Break job from H _ _ _ _ ! (Page 2/2)
Signupacct SEP 18, 12:02 AM
You have made two comments that are worth noting. First, you are not the first to mention how a brake system component can draw in air even and not have a visible leak. A very experienced long time mechanic mentioned that the calipers can do this, not leak but draw air in. I replaced the front calipers with a second set and didnt help.

I replaced the driver side front hard line for concerns regarding flow. So if that is replaced, then is it possible that the passenger side front hard brake line could be bringing air in. Assuming that because the rear brakes bleed okay and have a decent pedal until going to the front to bleed which is where it all goes bad.

Can we focus on this before discussing the proportioning valve which is no longer OEM but is a Wilwood with the Knob to adjust the amount going to the rear.

Joe k

https://www.wilwood.com/mas...rod?itemno=260-11179

[This message has been edited by Signupacct (edited 09-18-2024).]

Patrick SEP 18, 12:12 AM

quote
Originally posted by Signupacct:

...is it possible that the passenger side front hard brake line could be bringing air in?



If you haven't already done so, it might help to get a good look at the passenger side front hard brake line if the front tub has been removed.

[This message has been edited by Patrick (edited 09-18-2024).]

cartercarbaficionado SEP 18, 07:48 AM

quote
Originally posted by Signupacct:

You have made two comments that are worth noting. First, you are not the first to mention how a brake system component can draw in air even and not have a visible leak. A very experienced long time mechanic mentioned that the calipers can do this, not leak but draw air in. I replaced the front calipers with a second set and didnt help.

I replaced the driver side front hard line for concerns regarding flow. So if that is replaced, then is it possible that the passenger side front hard brake line could be bringing air in. Assuming that because the rear brakes bleed okay and have a decent pedal until going to the front to bleed which is where it all goes bad.

Can we focus on this before discussing the proportioning valve which is no longer OEM but is a Wilwood with the Knob to adjust the amount going to the rear.

Joe k

https://www.wilwood.com/mas...rod?itemno=260-11179





check that line. also I just faced this issue today but with the rears while noting my 84s pedal felt...off? so I smacked the master cylinder hard with a hammer and heard a pop and the pedal went to normal so I guess the seals can stick on new masters if made particularly poorly
the other thing is I needed to bleed before the soft lines before I got fluid out of them because of the large volume of air causing a lock so also bleed by cracking every fitting down the line and seeing where the fluid doesn't progress any
Yellow-88 SEP 18, 09:29 AM

quote
Originally posted by Signupacct:

So the work began.
New rotors pads discs calipers and new master cylinder and new S10 booster. And also new SS brake hoses from fiero store. We also used Rodney Dickman booster kit and bought both adapters and even clicked on the link on his page to buy the S10 booster from Summit racing. Based on measurements in the support material one of the extension rods was chosen and the S10 booster and pedal brake rod was nearly identical in length as the oem.

After flushing out the system and lines etc we try to bleed
the brakes we get good results after bleeding the rear brakes good pedal and then go to the front right wheel and first bleeding we get fluid and air, close the bleeding valve and lose the pedal we had and nothing comes out of the line when the bleeder valve is re-opened.




There might be something here. First, the vacuum booster is not part of the "hydraulic" brake system so we can ignore that. Your using stock hydraulic parts except the SS flex lines and a Willwood proportioning valve. You can ignore the SS lines.

A "good" peddle (Solid, no sponge at all?) after bleeding just the rear is pointing to something.

".... front right wheel and first bleeding we get fluid and air, close the bleeding valve and lose the pedal we had and nothing comes out of the line when the bleeder valve is re-opened. Can you please explain this a little better.

The Willwood valve is the only thing not stock and is related to front-rear "issues". Did it come with detailed installation instructions?

Also mentioned is bench bleeding the master cylinder. That is necessary on a new one. A master cylinder test would be to plug the ports. You should have a rock solid peddle with the ports pluged. You can make plugs with a fitting and a flattened break line. It is rare but brand new parts can be defective.
Signupacct SEP 21, 11:04 PM

first thanks to everyone who has weighed in on this.

Yes I did bench bleed the master cylinder following the instructions enclosed on the box. Yes I am following the furthest from the master cylinder first taking into consideration the brake splitter on the rear etc.

LR to RR to FR to FL

I am taking into consideration the different suggestions and will report back tomorrow.

I have noted the isolating the different sections and in the process of that now.

The one comment that if the pedal has to be pumped up that it is likely a symptom of a master cylinder

Joe k
Signupacct SEP 22, 03:52 PM
Is this the functionality of the OEM fiero master cylinder ?

https://www.youtube.com/watch?v=I8kzs_55Uo0\\

If so this may explain some of what symptoms I am seeing with this

btw some of this functionality is attributed to the proportioning valve and I had read that the fiero is really a combination valve and that the fail safe functionality is what is depicted in the video and is a function of the master cylinder and the proportioning valve just senses the imbalance of pressure and triggers the light on the dash

much appreciated in advance the experienced on the forum to weigh in and provide clarification

When I call wildwood on monday I will be asking them if the unit they recommend will not only have the same or close to same bore size and the twin resovoirs and take that into consideration before deciding what master cylinder to go with

???


Joe k

[This message has been edited by Signupacct (edited 09-22-2024).]

cartercarbaficionado SEP 22, 06:45 PM

quote
Originally posted by Signupacct:

Is this the functionality of the OEM fiero master cylinder ?

https://www.youtube.com/watch?v=I8kzs_55Uo0\\

If so this may explain some of what symptoms I am seeing with this

btw some of this functionality is attributed to the proportioning valve and I had read that the fiero is really a combination valve and that the fail safe functionality is what is depicted in the video and is a function of the master cylinder and the proportioning valve just senses the imbalance of pressure and triggers the light on the dash

much appreciated in advance the experienced on the forum to weigh in and provide clarification

When I call wildwood on monday I will be asking them if the unit they recommend will not only have the same or close to same bore size and the twin resovoirs and take that into consideration before deciding what master cylinder to go with

???


Joe k



yes it is. the proportioning valve isolates the flow between the front and rear and changes the pressure and fluid flow to an extent. can definitely recommend willwood for good masters though