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Coolant Change

2782 Views 14 Replies 9 Participants Last post by  sjperks
Just been checking the levels on the car tonight after been in storage over winter. I have noticed the coolant is really rusty brown, so need to give it a coolant change. The engine would need flushing out I think, what sort of job am I looking at, and can an engine flush be done?


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Hi there,

I have not done this on my 5 but on my Volvo and it is a piece of cake...!!

1. Drop the coolant
2. Leave the drain plug open, stick the hose pipe in the radiator and let some water circulate through the system that way.
3. Do up the drain plug, fill the system with plain water, run the car until it starts to warm up, kill the engine and then drain the system again. Remember it will be hot water that is going to be coming out so it will burn!!
4. Do this a couple of times until the water runs clear if needs be.
5. Refil the system with the correct level and mixure of water/coolant.

Others may well have used a different method, however this did the job for me.


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does a mx5 have a drain plug? i need to do this too and would appreciate some guidance on how to do it on a mx5.

im used to doing it on VWs which use a sealed expansion tank rather than a top filled rad etc
i usually just pull the bottom hose off the rad.

Gives you another access point for the hosepipe too for a good flush out.
i usually just pull the bottom hose off the rad.

Gives you another access point for the hosepipe too for a good flush out.
Same as but i put rad flush in that stays in for about 30 miles then drop the water out again i also took the header bottle of only three nuts and gave that a wash out as mine was realy brown plus i changed the stat 2 min job.
Yup as Skuzzle said I too pulled the bottom hose off. Flush through as has been detailed above.

Some people have had problems when refilling with airlocks and a tendancy to overheat.

This can be avoided by slightly lifting the front of the car up before you fill the system. It enables the engine block to fill up from the bottom rear. Therefore allowing the air to escape. Run the car up with the radiator cap off massaging the top hose to encourage any trapped air out. You will be able to see the coolant begin to move as it heats up.

When the fluid begins to move replace the cap and allow the system to get up to working temperature. Keep an eye on the temperature gauge it usually stops at the 12 o'clock position and doesn't go much higher. Mine never did.

Once it has got to operating temp shut the engine off and allow to cool down fully.

Once it is cold check the level in the expansion tank and the radiator. If levels are all good job jobbed. if not top up and give it a good blast.

I think thats about it off the top of my head. If I've forgotten anything I'm sure someone will point it out.

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make sure to have the heaters on after getting up to temp to help get any air out of the heater pipes etc.
make sure to have the heaters on after getting up to temp to help get any air out of the heater pipes etc.
this makes no difference on the 5 except it takes longer to get up to temp.

The coolant passes through the heater matrix no matter what.
Thanks to every one who has given their advice, will be doing it this weekend. Someone mentioned about using distilled water mixed with coolant, what are your views on that?
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there is a bung in the bottom of my radiator. Dead center. Only plastic and a crosshead screwdriver fits it. I use that to drop my fluid.
I don't mess about with the hosepipe. Sticking it in the top of the rad only makes it come out the bottom. you dont get a propper flush through the block unless you stick the hose in elsewhere. Perhaps the back of the head where the heater gets its water from. Myself, i just stick some tap in, run it for a bit, then drop it again. Dropping it via the little bung is sooooo easy by just kneeling down at the front of the car. Rad cap off ofcource
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Right, tap water it is then, and thanks again for all the advice given.
I only used the finest Brita filtered water for my automotive applications! ;)
did mine last weekend very easy job to do id use some rad flush as i kept the hose in mine till it ran clear, then used rad flush and the amount of rubbish it brought out was worrying lol.

also when refilling rad leave the cap off for a bit and let it run to let any air locks come out!
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