Hello XK8/XKR forum,

Been suspecting a vacuum leak (long time fuel trims are a bit high around +12%) and finally managed to create a simple smoke test setup with a compressor and a mosquito smoke in an empty paint can.

I've had done a full primary & secondary timing chain & tensioner replacement last summer, and at the same time had the bank 2 cam cover and the full load breather replaced as those were leaking.

To my surprise the full load breather's connection to the air intake duct (see the red arrow on the picture) is leaking. The o-ring on the breather's norma connector is fine, as is the whole breather. As far as I can see the intake duct is also ok. I cleaned it as there were some oil residue but that did not help. If you twist the breather sideways the leak gets worse.



I've seen from the forum that the breather (full load or part load) leak is somewhat common, but I can't recall seeing this kind of leak which might require changing the air intake duct. Have any of you seen it like this and fixed it with by getting a new air intake duct? I suppose that is my only option here...

 

O-rings compress over time and proximity to heat; although the o-ring may 'look' fine, you cannot be sure that it's outer diameter and thickness have not been compressed and compromised. I have an assortment of o-rings, packed in a plastic box with dividers and a chart affixed to the lid, you can pick up one of these o-ring assortment kits at the auto parts store, or home improvement plumbing department, and they are fairly cheap, ~$5.00 US for ~20 different outer and inner diameter o-rings, 5 or so of each. Match your old o-ring to the chart on the lid, simply lay the old o-ring over the chart and you will be able to determine what your original o-ring size and outer diameter was and replace it. Same thing with a leaky faucet, the o-rings do not last forever. I have used these on my Mercedes intake when I was having the same issue, and although the old o-rings inner diameter, when laid atop the sizing chart, had not changed, the outer diameter had, and was just barely noticeably thinner, I almost did not change it, but since I had it in hand I decided to replace it with a new one and see how it seated with the new o-ring. This worked perfectly, the new o-ring, with the proper o.d. was snug and took a small amount of effort to snap it back into the intake, but to me that seemed exactly as it should be fitting to form a proper seal; snug and without 'play'. If your connector snaps right in without any effort, or with minimal effort, the o-ring is bad, as it should not move around once seated, or have excessive, or any 'play' when grasped and moved side to side.

 

nice rubber glove

 

Haha yeah, got a full box of 'em but didn't knew that they would be used for this

Thanks 03 XKR, that actually sounds a very viable solution. The o-ring's outer diameter seems to be about 15/16" or a bit less. Hafta do some browsing...

 

A follow-up. On the right, Jag's original o-ring, about 18x2.5mm or so. On the left, a new bigger o-ring 18x3mm. Fits in nicely and the connection is firm. The looseness is gone, and the leak as well. Now the breather is ok.



But now it seems that the intake duct connection to the throttle body is also leaking some smoke... the seal looks a bit worn so I'm gonna replace it as well.

 

Yes, the 'chain reaction', or 'domino effect'; after you replaced the 'weakest link', the leak moved along to the next most vulnerable seal, and so on, etc. Glad you got it fixed; the great thing about this is the price. I am sure you would have paid $$$$$ for Jaguar to do the same thing, plus you know they would have kept the car a few hours to pad their bottom line for a 15 minute repair, plus charged you $195.00 for a 0.17 cent o-ring.