AJ16 Exhaust Manifold Cracks

[davidr]

The rear manifold on my 1996 Celebration has 2 cracks in it. I hadn't noticed until I took the heat shield off to take some photos for a magazine piece! They aren't noisy but they are definitely leaking as I can see soot on the inside of the heat shield.

2 distinct cracks in the rear manifold

Tell-tale soot marks on the back of the heat shield


So my options are
a. Live with it
b. Find a second hand one
c. Get it repaired

Any suggestions? I think they are the same for any AJ16 engine but does anyone know if one from an AJ6 will fit?

[steve_m]

Would JB Weld be any good or is the temperature too high?
It worked well on the cracked filler neck of the intercooler on my boat.

[Tintin]

Hopefully this will be one of the parts Jaguar Classic will be re-introducing - if the cracks aren't too bad and you can put up with it I would be inclined to wait until the new ones become available. Any salvaged manifolds may have the same weakness and be on borrowed time. Otherwise I would go for a repair. Samar Precision Engineering in Andover did a good job on my XK manifolds - the chap there (name escapes me for the moment) is also a petrol head.

Robbie

[PaulGover]

Would JB Weld be any good or is the temperature too high?
It worked well on the cracked filler neck of the intercooler on my boat.

Not a chance; AFAIK basically it's an epoxy resin, and they denature at something less than 200C.

[davidr]

My good friend BrakeBuster noticed one for sale at a reasonable price on eBay so that's on its way now.
I sent a picture and an enquiry to a firm that welds cast iron and their minimum price to repair it was £300 + VAT so £57.50 for a good used one looks like a bargain!
More to follow when the eBay one arrives

[ptjs1]

David,

As I recall, the stud pattern is different on an AJ6 manifold. I remember writing in the magazine many years ago that I suspected that 50%h+ of the cars were running with unknown cracks in the manifolds. the only indication being a very slight chuffing sound on immediate startup that settles very quickly indeed as the early heat buildup in the manifold closes the cracks. That's why you don't even see much sooting behind the heatshield.

I'd like to see a welded repair but I understand it's really difficult to do and not just move the problem to elsewhere in the manifold.

If you're buying a used one, don't overpay as eventually that will crack also anyway even if it hasn't got a crack now.

Also be very careful to support the downpipe when you undo it from the manifolds. As you know the really weak spot in the AJ16 system is the welded 2-1 collector at the end of the downpipe. Leaving the pipe disconnected and unsupported puts an additional load on this very split-prone weld point.

Cheers

Paul

[ng4xjs]

Mine too has a crack and is leaking but okay when warm. Was marginal on MOT this year. Can a leaking manifold cause a big decline. Normally okay on emissions so wondering what to do for next year. Have sine put some CAT cleaner through the system and always run the higher octane option. Mileage okay so nothing really obvious. Any thoughts.

Nick

[greenie60]

replace it don't bodge it with jb etc.
just replaced mine on my Daimler (xj40)

[PPV]

My company used this one a few years ago: https://castironweldingrepairs.co.uk/

[poprivet]

Bronze welding is relatively easy, but the manifolds are a difficult shape to hold when skimming flat afterwards.

Al

[ng4xjs]

I'm planning on taking mine away for a short break shortly. Only marginally audible manifold noise when cold (think it's the rear one) so I'm hoping the consensus is to carry on using it until something newer or better comes along? I've also just taken to lifting off slightly when the auto-box changes from 1st to 2nd to avoid harshness.Okay when warm. Otherwise it means taking the XType.

I guess our old cars are just getting older (I'm thinking of retiring this year)

Happy Days
Nick

[J44EAG]

The problem. These manifolds are known to crack and leak given age and highish mileage. I`m an ex-licenced aircraft maintenance engineer and from experience I know the aircraft industry would never tolerate manifolds which fail so readily and endanger people, air travel or third party damage.

The understanding of the problem. If I were to experience these issues if running an AJ16 engine, then I would be looking for a reliable solution to the problem. The diagnosis would be that the manifolds thin and crack with use and endanger users through the possibility of noxious gases entering the cabin which may lead to occupants inhaling poisonous substances that are known to cause un-conciousness or even death.

The solution. A re-design of the offending components using welded stainless steel "banana bunch" exhaust down pipes sourced from a reputable local or national exhaust fabrication business.

My take on the matter.

Mike K

[ng4xjs]

Agreed Mike. Recent garage inspection passed it as serviceable but your points are very valid.

Anybody got a spare manifold they no longer need?

Nick

[cafcpete]

Nice stainless steel version.
Despite what it says (AJ6) it’s for the AJ16. I have just ordered one for my XJR6 but it is a 10 week waiting time...

https://www.haywardandscott.com/jaguar/ ... ifold.html

[J44EAG]

That is just the sort of thing I had in mind...see my last post above.

At £1260 inc VAT, the price is not lightweight but the build quality shouts the excellence of the finished pieces. The components certainly look beautifully made. That is no amateur production.The banana bunch tubing should bring performance and some economy not to mention getting away from the cast OE renditions. How I wish there were a similar units available for my X350R where lack of space would seem to dictate an exhaust gas stifling arrangement.

Mike K