Which coolant?
 

With all this warm weather I thought it can't hurt to change the coolant. So which would you recommend for a blob WRX running 346bhp?

It's my first time changing it (usually done be a garage) and I've been reading up on what to do and all seems fairly easy, open rad plug and drain then replace plug and fill from header tank with 50/50 mix of distilled water and coolant, also filling the reservoir to the full mark. Once the fluid stops dropping replace the header tank cap and start up the car with the heater controls set to max heat and low fan. Run the engine for 5 minutes for the temp to rise then turn off and allow to cool. Remove the header cap and top up with more 50/50 mix allowing the any air trapped to bubble to the top, then repeat the warm up process until the temp gauge holds as normal also making sure the fans cut in.

Is that about jist of it?

Got a long drive on Wednesday so would you recommend taking some spare mixture or will the burping process get rid of most of the air?

First off, fill by removing the rearmost pipe from the metal header tank and stuffing a funnel down it. Fill SLOWLY and DO NOT allow it to gulp.

This is important: filling from the header tank allows the coolant to swirl before going down the pipe, often resulting in air going with it. If it gets a really bad airlock, the ONLY way to shift it is to start again. Filling using that pipe fills from the bottom up.

Once full, start engine and allow to run with heater still on hot and cap OFF. watch for bubbles. Top up or mop up as needed.

Once the fans kick in, switch off, replace cap, go for a drive round the block.
allow to cool, open cap, top up as necessary and job's a good'un.

Use any coolant which is guaranteed for alloy engines.

And you MUST have the heater controls set to HOT all the time while filling.

Comma Xstream G30 concentrate - 5 Litres for about £22.95. Dilute 50/50

http://www.ebay.co.uk/itm/COMMA-XSTR...item2a2e8a73b6

I'm planning to do the same at some point :-)

What brand of coolant do you use? or are they all the same if they are guaranteed for alloy engines?

I've not seen it mentioned before about filling from the rear most hose on the header tank, will give it a go.

I just went to a decent motor factors, told them it was for an alloy engine and bought what they gave me. it's red in colour, but the colour is just a dye.

I also asked Harvey, and he said it was right.

With regards to the refilling the cooling system what alcazar has said is spot on and should be the "usual" way of refilling. Even a sticky might be useful as its not very common knowledge.

just done this and worked a treat just waiting for it to cool down and top up

also i found shaking the rad help expel more air as well