Thread: HITACHI ALT160502 Alternator

The saga continues ... the vacuum booster adjuster is set correctly, I purchased a vacuum tester to make sure the booster isn't faulty, it isn't.

Out of curiosity I connected the vacuum tester directly to the alternators vacuum, oil filled the line to the tester at 3 atmospheres, I may have found the problem with the brakes ... I hope.

Glenn

Sounds like the hoses are around the wrong way on the vac pump.

The hoses are on correctly, vacuum when the engine runs is 25 atmospheres, after more tests with the vacuum gauge (by-passing the diff lock). the vacuum pressure falls until the pedal hits the floor, pressure stays down until the pedal is released.

Glenn

Something is not tallying up.

It is virtually impossible to reach even 1 atmosphere of vacuum, i.e. an absolute pressure of zero. 25 atmospheres is equivalent to 367 psi.

I suspect your vacuum gauge is more likely calibrated in inches of water, or inches of mercury (Hg). 25 inches of Hg is approx 0.84 atm or 12 psi which is a lot of vacuum.

Hi

I have a similar problem with my Isuzu County, brake pedal rock hard, ( not
sinking to the floor.)
The vehicle has been converted to disc brake rear and has defender m/c and booster. Checked vacuum to the booster and when connected can only get 3 to 5 "Hg,( from vac pump only get 21 "Hg.)
Purchaced dual stage D1 booster from wreckers in Perth and when connected directly to vac pump get zero vacuum and can hear a hissing noise from inside the booster. Removed booster from my 95 defender and when connected directly to vac pump same problem as D1 booster, ( Defender has been parked up for a few years but brakes were fine when last driven ) Connected a 82 Range Rover booster direct to vac pump and it will hold full vacuum eg 21"Hg.
I now most likely have 3 unservicable brake boosters but I will do a few more checks before buying a new booster for the county and defender.

Mocky

Originally Posted by Mocky

Hi

I have a similar problem with my Isuzu County, brake pedal rock hard, ( not
sinking to the floor.)
The vehicle has been converted to disc brake rear and has defender m/c and booster. Checked vacuum to the booster and when connected can only get 3 to 5 "Hg,( from vac pump only get 21 "Hg.)
Purchaced dual stage D1 booster from wreckers in Perth and when connected directly to vac pump get zero vacuum and can hear a hissing noise from inside the booster. Removed booster from my 95 defender and when connected directly to vac pump same problem as D1 booster, ( Defender has been parked up for a few years but brakes were fine when last driven ) Connected a 82 Range Rover booster direct to vac pump and it will hold full vacuum eg 21"Hg.
I now most likely have 3 unservicable brake boosters but I will do a few more checks before buying a new booster for the county and defender.

Mocky

Defender boosters are known for cracking around where the M/C bolts on, so have a look around there.
I know some boosters rely on the master cylinder to seal, (pretty sure both Defender and D1 are like that) and I recall someone recently that had fitted a new booster, but was missing the O ring that seals the M/C to booster, so had huge vacuum leak.

BTW - the D1 dual stage boosters and M/C are the ducks nuts for a rear disc County

Steve

Glenn

Does your rangie have daul brake system (2 lines to each front caliper)?

Jim

Originally Posted by yt110

Glenn

Does your rangie have daul brake system (2 lines to each front caliper)?

Jim

Sure does, Pat the mechanic and I couldn't find anything wrong there ... what's on your mind Jim?

Bush65 I'm sorry if I incorrectly referred to atmosphere of vacuum instead of inches of mercury (Hg), I'm not used to these references yet and thought (Hg) was atmospheres.

I managed to talk with Brian at Land Vehicle Spares in Silverdale, he recons I've got a dodgy Master Cylinder, and it isn't unusual to have a bit of oil in the vacuum line, the vacuum keeps the oil away from the Booster.

I'll keep you informed how the saga progresses.

Glenn