Coolant Rust

chadzeilenga

Active member
Hi All,
I'm looking for some additional input on an issue I've been struggling to solve. The issue is rust in my coolant. I've noticed since I first purchased back in March 2018 and below are the steps I've taken to solve it.

So far I have done the following since I purchased the vehicle back in March listed in order:
- 2 rounds of Blue Devil Cleaner flush. Drove for a few days with this in. Still had rust in coolant.
- 3 rounds of fill and drain from lower radiator hose with water on warm engine and thermostat open (dumb idea)
- Backflush of coolant system with garden hose through Tee installed by previous owner in the heater core hose. Started engine and ran until water out of radiator was clear.
- Added 16oz/1gal mix of Sulfamic acid to remove mineral deposits. Ran without thermostat for ~3hrs on highway. Allowed to cool and drained from lower radiator hose
- Added 16oz/1gal mix of Oxalic acid to remove rust deposits. Ran without thermostat for ~3hrs on highway. Allowed to cool and drained from lower radiator hose. Did this twice
- Neutralization with 16oz/1gal mix of washing soda and run for 15min to mix and then drained when cool.
- Removed aftermarket radiator and did backflush on cold engine through the tee in heater core line. Let water run for ~15-30min. Plugged lower radiator hose so that coolant came out of bypass hose connections.
- Poured (2) gallons of distilled water into the tee on heater core hose to displace and minimize the existing tap water from block.
- Installed recently rodded OEM radiator and all new radiator hoses, heater core hoses and coolant bypass hose.
- Added 1 gallon of straight Green antifreeze. Allowed to mix with existing straight water in the block and then topped off with 50/50 mix until all air was bled out.

I ran with this configuration for a few days and I'm getting a significant amount of rust sludge floating in the top of my coolant when I remove cap and also it is stuck to the bottom of the cap. Below is what I have after 2 days of driving around town.
Montero Radiator.jpg

Is it possible that the coolant loosened up rust that was stuck in the block? I would think that after all of the efforts listed above this would have all been clear or I would have seen just a little bit. Maybe the new radiator is allowing higher flow rate in the engine?
Rust Powder.jpg
This is a chunk of the rust that I pulled out this morning and let dry. It just turns to powder, so there doesn't appear to be any oil
 

Toasty

Looking for that thing i just had in my hand...
Just keep at it, I don't use chemicals or corrosives in cleaning cooling systems but i have rehabbed a number of these things. Start with no thermostat then I flush, fill, drive it hard and repeat. Depending on how bad it is i'll start with hose water then start working in distilled, then antifreeze then quality antifreeze. It takes a while but it's not really hard, just check it before every drive on a cool engine and then flush and fill each time. Right when you think you've got it a bunch more breaks free which is great because that's less trapped in the engine. Once you get repeated clean results remove and clean the radiator again.
 

DaveInDenver

Middle Income Semi-Redneck
I'd do a couple of flushes before I gave up, there's a lot of places for coolant to settle and if it was left in long past when it's anti-corrosion was still active there could be rust still coming out. Does it seem to give you heat inside and the engine stay cool?
Are you positive it is rust and not some sort of cooling system sealer?
It does look like it could be Stop Leak, which is copper powder. Although it's pretty fine powder in his photo. If he has a magnet it's would be really easy to figure out.
 

coffeegoat

Adventurer
That sure looks to me more like stop leak of some type (it's really powdery). You could try mixing the powder you find with oxalic acid to see if you get a reaction, though the magnet trick would probably be easier.

If it's just a stop leak compound, then a more conventional cleaner (like the blue devil) or degreaser might help. Though - be really really that it doesn't react poorly with metals. For example, simple green (the normal stuff) will happily dissolve some metals.
 

Toasty

Looking for that thing i just had in my hand...
The best way is to disassemble the engine, pop the freeze plugs out and dig it all out but that's a lot of work but with stop leak stuff it may be necessary. I had to do that with my diesel, it really wasn't terrible and when i was done i knew it was clean. I say just keep working at it.
 

Salonika

Monterror Pilot
Most important unanswered question: is the engine cooling properly? With all the chemicals you threw at it (and maybe the previous owners) you are bound to end up with some sediment. Is there a petcock you can open up to get a lower flush on the radiator?
 

Tliska10

Active member
I had some bad coolant rust and I used evaporust and man, did it do wonders.... Got it at Walmart was like 20 bucks
 

chadzeilenga

Active member
Hi All,
Some really great responses, shame on me for not keeping up with answering all of you today, but here goes.
I haven't had any temperature issues with the engine and that is after going through a NC summer daily at 90F+. With the prior aftermarket radiator the temp gage needle was just below half and now that I have a freshly rodded OEM radiator installed I'm stabilizing slightly below that. The heat inside is great while running as well. I'll get a picture tomorrow after driving to work. I don't know what treatments the previous owner did, but he did have the heads off to re-do the HG prior to my purchase.

The list of flushes that I have done started around May this year and I'm counting ~10 of them. All of them had a rapid drain through the lower radiator/hose connection to maximize the amount of sediment removal. Each one concluded with clear water coming out of engine. I would say the most effective treatment that I did was the oxalic acid mixture. I'm thinking that this is probably as good as I'm going to get so I'll do a flush every few months to continue getting sediment out until I eventually have the engine out and I hot tank it with the freeze plugs out of it during the rebuild like Toasty said

I hit the powder with a magnet after work today and it stuck when dry so I'm assuming that there is some iron/steel in there. Maybe the new radiator allowed a higher flow of coolant to move the sediment?

magnet.jpg
 

Kevin108

Explorer
I had a Jeep 4.0 with a similar problem a few years ago. I spliced a Peak flush kit into the heater hose, so that made flushing things effective and easy. I ran the engine and the heat the entire time I was flushing. It took a while to flush it clear.

From there, I mixed some Cascade dishwasher detergent with water. This is NOT Dawn or some other type of dish washing soap, so be careful when you shop. I mixed a full cup of detergent with a gallon of water, and added that to radiator. After that, I topped off the cooling system from my water hose. I ran this concoction for 100 miles, then flushed the system until clear. I refilled the system with the proper coolant and had no further issues.
 

Toasty

Looking for that thing i just had in my hand...
Chad, do you have an IR thermometer? Mine runs just below where yours does, I'm trying to learn on a Gen 1 V6 what temps are relative to the needle and how many degrees inaccurate it is.
 

chadzeilenga

Active member
I have one at work I can likely borrow for a weekend to get some data.

I've always considered those gauges to be a way to see if something was "off" from normal as I rarely see any fluctuation in the level.

Has anyone ever considered adding a coolant filters on these? Any recommendations on where to splice the filter in or mount it?
 

DaveInDenver

Middle Income Semi-Redneck
I've always considered those gauges to be a way to see if something was "off" from normal as I rarely see any fluctuation in the level.
Unless the gauge is known to be truly a temp gauge I wouldn't trust it to be accurate enough for this. A real gauge will have a scale on it and the needle will move around a lot even on a daily commute, rise when you're at a stop light, dip when you're on the highway.

If the needle stays firmly in one spot then it's more a relative indicator or maybe even just a quasi-gauge, basically a warning light with a needle.

It's pretty common for Japanese trucks even with real temp senders to have a fairly wide dead zone on the gauge where the needle doesn't move. You can Google ways to make it linear, usually replacing a pair of diodes on the back of the instrument cluster with resistors. If yours is like similar vintage Toyotas, you have to look at the temp gauge like two scales. Say you have a 185 t-stat they'd design it to be cold-to-175 on the bottom and a 195-to-max on the top. When the needle is normal it's at a static position between those two ranges.
 
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