Header tank

[chrisash86]

I’ve managed to get a second hand header tank for my v6 to fit it do I have to do a full engine flush of the anti freeze?

[Robsey]

Hi Sir,

I am assuming you mean the coolant system - (Silly comment, of course you do, you said anti-freeze).
The answer is down to three things -
1 - How clean is the existing coolant.? Any contaminants from a previous issue?
2 - How long is it since the coolant was last changed.? More than a couple of years?
3 - How long is it since you last checked the concentration of the coolant.?

Additionally - are you having any issues with the engine getting hotter than expected, or the internal heater not getting very warm.?

If any of these are in doubt, then yes give the system a good flush through - not forgetting the radiator and heater matrix.

Like anything else though, sometimes disturbing fluids can release sludge but can also dislodge something that has plugged a leak. More common with flushing the engine oil, but the heater matrix has been known to suddenly weep after a thorough coolant flush.

If it was me, I would simply drain out the old stuff and refill with fresh coolant of the correct specification and mixture ratio / concentration.

My preferred fluid is red long life coolant - there are some that say that you should use the old blue stuff for vehicles before 2001, but I have used the red stuff for years with no ill effects.

[chrisash86]

To be honest the coolant needed changing as it is. Is there a guide on here ? There’s no issues I.e overheating or using a lot of coolant

[Robsey]

There is no guide that I am aware of.

Simply a matter of undoing your big radiator hoses and pumping water into the engine with a hosepipe.

Just keep going until it all drains out clear.

Then pump water into the radiator to wash out any silt or muck.
Squirt into the top hose stub on the radiator and let it drain out of the bottom hose.

As for the matrix - usually best leaving this alone unless you start to get poor cabin heating.

When flushing the engine, remember to set the heater panel to hot on the slider.

When done, refit the hoses and top up to the 'kalt' (cold) marker on the header bottle with a good coolant mixture.

With the cap still off, run the engine for just a couple of minutes to pump the water round, and give the top radiator hose a few good squeezes to ensure that all air pockets are removed. You should see any air being burped out into the header tank.

Stop the engine and top up the header tank.
Refit the cap and run until the radiator fan kicks in.

[chrisash86]

Cheers but where do I pump water into the engine exactly?

[Robsey]

To flush the rad, disconnect both top and bottom fat hoses.
(Don't worry about the small hose that runs along the back of the slam panel).

Squirt the hosepipe into the top stub and let it drain out the bottom stub.

Then to flush the engine, squirt the hosepipe into the header tank and allow it to drain out of the pipe to the radiator near to the radiator fan

If you do want to flush the heater matrix, you just disconnect two of the rubber pipes that go to the bulk head from the plastic hose across the back of the engine.
Squirt the hosepipe into one metal matrix stub, let it drain out of the other stub.
Then swap stubs and repeat.

You cannot flush through the thermostat housing because it will be closed inside due to the coolant being cold.

Obviously, be sure that all hoses / pipes are refitted and securely attached with their respective jubilee clips.

[cavalier1990]

Being v6 probably best change it and replace with correct gm red anti-freeze. Might be similar to omega flush as same engine, i think there is guide/advice on omegaowners forum somewhere.