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[darren5354]

Hi all, Just got back from a drive in my puppy (Omega). When I got out of the car there was a lot of water leaking from the expansion tank. On closer inspection (I opened the bonet) the expansion tank was bulging & the water escaping. I opened it & let the water flow. When it stoped there was very little water left in the tank so I topped it up. I then ran the engine with the expantion tank filler cap removed & got the same result the water gushed over & when in settled the was nearly no water left in the tank.

My theory was that there may be air in the system as I have recently had it flushed & renewed. So I went to my haynes manual to see if there was a bleed valve/screw. The haynes mentions nothing of a bleed valve but does state to firstly fill the system through the heater supply (upper) hose connected to the bulkhead & then to fill the expantion tank.

My questions are:

Is my theory correct???

I havent got a clue which is the right hose to disconnect & how to identify it??

Can any of you help.

Thanks in advance for your posts.

[darren5354]

Is there anybody out there???

[razzo]

I wouldn't worry about disconnecting the hose if there is air in the system but have to ask why did you flush the system in the first place. What does the temp gauge on the dash say as the header tank blows

[CaptainZok]

I seem to remember being told to fill through the heater pipes first.
IIRC at 100 degrees the electric fans kick into high speed to cool the system are they doing this, if not there may be a prob with the fan temp switch.

[JasonH]

Haynes is talking rubbish. The heater pipe they talk of would be a pain to remove.

I've drained and refilled my system a number of times for various reasons.

Fill it up then run the engine with the expansion tank cap off, keep topping up, give all the hoses a good squeeze and let the car run up to temperature, cap still off.

Put the cap on, check when cool.

Use the car but keep an eye on the water level for a few days as the last of the air works its way out.

[Admin]

Ideally you would fill the heater matrix first then fill via the header tank.

However, as that is a pain to do, just fill via header tank and then run up to temperature (from cold this will take a good 15 mins) with cap off.

Make sure temp controls are set to Hi and vents are open.

If air is in the system it will force its way out, often via a small eruption at the header tank.

Note whether there is any sign of water loss round the heater bypass valve also.
This is the black connector at the back of the engine on the drivers ide with 3 coolant pipes and a vacuum pipe on the top.

Water loss from this will often drip onto the bell housing of the gearbox.

if this is leaking, it will also suck in air, causing overpressurising of the system and the symptoms you describe.

If this is a problem worry not. A replacement is £30 max from a dealer and takes about 30 mins to fit (with scuttle removed).

[Mike Collins]

Maybe wide of the mark, but failure of the auxiliary pump near the top hose can cause overflow after shutdown. Mine appeared to be caused by liquid leaking into the pump motor.