Empty expansion tank - what now?

[fivepints]

Hi all,

HAPPY NEW YEAR!

We had a split radiator a few months ago and had it replaced and coolant changed by a reputable dealer. They told us to watch for header tank movements and so we did, topping up once or twice with small (<100ml) amounts water.

All was good - and I'd not bothered to look at the coolant for a month or so when - to my horror - as I was filling the screenwash today I saw that the expansion tank was empty!

I put in about 900ml and it ran to "full" (wanted to check the rad hadn't gone again) but, just now, I saw a post from Haydn saying not to drive before bleeding - I guess I've just answered my own question but we are due to drive 40 miles from my folks to home tomorrow and I'm wondering whether to take the risk. Otherwise I'm off to Halfords and staying for another few days!

Any thoughts?

[Bob]

Personaly I wouldn't drive it until its bled properly.

Its a pain, but not such a pain as doing the head.

[Simon Jones]

Even though you have a V6, you should bleed it as per the diesel engine. Sounds like you have another leak somewhere such as a pin hole in rubber hose or steel pipe, or even around the radiator or expansion tank caps. Every Bongo should have a Haydn low coolant alarm and these issues will be detected before they become a serious problem.

[Northern Bongolow]

its a tough call this one. its not really that it lost maybe 900ml of coolant, its more about has it got an air lock of maybe 900ml.
it must have a leak somewhere or a fault somewhere to be loosing any coolant. if the leak is high up on the engine/rad it may not have an air lock at all, but if the leak is somewhere low down on the system it may have an air lock.
is there any signs of the leak to help give a clue. do a search on here for ( leaking and water pump) this may help you find a possible cause, as bob says the water pump is hard to spot when leaking as it usually only leaks when the system is at rest or recently started, when it warms up the pressure in the system can seal the leaking pump.

[fivepints]

Thanks all. I think I'll probably have a go at pressure testing it with a bike pump tomorrow. No evidence of a leak as yet, although water pump was replaced at same time as rad so there might be an old hose somewhere which has just given up. I agreed about the Coolant alarm. We hadn't got round to it but this is our second warning!

[fivepints]

Right - I had intended to do the bike pump test but called the AA instead as I was hoping we'd be recovered and then I could work at it over the weekend. The AA dude did said bike pump test and the system held pressure for a good 10 minutes without a leak. Then he checked the head gasket and that was OK (no exhaust gases in coolant). The thermostat opened, the bottom hose got hot, the top hose was hot too (should that happen?), but he is convinced it's fine for us to drive.

As you have all said - the coolant must have gone somewhere - but it's obviously going there very slowly.

Guess the only option is to bleed it and then keep an eye on it.

Will DEFINITELY fit a coolant alarm now!

[wonkanoby]

you can buy uv dye in a kit with a uv torch can help in tracing on ebay

[fivepints]

Thanks. We drove home fine - but after 40 miles at 60mph, albeit with it only being about 5-10 degrees today, the bottom hose was still cold. Is this normal?

[Simon Jones]

That's normal - the bottom hose will only get warm / hot when the 'stat opens which will only happen when there is a heavy load on the engine or minimal airflow over the radiator e.g. stuck in traffic.