But not convinced this would cause my codes?
Another thing I noticed today is a sucking or whooshing sound coming from the foot well that changes when I press the brake... Vacuum leak around master cylinder?

 

The "whooshing" sound is most likely air being drawn into the atmospheric side of the brake booster chamber.

 

Thanks, and would that have an effect on vacuum and in turn cause a lean condition?

 

It will if it's leaking, do you notice any effect on the braking?

Here's a diagram created by Rick who coincidentally started this thread.

 

Yes, seen this diagram, brake booster on other side of course for RHD so going to check yellow and red lines.
Brake performance seems fine and the pedal is hard when engine isn't running. They maybe feel a bit soft when it is running but brakes passed MOT checks...

 

Who is watching this conversation .

 

So what do you think is whooshing then?

 

TBH I am not quite sure.

I do know that spraying carb/brake cleaner around vacuum lines is NOT an accurate check for vacuum leaks on modern day engines. At the time of my OP, I was told to do so by a former Jag tech here. I need to have that part edited out somehow (thoughts Norri)?

First I would definitely change IMT orings. Especially if you do not know if they have been updated.

When I broke my quick connect on the backside of plenum for the brake booster vacuum line. In our S Type it felt like something was giving a swift kick to my **** when slowing down and vehicke down shifted from 2nd into 1st gear. There was no "whooshing" or hard brake pedal AIR.

When checking the "red and yellow colored" vac. lines you will have to go by feel as you cannot see them while plenum is attached to motor. Start vehicle and slightly move those two lines around and hear what happens. One has a rubber 90 degree elbow (NOT TO BE CONFUSED WITH THE LOWER INTAKE RUBBER ELBOW ON PREFACE LIFT 3.0's), the other is the quick connect. Be easy with those lines!

I would then inspect the other vac. lines as well and I would look at the underside of the plastic intake tube and resonater very closely.

Is the MAF sensor dirty? Not to often cleaning works nor does changing MAF with a new CHEAPO model. Use only OEM (Denso) for replacement.

Thats my thoughts....

 

Thanks a lot for your reply, very informative!

MAF is clean (presumably cleaned by previous owner) I've cleaned it myself too. It's a Denso one that's in, what’s the best way to diagnose a dodgy MAF? I had a look at data and it seemed to increase well with throttle change... Also, it's worth mentioning, apart from the brake noise the car runs perfectly, idles great and accelerates smoothly (when codes as cleared).

I've got new o rings so will get them fitted and then more poking about lines or get a smoke test I guess...

Either way my radiator decided to be quite sick and throw out all its coolant a couple of days ago so need a new rad before tackling this again.

 

As Norri mentioned, remove cabin air filter box to create more hand room while changing out IMT orings. Might as well change out filter as well.

Good luck on radiator.

To bad your not state side. I would send you a known good extra MAF Denso sensor to try out I have on my work bench.

 

Thanks all,

How much would shipping to the UK cost? I could cover it here and back if it's less than buying a new sensor?

 

+1 on the carb cleaner not being effective, you need to check the fuel trims at idle and 2500 rpm to verify if you have an air leak.
Good luck with the rad.

 

Yeah agreed, had to spray it right in the intake for the engine to take any notice.
So what I'm is looking for specifically in the trims?
Cheers.

 

You will see high positive numbers at idle dropping as the throttle is opened.

 

Little update. Rad fixed (eventually) car is running great now apart from still getting the lean codes. Got the o-rings to install so that's the next job. It is oily back there but struggling to believe that's the cause of my problems. Car actually idles OK. Checked reader and tirms do drop under load but don't zero so not sure... Brake still makes the weird suck/hissing noise, I also noticed it seems to go away when I accelerate... The only hose I can see going to the booster is a hard nylon one though so unlikely to be that. Wish I had a smoke machine...

 

So IMT o-rings done today, took a little time but reasonably painless. Had to remove a bolt from the metal back plate the wiper motors are in to get a socket to the highest bolt (took a pic). Codes reset, went for a drive and code came back :-( pretty quickly this time, after I got the rad replaced it stayed off for few days, might be because it's warmer at the moment also... Either way I am convinced is something round the brake booster as I looked at trims and they go down when revving but also when the brake is fully pressed. I get the suck/whoosh noise when not pressing brake then it continues as I press until it is fully down and it goes away, so I'm sealing the leak by the sounds of it. Faulty brake booster? I checked the lines and I can't see/feel anything and the noise isn't noticeable under the bonnet only I cabin. There is a grey bung thing on the booster maybe that? Bit lost, need to probably get a smoke test done...

 

A leak you can hear is a big (or even huge) one.

Even a tiny on will set codes.

They can be a pain to find but you're doing the right kinds of things.

Some can be found by watching STFTs as you spray small amounts of a burnable substance (e.g. propane) but you need to be near the leak and have someone watch STFTs attentively.

 

but I wanted to say that I replaced I MT O-rings when I had the cabin smell and no change.But now I have the thing torn down again(2004 V6 Lincoln LS) and intake removed. My problem must have been the Valve cover gaskets all along. Monday I will replace plugs,coils, intake gaskets, and valve cover gaskets. I hope the smell will be gone..