Disappearing brake fluid.

[pk]

Guys, ya gotta help me, my brake fluid is disappearing at the rate of 2 reservoirs full per week.
There are no external leaks. - No kidding, I have traced every pipe, hose, checked all 4 calipers, and no sign of fluid between master cylinder and booster.
The only other symptom is that when sitting at the lights holding on a hill, my brake pedal goes down very slowly.
Apart from that, the brakes are working perfectly.

Any ideas would be appreciated.

Regards

PK

[mudslinger]

wada bout checkin your proportionig valve? is that leakin. good mystery tho be interestin to hear wat it could be.

[geeves]

That quantity of fluid has to be going somewhere. The only places it could go without being obvious is out the back of the master cylinder and into the booster The only way to tell for sure if this is happening is to unbolt the cylinder from the booster.

[logger1]

I would agree with geeves if you have checked all cal and hose conections etc the only place it can go is into the booster unusual not to show signs wet front booster .
if you hold your foot on peddle and it goes slowly to the floor that would point us to the master seals .

cheers

where do u live ??

[pk]

Thanks for the help guys. My old 91 MU doesn't have a proportioning valve. Pulled the master cylinder off and found some fluid weeping out the back of the cylinder. Seal between cylinder and booster was upside down, so telltale hole at top of joint. Waiting for a kit to come in at the moment. Have to drive my wifes Subaru Forrester, or sons WRX. Damn.

[geeves]

Did you price a new master cylinder at the same time. Sometimes the cost of a new cylinder is so close that it is not worth mucking round with a seal kit.

[ken]

Just had the same problem with my 94 Bighorn. It had been sitting in the garage for two or three weeks when I noticed some nice clean oil on the floor, and the brake fluid level low. Finally found path of leak by looking under the wheel arch.
Interesting prices for a new master cylinder. Kit sets are not available. Local spares shop $210. Christchurch spares shop quoted $120 but when I went in to get one it was $520!!! I told them I would check the wreckers. I went back home and took the thing to bits as much as I could, cleaned it up reasembled it and surprise surprise - no leak.
Makes you wonder how they determine spare part prices.
Ken

[pk]

Looks like the ABS shop in Hobart has a different parts list to others.
2 master cylinder kits available for imported Isuzu's.
15/16" bore is K8588X for $22.00.
1" bore is K8586X for $22.00.
New cylinder around $186.00.
Mine was the 1" cylinder - put a kit in and no more problems - pig to bleed tho.

PK

[geeves]

Looking through the manual last night for something else I noticed the manual states these are not rebuildable. This probably means Isuzu didnt buy the spare parts but if you can get them after market and the bores are in good condition why not rebuild

[ken]

I was having trouble bleeding the brakes as well. A book out of the library said bleed each master cylinder outlet first by putting some tubing in each outlet and let it empty out into the reservoir under the oil level and pump it a few times. Some of the clear plastic tubing you can buy at a hardware shop fits nicely. After doing this bleeding at the wheel cylenders was easy.
Ken

[1logger]

with the new master it is easier to prime it on bench b4 istalation .
the bleed at the master is common in brake shops .
As to the kits they are avail but you only realy need seals I can get the 1" seal numbers and post if any 1 interested . and i will check the kits and replacement aftermarket master .

cheers jeff