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Looking through the service invoices for my 350 TDVi there is a note that the "port de-activation valves are split".
Does anyone know what his means? Is it the 2 vacuum operated solenoids that open and close the secondary air inlet butterflies?
Any help would be much appreciated!

No replies but for the record my suspicions were correct. These are vacuum operated pushrods that open or close dependant on engine conditions to operate an additional set of inlet butterflies. They are positioned on the inlet manifolds towards the back. There is one for each cylinder bank.
I took mine out and one was indeed split!
It wasn't a hard job to do but access was a little fiddly. It took less than an hour and I certainly noticed the difference when it was done. Jaguar have a kit (part number C2C41233) which costs about £25 to replace the affected parts.
There was a very helpful article in the S Type Forum page of the December 2011 club magazine (page 98) which gives details of how to do the job.
One good point is that access on the XJ350 is considerably easier than the SType or XF where most of the job time is taken up in dismantling things to get at the bits you need!

Hi
At what milage have the valves split?

Jeff

It was noted on the service bill at just over 125k miles. The car had done about 127k when I replaced them. Only one had split.
Regards
David

Thanks David
Mine's only done 54k so they should be ok. I've been reading post's on another Jag forum about blanking off or removing the EGR valves.
Apparently it makes quite a bit of difference to the power/smoothness to the engine. I've asked a question about emissions ect for the MOT, but no reply yet.

Jeff

I removed the EGR valve, blanked the exhaust and put in a by-pass on my Td5 Land Rover and it made a huge difference. I couldn't believe how much the EGR valve was strangling the engine's breathing. It now revs much more freely and sounds much happier.
However, the Jag TDV6 engine is much more complex than the Land Rover Td5 with its DPF, more sophisticated electronics etc so I would guess that it's not so easy to remove the EGRs without risking damaging something else.
Regards
David

In regard to the port de-activation valves, they can be checked by applying a vacuum. If the rubber diaphragms are split then of course the vacuum will pull air through them.

In regard to the port de-activation valves, they can be checked by applying a vacuum. If the rubber diaphragms are split then of course the vacuum will pull air through them.

Reading this thread yesterday, I decided to test mine, and indeed one actuator is leaking, so I'll pick up the kit and change them. Not sure about your earlier

One good point is that access on the XJ350 is considerably easier than the SType or XF where most of the job time is taken up in dismantling things to get at the bits you need!

I guess it's easier than say amputating ones own leg, but in best Jaguar tradition, there's barely enough space to get at the various fixings in the way.

While investigating this (symptoms were higher fuel consumption than others achieve, and a lack of oomph on kickdown) I checked the oil, which has gone up. Given that the last 300 miles were all on motorway at 70, and before that long driving days on the Entente Cordiale, I suspect the DPF is clagged. At one point during the Entente, the computer showed 48 mpg sustained for about 80 miles, but a later 120 miles it did only 38, all on the motorway. A chat with the dealer and my extended warranty supplier seems called for.

OK, changing the diaphragms wasn't too difficult. The hardest part was removing the rear RHS (looking forward) bolt retaining the wiring harness carrier. From above the clearance for a spanner is tight, but the trick is to put your arm down the gap between the engine and firewall on the LHS - then there's plenty of space to get across to the bolt from behind and below.

Take care not to drop anything - I now have a screwdriver rattling about on top of the plastic undertray

The fault was a split about 4mm long in the LH diaphragm. All easy to replace with the kit, and I could immediately detect better performance. Before, the car accelerated less with kickdown than without! After, it's almost like adding another turbo.

I sucked about 1/2 litre excess engine oil out using some spare screenwash hose and a syringe to get the oil level back to acceptable, and drove down to the dealer's garage for a full service (it was due next month anyway), so new oil, filter. They flashed the engine management system with the latest set of software updates, and ran a procedure to regenerate the DPF.