Hi all,

I've been through a lot trying to diagnose my lean codes (P0171, P0174) including changing my IMT O-rings.

However, I have found that my brake booster is at fault. I can hear some hissing/suction noise from the brake pedal so did suspect my brake booster but confirmed it by disconnecting the hose from the intake and sealing it - fuel trims dipped back to normal therefore booster causing the issue.

Anyway, my question is: I have had a hunt about but I can't seem to find a how to on replacing the brake booster on a 3.0 V6, can anyone help?


Thanks,

Gordon.

 

My car is a 2008 4.2 Stype and the brake booster failed. It rusted out at the collar that goes through the firewall, apparently a common problem. My finding was that there are no rebuild kite available for after model year 2005 and here in Canada I could not find any supplier except Jaguar. In the end I ended up spending $1200.00 Canadian for a replacement unit. Fortunately it is not a difficult job to change for someone of moderate skills. I hate to think what Jaguar would have charged to replace it.

 

David manners seems to have them for the best part of 500 quid.

SNG Barratt also says they can get them in a couple of days but a little pricier.

Jaguar Partno_XR843546_BRAKE BOOSTER S-TYPE RHD NOT S/C_David Manners Group

 

Yours certainly looks knackered! I suspect mine has failed near the same location as the noise can be heard cabin side.
Hopefully it's a job I can do myself in a couple of hours *fingers crossed*

Yeah new ones a very expensive, used are about £150 on a well known auction site. I managed to get a used one from a breakers for a bit of a bargain at £50. Arrived today and in very good condition indeed, practically new looking, was quite surprised. Its off a 4.2 non-SC so should fit my 3.0. The part number is a little different but hopefully OK.

Was really looking for how it's removed/installed. Bolts out the front and master cylinder out the way I assume. Then how do you get to the pedal side bolts?

 

I suppose it depends on how big you are but on both my Jags, XK8 and Stype I take out the drivers seat to work under the dash. The four bolts that hold the booster are quite accessible. Biggest pain was bleeding the breaks as you have to undo the brake lines at the master cylinder.

 

That might be a good shout. Do the brakes really need bled? can the master cylinder not just be disconnected and moved out the way?

Also the brake booster I've received off a 4.2 is part number: 2R83-2005-BB, and my part number is: 2R83-2B195-DF. Looking online both part number come up as the 2.7 diesel but also all the petrol except supercharged, so presumably interchangeable? I know from looking for an EPB module that the middle block of numbers is usually the unique part identifier.

 

I tried first just removing the Master Cylinder, but it was not possible to move it out of the way with ought bending the brake lines severely. I was not comfortable this that, perhaps there is more clearance in the V6 engine bay than the 4.2. Another thing you have to do is remove the plastic valance that runs cross car under the windshield. The plastic pins that hold that in on my car are a one shot deal, I think there was 8 of them at $2.35 a piece.

 

Thanks for that. I'll see what it's like and drain the brakes if needed. Yeah I've had that off before to change my MIT o rings so clips are already knackered.
So just take bolts out from driver foot well, disconnect it from brake pedal, take bolts out from engine bay. Is that it? Pulls out engine bay ok?

Cheers. G

 

Just thought I'd finish this off.

Booster replaced, total different part number off of a newer 4.0 n/a but looked exactly the same apart from the cabin side was different metal. Either way replaced without having to drain the brakes, clearance was fine after removing the bracket holding the brake pipes in place.

Good news is problem solved! Reset codes and STFT are well negative and LTFT going down. No more noise either. Old booster had a little fluid in it, hoping the seal on the master cylinder have not gone otherwise I'll need another soon enough. But I think the problem was when replacing brake I had to wind in the caliper pistons and fluid leaked out. The cap was on and the previous owner had over filled so I think fluid has been forced into the booster.

Anyway the cat is running great :-)


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Thank you for follow up!!

 

About two months ago my 2000 3L V6 started to drop revs when stopped in Drive, only when at operating temperature. Not in N or P, only D. Drops a couple of seconds after complete stop, nearly stalls (occasionally does), then picks itself up and resumes a nice 750rpm. Smooth idle through accelerator pedal - foot feel thing..

My guru suggested brake booster vacuum leak, replaced it and master cylinder, to no avail. In fact, after fitting, an audible sucking/bellows type noise is heard from brake pedal in cab. Not a normal noise?

Leak tested by spraying light mist of aerosol around running engine - nothing.

Cleaned throttle body, seemed clean. Nothing improved.

Plugs and fuel filter replaced. Nothing. Manifold gaskets in woeful condition - replaced - no improvement.

My beautiful girl is not happy, and I’m out of ideas.

280k on the clock so yes lines are probably getting heat hardened. Replaced the L shaped one under manifold 100k ago - time to check again?

Any ideas welcome, please.
thanks
Barbara

 

Good job at getting to 280k first of all!

The sucking noise at the brake pedal was the first thing I noticed when I started having trouble, and it's now gone with my replacement booster.
Is it possible your replacement is gone too?
Are you 100% it's a vacuum leak? I had a pretty big one and my symtoms were no where near as severe. Are you getting EML on? Have you looked at codes/ fuel trims?
The way I 100% diagnosed my booster was at fault was to disconnect the vacuum line going from the intake manifold to the booster; look at fuel trims and cover the end that would connect to the booster, short term trim dropped instantly to negative which they did not do when connected to the booster, therefore air was getting into the booster and thus no vacuum. The suction isn't that strong, you can cover with a thumb, although you'll probbaly need 2 people.
Only other things I can think of is the IMT o-rings that can cause leaks, and in the earlier models like yours there's a right angled hose under the manifold that's prone to cracking.

Hope that helps.

G

 

Unfortunately, that's not a valid test with electronic fuel injection. The computer will quickly adjust the fuel to maintain a steady idle. The RPM typically won't vary much at all. You have to watch the fuel trims on a scanner to see the response to spray reaching a vacuum leak.

Is your check engine light illuminated? Are there any fault codes stored?

 

No fault codes stored, check light never comes on.

New gearbox and TC installed 6 months ago, had it back to the installer who could find nothing amiss with the box. Test drive diagnosis only though.

Thanks for any and all input!
Barbara.

 

No EML or code...? Doesn't sound like it's running lean then as the ECU will definately flag if it's adding extra fuel due to a vacuum leak or other lean condition. Sounds like the issue is elsewhere in my opinion.

 

Couple of things I'd maybe look at if there's no EML:

• MAF - clean, replace, check wiring
• Fuel pump - most obvious but doesn't match up with it only a problem in D though?
• Wiring loom or loose connection somewhere

If the engine is essentially cutting out due to no fuel then either the engine isn't adding fuel or cannot get fuel to add.
The fact that it only happens in drive, feels to me like an electrical issue i.e. ECU behaving differently in D and due to an issue causing symptom.

 

I'd suggest checking the fuel pressure with a mechanical gauge and comparing it to what the scanner sees.

Not all faults will set a code. The OBD II system is primarily for emissions-related problems. Strange as it may seem, the computer doesn't consider stalling to be an emissions problem. That's a drivability issue, so you may have to do some basic troubleshooting to find the root cause. I'd start with the fuel pressure and go from there.

 

I’d be disappointed but not overly surprised if the replacement booster was a dud - second hand, so anything is possible.

Vacuum leak is the thing that most people suggest when I relate the symptoms so have been exhausting that possibility first.
No EML - no codes, haven’t done fuel trims.
She is so beautifully behaved at all other times, my gut says fuel delivery is okay. Fuel economy hasn’t changed. Not very scientific I know, but I know the car very well.

And yes, 280kms is a goodly number...regular maintenance and good luck I think! When I read some of the horror stories of bad luck some people experience, I’m pretty happy with mine.

My sincere thanks for your input - not giving up, it’s got to be something!

 

Agree, the only in D, and only at operating temp are the only symptoms I’ve got to go by.

I have an electrical guy who has done miracles for me in the past - time for a visit to him methinks!

Poor old girl...apart from this minor yet maddening issue, she’s a fabulous example of the marque..

 

Yeah I'd get the electrics checked next.
As for fuel economy if you had a vacuum leak you would also have awful MPG as its running lean and engine is adding more and more fuel (up to 30% I think) I know mine was terrible until it was fixed.