Noise after turned off car - Advice please

[Stevemarsh]

Hello, I noticed after I had parked car in garage tonight after a drive, that when I car back to get something out the car that towards the back of the car was coming a noise, hard to describe , but bit like the noise that comes from your home boiler / a Woshy / air / kind of noise , it’s still going. 

Is this just something letting air out or something to do with fuel pump? 

Thanks in advance !

 

[GaryD1971]

Fuel tank pressure equalising? Could mean that the tank vent isn't working properly as I thought they were meant to prevent that? 

[Quinten]

53 minutes ago, GaryD1971 said:

Fuel tank pressure equalising? Could mean that the tank vent isn't working properly as I thought they were meant to prevent that? 

Almost 100% sure it will be this.  Next time you've driven it, open the fuel cap.  If you hear air rushing, you've found your issue.  It needs to be able to 'breathe'

[TableLeg]

48 minutes ago, GaryD1971 said:

Fuel tank pressure equalising? Could mean that the tank vent isn't working properly as I thought they were meant to prevent that? 

Agree with Gary, sounds like tank equalisation.

And as Gary says check the tank vent is working, and if you also want to prove it remove the filler cap and see if you get a suction whoosh. If so that'll confirm you have a tank vent issue.

[Stevemarsh]

Thank you, if this is the case how would I fo about sorting this? Or can it be left? 

[GaryD1971]

I wouldn't leave it personally. There should be a fitting welded to the top of your tank which may have a breather screwed directly into it, or a piece of tube coming off it with a breather attached to this. It allows the tank to breathe/equalise and also stops fuel from spilling out in the unlikely event of a rollover. They are not expensive to replace and are available from most kit car part suppliers online. Check the unit is working using the method both Jared and Quinten have mentioned first. 

[GaryD1971]

If its on a length of tube, check this hasn't been crushed at all too. This could give the same results if it is.

If the tank can't breathe, it creates a vacuum inside the tank as the fuel is used which is slowly replaced with air when you stop. This is most likely the noise you are hearing. Hence removing the filler cap will allow a rush of air into the tank, replacing the vacuum inside.

[TableLeg]

The rollover/vent can be seen in Red in this image

[stephenh]

It wasn't the sound of your electric cooling fan running on, was it? In this warm weather that would be perfectly normal.

[BugMan]

Tank is definitely No1 suspect, but it could be related to the fuel pump.  Was the ignition totally off or did it happen when just turning on b4 starting?

 

[Stevemarsh]

Hi no defo not the fan, this stops when I turn off the engine, is there a way of making this say on after ignition off? 

[Stevemarsh]

14 hours ago, stephenh said:

It wasn't the sound of your electric cooling fan running on, was it? In this warm weather that would be perfectly normal.

 

14 hours ago, BugMan said:

Tank is definitely No1 suspect, but it could be related to the fuel pump.  Was the ignition totally off or did it happen when just turning on b4 starting?

 

The car was totally off and keys out , o may have also been to do with the particular hot day and my car has been sat in direct sun all day too 

[WINGNUT]

Mine also does this I've noticed more so on the last couple of petrol station visits. As @TableLeg and the others have said  @Stevemarsh there is a valve in the top of the tank. They look to be around £30, you can see mine through the N/S wheel arch even with the wheel on. So long as it comes out easy it's seconds of a job. Mine appears to look like this

 

[stephenh]

Good practice is for the cooling fan to be wired directly, in the sense of not being wired via the ignition switch, so when you stop the engine the fan can still work until the temp cools down.

[6carjon]

It's a good idea but don't forget the current draw on your battery if it's a small low amp hour one.