I found the leak in the vee in my 2005 4.2 NA at 72k miles - what is actually a $1.50 O ring ($16.45 dealer list) on the thermostat "duct to pipe" AJ83526 on the thermostat housing. First photo shows l' orange" staining on the pipe. (no it is not missing the special yellow retaining clip, I had to reuse that on the new assembly that came without one)

Chasing the source of the leak I decided to replace all the water hoses, water pump, serpentine belt, complete t-stat housing assembly w/ t-stat and sensors & gaskets complete since the car is now at 15 years and 72k miles.

My question is the intake manifold has two sound deadening pads - second photo with them removed, one fits on the top of the vee on the LH side and one stuffed up vertically in the space between the LH intake planum and lower intake.

Any thoughts about leaving them out other than "Jaguar thought enough to put them in place by design" Now since it appears to surround the LH knock sensor, I am wondering if it was a fix to a different intake from the 4.0 and the KS on teh 4.2 was falsing due to noise around the intake / injectors , hummm I would think that when those pads deteriorate knock sensor codes would increase if that were the case ... go figure

4.2 Thermostat housing "weep" at O Ring

4.2 L intake Manifold sound deadening pads removed

 

I kept mine in bc I had the same concerns. Plus it keeps the heat off the blower a lil

 

The plastic pieces on mine, were both in need of replacement, them being plastic.
I would get a new one, just in case.
Do you really want to chance doing it again?
As far as the sound pads, i put mine back in.
But would probably leave them out if i'm ever in there again.

 

Well I guess it is easier to leave them in than have to have to put them in later I cannot find them in the workshop manual though.

 

I hadn't seen those before, are they not apparent until you pull the intake? I would probably try and refit them for your stated reasons, and yours look to be in fair shape.

Question: Did you replace the "valley Hose" - the convoluted one that has a larger to smaller diameter section, that returns to the throttle body? I am about to do all the same work, have a belt, Thermostat housing, complete, and added tensioner and idler pulley since I have had them go noisy on previous car and want to knock off most potential issues. I am still wrestling with whether I want to do the valley hose. I probably should have it on hand in case I decide to do it, since I don't want to pause the work for a day or two to get a hold of one.

Are you changing out any pulleys? They tend to fail bearings somewhere between your mileage and 100k, it might be worth doing them while you have it apart/ My idler pulley went all squealy first, then the one on the tensioner, which can be replaced separately, but I chose to do the tensioner as well, since I prefer the round type springs vs. the stock flat springs, just from personal experience. I also considered putting a water pump in, both in the old car and on the one I am about to do, but logic and my slight modification of the old "if it ain't broke, don't fix it" (my version: "If it ain't broke, don't break it") -tells me to leave it. To be honest, I also found TOO many aftermarket pumps with a mix of gasket designs, and the factory fitted ones are no longer sold as two-piece units; it looks like they are simply selling aftermarket ones at Jaguar prices. I haven't figured out what brand, because there are so many, but something about paying $200 for a unit that sells for $39 elsewhere bothers me, I am fussy that way.

 

The flat pad fits horizontal on the heft hand top rear of the Vee between the Vee and the intake manifold, toward the back of the engine on the LH side (viewed from driver position), partly covering the diamond shaped rubber plug in the Vee . The long one fits vertically between the left side of the plastic intake manifold (mine is Naturally Aspirated) and the metal lower intake manifold. It has a semi circular section to fit around the LH knock sensor. The probable reason there is not a vertical or horizontal set of pads on the RH side is that is where the ERG pipe is routed and it would have to be very heat proof.

Yes I am of the opinion of "while I am in there, replace it" because I do not like to have to tear it down twice for a different failed part.
So full rubber hoses including the one in the Vee, water pump, serpentine belt, complete thermostat housing assembly, TB gaskets, all from the JLR dealer at my 20% parts discount. I too have found cheap aftermarket water pumps that would not last. I get the pulley bearings at my local specialty bearing supply for about $6 each, press out the old bearing from the housing and press in a new one has always worked well for me. The only issue with some of the pulley bolts is that the pulley bolt self destructs when removing the pulley and needs a suitable upgrade to make them rebuildable.