Poor braking and a very stiff pedal

[grb184]

Hi all, looking for some advice.

On my 260z I have a very stiff brake pedal with minimal movement on it, and braking that I can only describe as poor

The previous owner had upgraded the from brakes to 2wd Cosworth Sierra calipers and disks and upgraded the master cylinder to a 1" Willwood. The booster is standard as far as I can see.

I had assumed it was a vacuum/booster issue.

However..
I have checked the vacuum from the inlet manifold and I am getting about 15-16 “Hg (inches of mercury) at idle;
Replaced all of the vacuum pipes;
Ensured the check valve is working properly; and
confirmed that the booster is holding vacuum (with my trusty vacuum pump)

any suggestions for my next move?

Thanks

 

[jonbills]

what does 'poor' braking mean? can you lock the wheels up if you try?

 

[grb184]

what does 'poor' braking mean? can you lock the wheels up if you try?

If I press with all my might I can just about get the car to lock up, but even just to stop have to press really hard and have no feel when braking

 

[Farmer42]

My first thoughts would have been booster but if you think it all checks out ok, the next port of call would be siezed caliper pistons.

 

[jonbills]

yeah agree with @Farmer42 , but I'd still try with the booster disconnected and vacuum hose plugged - is it worse or the same?
if it was the calipers seized, they'd stick on I think once you had moved them, so you'd expect hot calipers.

 

[Farmer42]

Could also be a siezed piston in the Master Cylinder. Again if all checks out ok after doing what Jonbills suggested, try bleeding the brakes and if the pedal goes to the floor when you release the bleed nipple that rules that out. Its a process of elimination I think starting with the booster, ending with the calipers. I would also check for crushed or collapsed brake pipes.

 

[johnymd]

First move would be as Jon suggests and rule out the servo. If when disconnected the braking is the same then it looks like the servo or servo rod.

I used my zed for a few weeks without the servo working. You could still stop the car fine but needed a lot of foot pressure.

 

[grb184]

First move would be as Jon suggests and rule out the servo. If when disconnected the braking is the same then it looks like the servo or servo rod.

I used my zed for a few weeks without the servo working. You could still stop the car fine but needed a lot of foot pressure.

Worse with servo disconnected hardly any brakes at all!

 

[jonbills]

Worse with servo disconnected hardly any brakes at all!

your servo works then

 

[MCBladeRun]

Are the rear brakes drums? Have you checked their adjusted properly? I thought they were also related to the entire system and no one has mentioned, shoot me down if I'm wrong though

 

[Rob Gaskin]

Has the braking been like this ever since you've owned it? Did you test drive it and if so was it the same? What does the previous owner (Dick?) say about the pedal feel?

I'm thinking that the calipers, master cylinder and existing Datsun components may not be compatible/matched.

However the pedal feel sounds just like the feeling you get if you have exhausted the vacuum from a system.

 

[Mark N]

It sounds like it could be an issue with either pedal travel or master cylinder piston travel.
If you unbolt the master cylinder and move it forward (if your brake lines permit), you should be able to depress the pedal and ascertain if there is anything restricting the movement between the pedal and the booster rod.
This will also give you a chance to check the rod adjustment length as well as check how it locates in the Wilwood master cylinder.
If the rod is too far forward or has engagement incompatibility with the master cylinder, it may be pushing the piston to where it bottoms out with very little pedal travel.

 

[grb184]

After a lot of toing and froing, and having taken lots of advice, finally had the servo and master cylinder replaced this week.

Decided to go with an upgrade to a Ford Ranger servo and master cylinder, has made the world of difference! ... I now have fully working brakes!

 

[Mark N]

What type of hose is that coming off the reservoir, is it EPDM or just standard fuel hose?

 

[grb184]

What type of hose is that coming off the reservoir, is it EPDM or just standard fuel hose?

I believe its EPDM brake hose

 

[Texasroadrunner]

My brake pedal used to be very firm with not much movement and a strong push was required. Last week I took a close look at the non-OEM vacuum check valve, tested it and it was good. What I found was
the rubber bushing in the booster can was very loose and seemed like a potential vacuum leak. I sealed it with 3M Super weatherstrip adhesive, rotated it until it started to dry. After plugging the check valve
back in, it felt secure. The next day I ventured down to a monthly show and shine about 30 minutes south. The brake pedal now seems easier to push and there is more actual travel. The braking is also
stronger. I'm sure that vacuum leak was the source of the booster not working like it should.

 

[arcdef]

After a lot of toing and froing, and having taken lots of advice, finally had the servo and master cylinder replaced this week.

Decided to go with an upgrade to a Ford Ranger servo and master cylinder, has made the world of difference! ... I now have fully working brakes!

View attachment 47324

Is this a common 'upgrade' ?

 

[grb184]

Is this a common 'upgrade' ?

Was something my friend had done to his Sam at our local garage, so I was just copying him!

I believe it was on the basis of a discussion and recommendation by Dave Jarman

You have to use a specific year and model though mine was from a 2008 Ford Ranger Wildtrack 3litre manual gearbox (I believe it has to be the manual as the linkage is longer)