Hydro boost problem.
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Hydro boost problem.
Having a hydro boost problem in my 99 F450. Brakes and steering works fine, except that after 2-10 miles, the brakes apply and won’t let up until you bleed off brakes at wheel cylinder. That happens whether you apply brakes or not. I’m thinking pressure is bleeding through to master cylinder from defective hydro boost? The only aside to this, it is a boom truck, which could possibly have a mico brake to set hydraulic park brake, but I haven’t found any sign of one. What y’all think?
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Normally I would say check the rubber brake lines as they can wear inside and create a check valve condition. But you state this happens even without touching the brakes. And it sounds like this is on more than 1 wheel?
Could it be heat related?
The hydraulic parking brake aspect is over my head.
Throw in some more details and maybe some of the smarter than me guys on here can toss out some ideas.
Could it be heat related?
The hydraulic parking brake aspect is over my head.
Throw in some more details and maybe some of the smarter than me guys on here can toss out some ideas.
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From: Henderson, NV
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Thanks.
Normally I would say check the rubber brake lines as they can wear inside and create a check valve condition. But you state this happens even without touching the brakes. And it sounds like this is on more than 1 wheel?
Could it be heat related?
The hydraulic parking brake aspect is over my head.
Throw in some more details and maybe some of the smarter than me guys on here can toss out some ideas.
Could it be heat related?
The hydraulic parking brake aspect is over my head.
Throw in some more details and maybe some of the smarter than me guys on here can toss out some ideas.
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Is your Mico lock the version that has the electrohydraulic pump and has an interlock with the boom system? If so, there might be a short in the interlock or electric pump circuit causing the pump to build brake pressure.
Thats been a thought, but I haven’t found anything that I thought looked like a mico brake. Problem is, I haven’t worked on any this new that might b electronic. Would you think they would tie into the master cylinder, or right into brake lines? Can they build pressure on their own as opposed to merely trapping pressure?
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Thanks for input.
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From: Henderson, NV
Thanks.
Thats been a thought, but I haven’t found anything that I thought looked like a mico brake. Problem is, I haven’t worked on any this new that might b electronic. Would you think they would tie into the master cylinder, or right into brake lines? Can they build pressure on their own as opposed to merely trapping pressure?
Thats been a thought, but I haven’t found anything that I thought looked like a mico brake. Problem is, I haven’t worked on any this new that might b electronic. Would you think they would tie into the master cylinder, or right into brake lines? Can they build pressure on their own as opposed to merely trapping pressure?
As for the Mico brake lock, this is what I was referring to. If this is what the truck has then it is most certainly capable of building pressure on its own. It sounds like you may not have one of these if you can't find anything that looks like a Mico brake lock. All those bits should be pretty obvious. Maybe take pics of the entire brake system so we can see what you're seeing?
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I just realized I have not answered your original question. No, Hydroboost hydraulic pressure cannot bleed into the master cylinder since they are only mechanically linked. There have been rare occasions where the Hydroboost self-activated but that will take a very specific jamming of the internal spool valve by contaminants in the fluid coming from the PS pump.
As for the Mico brake lock, this is what I was referring to. If this is what the truck has then it is most certainly capable of building pressure on its own. It sounds like you may not have one of these if you can't find anything that looks like a Mico brake lock. All those bits should be pretty obvious. Maybe take pics of the entire brake system so we can see what you're seeing?
As for the Mico brake lock, this is what I was referring to. If this is what the truck has then it is most certainly capable of building pressure on its own. It sounds like you may not have one of these if you can't find anything that looks like a Mico brake lock. All those bits should be pretty obvious. Maybe take pics of the entire brake system so we can see what you're seeing?
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Thanks for the link, was not what I expected. Found Mico brake hyd unit behind mud shield. It has been disconnected long ago. Got enough stuff taken off to see every inch of brake line, nothing goofy there, just basic brake system. That said, definitely not Mico brake. That seems to leave two options. Pressure bleeding through hydro boost to put pressure on spool of master cylinder, or something I just came up with, possibly brake pedal not staying up, but putting slight pressure down, activating brakes. I never did check this before. Punch line is, the bugger quit applying brakes on its own. Works perfect at the moment. Thanks, you’ve been big help. I’ll let u know of more developments.
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