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Schiffer

How To Flush And Re-Fill Radiator Coolant

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well good one schiffer. few things i want to clarify.

1* what is the purpose of running the engine with heater on?

2*Step 3:

* While the drain tap is open, run a hose from the radiator cap with slow flowing water so it wont overflow
* While the water is running through the radiator, start the engine and let it idle with the heater on for another 10 minutes (might need a mate for that)

you mean with out fixing the drain cap whaile pipe supply the continues water start the engine & run ??

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Yes, this is something to clean the water that's running from radiator to the heater core inside the system.

switching on the heater circulate and fush out the water inside the heater core as well.

Also another reason you have to keep it running for 10 minutes or more is to circulate and flush the water after the thermostat is on.

And yes, without closing the drain tap start and run the engine while continuously supplying water :)

Edited by Schiffer

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Great write up Schiffer,

2 simple questions,

1. For what extend we should squeeze those pipes? isn't there's a chance to break or dislodge them? (they feel bit harder)

2. What's that mixing water for coolant? Distilled water?

Edited by Charith H Jayasinghe

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Thanks :)

1. Sqeeze the pipes softly but dont squeeze them all the way

Those pipes are pretty strong. When u squeeze them u will feel the water flowing through them

2. I filled normal minaral water off of a water filter. But its better if u could use distilled water.

When filling coolant usually u have to mix 50% water and 50% coolant

But the coolant i used (wurth) i had to mix 1:3 ratio

Eg- for 1ltr of coolant. I had to mix 3ltrs of water.

Edited by Schiffer

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Excellent work. Thanks for posting. Few more things needed to ask from the experts.

  1. What is the life expectancy of coolant (Suppose a brand-new radiator is installed and filled with coolant [diluted] for the first time.)
  2. How do we identify that it is the time for flushing the radiator if there is no color change on coolant or corrosion seen in the radiator?
  3. What would be the best to use? concentrated and diluted ? (If the water is having higher minerals such as calcium carbonate)?
  4. Even if diluted coolant is used, it is possible that the radiator gets corrosion inside ?

Appreciate sharing your knowledge and experience. Thanks so much in advance.

Edited by Nishan.dj

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Good write-up. Thanks for sharing

a couple of clarifications pl;

1) In Step 3, how do we make sure that water is actually circulating through the engine and not just running down the radiator core and draining off?

2) How do we find out if the engine has cooled down enough to pour in cold water / coolant? I guess diferent engine blocks cool down at different rates and a diesel may take longer?

Edited by HardHat

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nice work Schiffer +1 and very good step by step writeup after seen this i want to flush and refill the radiator coolant my self. :)

btw when i trying to do this and things went horribly wrong i'm going to haunt you. :P :P :D

Edited by nexus

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Thanks mate :)

haha, its a simple job, just take some time and patient

if you want to flush, the best thing is to do at home, since it takes some time, service stations and other garages dont really fully do it. they tend to cut corners.

just be cautious mate. of spilling water everywhere. oh and make sure not to use too much force on the drain tap, it feels a bit fragile

good luck :D

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Great work done by Schiffer. Thank you very much for it.

I'd like to remind Nishan.dj's quote above 'cos it has not been answered.

  1. What would be the best to use? concentrated and diluted ? (If the water is having higher minerals such as calcium carbonate)?
  2. Even if diluted coolant is used, it is possible that the radiator gets corrosion inside ?
Edited by SAB

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Bringing up an old thread to put some doubts that i have about using Rad flush. My cousin has a Jeep recently bought with a 4DR6 engine and it has been using plain water as the coolant. I think the engine is only done abt 20000 km according to him and he wants to switch to Coolant/water mixture as well.

The water now in the radiator is very brownish and there’s this thing that i remember someone said, to be careful when switching to coolant from water in old engines, and specially using flush materials, coz it might dig in to rust n things and make the cooling system more vulnerable for leaks and damages.

Anyone can shed some light on this matter please. Thanks.

PS-Found the answer on this thread..
http://http://forum.autolanka.com/topic/14094-radiator-coolant/?hl=%2Bradiator+%2Bclean#entry215889

Edited by charithtg

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If you flush the system with clean water, ensure that all hoses and clamps and gaskets are in good condition, you can try a 1:10 ratio of water and coolant for an older car. The coolant will be primarily to inhibit the rust.

The rust is caused by the minerals and salts in the water you use. Ideally you should be using distilled water in your coolant system. Well water or tube well water is a big no no. Especially if you are in an are where the water is hard.

I am planning on a complete overhaul over the weekend on the Forester coolant system. Already got the Original Thermostat delivered with all gaskets and the coolant also is here. Can get the distilled water from chemical shops or even a battery shop.

Since I removed the thermostat housing twice already the coolant circuit has got a good flush.

Edited by VVTi
  • Like 1

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Thank you for this very detailed guide.

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I know this is not a good idea but when ever i open my coolant tank there is a awful smell coming from the coolant . is this normal ? i did a total flush about 20000Km's back.

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Did it finally... used Wurth for flush and coolant. So far no issues. I checked coolant level 3 times so far after refill level was gone down. so we need to check coolant level several times for air bleed.

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Hi everyone,

I need to flush the radiator of my van.
My question is., after flushing, when i mix coolant with water, is it ok to use boiled water..??

thanks in advance.

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Hi everyone,

I need to flush the radiator of my van.

My question is., after flushing, when i mix coolant with water, is it ok to use boiled water..??

thanks in advance.

If the idea is to remove hardness of water then of course you are going to use the wrong type of water for your radiator to begin with. Use some distilled water to mix with the coolant. Even the water you find in areas like Rathupawala (very appropriately named for red soil or laterite) known for its acidity is not suitable. Boiling will not help at all in these circumstances.

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dont think boiled water would do any harm but ive heard its better to use distilled water.

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Welldone Schiffer,

though even it looks like simple job when we go to service centers they charge some nice amount for this . any way thak for sharing the pics and process on AL .

and i always like this DIY jobs. :sport-smiley-003:

I did the same thin twice but didnt mesure the coolent and water ratio i just put entire coolen bottle to the radiator and filled rest with water. :speechless-smiley-004:

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dont think boiled water would do any harm but ive heard its better to use distilled water.

Boiled water has more mineral deposits. Concentration is higher. Always use distilled water.

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One small thing to note, Coolant is extremely poisonous and you should take a lot of care when handling it and probably should wear gloves.

Also if you are flushing a radiator, please try not to dispose it into a standard drain which will mix with fresh water supplies. I'm not sure what you can do, but it needs to be disposed of safely so it does not come into contact with fresh water supplies, where there is a danger of people or animals drinking it.

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thanks everyone for the valuable info.
Where can i find distilled water..?? is battery water distilled..??

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Boiled water has more mineral deposits. Concentration is higher. Always use distilled water.

ohhh so it seems its better to avoid boiled water then.

thanks everyone for the valuable info.

Where can i find distilled water..?? is battery water distilled..??

yeap, battery water is distilled water, some places sell them in bigger cans, its easier to use for radiators

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Thanks Schiffer.. :)

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