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How important is proper flushing of the cooling system?

lozzd

Trekker
When I replaced my thermostat a little while back, I simply took off the top pipe, waited for enough water to drain out, did the job and then refilled into the expansion tank until it was back up to normal level. Was this a really stupid thing to do? Could that be why when I do 70 for a while it goes slightly above the middle mark? Is there a correct way to "purge" the cooling system, or should I drain it all out and start again?

Thanks
Laurie
 
Don't worry about flushing it out, I never have!
When you refil the cooling system you should remove the plastic bung on top of the radiator, the one with 'WARNING DO NOT REMOVE WHEN ENGINE IS HOT' sticker below it. You may need a new one as the gets pinched and the plastic cap cracks. They're the extortionate price of about 80p:D Fill up from the expansion tank, keeping an eye on the level in the rad. Fill it until the water is up the rad and put the plastic cap on and run it, top up the expansion tank as required. Taking the plastic cap get the airlocks out, apparently they can be a b*gger to bleed.
Should be 50/50 mix, anti freeze water. Don't use ethanol antifreeze, use glycol. If your draining and starting from scratch, its 12 liters in total, 6 antifreeze and 6 water.
The temp probably goes above 1/2 way at 70 because its hot:D Mine does.

Cheers, Ben
 
Last edited by a moderator:
Brilliant thanks Ben. I won't worry too much then! The temperature is pretty stable, shoots up to half way and stays there most of the time, if I do 60-70 it does up to almost 2/3s of the way up but as soon as I stop, it goes back down to centre again.
I'm just being paranoid again, and this "OMG my temperature needle actually sits in the middle now" is very new to me.. Been driving round with a duff thermostat for a year :rolleyes:

Cheers mate :D
 
No worries. Mine sits at 1/2 way usually and goes up a bit if I do 70 for a while, cools down again though. Its when it gets into the red you wanna worry:D

Cheers, Ben
 
When I replaced my thermostat a little while back, I simply took off the top pipe, waited for enough water to drain out, did the job and then refilled into the expansion tank until it was back up to normal level. Was this a really stupid thing to do? Could that be why when I do 70 for a while it goes slightly above the middle mark? Is there a correct way to "purge" the cooling system, or should I drain it all out and start again?

Thanks
Laurie
When I take a shower I figure that, since I've gone to all that trouble to get starkers, I may as well wash my hair as well. So if I'm going to do radiator maintenance that includes draining the coolant, I may as well flush the rad with a hose pipe.

Ok, it's very dusty where we live, and maybe there's more risk of crud in our coolant than yours. But what the heck - if it's drained there's no big shakes in flushing it, and you may improve its cooling efficiency slightly.

Cheers.
 
An excellent analogy! I didn't bother draining it completly, only the little bit that came out when I took the pipe off! Otherwise I probably would've done the same. Ah well, next time!
 
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