Rust in thermostat housing

Discussion in 'Engine Performance + Maintenance' started by deven bullis, Mar 1, 2021.

  1. stutaeng

    stutaeng I'm Awesome

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    Um, no idea what those intakes really look like....but, if it is cast iron, then the casting must be fairly thick and complete rust-through seems highly unlikely, no? I'd say dunk it in that cleaner, but probably will need mechanical means to remove heavy rust. Don't those marine boat engines use the surrounding water to cool the engine? How does that work if boat is in the sea with salt water?

    Can you post an overall photo?

    I'm not sure how you would get in there though. Maybe a die grinder with a flap cookie disc or scotchbrite disc?
     
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  2. Erik the Awful

    Erik the Awful Supporting Member

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    I'd brush the crap out of it, deck the thermostat surface, verify the lip that holds the thermostat isn't trashed, and reassemble it.
     
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  3. deven bullis

    deven bullis AWS Certified

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    [​IMG]
    Here is a comparison vs the stock L31 intake, I do have a sandblast cabinet so I might try to sandblast the inside but I’m afraid of knocking off more of the thermostat lip


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  4. stutaeng

    stutaeng I'm Awesome

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  5. deven bullis

    deven bullis AWS Certified

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    Thank you for the info! I want to at least try to save it, it’s too rare of a part to just throw away without at least trying to save it. I’ll try hitting it with a wire brush/wheel when I get home from work and go from there.


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  6. Schurkey

    Schurkey I'm Awesome

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    In MY shop, I'd knock-off any loose rust in the glass-bead cabinet, or with a wire brush, or whatever I found handy. Then, it'd get set-up in an elecrolyte solution, and have a battery charger hooked to it.

    Electrolytic rust removal of cast iron will remove ZERO non-rusted material; you could leave it in the tank for weeks if you wanted to. The downside is that it doesn't work real well on interior surfaces, and that's a major part of where you want the rust gone-from.

    You'd need a plastic tank big enough to contain the part you want to treat. A plastic 15- or 30-gallon drum works great. Small parts could go in a one-gallon plastic pail.

    You fill it about 2/3 with water, and add WASHING soda. This is not the same as baking soda, and it's harder to find in the grocery store.

    [​IMG]

    You grab a sacrificial chunk of iron or steel. Something that can rust away to nothing and you don't care about it. Scrap sheetmetal works great, especially if you form it so it's wrapped-around the part you want to "save". Old exhaust manifolds work OK. DON'T use stainless steel.

    You need a battery charger--more powerful is better. I bought a 24-volt charger specifically so I could do electrolyte rust removal quicker than with a 12-volt charger. But don't get me wrong--a 12-volt charger works fine, just takes longer.

    You bolt a STEEL strap to the part you want to clean, and a STEEL strap to the "sacrificial" iron/steel. Both parts go in the electrolyte solution--close together but NOT TOUCHING. Hang 'em from the rim of the plastic barrel, or from a non-conductive (wood dowel or similar) laid across the top of the barrel.

    Connect your battery charger leads to the steel straps that stick out of the electrolyte. DO NOT SUBMERGE THE BATTERY CABLE CLAMPS!!!!!

    Really, really important: The positive lead goes on the SACRIFICIAL item, the negative lead goes on the part you're trying to save. Do not screw this up.

    Skim the scum off the top of the electrolyte now and then.

    As the battery charger pours electrons into the parts, the rust jumps off the part you want cleaned, and corrodes the sacrificial iron/steel. Depending on the piece you use as a sacrificial element, you may need to disconnect power, remove the sacrificial piece, and sandblast it clean again. That restores the current flow and speeds-up the process.

    And you'll almost certainly have to rearrange the parts--this process is most effective where the rusty part and the sacrificial part are closest together, so you'll have to move them around to get the whole part cleaned.

    Your "cleaned" part comes out of the electrolyte with a black discoloration. Leave it, or wire-brush, sand, grit-blast the "black" off. You'd do less damage to the part to remove the rust with electrolysis than with heavy grit blasting, then remove the black with light grit blasting.

    This does not work with aluminum, I don't think it works with brass, magnesium, copper, etc. IRON/STEEL ONLY, and don't put stainless steel in the tank either.
     
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  7. Supercharged111

    Supercharged111 I'm Awesome

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    He's not the only one. See sig. They've become unobtanium, I bought mine back in 2012. I believe there's a version out there with a 4 bolt throttle body, but the 3 bolt ones are about extinct.
     
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  8. deven bullis

    deven bullis AWS Certified

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    Wow! That makes me want to try and save this even more, this one is a 3 bolt throttle body intake. IIRC the seller told me the Mercruiser intakes were 4 bolt and the Volvo Pentas were 3 bolt.


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  9. JeremyNH

    JeremyNH Newbie

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    Here's mine, to be installed in May when the weather improves. It too was rusted some, though not as bad as yours. I hit it with a medium abrasive blaster to clear the heavy rust then soaked in Evaporust for 2 days. After sandblasting it wasn't near so bad as I had though it to be. With your picture I would be most concerned about the thermostat seat. The O-ring won't seal if you have any deformation on the surface.
     
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  10. JeremyNH

    JeremyNH Newbie

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    upload_2021-3-3_14-35-9.png upload_2021-3-3_14-36-19.png
     
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