Reply With QuoteIME pedal going to the floor slowly usually means the mc is leaking fluid back into the reservoir. There won't be any fluid loss when this happens.Originally Posted by The Mutt
Anyone know the vacuum reading of the HITACHI ALT160502 Alternator, I'm having brake problems.
We have a 1988 Rangie with an Isuzu 4BD1 fitted with a HITACHI ALT160502 Alternator.
When the brakes went out I replaced the Brake Booster (broken bits inside)
Then when the motor is running the brake pedal slowly meets the floor, with the motor off the brake pedal is hard, I then replaced the Brake Master ... same problem (looks like I have the old Brake Master for backup)
Re-bleed the lines at the Brake Master then at each wheel starting with the furthest from the Master again (so far the system has been bleed 6 times)
When the problem continued I then got a mechanic mate to help.
We then tested the vacuum (over 25 in Hg vac) where the vacuum hose connects to the Booster
Next we inspected each flexible hose for bulging followed by clamping each flexible hose one at a time ... still got that sinking feeling.
As we still run the 4-speed gearbox I removed the vacuum line that goes to the transmission lock and connected the vacuum gauge at the 'T' junction ... with the engine running and the brake pedal untouched the reading is around 25, when I pump the brakes the reading goes around 5, when the pedal is held firm the reading very very slowly goes to 25 all the while the brake pedal slowly tries to meet the floor, are these normal vacuum readings?
The brake fluid is not getting any lower so there is no leaks
When the motor is running and the pedal is depressed removing the vacuum line from the Booster makes the brake pedal go up and hard ... no viagra jokes please.
In my mind it must be either the vacuum booster or the alternator vacuum.
Any ideas from the brains trust??????
Glenn
Swaggie
IME pedal going to the floor slowly usually means the mc is leaking fluid back into the reservoir. There won't be any fluid loss when this happens.
I forgot to mention we removed all the brake lines from the master cylinder and replaced them with bolts, the pedal stayed hard.
Glenn
RoverLord
it can also mean that the booster is not sealing in the rest position, moving it away from its stops lets it close up and then the engine begins to pull vac down, this then lowers the pedal.
do it with the engine off and if it keeps creeping down you have either MC recirculation or the fast fill ports are not closing off.
I have also seen
the vac lines going porus
the one way check valve leaking
the seal that holds the check valve leaking
the line to the vac switch for the diff lock damaged
the vac switch not closing off correctly
the diaphragm split on the gear box
the line off on the diaphragm for the high range side.
Dave
"In a Landrover the other vehicle is your crumple zone."
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it can also mean that the booster is not sealing in the rest position, moving it away from its stops lets it close up and then the engine begins to pull vac down, this then lowers the pedal. How do I fix this?
do it with the engine off and if it keeps creeping down you have either MC recirculation or the fast fill ports are not closing off. Pedal stays hard
I have also seen
the vac lines going porus If I have any spare pipe I'll replace it Tommorrow
the one way check valve leaking The new Booster didn't have a valve, I bought an new in-line valve that tested OK
the seal that holds the check valve leaking In-line with new cable clamps
the line to the vac switch for the diff lock damaged I replaced the diff lock with the vacuum tester at the 'T' junction
the vac switch not closing off correctly
the diaphragm split on the gear box
the line off on the diaphragm for the high range side.
OldBushie
Rubber brakes hoses expanding?
Already checked the hoses they looked at them held them with my hand while the pedal was applied, No swelling obvious.
Glenn
I think Dave's on the money here. This is the only thing that would cause the brake pedal to depress with the engine on. This is fixed by adjusting the push rod in the Servo. You'll need to remove the master cylinder then adjust the reach of the push rod so that there is 1/16" free play between the push rod and the Master Cylinder plunger (brake pedal up). It's a bit of a measurement headache.
TopicToaster
How do you adjust the push rod? I had my MC off the booster half an hour ago trying to do just that, the shaft is slick apart from the thread and I didn't want to score the shaft. Just grip it with vice grips and not worry about scoring? I think the nut and end of the shaft have burred into one mass anyway
Please don't tell me the push rod is keyed to not rotate or similar
Not all brake servos allow push rod adjustment and yours may be one of those. There should be a hex head screw that screws into the threaded push rod something like the photo below. When adjusting I did have to grip onto the shaft of the push rod while turning the screw but it wasn't a particularly tight thread that caused any grief.How do you adjust the push rod? I had my MC off the booster half an hour ago trying to do just that, the shaft is slick apart from the thread and I didn't want to score the shaft. Just grip it with vice grips and not worry about scoring? I think the nut and end of the shaft have burred into one mass anyway
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