S 10 brake booster causing spongy pedal? (Page 3/3)
theogre OCT 12, 07:35 PM

quote
Originally posted by 82-T/A [At Work]:
OGRE, are there any "stainless" brake lines you recommend at all for a car that you were completely restoring / rebuilding? Or would you just use the rubber lines you mentioned in the link?

For all street cars...
Always use the SAE j1401 "rubber" hose whenever possible. This is DOT rated with same OE hardware including bracket in the middle most vehicles need.
Many New cars have this as OE when made at whatever factory.

"Old" DOT "rubber" next because have correct hardware. This "Old type" DOT rubber is a lot better then SS hype claims and easily last another 10 15 or more years for most cars.

New "old type" DOT rubber and SAE sets look same but SAE hose marked both DOT and SAE J1401.

Most think SS lines are better have no clue have many problems even w/ "DOT Approved" sets and not just having universal end(s) and missing support bracket.
Yes, Either "Rubber" can wear out but so can SS lines but the Hype Train never will tell you that. Worse Most DOT SS have clear plastic that hates UV etc and when that cracks let dirt and other road crap attacking the SS and/or the liner.
IOW Crack cover on SS lines is as bad or often worse then cracks on rubber hose.
Rickady88GT OCT 12, 08:46 PM

quote
Originally posted by Mickey_Moose:

I recently had this problem as well. I just had to remove the master and bench bleed it properly - all is good since doing that at the start of the year.



This is exactly what am am doing right now. The combination value came off as well. The proportion valve just seemed strange that it wouldn't bleed like I thought it should? So I took it apart and the cup seal on the spring loaded proportion value was stuck in the boar as I removed the red plunger. The boars of the valve body were in good shape after cleaning, but gummed up pretty bad as it was. So, I got it cleaned up and am now bleeding the system.
Rickady88GT OCT 12, 08:49 PM

quote
Originally posted by theogre:

[QUOTE]Originally posted by 82-T/A [At Work]:
OGRE, are there any "stainless" brake lines you recommend at all for a car that you were completely restoring / rebuilding? Or would you just use the rubber lines you mentioned in the link?



quote

For all street cars...
Always use the SAE j1401 "rubber" hose whenever possible. This is DOT rated with same OE hardware including bracket in the middle most vehicles need.
Many New cars have this as OE when made at whatever factory.

"Old" DOT "rubber" next because have correct hardware. This "Old type" DOT rubber is a lot better then SS hype claims and easily last another 10 15 or more years for most cars.

New "old type" DOT rubber and SAE sets look same but SAE hose marked both DOT and SAE J1401.

Most think SS lines are better have no clue have many problems even w/ "DOT Approved" sets and not just having universal end(s) and missing support bracket.
Yes, Either "Rubber" can wear out but so can SS lines but the Hype Train never will tell you that. Worse Most DOT SS have clear plastic that hates UV etc and when that cracks let dirt and other road crap attacking the SS and/or the liner.
IOW Crack cover on SS lines is as bad or often worse then cracks on rubber hose.



Thanks for the info, my next set of lines will not be SS. Standard will work just fine for me.

[This message has been edited by Rickady88GT (edited 10-12-2021).]

Rickady88GT OCT 12, 11:08 PM
Got it all together and did the bleeding as best I could. I gravity beed the brakes one at a time then bleed them with the pedal. They feel better but not what I had in mind. I feel like they should be more solid.
theogre OCT 14, 11:32 AM

quote
Originally posted by Rickady88GT:
Got it all together and did the bleeding as best I could. I gravity beed the brakes one at a time then bleed them with the pedal. They feel better but not what I had in mind. I feel like they should be more solid.

Duh. When you Add booster power, you feel less w/ your foot. Is like having a longer pedal arm adding more leverage.

Or worse comparing old booster w/ problems to any new booster.

And That's assuming the rest of brake parts still don't have problems like Slider w/o or wrong lube and more covered in cave.
Everything in brake section of the cave covers 88 but have to account for really minor differences to mount the calipers and pads etc.
Like Still uses same type MC and rear pistons but different sizes.

[This message has been edited by theogre (edited 10-14-2021).]

Rickady88GT OCT 14, 07:00 PM

quote
Originally posted by theogre:

Duh. When you Add booster power, you feel less w/ your foot. Is like having a longer pedal arm adding more leverage.


I was talking about the pedal feel with the engine off.
There is clearly something else that needs to be addressed.
I have not driven the car sense I started this brake job.
I had hoped that bench bleeding would help.

quote



And That's assuming the rest of brake parts still don't have problems like Slider w/o or wrong lube and more covered in cave.


The sliders are fine. They are not sticking or rough, they are smooth.

quote

Everything in brake section of the cave covers 88 but have to account for really minor differences to mount the calipers and pads etc.
Like Still uses same type MC and rear pistons but different sizes.



I have clicked on a couple of links for the cave, in various threads and the page said something like it is a dead link?

[This message has been edited by Rickady88GT (edited 10-14-2021).]

theogre OCT 17, 11:45 AM

quote
Originally posted by Rickady88GT:
1. I was talking about the pedal feel with the engine off.
There is clearly something else that needs to be addressed.
I have not driven the car sense I started this brake job.
I had hoped that bench bleeding would help.

2. I have clicked on a couple of links for the cave, in various threads and the page said something like it is a dead link?

1. Engine off then Pedal Feel is useless. Plus actually stop the car with pedal or using P-brake properly is very hard pedal often need both feet to push the pedal w/o vacuum in the booster.

Worse If you bought Used Booster as that thing maybe bad. Bad diaphragm(s) bad/weak spring etc.

Test w/o engine running need a vac pump.
Small Mityvac and similar work but can take a long time to pump down a big part like the booster.
Electric pumps are good but need carefully attention to Not pump too much.
Boosters need ~ 18 - 22 in-Hg same "normal" vac from an engine at idle or cruise. Do Not pump down like AC that need max vac from most E-pumps.
Unplug vac line up front and use spare hose(s) etc to make whatever pump to fit plastic valve on booster case.

2. Old cave links years ago are dead because Comcast and other ISP killed them. Use link above and other links < ~ 5 years old or search archive.org
fieroguru OCT 17, 02:26 PM

quote
Originally posted by Rickady88GT:
My 88 has a good pedal feel with engine off, but start the engine and the pedal gets spongy. I know the booster takes out some petal feel, and that the pedal will go down a bit, but this seems extreme. So does the booster go bad like this?



When the booster fails, you will not feel a difference in the brake pedal when the engine is on/off. The pedal will be super hard at all times and braking performance will be about 1/3 of normal.

This thread has a lot of measured results from the stock brake booster and S10 brake booster at various pedal forces so you can see exactly how much assist the stock and S10 booster create.
https://www.fiero.nl/forum/...0323-2-121747-2.html

Without the engine running, the pedal should be as hard a brick with very limited movement. If you stand on the pedal and put 100 lbs force to it, the resulting front caliper line pressure will be about 475 PSI.

When you turn on the engine with the the stock brake booster, the same 100 lb force of brake pedal will create 1475 psi, which means the stock fiero booster generates 1000 psi of assist. This is enough to flex hoses as well as brake pads and the reason the pedal feels a lot softer with the engine running.

With the S10 booster at the same 100 lb force on the pedal, you will get 1700 psi line pressure or an increase of 15%. At low pedal forces, the S10 booster gain vs. stock 88 is up to 40%, which will make the pedal feel softer vs. stock when the engine is running. Most of the time people install the S10 booster so they can press the pedal less for the same stopping performance.

Pad compound can also make a significant difference. The carbomet pads were very hard, which gave a super firm pedal even with stock brake assist. Wagner thermoquiets were much more compressible and made the firm pedal feel spongy - They also didn't have the same initial bite or overall performance, so they didn't stay on the car long.

The pedal getting softer when the engine running is normal - that is the booster providing assist.
The pedal being even more soft with the engine running after the S10 booster install is normal - it is a larger booster with more assist.
If you changed brake pads as part of this change, they could be softer than the ones on the car originally and contributing to the soft pedal feel.
If the brakes are engaging further down in the pedal travel, that could be air in the system or the caliper pads too far from the rotors.
Rickady88GT OCT 20, 11:44 PM

quote
Originally posted by theogre:

[QUOTE]Originally posted by Rickady88GT:
1. I was talking about the pedal feel with the engine off.
There is clearly something else that needs to be addressed.
I have not driven the car sense I started this brake job.
I had hoped that bench bleeding would help.

2. I have clicked on a couple of links for the cave, in various threads and the page said something like it is a dead link?

1. Engine off then Pedal Feel is useless. Plus actually stop the car with pedal or using P-brake properly is very hard pedal often need both feet to push the pedal w/o vacuum in the booster.

Worse If you bought Used Booster as that thing maybe bad. Bad diaphragm(s) bad/weak spring etc.

Test w/o engine running need a vac pump.
Small Mityvac and similar work but can take a long time to pump down a big part like the booster.
Electric pumps are good but need carefully attention to Not pump too much.
Boosters need ~ 18 - 22 in-Hg same "normal" vac from an engine at idle or cruise. Do Not pump down like AC that need max vac from most E-pumps.
Unplug vac line up front and use spare hose(s) etc to make whatever pump to fit plastic valve on booster case.

2. Old cave links years ago are dead because Comcast and other ISP killed them. Use link above and other links < ~ 5 years old or search archive.org [/QUOTE]
Thanks