• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

240 Use acid to free weld-rusted exhaust bits

Rust at the exhaust manifold studs and nuts. Rust has welded where the flange nut meet the manifold. Rust at the manifold to header pipe. And one hanger. The used Cat back from 2015 is done. All welded together. yay.

Recent research suggests the user of either muriatic acid (a dilution of hydrochloric acid to <9) or white vinegar. Eye dropper or toothbrush. Rather vinegar as it is far less reactive.

I understand with Kroil or Zep, as these have a rust dissolving action, it can take days, week, months. Cycle the heat by running the engine.

Have you folks use acid to free them rusty nuts and bolts like in the exhaust?

Please advise.

Thank you.

Bruce

--

<img src='https://brickboard.s3.amazonaws.com/brickpix/13953.jpg' width='1000'><br />
<br />
<img src='https://brickboard.s3.amazonaws.com/brickpix/13954.jpg' width='1000'><br />
<br />
<img src='https://brickboard.s3.amazonaws.com/brickpix/13955.jpg' width='1000'><br />
<br />
<img src='https://brickboard.s3.amazonaws.com/brickpix/13956.jpg' width='1000'><br />
<br />
<img src='https://brickboard.s3.amazonaws.com/brickpix/13957.jpg' width='1000'><br />
<br />
<img src='http://cleanflametrap.com/imgcode.jpg' width='900'><br />
 
Just use a plumber's torch on the manifold studs/nuts. Nothing in the pics looks to be salvageable.
 
With 5% acetic acid vinegar (the stuff you put on your chips), it will probably be 2121 before the rust disappears. Muriatic acid will dissolve rust fairly quickly; but, you need to keep the part continuously immersed. Eye dropper / toothbrush is not going to cut it. Phosphoric acid is also an effective rust remover. I think that is what POR Metal Prep is. A better choice might be Naval Jelly which is also phosphoric acid based and is jelly like so you can brush it on and it stays put. Generally not as fast as immersion in muriatic acid.

Kroil is just penetrating oil. ATF mixed with a little solvent will work just as well. Penetrating oil (including Kroil) does not dissolve rust.

Heat is the 'hot' ticket. Perhaps a pre clean with some Naval Jelly if you need to see what you are doing. An Oxy - Acetylene torch would be ideal; but, a MAPP torch might also work. I am sure you can find some You Tube videos showing removal of exhaust studs with a torch.
 
Just pick up a can of PB Blaster and spray the threads a couple of times over the next few days. I was skeptical about the product and resisted buying it for several years. It really is a miracle product. I have not had a Volvo exhaust manifold nut not come off ever since trying the product.
 
Just pick up a can of PB Blaster and spray the threads a couple of times over the next few days. I was skeptical about the product and resisted buying it for several years. It really is a miracle product. I have not had a Volvo exhaust manifold nut not come off ever since trying the product.

PB Blaster and Kroil are very nice with anything rusty! My first experience with PB was on O2 sensors. So helpful.
 
Just use a plumber's torch on the manifold studs/nuts. Nothing in the pics looks to be salvageable.

Exactly...Get the manifold to downpipe nuts off, drop the whole exhaust, you might be able to salvage the down pipe and cat. If you wanna do it piecemeal, cut the clamps or bolts with a grinder, or break them by twisting on the frozen fastener.
 
Phosphoric acid would convert rust to ? iron phosphate?

I got a Volvo cat back with Starla clamps and hangers, so I'll use the Volvo hangers.

Slather nickel anti-seize in and on exhaust unions from the cat back tube onward and all hardware.

I'll continue to apply drips of Kroil and (just found the can!) P'Blaster. I'll begin the tap-tap with penetrant oil soon.

Hope to replace from header pipe and reinstall thge cat back on an all stock system.

Before rust gets this 1990 240 DL (li'l red) Wagon, hope to find a rustless (HA!) 242 and place 1990 drive line there in the dreamed for 242. ...
 
Sawzall and cutoff wheel looks like the way to go. PB Blaster or Kroil on the manifold nuts. You want to save the hardware or something? Looks like you could just cut all that crap out, nothing worth saving there.
 
Whatever panther piss concotion you have followed by flame to boil the rust out, repeated until they move.

Bingo! Dad and I have been using Deep Creep lately because it doesn't stain surfaces, clothing, etc. like the PB juice. And it seems to enjoy torch application


also +1 pop that manifold off and drop the whole assembly to salvage the downpipe, that's nasty
 
As has been said above, if you are removing the exhaust (none is factory in your pics) it looks like it all needs to go in the bin.

The only thing that matters is getting the manifold off the head without snapping the studs. I'd use a torch to heat the flange nuts, they typically come free after that. You can try (with the engine hot) just tightening the nut a fraction & then undoing them - that will often break the rust free. You will probably have to replace the three studs for the DP in the manifold no matter what, so might as well just get it off the car first.
 
Back
Top