GTV expansion tank overflow

[poohbah]

Basic question.

My GTV has never had an issue with overheating in the past, but in the last few days it has been running a bit warmer in traffic (admittedly weather has been fairly warm). Still mostly sits between 85-95'C, though normally it barely moves from the 80'C mark. The fan does seem to come on as normal.

However, when I stop and switch off, I seem to lose an awful lot of coolant from the expansion tank through the overflow hose. Its not leaking anywhere else, but I can hear water bubbling in expansion tank til it cools down.

Any obvious suggestions - blocked radiator maybe?

Forgot to add - have checked the oil and it seems fine, I can't see any obvious signs of water in it, so hopefully head gasket is okay.

[bonno]

Hi Poohbah
Check that the thermostat is working correctly, ie; remove and test in boiling water and see that it opens. If faulty, it's a cheap fix  just need to replace thermostat and gasket.
bonno

[poohbah]

Cheers Bonni, will check. Fingers crossed that's all it is.

[four90s]

Hey Poobah,

Maybe the fan sender. It's the sender in the top of the thermostat housing and they go as well.
If it's been warm and you've had the a/c on, the fan could be coming on for that but not for the radiator.

This is another "ask me how I know moment".

Cheers
Steve
Adelaide

[carlo rossi]

Next time check if there is any pressure in the system

BE VERY VERY VERY VERY careful when doing this
if NO then you have an airleak generally near the cap the tank does crack with age

[poohbah]

Thanks for those tips too guys. Will investigate all today. Having thought about a bit,  I remember having a worn spring on the cap a while back, so tank didn't maintain pressure. But the cuurent cap is relatively new, so possibly there is an air leak in tank itself. It did look like some coolant was beading around the neck of the opening, but I assumed that was just spillage.

[carlo rossi]

if it is a cracked tank what i did was drill the crack all the way like a windscreen to stop it going further
then all of the crack itself and then I used aryldite to seal it
seems to work well
they all break in the same spot
or get a new one around $100

[Alfapride]

Do a flush I used a heavy duty tectaloy flush cleaned all the cooling galleries solved my overheating problem also bleed the system might have a air pocket

[four90s]

Ignore what i said. I was thinking it was a 916 GTV.

Steve
Adelaide

[poohbah]

Ha, no problem 490s. Thought it was unlikely - AC in my GTV has never worked!!

[poohbah]

Starting to narrow things down. Tank seems completely fine, its actually fairly new, and no sign of cracking anywhere.

Is there a trick to removing the thermostat housing? Got the bolts out fine, but I couldn't budge the top half from the bottom of the housing itself. Its sealed tight.

Regardless, I ran the engine up to temp, and fan came on like clockwork just over 80C.

However, I also have a fan fitted to the front side of the radiator and it didn't come on at all. So I suspect that may be the culprit. Now to find out why its not coming on. It will be a pig if I have to remove the fan itself, its a bastard to get to.

[poohbah]

I reckon you may be right that the front fan is for the AC, but I also think its aftermarket addition. Can't see any reference to it in Haynes manual. Most other Alfettas/GTVs I've seen with dual fans have had twin fans mounted side by side behind the radiator.

To be completely honest, I'm not sure if the front mounted fan has ever worked under my ownership. Since day one, when I've turned on the AC, nothing at all seems to happen (can't hear AC clutch engage) other than the blower in the console comes on

I'll go and give it a whirl now.

[bonno]

Poobah
Try tapping the thermostat housing using a piece of wood and hammer, just enough to break the seal. 

[poohbah]

Thanks Bonno, will give it a go on the weekend. Was a bit wary of not being able to put it back.

[poohbah]

Doh - have also just realised another obvious likely contributing factor.

I had to top up the expansion tank twice over the last few days, but didn't have any coolant on hand. (I suspect the level was already on the low side before the first top up - I hadn't driven the car for a while, and forgot to check the coolant level before heading out for a longish run on a warm day).

So in the course of two top-ups I basically diluted the coolant significantly. Which obviously lowered the boiling point significantly...

Will now do as I should have done from the start, drain the system and replace with coolant. Will then be able to better gauge if there is still an issue.

As a matter of interest - what do you guys recommend as best coolant for the 2L?