inside the hose, so kind of built in valve. Tested valve, worked fine. Next problem, due to an aftermarket intake I think there was not enough vaccuum to fully decompress the brake booster. Quick fix - loosen intake, start engine, rev up engine and quickly remove intake and cup hand over throttle body to make a seal. The brake booster will have tons of vaccuum applied to it! I did this with the brake pedal up and down. It seems the brakes are working 100% better now! I hope this helps anyone who has problems like this. Also, I've replaced/repairer nearly everything on my 1999 Isuzu Rodeo, so if anyone has any questions, I'm sure I can help.