how does one flush out rust from block?

[BRICH1260]

It will immediately start rusting again as soon as you de-rust it. Unless you plan on doing it frequently, you may not be gaining a whole lot. I am not aware of any coating that you can put in there that would last.

 

[1975oday22]

It will immediately start rusting again as soon as you de-rust it. Unless you plan on doing it frequently, you may not be gaining a whole lot. I am not aware of any coating that you can put in there that would last.

i realize that, wasnt asking if there was a coating to prevent rust. just something to remove it . lol. anyways thanks for the advices on here . i will just pressure wash with the hose and be done with it. hopefully the water will still go through the riser as i do not have a new gasket for it . i will most likely do that this winter when season over when i have the money to rip it all apart and have the gaskets on hand.

 

[Lou C]

I’ve thought of this over the years but never used anything to clean out the rust other than just flushing with water at the end of each season. I have filled the engine & exhaust with the best PG antifreeze I could find. Did that help? I think so…

 

[flashback]

If I thru a little acid into the river I boat on it would probably help the chemistry.

 

[BRICH1260]

Has anyone ever tried a product such as Evapo-Rust and let it sit in the block for a few days? I`ve used it on other items and have been fairly pleased with how it converts rust. It`s very fluid, not a thick paste and would flush easily without clogging small passages.

 

[Scott06]

Has anyone ever tried a product such as Evapo-Rust and let it sit in the block for a few days? I`ve used it on other items and have been fairly pleased with how it converts rust. It`s very fluid, not a thick paste and would flush easily without clogging small passages.

I have used this on classic cars but leave it in for a while. It is made by the evapo rust company. Got a lot of chunks out of my block on a 65 Pontiac. to really do it I think you would need to rig up a big tub under outdrive and idle relief ports, fill block and tub with this, rig up a sump pump to pump water to muffs out of tub... I think not moving you wont dislodge much

https://www.summitracing.com/parts/...MIwangk4KO_wIVTBOzAB3b7gf2EAQYASABEgIHU_D_BwE

 

[tpenfield]

I have only used Evapo-rust on surface rust . . . automotive body panels, etc. It is not very aggressive (IMO), so maybe it would be OK in an engine block.

 

[1975oday22]

as i said i will use my pressure washer in it. thanks.... id sooner be safe then sorry at this point. (wildlife and other animals, pets) yes exhaust is not good in water either however the alkaline in the lakes are far greater and eat it up..... anyways . not getting into a big debate here. everyone uses what they think will work . as for the riser . i havent touched that as of yet. gonna have to wait to get a gasket for that. i just hope that it is ok and lets the water through....

 

[Scott Danforth]

evaporust is just citric acid. similar to citrisurf.

however most motor forums use oxalic acid for restoration

run a bit of baking soda thru after and it neutralizes the mild acid.

 

[nola mike]

I’ve thought of this over the years but never used anything to clean out the rust other than just flushing with water at the end of each season. I have filled the engine & exhaust with the best PG antifreeze I could find. Did that help? I think so…

We're definitely on opposite ends of the spectrum on our thoughts on this. I think the surface rust you might get by storing an empty block is nothing compared to running warm salt water through it during the season. We should do an experiment...

 

[1975oday22]

here is before and after shots of the thermostat, before buying a new one, i decided to see if this one still operated. let it soak in vinegar for a few hours then took my brass wire spinner on my drill to it to clean it up. came out fantastic. dropped it into a boiling pot of water and whamo, it still works.

 

[Lou C]

We're definitely on opposite ends of the spectrum on our thoughts on this. I think the surface rust you might get by storing an empty block is nothing compared to running warm salt water through it during the season. We should do an experiment...

When I start up after winter storage I see no rust in the exhaust water after the AF washes out. Still running the OE intake manifold which as we all know tend to rot out right under the stat housing.
Discussion with local marine mechanics suggested that raw water cooled cast iron blocks rarely rust thru but the cyl heads start getting thin behind the valve seats after 15-20 years of salt use. So changing the heads on an engine that age may avoid a hydrolock. As we know the elbows rust worst of all even faster than the manifolds because they are exposed to hot exhaust gas & salt water.
We should do a test I agree.
Merc does put filling the raw water cooled engines & exhaust with PG antifreeze in their maintenance manuals & has for a long time. So I guess they think it helps.

 

[nola mike]

When I start up after winter storage I see no rust in the exhaust water after the AF washes out. Still running the OE intake manifold which as we all know tend to rot out right under the stat housing.
Discussion with local marine mechanics suggested that raw water cooled cast iron blocks rarely rust thru but the cyl heads start getting thin behind the valve seats after 15-20 years of salt use. So changing the heads on an engine that age may avoid a hydrolock. As we know the elbows rust worst of all even faster than the manifolds because they are exposed to hot exhaust gas & salt water.
We should do a test I agree.
Merc does put filling the raw water cooled engines & exhaust with PG antifreeze in their maintenance manuals & has for a long time. So I guess they think it helps.

Merc also said just run it dry forever before they recommended af. Again, you're storing your boat with salt water just sitting in the block/manifolds for what, 5 or 6 months a year? I find it hard to believe that that doesn't cause orders of magnitude more rust than flushing the engine, draining, and storing it dry. Just doesn't make sense.

 

[Lou C]

What causes the rust (iron oxide) is the oxygen. So how much 02 is in salt water vs air?
Engine restorers of classic cars usually store them with AF even when not running them or else the engines suffer bad internal corrosion over years of storage

 

[steegie]

can these oxalic acid treatments damage head and intake gaskets?

Maybe take some new (or used) gaskets, let um sit in that stuff, and find out. I used to work with wood bleach and it's pretty nasty stuff! Thing is, I'm not sure the effort is worth it. Let us know what you find out.

 

[nola mike]

What causes the rust (iron oxide) is the oxygen. So how much 02 is in salt water vs air?
Engine restorers of classic cars usually store them with AF even when not running them or else the engines suffer bad internal corrosion over years of storage

True, more o2 in the air But it isn't that simple. You definitely need water, and of course salt water accelerates the process. Also, once you have a thin layer of the surface rust, that slows additional rust. So again, flowing warm salt water will also scrub the surface rust more. Again, rusting blocks aren't a problem on freshwater blocks regardless of how they're stored. A dry freshwater block is in the same environment as a dry saltwater block, in use not so much. How would we do an experiment? Or, calling all chemists...