Hi all, regarding the joint between the downpipe on my 5.3 v12 and the manifold. I recently replaced the sealing rings both sides and did all four. One side was replaced using the original nuts and studs while the other had new studs and brass nuts. The side with original studs and nuts I’ve nipped up a couple of times after running and all is good. The other side however needs at least a couple of nuts nipping every time and still isn’t sealing. These new brass nuts aren’t as deep as the original nuts and I’m wondering if they are coming loose. Not all four need tightening each time on the bad side, it varies. Do I just keep nipping them up until eventually all settles in or should I double nut them do you think? Thanks in advance

 

Jaguar seems to have discontinued using brass fasteners when the cataverters were introduced.
The replacement fasteners are steel nuts with stainless steel insert threads. (helicoil type threads)

The extra heat generated was likely the reason for the change?

 

Brinny
Genuine Jaguar crushable manifold to downpipe sealing rings are NLA. The aftermarket ones are not as reliable, and I have found need nipping up for about 4 months of use before properly being tight. I am not saying this is your trouble, it might be the fixings, but if you used aftermarket rings, it is probably the reason.
I have four genuine ones in stock against the day I cannot afford petrol and decide to rebuild the motor to keep myself occupied!

 

Thanks. I’ll keep nipping up then!

 

Greg - how do these compare with your originals? I just got these from SNG last week and they look exactly like what I'm replacing, albeit not compressed Should I be concerned with these not getting right?

 

They will work OK, non-OEM ones do look like the OEMs, but they are not quite the same, but you have no other options as far as I know. They just need re-tightening a few times, so make sure you can get a long extension up from below to do that, after the car is back together.
I find this NLA situation from Jaguar really annoying and casual; nearly all the classic models use this part and it is quite obvious they could be made to the same spec if a bit of effort was to be made.