There is a one way valve on the reservoir tank to the outlet port connecting to the brake booster. It mostly got clogged by oil ruin the seal inside the one way valve so the one way valve no longer served its duty.
putting a vacuum gauge at the vacuum pump and then if plenty of vacuum there ( 30 in or more ) , put the guage on the hose that leads to the booster , if vac is lower there it could be a leaking hose , blocked hose or blocked check valve.
Hi alex, watcing the gauge , it builds up vacuum fast enough ok, 30hg inches of mercury is plenty, seen many truck run at 25hg with no problems, you should get at least 5-6 pumps on the pedal with the engine off and still work at 15hg, and on the gauge the vac is depleted very quick on the brakes, check th lines, has it got reservoir tank,if so there could be a blockage at the tank, if this doesnt help then i would install one on the chassis, then you would have plenty for brake/clutch
Alex, on this truck, the vacuum pump is on the back of the starter motor, its a drag to fix,, you can buy that part separately, or look into replacing the seals inside it, its a very difficult unit to fix, like i said, but it can be done.
Alex were you able to fix it? I have a 1993 FB Hino I'm working on brakes aren't working well. In wet weather I noticed the fronts would lock up & slide so I started thinking the rears weren't holding very well. The brake pedal gets hard about 1/2 way down I pump pedal & it get hard near the top & hard to stop truck. And 29-30 inches of vac is the max vac.
one pump increases pedal resistance dramatically. if you pump the brake once, then try to clutch, you dont have enough assistance :) im starting to think my original diagnosis at the customers premise was correct.. vacuum fault caused by weak pump!
Having the same problem with my isuzu elf truck. Brake and clutch gets extremely hard when the truck starts up and you hit the break pedal a few times. There is a leak in my hydrologic break hose, havent replaced it yet but i am wondering if thats the culprit, and also the hose which supplies oil from the engine to the alternator is kinked so i am wondering if enough oil isnt being supplied to the alternator to allow the vacuum pump to work at full capacity.
As a non mechanic i would see how fast the pressure drops when the engine is off, and not touching the brake/clutch. If it stays up then at least there are no bad leaks. Is the pump on a direct drive system or some kind of pressure controlled clutch. Are you being conned by a double failure in the clutch/break ? I see what you mean, it does not have a quick enough recovery to deliver constant pressure, are the lines from/to the tank kinked and restricting the recovery? hmm..
Hey what's up Alex's, I have a Hino 2001 for some reason it won't take speed, I thought it was gas fuels but it's not cause I just change them. What is the problem you think might be?
I find vacuum systems very hard to understand as everything is in reverse. Only thing i know about vacuum pumps is they usually need oil running in their system to work, without it they lose ability to seal, sort of like rotary screw compressors. I think these may use oil from the engine, just a mist and put it back but to be honest i have never investigated one so stabbing in the dark.
already thinking the second hand route for the customer benefit as a "test" subject, but also, the problem with the truck wreckers here, they have the supremist attitude as they are the only truck wrecker in the area, and will charge you, two axles, an arm, a leg, and a gearbox, for a simple vacuum pump :)
Yes it gets odd, and if you include the local air pressure on this planet, the understanding gets odder lol. I choose to ignore planet air pressure, and its suction and not negative pressure in respect to....lol. I find the same mental block with switching negative wires instead of positive, im odd that way :-)
it does have a vacuum tank, and at reasonable revs, the problem still exists, therefore the diagnosis of the pump being faulty becomes even more valid.
have leak tested.. no leaks that i can find. pump is directly driven by the engine via a gear. the clutch works fine if you dont touch the brake first, as there is enough assistance, without the vacuum assist, you better start going to the gym and work that leg 5 times a week :) the double failure idea.. yes i am being conned, by the owner of the truck who thinks it will be fixed for $50 :) afaict, the only failure point which would cause these problems is the pump, but its a $1000 gamble :)
what was the end result mate? My 2003 Dutro's having the same issues I have a spare cylinder sitting here debating whether or not to change it over...
Got similar issue. Was told by local mechanic that if your brakes are too low they will travel long distance to get to touch the drum and they will use alot of air
If the clutch has plenty of vacuum assistance but the brake doesnt you have to ask if the brake booster diaphragm is leaking , if you put an inline regulator on a compressed air line and pressurize the brake booster with 30 - 50 in/mercury it should maintain pressure as long as the brake pedal is up ??? Is the clutch and brake Tee'd on to the same line in series or do they have a check valve on one of them ?
im worried that taking it apart, it is sectioned, may render it completely inorperable.. i dont want the customer accusing/blaming me for an immobile truck, even though its out of work in its current state.. for $1000 i want to get the customers OK first :) convincing him to risk that, is another problem, as even with all my experience, ive never had this particular problem before, even though im 90% sure :)
by the way, the brakes dont have enough assistance to stop the truck when loaded, so that tells me it needs more vacuum, but the pump is lazy, cannot provide it.
There is a one way valve on the reservoir tank to the outlet port connecting to the brake booster. It mostly got clogged by oil ruin the seal inside the one way valve so the one way valve no longer served its duty.
putting a vacuum gauge at the vacuum pump and then if plenty of vacuum there ( 30 in or more ) , put the guage on the hose that leads to the booster , if vac is lower there it could be a leaking hose , blocked hose or blocked check valve.
I’m going through the same thing hoping you would’ve had an answer
Hi alex, watcing the gauge , it builds up vacuum fast enough ok, 30hg inches of mercury is plenty, seen many truck run at 25hg with no problems, you should get at least 5-6 pumps on the pedal with the engine off and still work at 15hg, and on the gauge the vac is depleted very quick on the brakes, check th lines, has it got reservoir tank,if so there could be a blockage at the tank, if this doesnt help then i would install one on the chassis, then you would have plenty for brake/clutch
I do also have the same problem with my hino 300 713, the brake pedal is depressed 2 to 3 times in order to stop the truck.
any progress? 5 years I know, but I have a Dyna, and I lose clutch engagement, and it holds in gear as well.
Alex, on this truck, the vacuum pump is on the back of the starter motor, its a drag to fix,, you can buy that part separately, or look into replacing the seals inside it, its a very difficult unit to fix, like i said, but it can be done.
some models have the vac on the back of the starter and others have it on the back right side of the engine block
Alex were you able to fix it? I have a 1993 FB Hino I'm working on brakes aren't working well.
In wet weather I noticed the fronts would lock up & slide so I started thinking the rears weren't holding very well. The brake pedal gets hard about 1/2 way down I pump pedal & it get hard near the top & hard to stop truck.
And 29-30 inches of vac is the max vac.
one pump increases pedal resistance dramatically. if you pump the brake once, then try to clutch, you dont have enough assistance :) im starting to think my original diagnosis at the customers premise was correct.. vacuum fault caused by weak pump!
I had a rotted 2" rubber hose I had to locate. Once I replaced it, it was working perfectly. It just takes a hole. The hoses are only rubber.
Having the same problem with my isuzu elf truck. Brake and clutch gets extremely hard when the truck starts up and you hit the break pedal a few times. There is a leak in my hydrologic break hose, havent replaced it yet but i am wondering if thats the culprit, and also the hose which supplies oil from the engine to the alternator is kinked so i am wondering if enough oil isnt being supplied to the alternator to allow the vacuum pump to work at full capacity.
As a non mechanic i would see how fast the pressure drops when the engine is off, and not touching the brake/clutch.
If it stays up then at least there are no bad leaks.
Is the pump on a direct drive system or some kind of pressure controlled clutch.
Are you being conned by a double failure in the clutch/break ?
I see what you mean, it does not have a quick enough recovery to deliver constant pressure, are the lines from/to the tank kinked and restricting the recovery?
hmm..
Hey what's up Alex's, I have a Hino 2001 for some reason it won't take speed, I thought it was gas fuels but it's not cause I just change them. What is the problem you think might be?
Alex's do you think it might be gas sensor or the ABS might go bad on it? And it's desiel.
I find vacuum systems very hard to understand as everything is in reverse. Only thing i know about vacuum pumps is they usually need oil running in their system to work, without it they lose ability to seal, sort of like rotary screw compressors. I think these may use oil from the engine, just a mist and put it back but to be honest i have never investigated one so stabbing in the dark.
already thinking the second hand route for the customer benefit as a "test" subject, but also, the problem with the truck wreckers here, they have the supremist attitude as they are the only truck wrecker in the area, and will charge you, two axles, an arm, a leg, and a gearbox, for a simple vacuum pump :)
Did you sort it out? Servo.....
rotary vane pump, a similar model had a recall because the pumps failed prematurely.. maybe this one has had its time :)
Yes it gets odd, and if you include the local air pressure on this planet, the understanding gets odder lol.
I choose to ignore planet air pressure, and its suction and not negative pressure in respect to....lol.
I find the same mental block with switching negative wires instead of positive, im odd that way :-)
Just got the same problem today..got no brakes and clutch either
No idea Alex. I thought brakes are normally by vacuum pump and clutch is hydraulic or mechanical.
you might want to check for leaks, but the pump is probably bad. look for a good second-hand part instead?
it does have a vacuum tank, and at reasonable revs, the problem still exists, therefore the diagnosis of the pump being faulty becomes even more valid.
have leak tested.. no leaks that i can find. pump is directly driven by the engine via a gear. the clutch works fine if you dont touch the brake first, as there is enough assistance, without the vacuum assist, you better start going to the gym and work that leg 5 times a week :) the double failure idea.. yes i am being conned, by the owner of the truck who thinks it will be fixed for $50 :) afaict, the only failure point which would cause these problems is the pump, but its a $1000 gamble :)
Did you ever resolve this problem? A friend of mine just bought a truck like this and it is having the same problem........
what was the end result mate? My 2003 Dutro's having the same issues I have a spare cylinder sitting here debating whether or not to change it over...
Got similar issue. Was told by local mechanic that if your brakes are too low they will travel long distance to get to touch the drum and they will use alot of air
Same problem with my Heino truck does anybody have a clue or are we throwing sand into the wind here
If the clutch has plenty of vacuum assistance but the brake doesnt you have to ask if the brake booster diaphragm is leaking , if you put an inline regulator on a compressed air line and pressurize the brake booster with 30 - 50 in/mercury it should maintain pressure as long as the brake pedal is up ???
Is the clutch and brake Tee'd on to the same line in series or do they have a check valve on one of them ?
Crack in vacuum tank maybe ,very common with hino 300
have you had a look on ebay for the workshop manual on cd, cheap enough and it might have the vacuum specs
Don't know anything about lorries so I'll just do a bit of moral boosting:
You'll fix it good in the end mate!
great idea, but not a fix i would present to the customer unless the mechanical replacement was not available
did Hino have a pump rebuild kit with Vanes and seals ? best to strip the pump first though and make sure the casting isnt scored up internally
im worried that taking it apart, it is sectioned, may render it completely inorperable.. i dont want the customer accusing/blaming me for an immobile truck, even though its out of work in its current state.. for $1000 i want to get the customers OK first :) convincing him to risk that, is another problem, as even with all my experience, ive never had this particular problem before, even though im 90% sure :)
Hino 500,, truck not moning,, when gear Is enguage,,
by the way, the brakes dont have enough assistance to stop the truck when loaded, so that tells me it needs more vacuum, but the pump is lazy, cannot provide it.
maybe the vac pump is a bit tired??
both in this case are vacuum assisted hydraulic!
maybe get 2 electric vac pumps and a tank to replace the tired mechanical vac pump???
it depletes very quickly.. one pump of the clutch and it starts to lose assistance already. it has a reservoir tank already from the factory
2012 fuso truck new clutch very hard
great idea.. i had considered this :)
Pedal going down
Too much noise can't hear you