GQ patrol brake system problems

[antpoo69]

i have a 91 model 4.2 turbo diesel patrol and im having some brake system issues.

It started out with the brakes going hard and not working very well wen stopping on steep hills. so i thought it may be a problem with the vacuum system so i checked the system for leaks and everything was fine. i changed all the hoses just incase there was a split somewhere that was leaking under heavy braking.

once all the hoses were done i started the car and now when i push on the brake pedal it slowly goes to the floor. which indicates to me that the master cylinder is no good. i had a spare master cylinder so i changed that aswell. blead the whole system and the problem is still there.

does this mean both master cylinders are no good or am i not bleeding the brakes enough.

Any help would be much appreciated

[Dan570]

I have been through this problem hust recently my self and solved the problem be removin the rear proportioning valve above the diff it does have a bleeder on it but made no differance to the brakes friends told be to remove it and it work.Made the brakes work the best they ever have,or you can replace it with a new one if you want to keep it the same as nissan intended.Good Luck

[Clanky]

I had a heap of dramas bleeding the brakes on mine. In the end I took it to a brake place and had them bleed them. Same as yours they were spongy.

Just another thought for you, when you said you changed hoses, were they brake lines or vacuum lines?

If vac hoses, is the non return valve in the right way around?

I have also heard about brake lines collapsing internally and can cause brake problems too, but not necessarily the same symptoms as you have.

I would let someone have a bleed.

P.S Was that spare master cylinder you had new? It might be knackered as well. I just had a brand new slave cylinder cause me untold dramas on the clutch. Put another one in and no more problem. Just a thought

[stevohanko7]

gday i am having the same problem with my 97 gq diesel wagon i have changed the master cylinder and all the flexy lines and the peddal still goes to the floor when the car is runnig but is firm when not running i thought it could be a booster problem has anyone had something simmilar happen to them and fixed it

[Clanky]

Take it to a brake place and have them use the vac sucker doo-dad on it. It only cost $60 to do

Mine is a 95 model and its the pits for bleeding up from scratch with air in the system. I rebuilt all the calipers etc and couldnt get the air out by manual bleeding. From memory it was the rear brakes I couldt get the air out of. Front were ok

If you are still keen to sort it yourself, there is a bleeder nipple on the proportioning valve above the rear diff. Might be a place to start

[bilby]

i have a 91 model 4.2 turbo diesel patrol and im having some brake system issues.

It started out with the brakes going hard and not working very well wen stopping on steep hills. so i thought it may be a problem with the vacuum system so i checked the system for leaks and everything was fine. i changed all the hoses just incase there was a split somewhere that was leaking under heavy braking.

once all the hoses were done i started the car and now when i push on the brake pedal it slowly goes to the floor. which indicates to me that the master cylinder is no good. i had a spare master cylinder so i changed that aswell. blead the whole system and the problem is still there.

does this mean both master cylinders are no good or am i not bleeding the brakes enough.

Any help would be much appreciated

Check the slave cylinder is shagged , its under the car beside the exhaust , you will see it , its covered by a heat sheild

[351ciofgrunt]

once all the hoses were done i started the car and now when i push on the brake pedal it slowly goes to the floor. which indicates to me that the master cylinder is no good. i had a spare master cylinder so i changed that aswell. blead the whole system and the problem is still there.

does this mean both master cylinders are no good or am i not bleeding the brakes enough.

Any help would be much appreciated

Check the slave cylinder is shagged , its under the car beside the exhaust , you will see it , its covered by a heat sheild

umm the slave cylinder is clutch related, he's talking about a problem with his brakes....

[HeathGQ]

have a look at the Brake Bias valve on top of the rear diff. Found mine was shagged after similar issues after changing master cylinder.

[Renton]

gday i am having the same problem with my 97 gq diesel wagon i have changed the master cylinder and all the flexy lines and the peddal still goes to the floor when the car is runnig but is firm when not running i thought it could be a booster problem has anyone had something simmilar happen to them and fixed it

If the pedal goes to the floor you need a new booster

[bilby]

umm the slave cylinder is clutch related, he's talking about a problem with his brakes....

i shouldnt post after an long arvo pub session

[croozer]

Had similar problem with mine found it was a vaccuum leak at the clutch booster relaced the front seal and was all good.
Just re read your post my brake pedal was hard not sinking to the floor.