Preparing to replace manifold - any tips?

[Wilky1974]

I have just bought a stainless steel decat manifold from another member and I am preparing my 2004 FL ready to fit it. I was wondering if anyone has any tips? I have removed the standard manifold. The five nuts that hold the manifold to the engine are all a bit nasty. They are off but I was thinking I could replace them. Would anyone know the thread specification or should I just go to a Toyota dealer? the gasket appears to be in good condition. Can I reuse it? I am guessing that I will need two new gaskets between the new manifold and the other cat? Again are these best bought from the dealer? Any advice would be greatly receieved.

Thanks,

Paul.

[MartinC]

Get the gasket from a dealer, as they seem to seal better than the after market ones.  While your there you may as well get the replacement nuts.  Loosely fit everything, then make sure everything is in the right position and tighten everything up to the correct torque.  5 manifold nuts are 33 ft/lb I think.  Manifold to cat are 46 ft/lb

[Carolyn]

My biggest tip is to heat-wrap it before you put it in (it's much easier to do a tidy job of it when it's on the bench).  Heat wrapping keeps the engine compartment temperature down and aids exhaust efficiency.

Make sure the grooves on the underside of the plate that connects to the cat are clean and clear of any build up.  Clean the face of the head and manifold.

Use new head-to-manifold gasket and new crush-ring gaskets.

Clean all threads with a wire brush.

Use a good high-temp anti-seize compound on all threads, including the O2 sensors.

[Wilky1974]

....... thanks so much Martin. Just what I wanted to know.

[Wilky1974]

..... it's been heat wrapped by the previous owner luckily for me  s:) s:) . Hadn't thought about the anti seize compound - will get some tomorrow. Thanks very much for the advice  s:) s:) .

[John is200sport]

Some great info here. I've been thinking about doing this on my 2005 to completely eliminate pre cat failure.

I'm not interested in sound or performance gains, would this be worth doing? Can it all be worked on from above or does the manifold to cat section need to be got at from underneath. I assume soaking the nuts the day before helps to prevent them shearing, at 11 years old and 94k.  

Thanks in advance.

[MartinC]

Definitely worth doing.  Plusgas is your friend doing this.  Should be possible from above, but easier to get to the 3 amigos (cat to manifold nuts) from underneath.

[John is200sport]

Thanks very much. I've not had much luck in life with Exhaust manifolds in the past. I've got a massive list of things to do on cars at the minute so it will definitely be on the list if things to do. Can't beat piece of mind and sensible preventative maintenance.

[Joesson]

I would not like to try to get to the "Three Amigos" from the top.
Many on here have had problems removing them from underneath, such is their camaraderie for the mounting flange they are reluctant to part company. ( Maybe that is why they are so called?)
For me the "difficult" nuts were the manifold to head nuts, because I foolishly tried to remove them with a multi point socket.
Lesson learnt!
I earnestly suggest the use of Plus Gas and hexagon/ six point sockets only on tight nuts.
NB. The OE manifold to head nuts are "deformed" locking type and should be replaced with a similar all metal locking nut.
I used CopaSlip grease on all threads when replacing the fixings, other anti seize products are available.
I chose to  remove the precats and reuse the OE manifold.
This is a serious piece of metal and together with the OE heat shield I suggest works at least as well as any low cost after market manifold with heat wrap tape, and saves ££ for other things.
At the same time I renovated the main catalyser heat shields. Mine polished up well with a wire brush on an angle grinder.
Stainless nuts and bolts replaced the eroded welds and an exhaust clamp at the bend eliminated the annoying rattle that had started in that area due to a broken welded bracket.