Petrol cap "hissing" & plugs Question..

[CosmosblueMR2]

Couple of Quickies...

1. Spark plug tools - what size for a Rev4 tubby please ? 12mm/14mm

2. Been reading a thread over on MR2OC about the "hissing" you get when you remove the screw petrol cap when filling up.... Is it right that if it "hisses" then the one way valve on the cap is broken and a vaccuum is caused inside the tank ?.. thus prossibly resulting is fuel delivery issues ?

I've had an MR2 or 2 for 9/10 years - cap has always "hissed" when i remove to fill up so just wondering really if it's a common fault or if it's not really a fault at all and what i've been reading is a bit naff.

thanks for any answers on either Q.

ta muchly

[gareth]

I've had mine for 3 years and its always done it.
But it gave the missus and my sister a shock when it did it the first time they took out the car. That was after the 10 mins in the petrol station trying to find out how to open the flap. Much to the amusment of other peeps in the forecourt.

[project7]

My MR2 does it, and so did a Corolla I used to have, so i assumed it was an undocumented feature of Toyotas.

[Rowland]

All 3 of my mk2 MR2's have hissed as the petrol cap is twisted off Frank, including my rev5 MR2.
It appears to be louder or under more pressure if driven hard before removal too.

[ducatichick]

every car does it hun in my experiance, nova gte,'2,silvia,RSt,M3,200sx,suzuki (not all mine some were the other halves lol) what you heared was babble hun

[MegatronUK]

Just about every injected car I've owned or driven does the same. It's normal, don't worry about it.

[crazylegs]

i always thought it was supposed to hiss.its designed to give a slight positive pressure to the fuel system.maybe

[Vindezal]

I always press the cap pssssshhhhhhhh! then open it.

[Milothicus]

the vent valve allows air into the tank, avoiding the possiblilty of a vaccuum,which is why when it's not working properly, petrol fumes are allowed out, and into the cab (mk1, anyway). the hissing is positive pressure in the tank, and i'm pretty sure it's normal...

[CosmosblueMR2]

Thanks everyone

I should stop drifting over to the OC... I'll stay where the knowledge is

ALL IN MY HUMBLE OPINION - don't want to start a club war teehee

[Dale_V]

My petrol cap doesn't hiss , My fiesta's does though

[tubby_d]

all the cars that I have own hisses (calibra,civics,golfs,renaults......).
I thought this was normal??

[splashnatz]

normal ... i'd of said that on OC too if i'd seen the question

[Spacey]

even the handbook says it's normal for it to his when the cap is removed