Hi all,


2.5 STi Spec D 07 plate


I would like to try and drain my coolant to see if I have an air lock. I guess bottom hose would be best to disconnect, but which end? Rad end or thermostat end?


Would I be best taking the thermostat out and testing it?


Refilling, I read that the best way is to fill via the rear most hose on the header tank, nearest the turbo. Slowly and then maybe a quick burp once warm.


I've tried burping the system countless times, but lots of coolant still being pushed into overflow tank. Yes, probably HG, but one last try for me would be to drain and refill the system slowly.


No overheating, fans working fine, hot air from heater (goes cooler when pedal to the metal)

What is the capacity of a 2.5 coolant system....5 or 7 litres perhaps?

Thanks in advance.

 

There is supposed to be water in the overflow tank.

 

If everything is working fine why do you think you have a problem?

 

Yes I realise that, but on cold I can set the level to half way between min and max, and after spirited driving, it's nearly full to the brim and bubbling like a Jacuzzi!

Sorry, I should have made that more clear.

I am thinking HG, but one last try if this is just a simple air lock.

I'd expect the coolant level to rise 2 or 3 inches, but not to nearly overflowing.
Could be only happening under big boosts like 4th / 5th gear etc.

And of course, I can't replicate high boost whilst stationary.

 

Sounds like HG failure unfortunately, to be 100% sure get a Hydrocarbon sniff test done at your local garage.

 

That's what I'm thinking, I have been doing sniff tests at the cap on the overflow tank (whilst bubbling) but normally the reagent dye stays blue.


It did go green (just) once, but not yellow. I don't really have much doubt in my mind that the problem is HG, but I would like to drain and refill slowly to be sure of outruling an air lock. Daft maybe, but how chuffed would I be if it is just an air lock.

 

Drain from the lower tap on the radiator over night into a clean container to re use if the coolant is ok. Mind to take cap off header tank while draining. Then follow proper re filling procedure, hopefully it is an air lock in the system, will save you a fortune!! Good luck!

 

Where is the proper procedure, there are several ways on here?

 

They are all much the same.

Drain and back-flush if needed.

With cap off header tank, (the one on top of the engine), and internal heater set to hot, remove the pipe at the rear of the header tank, and stuff a funnel down it.

Now fill SLOWLY through that funnel, not allowing it to gulp. You are filling from the bottom of the engine upwards, so air is expelled as you do so. Eventually you wil see the header tank fill up. Stop when it's full.

Replace the pipe, and start the engine. The cap is still off, so watch for any bubbles, mopping up or topping up as necessary.

Once the fans kick in, replace the cap and drive round the block.
Allow to cool and check the level again, topping up if necessary.

That's it.

 

Thank you. How would you drain? And do I need to touch the thermostat to let all of the coolant out (assuming once cool it is shut) ?

What is back flushing?

I can see the tap at the bottom of the rad (plastic butterfly tab), if I turn this anti clockwise, can I attach a hose to what looks like a spout to make the drain easier to control into a pan?

 

Open that tab to drain, or remove bottom hose from radiator end.

Back flush, just stick a hose up that bottom hose and into the rad, let it flush through.

Or remove top hose from rad, fill from bottom, allow to drain.

 

Drained, refilled / burped.
If this doesn't work, rebuild. The end.

 

Hawkeye D - I have watched your threads with interest - you are undoubtedly going through what I went through a few years back. Like you, I was somewhat in denial when I had similar issues with my Spec D. It was a relief when I finally admitted that it was HG failure (or lifting HG under boost) and did something about it. It was only at this stage that I started enjoying the car. 40k miles on and I'm still having a ball.
Go on - just accept the reality and get something done about it so you can enjoy what is a thoroughly great car!

 

Hit the nail on the head there Blues. I've been getting these issues for a few years now, but last night, bubbles in the overflow tank still.


What work did you have done, other than the HG's of course?


It kills me thinking about how much I will need to spend to make it good again. Can I really justify forking out £4k on a nearly 8 year old car?? On the other hand, I would never knowingly sell it on with that issue, nor sell it cheap as a known issue if you see what I mean. Rebuild seems to be my only way out - also a built 2.5 will hold some value at least, and make for a brilliant road car.


It's only done 50k miles.


Does the water level in your overflow tank now behave itself, and with no bubbling?

 

 

Are you still on your original HG?

Mine was replaced by Subaru under warranty in 2010, does anyone know if this would have been an uprated item to the original?

 

I don't really think you need to fork out 4k if it is just the start of HG problems. I priced around from a few decent builders and was getting quoted around the £1.2k mark for head gaskets.

 

As far as I'm aware yes. Loads of little black bits in the old coolant. None in the new coolant yet, but I'm hardly driving it. I have another car to use anyways.

 

Approx £4.5k would include VAT, oil pump, oil cooler / modines, ACL bottom end bearings, ARP head studs, Mahle pistons and Cosworth head gaskets, mineral oil / filter, various seals and gaskets etc, and a Rob Rawle map after 1,000 mile run in.


Assumed head / block skimming and rebore also included.