My Fiero has always had poor braking performance. (before and after the brakes were rebuilt)
After talking to Whuffo, he suggested that my brake booster filter may be plugged. He told me to bypass it with a hose to see if the brakes get better but I was thinking about replacing it anyways.

I know the Fierostore has them for $27.95 but can I find them locally at Kragen's, Autozone, Napa, etc...? (I need to have it by saturday, if possible) Does anyone know the GM p/n?

Thanks, Kit (86 GT)

that's odd, i've never seen a brake booster filter go bad.

The only thing I know is they are plastic and where they are located on the firewall they get pretty hot and sometimes crack. But if there is no leak in the hose they will not go bad. They are just a protection in case the main hose leaks and sucks in trash. If they crack you will know it by a fast idle from the vacuum leak.
Don

Kitskaboodles car acts like it's not getting much power assist to the brakes. I suggested bypassing the vacuum filter (it's metal, by the way) to see if that changed anything - if it's not that then we're looking at a bad booster...

You can buy a new power brake filter at autozone for sure. Help! part #80195. I just bought the last one at my store about 2 weeks ago. $9.95. Cheap!!! Hows your brake hoses? New hoses will help and have you bleed your whole system of the old brake fluid? After almost 20 years it breaks down quite a bit. Most suggest completly bleeding the system every 2 years.

Josh

quote Originally posted by ly41181: You can buy a new power brake filter at autozone for sure. Help! part #80195. I just bought the last one at my store about 2 weeks ago. $9.95. Cheap!!! Hows your brake hoses? New hoses will help and have you bleed your whole system of the old brake fluid? After almost 20 years it breaks down quite a bit. Most suggest completly bleeding the system every 2 years. Josh

Brakes were completely done about 4K miles ago (new rotors, rebuilt calipers, new pads, new SS brake lines, replaced back two e-brake cables and new return springs) At the suggestion of Whuffo, we just replaced the Carbomet (Fierostore pads) and put in Ferodo semi-metallic
ones. Brake feel and stopping power are still poor although we need to give the new pads a little more time to break in.

And yes, I purged out all the old dirty brake fluid.

Thanks, Kit

Check in Ogre's cave about the e-brake adjustment. This has improved the balance on my brake system (Delayed front lock-up). There is still some travel to my brake pedal but it stops just fine. I've gone with ss lines, new mc, calipers/rotors all around... even new brake cables.

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John DuRette
Custom 85 SE/87 Coupe
"Kinda makes you nostalgic for a Members Only jacket"

Hello,
I am a Brake booster engineer for a large automotive company supplier. I can tell you that the filter for the booster only affects efficiency of the boosters operation(the boosters ability to amplify input force(from pedal) into output force(into the Master cylinder) within a period of time). If the filter is gummed up(it's nearly impossible to block it). This will give you a slightly higher pedal force ( harder pedal). It will not give you unstable brakes or anything like that. You can remove the filter completely. This will make your booster "whoosh" noise increase significantly! (Yes your booster makes noise) Removing the filter can decrease the durability of your vacuum seals within the booster. This will not happen over a long period of time however, unless you live in a dusty place like near a desert i.e. Arizona ; New mexico, etc.....

Removing the filter will give you perceived faster pressure take up rates at the corner. This cannot substitue using a larger diameter Master cylinder or larger brakes.

A bad booster means basically your leaking vaccum to atmosphere. This means you are significantly not effectively amplifying your input force into output force. This should give you a very hard pedal with significantly lessened braking. So you would feel like your mashing the pedal and not getting enough "stopping power". I would inspect the booster for vacuum leaks externally. This can be done by exposing the crimped area on the booster shell with smoke ( from a cigar is best) If the smoke sucks into the crimped area, then your leaking at the shell crimp. If not the only place your leaking is at the vacuum seals inside the booster. This is very hard to diagnose. There are rubber diaphragms also inside the booster that can rip or tear over time. I wouldn't doubt failures within this ancient booster design. If your leaking alot, your pedal feel would be absolutely terrible.

Have you also made sure your FULLY bled? Air in the lines will give you awful pedal feel.

In addition. new pads need to be burnished or broken in. This means a series of stops need to be applied, about 1000 miles worth. Brand new brake pads will definitely not feel right. In the industry we call them green linings. I would suggest taking it out somewhere safe and do a number of consistently similar stops. Not hard stops, like a 30 mph normal stop, medium apply at the pedal. Make sure not to do them to close to eachother though, because you'll heat up your brakes significantly. It takes us quite a while to burnish brakes effectively ( usually 3 days). You can probably do it over a few hours.

If your booster isn't leaking and you still don't like your feel, then you probably need a larger bore MC and larger diameter rotors and larger pistons on the corners. Buy one of the upgrade kits if you have the money.

I hate my pedal feel in my Fiero. But I am trying to sell it so I am not going to do anything to the corners or MC.

Hope this helps.

Tim

[This message has been edited by brkeng (edited 01-12-2006).]

Welcome to the Forum and thanks for the news. This kinda news is what we like Thanks again
Don

Hi again!
After further review, I realised that there is an actual filter between the booster vacuum source and the booster!
That is VERY old technology! Indeed if this filter gets clogged, it could lower the vacuum level being sucked from the booster.
I would reccommend to try and find a check valve instead of a filter to use. I am actually quite floored to think there is a filter there, because in practice if that filter gets clogged, then it is basically the same as having reduced vacuum or reduced power assist, or none at all! Really though, there shouldnt be alot of debris coming from inside your booster. Perhaps small rubber particles from the seals and maybe dust. But I think it still shouldn't be enough to completely clog your booster filter. A check valve for boosters can be bought at any dealership. The only thing is you need to see if it will fit. I will take one home tonight and see if i can fit one of ours into my Fiero booster.

Tim

quote Originally posted by brkeng: Hi again! After further review, I realised that there is an actual filter between the booster vacuum source and the booster! That is VERY old technology! Indeed if this filter gets clogged, it could lower the vacuum level being sucked from the booster. I would reccommend to try and find a check valve instead of a filter to use. I am actually quite floored to think there is a filter there, because in practice if that filter gets clogged, then it is basically the same as having reduced vacuum or reduced power assist, or none at all! Really though, there shouldnt be alot of debris coming from inside your booster. Perhaps small rubber particles from the seals and maybe dust. But I think it still shouldn't be enough to completely clog your booster filter. A check valve for boosters can be bought at any dealership. The only thing is you need to see if it will fit. I will take one home tonight and see if i can fit one of ours into my Fiero booster. Tim

I really think that the filter on the Fiero is for protection only. The vacuum line is very long from the booster and I think they put the filter just in case the vacuum line under the car got damaged and would let dirt be sucked into the engine.
Don

The 88's don't have a filter and they seem to work fine.

I agree with USFiero. Poor brakes on a Fiero are often caused by the e-brake not working correctly. If you can feel any movement in the rear pads (rattle) the brakes are not adjusted correctly. Total clearance between pads, rotor, piston and caliper should be about .020" or .010" on each side of the rotor.

edit: Also, there is a check valve on the booster and the brake vacuum line runs through the passenger compartment.

[This message has been edited by spark1 (edited 01-12-2006).]

If you have the filter, replace it. after all these years they are likely full of crap.

Replacements are availably thru MotorMite in both HELP! and VacuumTite! I think. You may have to dig thru the MotorMite catalogs to find them and then order it. (You can also try motormite web site for part numbers... link on link page in my cave.)

The fact that later models did aways with it doesn't mean you should do the same... The long pipe thru the car can be prone to shedding rust and other crap. I've been tempted more than once to add it to my 87 for this reason.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurasic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

I think to start, do the parking-brake-pump test. See if your pressure comes up.

quote Originally posted by USFiero: I think to start, do the parking-brake-pump test. See if your pressure comes up.

I also pull a vacuum on the line at the plenum with a mighty vac and see if it holds vacuum.
Don

The reason for the vacuum filter - when you release the brakes, the booster pulls in air. When you press the brakes, manifold vacuum pulls that air back to the engine. Rinse, repeat, etc.

Over time, quite a lot of plain old unfiltered air goes down that line and it's that little filter that keeps the abrasive dust etc. from going through your engine. I'm not sure how may miles / years / whatevers that little filter is good for, but after 20 years it's probably at or past the end of its useful life.

Newer brake boosters have a built-in filter, older designs used the in-line filter. All vacuum operated power brake systems have a filter, though some aren't easy to see...

My 84 had one plug up not long after I got it back on the road (it had sat for 9 years) I was going down the driveway and when I got to the end no power assist.

If the car sat for a few seconds the vacuum built back up in the line to the booster and I had enough for about two stops and it was back to no power assist.

Replaced the filter and it was as good as new, the old one was plugged up good.

BTW the hard steel line between the filter and the booster hose runs through the center console and not under the car.

Steve

[This message has been edited by fierohoho (edited 01-14-2006).]

quote Originally posted by fierohoho: BTW the hard steel line between the filter and the booster hose runs through the center console and not under the car.

The line goes thru the car... regardless the inside of the line still sees plenty of moisture etc. It can corrode considerably inside, which is part of what the filter catches.

The 87+ L4 also has a about a foot of steel line on the engine for the booster connection. Not sure off hand if the older L4 or V6 is like that.

In the case of Fiero, even if there is a filter in the booster, the engine bay filter is probably still a good idea. A filter in/at the booster won't do anything about crap generated by or settled in the long steel line. Most cars don't have this problem because the booster connects to the manifold with a single rubber line that almost always outlasts the car.

quote Originally posted by theogre: the inside of the line still sees plenty of moisture etc. It can corrode considerably inside

Sorry, didn't mean to imply it couldn't rust because it runs through the inside of the car just wanted to let those that don't know where the line runs exactly where it runs.

I should have added that when I replaced my filter I disconnected both ends of the line, at the filter and at the booster, and I put some compressed air through it, lots O crap in there from sitting so long.

Steve

quote Originally posted by fierohoho: Sorry, didn't mean to imply it couldn't rust because it runs through the inside of the car just wanted to let those that don't know where the line runs exactly where it runs. I should have added that when I replaced my filter I disconnected both ends of the line, at the filter and at the booster, and I put some compressed air through it, lots O crap in there from sitting so long. Steve

Any pics of the line inside or under the center consol? I didn't know that the 88's didn't have a filter. Cool.

Update: according to my fellow club member (who has been working on my car for the past 2 1/2 weeks) the problem was due to a loose banjo connection at the passenger front caliper. He found the problem because there was paint missing near the banjo fitting. (I recently painted the calipers with Dupli-color orange paint) Also, he told me he was able to bleed out all the air in the rear calipers but wasn't able to bleed all the air out of the fronts.....no matter what he did! These two conclusions led him to the loose banjo fitting. (thanks Brian!) Now the brakes are much more solid.

Kit (86 GT)

Madcurl, here's the pic for you.

This is from a 85 coupe, the line is steel and comes out from the firewall and jogs to the drivers side where it runs the length of the center tunnel forward.

Sorry, no pic at the front, I may have my interior torn out but there's still plenty of wires in the way at the front.

Steve

quote Originally posted by fierohoho: Madcurl, here's the pic for you. This is from a 85 coupe, the line is steel and comes out from the firewall and jogs to the drivers side where it runs the length of the center tunnel forward. Sorry, no pic at the front, I may have my interior torn out but there's still plenty of wires in the way at the front. Steve

Hmm. So that's it. Does it look the same on a 88?

Should be about the same line thru the car for all years.

quote Originally posted by theogre: Should be about the same line thru the car for all years.

Okay. Sounds good. Where talking about the grey-ish metel tubing correct? I need to remove my center consol again because, I've never even noticed it before. Is it metal all the way up to front compartment fire-wall? I notice from the front tire compartment, it's rubber from where it is leads from the brake booster.