I have a 66 442 with a 455. I’ve flushed my engine and radiator several times. I’ve used different things like prestone, evaporust and oxalic acid. After flush all the rust out, and refill with fresh antifreeze, rust is back in a month. I don’t have leaks, the system is tight. I’ve heard air could cause rust so i fill radiator to the top and let excess bleed off to overfill tank. The temp runs about 210-220 in the florida summer, with the air on.
The engine does not sit level, the back sits lower than front, not sure if air could be trapped. i’d appreciate any ideas that might help me eliminate my rust problem.

 

In my opinion, you can't adequately flush the engine block without removing the block plugs...

 

Along with the plugs, you may need to pull thermostat. Would leave the flush in the engine for a few long drives and then flush with water and refill with distilled water/anti-frz.

 

The rear of the engine will be 3* tilted lower than the front. After driving around with Prestone engine flush in the engine for a few days, I just flush until the water runs clear with a garden hose hooked to an old Prestone heater hose connection.

 

A very slight head gasket leak will cause it also. Find someone with a combustion gas tester to see if that might be the issue.

 

I agree with removing the block plugs and thermostat to get a thorough flush.

 

Check for combustion gas as suggested. I agree the best flush when trying to clean up a dirty system is by pulling the block plugs and T-stat. You may need to remove the heater hoses and flush the heater core independently. I've entertained the idea but haven't done it of removing a block plug and flushing up through there and out the water outlet neck.

Good luck!!!

 

Your first action will be to do as Bill suggested. If that is negative, consider my experience.

I've had this problem with cars that have been run with only water in the cooling system.

I found an effective, simple way to deal with this... Buy a coolant filter and mounting base; plumb in series with the heater core.

Keep tabs on the filter. If the filter starts feeling cool after a drive, change the filter. The coolant will be sparkling clean very quickly and will stay that way after using a filter for about 10,000 mi.

 

I didn't mention it but I've flushed with the thermostat removed. I haven't tried the other suggestions but I will, thanks for the input.

 

Excellent advice by all above.

 

BTW, if by chance I've gotten all or most of the rust out on my previous flushes, is there something that would cause it to come back so quickly?

 

As Bill mentioned combustion gases getting into the cooling system or more sediment that got into suspension later. Are the engine ground straps in good shape? I'm asking because I'm thinking of potential stray currents/electrolysis being the cause. Do you see pitting in the cooling system?

 

I had a old Ford 351 in a 85 Pickup years ago ( I know different animal for sure ) , that thing had the rustiest coolant I ever saw. I was sure I could fix it. I flushed the cooling system and refilled it w fresh 50/50- antifreeze/ water and it was rusty looking again. I did it again- came back rusty again. I finally just left it. Drove it until I sold it a few years later. I dunno why it stayed so rusty...

 

Had similar experience with a Ford V8 from mid to late seventies flushed it a ridiculous amount of times but it never stayed clean.

 

Had a friend with an early 80s Riviera that did the same thing. Never could get rid of it. It was always muddy orange.

It does take quite a bit of flushing to get all the rust out. Especially if it's been in there for a while. It settles in the low spots and becomes petrified mud. Boiling is the only way to get all of it. Hard to do get a full flush with the system sealed up.

Always isolate the heater core. Flush it by its self with low psi garden hose.

Always suck out the tap water a shop vac and low psi shop air.

 

Agree with the petrified mud description.

I had gunk issues years ago after the trans cooler leaked and the entire cooling system had a coating of gunk. A friend recommended flushing with hot water and Castrol SuperClean, so I connected a garden hose to the hot water heater and used that to flush the system. Did a fair job.

 

Usually air entering your cooling system and interacting with the metal surfaces will cause rust in your system. Upload pictures of your radiator, radiator cap upside down revealing the condition of the underside of the cap, and a picture of your coolant inside the radiator. White residue around the mouth of the radiator usually is coolant leakage. You've probably not performed the compression gas test as recommended, but have you performed a radiator pressure test, or had your cap tested? When was the last time you washed the radiator cap and how often are you changing the coolant in this system prior to all this?

 

Correct, no compression gas test yet. I'm doing other work on the car so its not running at the moment. I haven't tested the old radiator cap but I bought a new one a few months ago. Coolant has been changed 3 times this year, refilled with distilled water and antifreeze. Driven no more than 500 miles for this year.

 

Until such time as you prove the health of your cooling system with the appropriate test take time to inspect the parts you can get at. I suggest to look for vacuumed and distended hoses; check the condition of the weep hole at the waterpump, if it's a flowing well you are taking air in at that location. The cooling system for these huge engines is a series of parts all designed to work in unision; the fan, clutch, belt, pulleys, waterpump, thermostat, hoses, restrictor , heater core, radiator, and radiator cap--all must be in working order to pressurize the system properly. Happy Motoring!

 

i remember an engine block years ago with the frost plugs out and compressed air a ton of sand came out of that engine, was common to have casting sand still in there i was told.

 

I performed combustion gas test, it was negative. I flushed the block with freeze plugs removed. Refilled with anti freeze and distilled water and will see if problem returns.

 

Read this regarding distilled water in cooling systems.

https://rislone.com/blog/cooling/why...ooling-system/

 

Darn, I wish I would have known this before I bought 12 gallons of distilled water for my flush and refill. There is good info in the text and video at that link.
Thanks for posting it!

 

Did the coolant look any different from previous flushes being flushed with the plugs out? Was there any crud behind the plugs? Good news about no combustion gases in the cooling system.

 

This site actually says distilled water is preferred for automotive applications. I have used DI water from work and never had any issues in my vehicle's cooling system.

https://www.chemicals.co.uk/blog/dei...istilled-water

 

Kenneth, that's the case when you use coolant (anti-freeze) with the DI water.

Those two articles had mostly good information, but some doesn't apply to our cars unless we are using 100% water.

With a coolant/water mix, there is no difference in corrosiveness or deposits whether you use distilled, DI, or softened water.

This is from accumulated wisdom, both from educational and industrial experience. I'm a Registered Professional Engineer with a degree in Chemical Engineering and I've designed many cooling systems in the last 50 years.

Gary

 

Thanks for the feedback. I had surmised that the antifreeze/coolant had the additives needed to protect the system. Also figured that I had nothing to lose if the DI water leached the calcium deposits out from the years of using hard tap water. 😀

 

Kenneth and Gary, thanks for your input. Now I don't feel badly about mixing distilled water with my coolant. I've always done it this way, and it's good to know I haven't been wrong. Seems like either I missed it, or a crucial bit of info was left out of the sales pitch write-up at https://rislone.com/blog/cooling/why...ooling-system/.