We have been having various problems with our 2011 FL2, hesitation, sometimes won't start, "reduced engine performance mode" etc and despite being to the dealer several times they can't fix it or find the problem. Claim is that there are a number of 11 and 12 reg FL2s with the fault and LR don't know how to fix it. One theory was fuel starvation caused by a blocked fuel filter so that was changed recently. However, I went to put some diesel in the car today and had trouble removing the fuel filler, when it did come off there was a huge inrush of air. Is this normal? Is something blocked? So I am now wondering whether the problems could be caused by some difficulty in sucking the fuel out of the tank due to a partial vacuum. Any suggestions?

Incidentally the LR dealer told me that if a message comes up on the display then a fault code is logged, however if after the engine is restarted the fault has gone away then the code is deleted. Coming from an IT background this sounds ridiculous.

Vacuum \ in rush of air turned out to be fuel filler cap in this thread: http://www.freel2.com/forum/topic19753.html 
Hung like Einstein, smart as a horse.

Posted on the thread mentioned back in July. Replacement of filler cap by dealer fixed the issue of partial vacuum in tank and it's been fine ever since. 2011 SD4 HSE Auto
(Previously 2007 TD4 XS Manual)

My dealer said it was normal and that the cars they drove did it too. As there seems to be differing views from dealers about whether this is "normal" and therefore warrants a replacement filler cap I PM'd Landrover technical services asking for clarification and got the response below.

"I have spoken with our technical team who have advised that this is not something they are aware of."

Makes you wonder what vehicles the Technical team drive.....

To prove the point if it is excessive and you are not topped up to the brim, remove and run it without the filler cap.

never had this on my FL2, but my MX5 does it every time, but doesn't seem to cause any performance issues.

Iain

There clearly shouldn't be low pressure in the fuel tank in any car. If you think about it, if the tank is sealed, then the low pressure in the tank makes it harder for the fuel pump to get the diesel out, and the more diesel it gets out the lower the pressure gets, until eventually it will just give up.

The filler cap has a very clever breather valve to make sure air can get in, but prevent diesel sloshing out. Just change the cap.

Strange this should come up, my old MY11 did it all the time and was plagued by the hesitation issues, touch wood the MY14 doesn't seem to hiss on opening the filler cap. MY14 TD4 manual XS Orkney grey.

MY11 TD4 Manual XS Lago Grey, privacy glass, rear spoiler, full ebony leather,rear seat entertainment. Gone
2001/51 plate Disco TD5 GS. Gone
95 N Disco TDi300. Gone

My real concern is that the LR technical dept don't seem to know whether it's normal or not and there is an inconsistency amongst dealers on the issue.

if the experts don't know, who are we to even comment

Iain

It's interesting that they don't know as my dealer told me they would be reporting it! 2011 SD4 HSE Auto
(Previously 2007 TD4 XS Manual)

I have the "hisssssss" and decided to have a look at the valve in the cap it would seem the cap works in both directions due to hot weather expansion ...the valve that allows the air in did seem sticky but now very free ....fill up time now ....

I'm getting confused ........... should there be ANY hiss on removing fuel cap ?

According to my dealer, no there shouldn't. They said they might expect a very little amount immediately after a long run. Certainly nothing as extreme as mine was doing after short runs and with the tank pretty full. I'd never experienced it before over many years with different cars, including a MY07 FL2, and mine doesn't do it now with the new fuel cap.
Ignore their "that's normal" or "they all do that" - it's not and they shouldn't - get the cap replaced! 2011 SD4 HSE Auto
(Previously 2007 TD4 XS Manual)

Took a look at my cap last night and could see no grime in the valve. I get massive hisses when opening after just a couple of short journeys.

Duckworth do replacement caps for about £20 which I'm going to go for even though it would probably be covered under warranty. The grief of taking it to my local dealer, leaving the car with them, getting home with the kids, and the risk of them saying nothing is wrong and charging me just isn't worth the £20.

Considering my cap looks brand new inside I hope a new one sorts the issue.