Classic Audi Technical Car detailing & polishing » Mucky coolant reservoir clean

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Old 06-07-20, 06:53 AM   #11
tractor Dave
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Try just the baking soda and boiling water. The critic acid will erode the metal if left too long. But it will also eat the rust. Just don't leave it in too long if you decide to try that
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Old 06-07-20, 01:50 PM   #12
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i wouldn't worry too much-unless all your cooling system is new (i haven't checked!) then you will find a limited amount of crud in every system...
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Old 06-07-20, 06:09 PM   #13
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The critic acid will erode the metal if left too long.
I don't know the part - is it particularly thin metal, or something other than steel? I use citric acid to remove rust from stuff (small things that the electrolytic tank is a bit overkill for), and I've left things soaking for days on end before now without any damage.
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Old 07-07-20, 09:52 AM   #14
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Originally Posted by droopsnoot View Post
I don't know the part - is it particularly thin metal, or something other than steel? I use citric acid to remove rust from stuff (small things that the electrolytic tank is a bit overkill for), and I've left things soaking for days on end before now without any damage.
I tried electrolysis using a vaiable 5/10/20 amp charger and got good results, I also use citric acid but if you leave something in too long it will start to get a coat of a concrete like substance on it which I've found can be removed by soaking the part in water starting the rusting process again .
Best to keep a daily check on the parts and remove them when the rust is gone rather than risk the concreting effect.
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Old 07-07-20, 10:09 AM   #15
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I also use citric acid but if you leave something in too long it will start to get a coat of a concrete like substance on it which I've found can be removed by soaking the part in water starting the rusting process again .
Yes, that's certainly true. I find that more often when the citric acid has been mixed for a while. I tend to scrape it off rather than soak again, but then stuff I'm soaking is usually stuff that's been rusty for decades, so a bit of surface rust isn't so much of a problem. The next stage is usually a good wire-brushing anyway.

Interesting on the reservoir cleaning at least, I have a few dirty ones from various cars that would benefit.
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Old 07-07-20, 07:17 PM   #16
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Yes, that's certainly true. I find that more often when the citric acid has been mixed for a while. I tend to scrape it off rather than soak again, but then stuff I'm soaking is usually stuff that's been rusty for decades, so a bit of surface rust isn't so much of a problem. The next stage is usually a good wire-brushing anyway.
Yes, agree it usually starts to form the concrete like build up when the solution has been in use for some time, I did try scraping it off but sometimes its too tough, I find that a soak in water for a while loosens it up and it comes off naturally after a longer soak, much easier than scraping.
The concrete stuff is strange as it also forms on the base of the plastic vessel I use as my soak tank. Once its starts to concrete I usually clean out the tank and start with a new solution the citric stuff is (it was but I've not checked recently ?) cheap enough in 25kg bags.

I do prefer to use the citric acid rather than electrolysis just my own preference, brings up brake cailpers a treat, even ones that look like they've been sat in the wreck of the Titanic for years.
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Old 11-07-20, 02:11 PM   #17
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Just tried baking soda with white vinegar. It worked a treat! Not perfectly clean but much better than before.
I underestimated the ferocity of the resulting effervescence so my garage ceiling is a bit cleaner now too.

Thanks for all your input chaps!

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Old 10-11-20, 04:15 PM   #18
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Im going to suggest a dip in an ultrasonic bath to get the grime off.
Not me! The reservoir!

I bought a cheap one from ebay and it completely cleared out all that brown gunge from a toyota turbo oil cooler that was clogged full of rust, (bit like the vw ones).
Just drop in a mix of water and truckwash, turn the heater on and let it rip for a while.
Bit trial and error but will remove probably every bit of it.
Try it!
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Old 10-11-20, 09:53 PM   #19
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Isn't this 'crud' the result of two types of antifreeze mixed together?
They react and turn into sludge and can block your heater matrix and rad , worst case scenario. ?
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Old 10-11-20, 10:01 PM   #20
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Isn't this 'crud' the result of two types of antifreeze mixed together?
That, or rust from the iron block due to incorrect coolant concentration or not changing it often enough. (Or all of the above)
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