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[x1xv45]

The one that is bolted on to the exhaust manifold. I want to get this off if possible to deal with a crack in manifold, right on top in middle, easy to get at - I just showed it to a welder who says it would be easy to weld up. First, do those bolts go right through the manifold flanges into the head? If they shear off, it would leave me with a head-off situation to drill them out. Second, if I can't get the pipe out of the way by unbolting, could I just cut it off and disable this eco-device without making the ECU shut down the engine or other dire results?

[Abiton]

The bolts that hold the SAI pipes into the manifold do not go all the way through into the head.  So no problem there.

You can block off those pipes without upsetting the ECU/engine, as long as you leave the solenoid valve in place that enables a flap valve in the air piping up near the power-steering fluid reservoir.

If you do try to get your manifold welded up, take it to someone who knows how to weld cast iron, i believe it's not completely straightforward.
Also check that the flange face that bolts up against the head is still flat; they tend to warp.

[x1xv45]

"The bolts that hold the SAI pipes into the manifold do not go all the way through into the head." - good news!  I'll try to find the solenoid valve you mentioned. As for the welding - the proper way to weld it would be manifold off, and from what I've read, some severe heating prior to welding. My problem with getting the manifold off is the possibility (likely?) of sheared studs would require the head to come off for drilling out - cost near the value of the car.

[Abiton]

Sheared studs are a possibility, but not always 'head off' to resolve/remove.  Just be sure to spray plenty of PlusGas on the nuts before undoing, and then some on the studs where they go into the head before attempting to get them out.

It may not be a problem at all though.  When I removed ours, a few of the studs came out as I undid the nuts, and the others without difficulty.  The one that had already sheared off (sub-flush with the head, the reason for removing manifold) was a bugger though, but still achieved without head removal. 

Just follow the rubber SAI piping and you'll find the valve I mentioned, 2-pin electrical connector.

[x1xv45]

That's encouraging, but after I've lined up a backup motor. I heard this is better than PlusGas: Ambersil Rust Flash. Has anyone tried it?

[Abiton]

I think technique is more important than choice of penetrating fluid.  Though, whatever you use it's a good idea to apply it a few times, at intervals during the 24 hours before you attempt the undoing.

Giving the bolt/stud/nut a sharp tap with a small hammer, using an appropriate 'interface' material to avoid damaging heads/threads will often crack the corrosion bond/cold weld that is causing the fastener to be stubborn.

Attempting to tighten (just the smallest movement possible) a bolt/stud/nut that doesn't want to undo, seems to help it go the other way, for reasons that I don't understand.


Best of luck. 

[Entwood]

I think technique is more important than choice of penetrating fluid.  Though, whatever you use it's a good idea to apply it a few times, at intervals during the 24 hours before you attempt the undoing.

Giving the bolt/stud/nut a sharp tap with a small hammer, using an appropriate 'interface' material to avoid damaging heads/threads will often crack the corrosion bond/cold weld that is causing the fastener to be stubborn.

Attempting to tighten (just the smallest movement possible) a bolt/stud/nut that doesn't want to undo, seems to help it go the other way, for reasons that I don't understand.


Best of luck. 

As was explained to me ... a very many years ago ...

The corrosion usually takes place between the nut and the unused portion of the bolt, as this is the area exposed to atmosphere. The bolt bit inside the nut, and the nut face that the surface is applied to, get very little corrosion.

So if you try and undo the nut you are forcing the threads over corroded metal, which is usually of greater volume than uncorroded, so it gets even tighter. If you "tighten" first, even a fraction, you are moving AWAY from corroded towards clean (ish), so have more chance of breaking the join.

If you wire brush the exposed bolt you can clean off much corrosion and make things easier.

Once the nut starts to turn, when you undo it do 1/2 a turn undo, 1/4 turn tighten, wipe the bolt, and keep going that way until you reach "clean" metal.

Its a bit like using a tap & die, you need to remove the rubbish from the thread rather than try and travel over it.

Was taught that in metalwork at school and it seems to have worked ever since !!!

[Abiton]

 
Nice one Entwood, that makes good sense. 

The wire-brushing bit is something I did, but had forgotten I'd done.  I love getting old...