Putting the downpipes back and was wondering if it would help anything to heat wrap the lines running between the downpipes and oil pan - seems it might help deflect some heat.

 

It will certainly help your starter motor when parked hot on a hot day.

 

You should ceramic coat your pipes

 

There is nothing good about the heat (especially in the summer) and the proximity of these CAT'd pipes tooooo near everything in the area coming out of the engine area. For me, before I knew anything about the XJS, hadn't even driven yet, the thought of them as close as they were to everything made me cringe... I guess I got this close up vantage point due to lots of attempts at dealing with steering rack problems early on.

Delete them... Take some time and hawk ebay and other sellers, and when you get the two used downpipes mount them up, have an O2 bung welded into them.

I think that if I ever get into a situation where inspection became a problem, without CATs, the downpipes are so easy to remove & swap, I would spend a day swapping out downpipes, getting the sticker, and swapping them back. That's just me. As it is now,,, if I pulled up with my car on fire,,, my guy would STILL give me a sticker, lol

 

Out of curiosity, how hard is it to remove the exhaust manifolds and downpipes? Ceramic coating would appear to be huge upgrade and help deal with excess heat in the engine bay.

Thanks

 

A pain on a V12 engine in car, theoretically doable, with horrendous access problems, but in practice very hard to do with old studs and corroded nuts etc etc. Easier and quicker to take out the engine!

 

I had a feeling that was the case.

 

I hate ta disagree. I really have no idea how long it had been since the downpipes on my car had been touched, but with a 15mm/9/16th wrench I was able to turn on 4 of the bolts without issue from above, breathers and their backplates out of course. For the other 4 bolts, car jacked up with heat shields removed (with CATs), a long extension and deep socket (can't remember if I used a swivel extension) the other 4 were not bad either. Pulling the downpipes out with the CATs I remember being a bit of a pain due to the tighness of the area where they lived...

Discon of each of my intermediate pipes which are held to the downpipes with with 3 easy to access bolts and a triangle flange with a little donut style gasket that makes life easy. I needed longer intermediates pipes after deleting CATs fabed by a local shop,,, the shop was a pain in the ****.

I have to say that I didn't think about swapping and the challenges of REPLACING CATs for a inspection situation, especially with the second CAT and shorter intermediates, which would be a tough thing, unless the intermediate pipes and old cats were left rightly connected, put oft to the side and could be just buttoned back up....

All that to say, at least for me, it was not that bad. If I had the doe$$$, I would prolly pay 100 or so to have them swapped the day before the "inspection". Pop them in the car and drive them to the shop... And swap them back when done.

I did NOT want the car in NYC summer heat cooking with the CATs in stop and go summer traffic. I like the idea of ceramic pipes, but it's also greater than what my wallet allows.

 

There are 2 cats on each side: a primary cat attached to the downpipes (1,2 in the schematic below) and a secondary cat (11,12) attached to the primary via a clamp.



It looks like the secondary cat can just be unclamped and replaced by a slightly longer intermediate pipe.

With the secondary cat off, would it be possible to ream out the honeycomb material inside the primary cat from the backside using a drill, saw blade, pliers, etc., without removing it and the downpipes from the engine?

The schematic makes it look like there is a short exhaust pipe at the back of the primary cat that might make it hard to get access to the interior cavity of the cat. But in the photo below, that pipe appears to be fairly short and wide.




Or am I trying to be too clever by half?

 

I had my cats gutted with a crowbar. Its fine just ensure any O2 sensors are removed before the ramming begins lol.

if you want to do your exhaust in ceramic coat yes access is abit painful but a good few days of soaking all of it in liquid wrench does wonders.

 

What you can't see from the back are the coils of catalyst at the inlet of where the forward catalysts attach to the exhaust manifolds. They are capable off falling in and blocking the larger catalyst,or blocking the inlet partially or completely. You can't get to them from the exit. See pictures.

 

JJJ
The manifolds, not the downpipes, are the things that are hard to remove.