Hello to all,
I have 1989 XJS. I replaced the starter about a year ago and ended up with a small but pesky exhaust manifold leak on right side.
I replaced the manifold gaskets and brass nuts that I bought from Moss Motors. The studs seem to be original (I don't want to snap them), so I haven't over torqued the nuts.
Any recommendations or suggestions?
Thanks for any help.
Joe

 

Your studs are reasonably strong, the brass nuts are not.
Use stainless nuts (won't rust) and torque to 25-30 foot pounds, that should seal the gasket surface if tht is where your leak is

Caterpillar (tractor manufacturer) sells exhaust manifold sealer that fills cracks, if that is your problem.

 

Is the leak at the manifold-to-cylinder head gasket? Or at the round "donut" between the pipe and the manifold?

If the later, and it's an original style donut, they're designed to be crushed a bit ...so it takes a bit of a grunt.

If by chance a stud breaks it isn't the end of the world. The are two unused stud holes on each manifold. Just install new studs an turn the clamping flanges 90º

Cheers
DD

 

Also make sure the flange on the pipe is tightened evenly too, it needs to be square with the pipe to compress the donut evenly.

 

If this is a V12 I'm surprised anyone is discussing torque settings - you ain't getting any torque wrench on the lower manifold nuts - you can barely get a spanner / wrench on the things - I suppose you could use a small one but it isn't exactly spacious under the V12 exhaust manifolds especially when the downpipes are in place.

If you have had a blow by on a gasket then no amount of tightening will solve as the gasket gets burnt away / eroded if it is run in this state long enough.

 

Thanks Doug for the info.
It's the round donut gasket type.

 

Yes Jagboi, I did evenly tighten each nut. I think i will replace with stainless steel nuts and tighten down they more

 

Very true Ben. Not much room in that area underneath or above.
I haven't driven the car much since I replaced the gaskets so I doubt I cooked the gaskets but anything is possible.
I have had so many other issues including no horn (just solved), transmission stuck in first gear (no access panel to the governor on passenger side), recently no brake lights (seems to be the flasher relay).
During the summer, I had a "no start" issue. I solved that many hours later discovering bad wiring six inches from the CTS.
These cars will test anyone's patience.

 

Good to know " TooMany" Thanks!

 

No worries, on reflection and a thorough perusal of this board, you will see that your maintenance issues are few and minor....for a 36 year old car 🤔

 

Do yourself a favour and dab a light smear of anti-sieze on all exhaust threads before installing a nut 😣

 

The brass nuts should work. The reason for them is that brass has a coeffecient of expansion that is roughly double that of steel, so the grip gets tighter as the exhaust heats. It helps prevent leaks.

As a beginning, I would tighten more and see what happens. Worst case is you'll need to replace the donut.

 

The brass nuts were originally fitted by Jaguar so that they would not rust solid to the studs; Half a century ago, the interface was as described above....Now, we often find that decades of use and abuse have rendered the thread grip ability of the brass to be inadequate (stud diameter has rusted smaller), and they often strip out before coming to torque, so stainless seems to work better

 

We like using "tall nuts" so that there is no stud thread beneath the nut, which rusts in free air and keeps the nut from being able to be removed

 

For sure they will, that bargain can soon be less so by the time you have paid for beer or psychiatrist visits - but if we all based what we do on common sense many more of these cars would have long since been scrapped. I think the biggest problem for these cars is those that get them not fully appreciating what comes next when it comes to ownership, many spare parts available are from unfinished projects, whether that's good or bad can be debated, I have found out the hard way that the shiny off the shelf stuff that is not 'genuine' can vary widely in quality.

The older Jaguars in general can not only be a money pit but a time vampire also, the challenge is that fixing one thing is likely to disturb something else so it is a never ending squirrel chase, if you're going to do a job on these cars better do it right because cutting corners won't end well, I think the electrical side of these cars is the worst followed by the 'bodges' imparted into the fuelling system because of the injection system immaturity.

Unless your totally crazy and tear the whole thing apart you won't stop chasing issues around but that can be part of the 'fun' of ownership ... no three guesses what I ended up doing though.

It may be worth noting that the reason brass is used it that it is less likely to come loose - at least thats my understanding.

 

No need to confess Ben! you are among fellow sufferers.

 

I'm reminded of the lyric "I've always been crazy but it kept me from going insane"
(Tip of the hat to Waylon Jennings)


True enough!

Really, though, as hobby cars these old Jags are easier to own than ever. So much much knowledge and experience and been documented and shared on the internet that we know more a lot about them now than we did 30 years ago.


There are 1001 ways to enjoy the car hobby. For many "the journey" is really the most important part. I know a guy who spent twenty years......twenty years.....on his hobby car project. That's what it took to for the end result to be just exactly what he wanted. I doubt he's driven more than 500 miles since completion. The journey was everything for him. And that's not a criticism, mind you. The sole purpose of a hobby, any hobby, is to derive pleasure. And he did, most assuredly.

Me? I do enjoy the work, and I like to do a good job, and I like to be proud of the end result. But mainly.....I want to get the car on the road. This usually means be satisfied with less-than-perfection. And that's Ok with me.

Cheers
DD

 

The exhaust leak does get quieter once the car warms up to temperature, so it does seem that I'm get close to sealing up the leak.