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[This message has been edited by tshark (edited 09-08-2018).]

The check valve should flow air in 1 direction only, if it does it's working fine and doesn't need to be replaced.

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[This message has been edited by tshark (edited 09-08-2018).]

Air flows when blow in the small hole goes to vac line?
Yes = Air thru check valve wrong way then valve is dirty or bad.
Vacuum inside booster will suck air every time you hit the gas pedal then the valve leaks.
Worse if/when engine dies on the highway then booster will loose vacuum reserve very fast. Likely won't even get 1 try to use the brake w/o fighting booster spring. (Normal is 2-3 time pushing pedal when engine dies.)

If you try to clean it... Remember Many things can eat plastic including brake and carb cleaners.

Exactly what part?
How much smaller?

If a bit smaller then can carefully use hose clamp to seal the joint.
Big difference then try OE number (google/ebay search and others) or ones from rock auto etc.
I don't have Dorman valve here and snowing today so can't get one. (Is cheap enough at many places to look/measure etc.)

GM used bigger vac line to pump down booster fast plus Fiero booster is a long distance from engine. If then line side of valve is smaller for just that joint then booster likely won't notice.

RE: https://www.fiero.nl/forum/F.../HTML/134756.html#p1
RA sells ACDELCO Part # 1791266... maybe?
With pictures of Dorman, Raybestos, acdelco... acdelco tube side looks bigger but Can't trust pictures to tell.

ACdelco.com says 179‐1266 good but no help on cars use when you search there. lookup for fiero doesn't show the part. (ACDelco require ‐ to look up some numbers.)

I don't know what other valves are good. 22P does have some parts w/ "wrong" info, like radiator cap.
If you find # that's direct fit to old valve then post the brand and number.

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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 (It's also at the top and bottom of every forum page...)

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[This message has been edited by tshark (edited 09-08-2018).]

quote Originally posted by tshark: Unfortunately, yes. I'm trying to find a part # on my current check valve. The valves I've found are WAY too small on the hose end. 1791266 and 18003614 are both the wrong size.

18003614 in Fiero parts book but often GM have different # that does same thing. Dumb thing can change #... valve made in white plastic are often different # then black ones etc.

Update.
Weather is good today and time to check.
But
22P is wrong... again. 87-88 uses different check valve, hoses and pipes.

I've checked 86 and 87, hose side connection. I don't want to risk my 87 valve to pull out of the booster.
86 use 3/8" hose
87 use 1/2" hose

87-88 likely is same.

Looking at pictures, Dorman and RAYBESTOS Part # CV89000 looks small. ACDelco looks bigger.
Also... RA does not List ACDelco valve for 86 Fiero. Only for 87-88. So maybe this will work.

Thanks. I'll try.

Does fit 87-88 Fiero... ACdelco.com and search for number, 179-1266