Ezrider Posted February 12, 2015 Share Posted February 12, 2015 trying to figure out a issue with a med duty single axle dump truck that has hydro breaks with a electric over hydrolic park break. its a 97 chevy cab kinda simular to like a top kick or kodiak but a bit older. its got a hydo boost break booster runs off the power steering made by bendex and a electric motor on the break booster witch i assume is how it apply the park break. have not spent more than a couple min looking it over so far but just got it pulled in and the snow melting off. any way the breaks seem to work good the park break mechanism seems to work good but when you release the parking break the the day time running lamps come on but then the park break light starts flashing on and off witch then flashes the day time running lamps flash on and off. the breaks are not actually applying. then after a little while the lights stop flashing and the service park break light comes on. this system is not something iv ever messed with fimillar with air breaks and hydo breaks but not hydro breaks trying to be air breaks. so if anyone knows this system. Quote Link to comment https://www.bigmacktrucks.com/topic/38885-med-duty-hydrolic-breakselectric-over-hydo-park-break/ Share on other sites More sharing options...
macattack Posted February 28, 2015 Share Posted February 28, 2015 check power steering fluid. hydro boosts run off your power steering pump.with your key on and engine off you should hear a buzzing coming from your hydro boost. park break switch?? Quote Link to comment https://www.bigmacktrucks.com/topic/38885-med-duty-hydrolic-breakselectric-over-hydo-park-break/#findComment-280896 Share on other sites More sharing options...
mrsmackpaul Posted February 28, 2015 Share Posted February 28, 2015 I have never seen any of these before but it sounds to me like a ground or negitive or what ever you call it is crook if all this started all of a sudden Paul Quote Link to comment https://www.bigmacktrucks.com/topic/38885-med-duty-hydrolic-breakselectric-over-hydo-park-break/#findComment-280899 Share on other sites More sharing options...
maint1 Posted February 28, 2015 Share Posted February 28, 2015 It has a an additional power steering pump on the right bank that only works the parking brake check the fluid in that unit, the stick will say check with brakes applied or released. ATF is fine to use. The chambers on the rear operate with a wedge that separates the shoes. Check all fluids, most of the problems I've had with them have been leaks.. Very expensive for wheel cylinders. 2 per rear wheel. Quote Link to comment https://www.bigmacktrucks.com/topic/38885-med-duty-hydrolic-breakselectric-over-hydo-park-break/#findComment-280901 Share on other sites More sharing options...
41chevy Posted March 1, 2015 Share Posted March 1, 2015 Seems the secondary pump is never checked for fluid on these systems. Yeah, most parts for the Hydro-Boost systems are pricey. I just did an Accumulator for one, only the leg to the knee costly . Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment https://www.bigmacktrucks.com/topic/38885-med-duty-hydrolic-breakselectric-over-hydo-park-break/#findComment-281107 Share on other sites More sharing options...
68-f-model Posted March 1, 2015 Share Posted March 1, 2015 I believe I have similar system on my single axle dump truck. The electric motor/pump on the master cylinder is a back up if the engine fails and you loose hydroboost it provides limited pressure boost for braking power. If you have a brake fluid leak it will run on and on before the engine is started with the key in the on position. It should shut of quickly once the system is up to pressure once the hydro boost and engine are running. Quote Link to comment https://www.bigmacktrucks.com/topic/38885-med-duty-hydrolic-breakselectric-over-hydo-park-break/#findComment-281126 Share on other sites More sharing options...
41chevy Posted March 1, 2015 Share Posted March 1, 2015 One important note. The system run up to 720 PSI. If you are going to get into it. Key off pump the brake pedal 20 to 25 times to dump the pressure in the system. Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment https://www.bigmacktrucks.com/topic/38885-med-duty-hydrolic-breakselectric-over-hydo-park-break/#findComment-281136 Share on other sites More sharing options...
Ezrider Posted March 11, 2015 Author Share Posted March 11, 2015 opps sorry i kinda forgot about this thread. it took a lot of poking around and messing with it to figure this thing out but turns out the actual park break pump setup is under the drivers step. park break has its own hydro pump and resivor then the actual mechanism works kinda like a maxi but uses hydro pressure to overcome the spring to unlock a drive line break. pressure sensor was bad causing the malfunction. Quote Link to comment https://www.bigmacktrucks.com/topic/38885-med-duty-hydrolic-breakselectric-over-hydo-park-break/#findComment-282252 Share on other sites More sharing options...
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