I have a vacuum leak at the filter on the firewall causing a high idle or eratic...Can I delete that filter and put a new one up front by the brake booster or just delete it all together..

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James Silver 1986 Fiero SE V6 Auto...Red 1985 GT 4 speed
Central Florida

Don't get rid of the filter. Its the only protection for your engine if your booster or lines start falling apart. Just replace it. sleek

You can't get new metal case filters. Dorman etc sell plastic case ones that can leak or worse because close to exhaust.

Delete is likely only fix for short term.

GM deleted this in 87 to use bigger hose & pipe to PB booster.

Not a lot of air flowing thru the booster & most vehicles don't have a filter but Fiero w/ steel vac pipe rusts etc & when have brake problems causing more booster air flow then engine can suck that crap cause more problems w/o a filter.

see https://web.archive.org/web...cast.net/~fierocave/ brakes

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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.
(Jurassic Park)

The Ogre's Fiero Cave

Why can’t a metal can fuel filter be used ?

You can still find NOS units, you just have to have a decent sized wallet.
https://www.ebay.com/itm/166349106524

⚠️ There are Metal case gas filters that might work for X time...
Example: GM/AC GF61 & maybe others has fuel filter about same size a Fiero gas filter but have standard hose barbs to fit normal hoses.


But diam of line is smaller then booster vac line & may seem to work but flow restriction can haunt you later & w/o warning & have little to no brakes because booster used up the vacuum in it.

Booster is a Booster but also its own vac reverse tank too & why have a check valve on it to vac line input.

Standard vac line most use in thousands of models from many brands doesn't matter in most vehicles because only a 1 to 2 feet max length. But Fiero has ~9 Feet of that is already barely handle the flow needed to run normally. Is "Why" many say need "big booster upgrade" in Fiero to AutoX but wrong... in short you need to re-plumb the vac feed adding proper vac tank or even vac pump to get enough vacuum to race. This is the Reason why GM deleted the filter to have 1/2" booster vac line in 87+ Fiero.

That's only line joints... The Fuel Filter Media in them may have problems causing flow restriction etc.

quote Originally posted by IMSA GT: You can still find NOS units, you just have to have a decent sized wallet. https://www.ebay.com/itm/166349106524

That is a Plastic body filter....

Go to a Kenworth shop or heavy equipment Shop they have inline filters up to 1/2".that should work. I might have to change mine out now . thanks Ogre
They use them for vent filters for diffs and tranys and sometimes fuel tanks

[This message has been edited by sleek fiero (edited 01-07-2024).]

The line pulls a vacuum, but unless there is an air leak in the booster, no air moves.

Delete it.

sleek fiero
Big trunk shops & related may have something. Careful how to ask because Many don't want to deal w/ general public.

quote Originally posted by olejoedad: The line pulls a vacuum, but unless there is an air leak in the booster, no air moves.

That line will flow air Every time you push the pedal activating the booster.
Worse w/ any problem causing Low Pedal forcing more booster moving.

Some Boosters have muffler/filter @ pedal rod for same reason. But old boosters wear out that "feature" letting small crap thru the booster.
Boost line or Booster itself can fail & thanks to Fiero Mild Steel line that rust & collect other crap can dump that in the engine.
Even People put crap in the Fiero Frunk then knock off the line or break the check valve w/ engine running does same thing.

Many would think open booster line = vac leak so big will instant kills the engine but often won't do that or soon enough so engine doesn't suck crap.
Often doesn't break completely open plenty of air flow allowing rust & crap sitting for decades to move.

Food for thought.....has anyone reported any Fiero brake booster going out and destroying the motor with debris?

quote Originally posted by Spadesluck: Food for thought.....has anyone reported any Fiero brake booster going out and destroying the motor with debris?

"Bad" Boosters etc often don't destroy engines right away but junk from them scratches cyl bores, blocks valve(s) & start to burn them, & other problems often not counted as a root cause by most.

Is mainly rust & other crap sitting in the steel pipe that's going to slug the engine w/ it if have a leak in that part of car.
Rust/crap in the booster can hurt too but have to stir that up then get enough air to line check valve.

Most booster fails don't have huge vac leaks because fails are diaphragm(s) or control valve.
But plastic check valve can break or line pulls off then have a huge leak.

Note: Many think the line end is just a fitting/adapter to fit hose to the booster... Inside is a sprung Check valve that can have other problems causing poor or no booster performance sim to bad booster. This valve can be Replace w/o buying a new booster.