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73-87 Chevy _ GMC Trucks => Brakes, Frame, Steering & Suspension => Brakes and Braking Systems => Topic started by: SirTubbLord on May 22, 2018, 05:47:25 pm
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Hey guys, I've looked all over this forum but can't seem to find the simple answer to my question. I've got fluid leaking on the floorboard behind the the brake pedal, and I know it has to be either brake fluid or power steering fluid, but I don't know which. My common sense tells me power steering fluid because the hydroboost sits right up against the firewall, but I don't know for sure. I should also mention that it's just not a big enough leak to be able to tell by checking fluid levels. Before I go buy either a new hydroboost, or master cylinder, I'd love to get some input from someone who has experience and knows what they're talking about. By the way, my truck is a 77 3/4 ton, mechanically pretty tip-top (aside from this little leak), body is leaning towards ugly, but I think she's a beauty!
Thanks!
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I've been troubleshooting this topic on my truck with my father (mechanic since the 60's). From what it sounds like, it's probably the brake booster, I could be wrong so don't take my word for it. It seems like the likely culprit, hopefully it's not though I hear those can get expensive.
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You'll need to look and verify this, but I think you will discover P/S fluid seeping from the booster around the pushrod that connects the booster to the brake pedal arm. Replace the booster and thoroughly flush the P/S system using fresh fluid. Catch the old fluid in a clean pan and inspect it. If the old fluid exhibits a pearly sheen or glitter, replace the pump as well.
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Welcome
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Thanks for the help! I assumed it was the power booster since it's closest to the leak, but someone told me it could be brake fluid seeping down the rod as well. I guess I'll have to take it apart and have a look. I checked with the local NAPA and a new hydroboost is only 100 and change. Not too bad if it needs replacing.
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On a hydro boost system, there is a weep hole between the brake master and booster, so in theory no brake fluid should make it in the cab.
On a vacuum boost system, there isn't typically a weep hole, and if the vacuum booster should start to fail, brake fluid could then enter the cab.
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I had the same issue and it was the hydro boost. Replaced it and problem solved.
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