Brake booster test

[dom14]

Hi guys,
I just did a brake booster test on my RB30 GQ Patrol.

I used the test procedure from Haynes repair manual.
I attached the procedure as a PDF file here.

Here are the results.
If I follow the numbers as in the Brake Booster Check in the document.

21)With the engine stopped, depress the brake pedal several times
The travel distance should not change
Travel distance does change.. Travel distance decreases on each pedal depress. After around 5 presses or so, the brake pedal gets really hard and doesn't go down much. This happened when I did the test in different times(day)
The car was left alone over night or all day before I did this part of the test

22)With the brake fully depressed, start the engine- the pedal should move down a little
when the engine starts.
Yes, test performed as above.

23)Depress the brake, stop the engine and hold the pedal in for about 30 seconds -
the pedal should neither sink nor rise.
Yes the test performed as above

24)Restart the engine, run it for about a minute and turn it off. Then firmly depress the brake
several times - the pedal travel should decrease with each application.
Yes. the test performed as above.

So, other than the very first part of the test( No 21), the test performed ok.

How do I interpret this test result, guys?
Do I have a brake booster or vacuum line issue(either intermittent or permanent)?

Thanks in advance for any assistance.

[Rumcajs]

Mate,Travel distance does change.
If you had a booster vacuum leak it would change the idle RPMs (petrol engines only) every time you put foot on the brake.

When you say

Travel distance does change.

does that mean you can push the pedal down further or less? To me there seem nothing wrong unless you have intermittent problem.

If the engine is not running and all vacuum pressure has been exhausted and the pedal travel changes repeatedly then the problem is in the hydraulic section not the boost/vacuum.

Ignoring the first issue all the other ones suggest no issue in the brake booster section.

If your pedal "sinks" with no booster vacuum applied and pressure maintained then you have possibly master cylinder issue.

Regards

[dom14]

Mate,Travel distance does change.
If you had a booster vacuum leak it would change the idle RPMs (petrol engines only) every time you put foot on the brake.

When you say does that mean you can push the pedal down further or less? To me there seem nothing wrong unless you have intermittent problem.

If the engine is not running and all vacuum pressure has been exhausted and the pedal travel changes repeatedly then the problem is in the hydraulic section not the boost/vacuum.

Ignoring the first issue all the other ones suggest no issue in the brake booster section.

If your pedal "sinks" with no booster vacuum applied and pressure maintained then you have possibly master cylinder issue.

Regards

I meant I can push the pedal down less and less until it gets hard(the no 21, first part of the test).
This is how it reacts every time I do the No 21 test when the engine is cold and not running.
Since, there shouldn't be any vacuum in the booster and vacuum lines, I'm puzzled with that reaction
of the brake pedal.
I must insist, I was depressing the pedal moderately hard.

[Rumcajs]

You are pumping your brakes, this means that there is air present or fluid is badly contaminated. This is hydraulic issue not the brake booster circuit.
When was the brake fluid last time changed? You need to check/bleed the hydraulic circuit.

Regards

[dom14]

You are pumping your brakes, this means that there is air present or fluid is badly contaminated. This is hydraulic issue not the brake booster circuit.
When was the brake fluid last time changed? You need to check/bleed the hydraulic circuit.

Regards

I had to replace the front righthand side caliper hose & rebuild the caliper late last year.
I rebuilt the caliper first when one of the slide pins jammed.
I used the same pin, but polished inside the pin hole and pin with valve grinding grease.
Then the caliper hose was leaking, so I had to replace that as well.
I've never replaced brake oil, only topped it up during those leaky times.
I blocked the brake oil hose at the center of the front brake line to do the repair.
Then I bled the right hand side only(I couldn't see the need to bleed the other side at that time).

Do I need to clean the brake lines by draining all the oil?

[Rumcajs]

You didn't finish the job right, always bleed whole system especially when replacing hose/s rebuilding caliper/s.
I suggest that you do complete brake fluid replacement with proper bleeding procedure or in the interim just bleed the whole system first.
The brake fluid should be replaced every 2 years, it is also good practice to replace it too when replacing/rebuilding any part of the hydraulic system.

Regards

[dom14]

You didn't finish the job right, always bleed whole system especially when replacing hose/s rebuilding caliper/s.
I suggest that you do complete brake fluid replacement with proper bleeding procedure or in the interim just bleed the whole system first.
The brake fluid should be replaced every 2 years, it is also good practice to replace it too when replacing/rebuilding any part of the hydraulic system.

Regards

Crxp!!! Ok, cool. If I understood correctly, there's an apparent gunk build up inside the brake lines.
And I need to flush the brake lines properly.
I had no idea the brake fluid need draining and replacing like that.
When I was bleeding the van, there was lot of gunky dark brake fluid coming out of it,
so I bled the whole thing, taking my time.
I didn't think Patrol needed that, 'cos I drive it all the time, but apparently that's not the case.

So, I shouldn't use the old brake oil at all, right?

Thanx mate

[Bigcol]

as above Dom,
best way to go is buy a BIG bottle of brake fluid
undo the nipple on the passenger rear
pump ALL the fluid out (into a container) - just keep pumping the pedal and keep going for a bit after the Master Cylinder is empty

when your happy, add new fluid
keep pumping
when thats empty
fill up again, and get a mate to help you bleed the brakes properly
none of this Supercrap "self bleeding kits"
get a mate on the spanner
3 pumps on the pedal, holding pedal on the third pump - let the fluid out - pedal goes to floor, mate locks bleeder nipple, pump again, and again and again
(I always go for 3 or 4 times per wheel, until new clean fluid is coming out )

ALWAYS start at the nipple furthest away from Master Cylinder
so
passenger rear
drivers rear
passenger front
drivers front

if your getting AIR or crappy old fluid - keep going until its clean new fluid with NO air

[dom14]

as above Dom,
best way to go is buy a BIG bottle of brake fluid
undo the nipple on the passenger rear
pump ALL the fluid out (into a container) - just keep pumping the pedal and keep going for a bit after the Master Cylinder is empty

when your happy, add new fluid
keep pumping
when thats empty
fill up again, and get a mate to help you bleed the brakes properly
none of this Supercrap "self bleeding kits"
get a mate on the spanner
3 pumps on the pedal, holding pedal on the third pump - let the fluid out - pedal goes to floor, mate locks bleeder nipple, pump again, and again and again
(I always go for 3 or 4 times per wheel, until new clean fluid is coming out )

ALWAYS start at the nipple furthest away from Master Cylinder
so
passenger rear
drivers rear
passenger front
drivers front

if your getting AIR or crappy old fluid - keep going until its clean new fluid with NO air

Cool, thanx mate. Obviously I did a dodgy job last time.
It's time to get my butt cracking this time.
Cheers

[Rumcajs]

I would not waste time to pump the system empty first, just empty/evacuate the reservoir and top up with new fluid and keep bleeding/pumping until new fluid comes out, regularly topping up reservoir with new fluid that way you avoid creating unnecessary air locks as well which will actually speed up the job .

Don't mix different grade brake fluids though.

Regards