Leaking expansion tank.

[Old Mac Rocco]

Looking for some advice from the professionals on here.
Recently my wee 1.6 carb developed the habit of ejecting water from the expansion tank all over the gear box.
I tried a new cap thinking it was knackered - problem continued.
I tried a new expansion tank thinking that the thread was perished / worn - problem continued.
The head was skimmed and a new c/h gasket fitted a couple of years back with excellent results.
I am tempted to try a new thermostat just in case it is not working properly at the required temp.
I have also heard that Old Skool mechanics sometimes drill a very small hole in this so that there is a continuous flow of water no matter what temp it is at. Is this true or is this just an old wife's tale.
I am a bit wary about driving the car but with a 500 mile round trip to Leeds on the horizon I have to get this sorted.
Any advice, tips or general contributions welcome and greatly appreciated as usual.

[PeteGLi]

Is it ejecting hot or cold water out of the expansion tank cap?

If hot, then it seems to me, that it is overheating.

How far up the coolant gauge does the needle go, and dDoes your radiator fan come on?

[Old Mac Rocco]

Hot water only.
I have got into the habit of making sure it is dry before starting any journey and then rechecking when I've done my trip and invariably it has been spewing out water while being driven.
Normally my gauge sits at about 5degrees off to the left of tdc (top dead centre).
In slow moving traffic this sometimes goes to 5degrees to the right of tdc but very rarely past this and returns to normal when the airflow is normal again.
My fan occasionally kicks in when I switch off but not very often when travelling.

[Old Mac Rocco]

I have checked with the cap off and on tweaking the carb the flow increases as it should, so it would appear that it is flowing as it should.

[DannyH]

Double check the cap and make sure it is the correct BLUE one the black ones are deadly it sounds very similar to problems i had years ago that were down to the cap. also not all of the blue caps are right. the other problem that i had that was similar was a leak around the sensor in the top of the expansion tank.

[Old Mac Rocco]

Cheers Danny.
I have tried both black and blue but I will buy another blue and see if that works.
At about £4 to £5 it won't break the bank.

[steve bain]

Where is the leak coming from exactly. As the whole system is under pressure it could be a poorly champed hose joining the expansion tank for instance.

[Old Mac Rocco]

Hi Steve,
Top of the expansion tank and running down over the tank sides.
To me it is a pressure thing but with both a new tank and a new top I can't figure it out.
I'll try and get some pictures up today.

[steve bain]

From the level sensor? That shouldn't be able to leak. The cap should let it go first. Pic would be helpful. Like I say, under pressure all the time so the smallest pin hole will leak.

[Old Mac Rocco]

Hi Steve,
I don't have a level sensor, it's only a wee 1.6 with just the basics on her.
I've fitted a new tank and cap so i'll give her a run tomorrow and see what's happening now.
Hopefully this will have sorted it out.

[mark1gls]

Make sure the coolant level is not over the max level on level ground, try a little less coolant in the tank to see if that also helps.

[Old Mac Rocco]

Hi Mark,
Will do.
It was getting a bit cold and dark so I have still to top her up before her test drive.

[james butler]

mine does the same thing and has done for years.
i changed the expansion tank and cap and still the same thing although mine only leaks if i thrash it so the coolant is sloshing up the inside of the cap.
when its driven steady or stationary i get no coolant loss.
ive also replaced the headgasket and had the head skimmed but its allways been the same.

[Old Mac Rocco]

I think I may have cracked it but I never got a chance of a blast due to having visitors most of today.
I got ten minutes before it got too dark, so I'll give her a run tomorrow.
Fingers crossed.

[steve bain]

You can get a new tank off eBay for a tenner. Be suprised if you cracked it though.