flushing the coolant

[bongomike]

I going to do the coolant change tommorow, does anyone know the best way to flush the system, my expansion tank looks like new, there's no brown stains. Would I be best not to flush the coolant.

thanks
Michael

[missfixit70]

If you're doing a change, you've got to flush the coolant really.
As per the other thread where you asked

I usually empty from one of the rear heater hoses & the lowest points on the large bore hoses in & out of the engine aswell, if you just drain from the rad, you'll leave a load of coolant around the rest of the system due to the way the hoses & pipes run. Have the rad cap, header cap & bleed hose bung out (only take the bleed bung out after removing header cap, it tends to spray all over when you forget .
Then flush through everwhere with a hose till it runs clear everywhere, making sure not to get starter/alternator etc wet. If you're fitting a new stat, I'd run it up with no stat in for few minutes just to circulate everything & hopefully dislodge any crud lurking around, don't get it too warm unless doing a chemical flush or you'll have to bleed it & then allow it to cool a bit before flushing with clean water again.
Then fit the new stat, put in the neat coolant & top up with water & commence bleeding.
That's for a diesel, not done a V6, but it seems to be essentially the same cooling system set up.

Or you could go for the hose in the header tank method, open the bleed hose up, have the engine ticking over, one person on the bleed hose emptying, one on the fresh water hose going into the header, don't let the level drop out of the bottom of the header, keep going til it runs clear. Not sure it'll get all of the old coolant out as the stat won't open doing this & you don't want to be mixing coolant if there's old unkonwn stuff in the system.
If you try adding the neat coolant into the header this way, I've found that it starts coming out of the bleed hose before you've got all the neat coolant into the header end, so your coolant concentration may not be right. I think this method works for some though, as with bleeding, there'll be many different method & not necessarily any "best method". It's a matter of finding one that you understand & can undertake.

[bongomike]

I asked this before haven't I sorry must of had a blonde moment

so basically I flush the Rad, header tank, where the large bore hose comes out of and the header hose pipe?

[missfixit70]

You need to flush the whole system, front & rear heaters, etc, it's all one system, find Widdowsons excellent diagrams of the system. If you don't get it all flushed out, you'll end up with old coolant mixing with the new which can result in all sorts of problems.

[bongomike]

Found them thanks. I think what I was trying to say that is there somewhere I flush the system leave the bleed hose bung out that all the water will work it's way round and come out of the bleed hose?

Thanks michael

[missfixit70]

Not really - read my post above through again

[bongomike]

Ha ha ha, sorry for being a pain, pm me your address and I'll send u a bottle of Aussie rum for my sins

[mikeonb4c]

I'm a lazy b*gger. My header tank and coolant look pristine (the latter even when draining old stuff). So I don't bother draining the rear heater, and I don't bother flushing. No probs in 5yrs. I reckon if you are prepared to make a personal assessment and you judge yours to have been properly looked after (coolant changed at recommended intervals) then just throwing away most of the old stuff and putting in new stuff, ought to do the trick. I use plain ethylene glycol stuff (in a form suitable fo aluminium engines) just like the Mazda sticker under the bonnet says I should.

Somebody slap me

[missfixit70]

Slapped If you don't know what was in there before, you could be asking for trouble with mixing coolant, you can't go by the colour either.