I did search on this subject and yes, I read all the posts but I still need help if y’all don’t mind.

Took the car out for a 120 miles drive yesterday, it was pretty hot 90*(Dallas, TX). During mild to hard acceleration we heard a short hissing psssssssssss sound…soon followed with gas smell. This all came somewhere from the driver side door. No smell during normal driving, no smell during idle after 50 miles drive.

What’s wrong?
How much to fix? Can I do it myself?
What are the danger if not fixed?

My brother has experienced this gas smell for a while now.

TIA

 

Is it the check valve of the purge control system?

 

fpd is possilby leaking

 

Should there be gas smell on the passenger side during idle if the FPD is leaking? In my case there is no gas smell under the hood.

We only smelled gas inside the car from the driver side. The sequence took place in this order:

1st hard accelleration
2nd hissing sound (2-3 second long)
3rd gas smell (all went away about 2-3 minutes)

 

Check the Brake Booster line. It has a one-way check valve in it that sometimes fail. When it does, you'll get the exhaust/gas smell on the drivers side coming up from the footwell/pedal area.

 

Will do. Thanks.

I assuming like most car the brake booster is mounted on driver side firewall…how hard is it to replace the check valve? I can do almost everything to a Mustang but kinda lost with the FD.

Oh, any idea about the pssssssssss hissing sound?

 

Yep, the brake boost is on the driver's side. There are two vacuum tubes for it:

* One runs from the brake booster to the hard line on the firewall (it should contain the check valve).

* The second one runs from the hard line on the passenger side to the UIM.

Originally the check valve was in the passenger side line. However, due to the heat of the turbos, it failed too often and was relocated to the driver's side. There is a kit you can order from Mazda you can order which will be both hoses and the check valve will already be in the driver's side hose.

The hissing sound could be because of the check valve not functioning. However, it's all guessing without being able to be there to hear it in person.

I would start checking their first. It's very easy to get to. If that's not the problem, there are a few other places to check but start with the easy ones first.

 

Mahjik Thank!!!!!!

 

The other possibility of hissing is if the diaphram inside the brake booster has torn. Those are easy to tell though because you'll only hear the hissing when you apply the brakes and at the same time the idle will get poor whenever the brake pedal is depressed since a torn diaphram causes a vacuum leak.

Your case certainly sounds more like a check valve issue.

 

My problem (gas smell under boost) turned out to be the brake booster hose. The purge control check valve was leaking, but just a little.

I did not know that the brake booster hose had a check valve in it. I replaced mine because the one that was on there literally crumbled in my hand when I pulled on it. The replacement hose (8mm silicon) did not have a check valve. I used an old Honda brake booster check valve in the middle.

Sonny

 

dont forget the injector grommets. if they are not sealing to the engine on the primary especially it will blow fuel mix out pass them.