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Old 06-26-2009, 04:41 AM
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claymore claymore is offline
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Default DIY Changing your coolant

The Jazz/fit is a real pain in the butt to get all the air out after changing your coolant but I have worked out the easiest way to do it. Sorry no photos because it's so easy.

Since I'm a maintenance nut I change my coolant every oil change at 5000 KM. It's cheap insurance with coolant costing only 5 bucks or so for a bottle of mix it yourself. There are several brands out there that all work just fine but just because I have been using it for years I normally use good old prestone.

I change often because I have seen cars come into the shop with RUST and crap built up on the inside of hoses that you can feel. If you grab your coolant hose and squeeze it you can actually feel and hear the crap rust beings broken off inside the hose on cars with high mileage and no changed coolant.

I normally just start it up just for a few minutes then shut it off and take out the drain plug at the bottom of the radiator BE CAREFUL OF HOT WATER it hurts. You can do it with the engine cold same thing just take out the plug and the old coolant will start to drain fairly slowly then get everybody out of the way and take off the radiator cap and the water will shoot out very fast under the car. I wait until the water stops coming out then I run a water hose into the fill up opening and wash out the radiator until the water coming out is clear.


Now the problems start. I use one 1 liter of mix your own coolant and you just put the plug back in the bottom of the radiator pour in the coolant and top off with water LEAVING THE RADIATOR CAP OFF.

Then I start the engine and run it for about 10 minutes with the cap off. Now here is where the problems occur. The problem is even with the engine warm the fresh water you used from the hose will close the thermostat. Now there are parts of the engine and hoses that have air trapped in them so when you start the engine the trapped air will stop the fresh coolant from reaching the thermostat and it stays closed.

So there you are an engine with air trapped in it and the catch 22 of hot water not being able to reach the thermostat to make it open the result being the engine gets hotter and hotter because no water is being allowed past the thermostat and no water gets close enough to it to open it.

So the engine gets hotter and hotter but your gauge doesn't know it because no water is flowing past the sensor just trapped air. I used to just let it run but then when the air gets hot enough the temp light starts blinking even when the coolant has been topped off with fresh coolant.

The best solution I have found is to just top it off at the radiator cap and let it run for about 10 minutes. Then shut it off and put the cap back on and make sure your overflow tank has coolant in it up to about half a tank or so.

Then the easy part just turn it off and walk away. Try and be patient and don't open the radiator cap or anything just let it cool off.

While it is sitting there cooling the heat from the engine will work through the metal block and work on the thermostat and after awhile it will open on it's own then the water will be able to circulate on it's own without the engine running and this fills up the air pockets through the entire engine.

After about an hour go back and CAREFULLY OPEN THE RADIATOR CAP turn it just 1/2 half way until it stops to let out the pressure then take the cap off and add a bit of water as it needs it to fill up the radiator. Some of the water in the overflow will have been sucked back into the cooling engine so check it's level and top off as necessary.

The coolant should be fine now with all the air having been let out while it was sitting there cooling and you are done but I normally drive it as usual then park it over night and the next morning I check the level at the radiator cap and sometimes I need to add less than 1/4 liter to bring it to the top.

Last edited by claymore; 06-26-2009 at 07:45 AM.
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