I just had my NEW Hall radiator repaired for leaks, and all the joints re-soldered, which cost about the same as a new one! Anyway, before I pulled it I had to break the cooling lines for various reasons over 1,500 miles or so. Each time, brown coolant. I was told by the re-builder that's what comes from cast iron heads, and not much you can do about it except maybe use a silicon based coolant, and service the system more frequently. I thought the engine passages were sleeved, or there was some built in protection from this. The rebuilt stock engine has about 3K miles on it.

Does this sound familiar? Does the type of coolant make much difference?
Original Post
Since you insist on using stock parts your front coolant tubes are steel. Steel + water = rust. I wouldn't be surprised if the rust from these tubes has not accumulated through out your whole system turning it brown. When I changed mine a rusty brown soupy mess was inside.

Hi Ray

If the engine were recently rebuilt, and if it had been hot tanked as a step in the rebuild procedure, the water jackets should have been nice and clean.

Although rust is obviously a possibility when the heads/block are cast in iron, it is not endemic to all engines employing iron castings, just those that have been neglected.

I've worked on cars in the past in which their maintenance had been so neglected that no amount of flushing would make the "rusty water" stop. On the other hand I've seen many high mileage cars which had received just an "average" amount of maintenance in which the water jackets were just clean and normal.

Use regular anti-freeze (green?). If the tap water in your area is soft or low in minerals you can mix the anti-freeze with your tap water, but if the mineral content is high I suggest purchasing the anti-freeze which has been premixed with water off-the-shelf.
I have not tried, but from another discussion on removing rust, I thought about this product

Their FAQ does give instructions on how to use it in a coolant system.

I am thinking when I go back together is to first bypass the radiator, heater core, thermostat and do a coolant flush.

another item I have seen on industrial engines is a spin on coolant filter that just loops a partial flow, like installed instead of the heater core with constant flow till it cleans out the system.
Okay, thanks for the suggestions. I think I will start with just several frequent changes of distilled water and a light mixture of anti freeze, maybe an additive and go from there. I do think it's block related though, wasn't hot tanked.
To elaborate on JFB's Evapo-Rust, their product to dissolve rust is Thermo Cure. If your engine is the source of the rust, you may need a stronger chemical to dissolve the rust rather than continuing to use distilled
water/antifreeze solution which may only coat the rust.
I have used the original Evapo-Rust product for rust removal on parts and pieces for my car and other projects. It works great. Can I say "amazing" or has that word been outlawed? If it was me knowing how the original product works I would give it a try. Reading the instructions on the Evapo-Rust Cooling System Cleaner I would buy enough to treat twice as instructed, 6 quarts.

Also do not use Distilled Water. Pure water is corrosive and will pull minerals from wherever it can get them. If you used distilled water that could be contributing to your issue. You want to use drinking water with "minerals added for taste".

Using just water, whether it is well, tap, distilled, de-ionized, bottled drinking water etc, is not a good idea as this will cause corrosion. Some sort of additive is recommended with possibly anti-freeze.
Prestone has demineralized water in their mixes I looked at and recommend flushing with tap water with distilled water for mixing when using conventional green antifreeze, which I use as I have a copper radiator and heater core.
Best to follow the manufacturers recommendations as to type of water to use.
Other links..

Iron rusts if it is exposed to oxygen with no protection. Water has lots of oxygen so it likes to make iron rust. The block, heads and water pump/impeller are all made of iron. So if you use distilled water it is just going to keep on rusting. Vinegar is an acid which in enough quantity can be used to eat the rust and iron but inevitably it will be added with water which will try to make the iron rust anyway.

As George said use pre-mixed antifreeze and just change it a little more frequently as it has a rust inhibitor added. After a couple of changes it will be clean again.
Hi all, the 351c from my Pantera was completly rebuild and inox steel renew for the coolant tubes but we fill with "Evans coolant" is a waterless coolant, using this product is impossible to have rust in any part of the engine.
If you want do a substitution of your coolant, previously you need to use a special liquit form Evans to eliminate all the water in the coolant circuit, after this process, you can put the Evans Coolant, is not cheap but is good for your engine conservation.
we did a test about the performance and we saw a temperature reduction about 3 celsius degree.

As an update, decided to use the "Evapo-Rust Thermocure" designed specifically for cooling system rust removal. After running the engine for 15 minutes or so a quick test sample of water is now jet black, Something is happening! A little more time in there, and a couple of flushes with plain water, and then back to regular anti freeze mix. I think that's enough obsessing about this problem, Smiler
Interesting, RR. The color change you observe is good. Iron oxide comes in two varieties: Fe2o3 is fully oxidized ferric iron, brown in color. FeO2 is partly-oxidized ferrous iron, black in color, so that treatment removed some oxygen from the iron (as well as some iron, too). Unless your coolant stays on the 'base' side with a pH of 7.0 or higher as measured by swimming pool test strips, the iron will slowly revert to the more stable form of red/brown. Keeping coolant on the basic side also slows corrosion of any aluminum in the system: radiators, water pumps and cylinder heads. Good info.
Originally posted by dvil:
Sure it's not exhaust entering the cooling system? It could turn the coolant brownish.

Makes sense, but I don't know how that could happen.

Even using the Evapro-Rust I had to pass about 30 gallons of water through before it was close to clear. I think it will always be this way, and just have to change more frequently.

Add Reply

Likes (0)