Hi Folks,not sure if anyone can answer this, but today I changed the thermostat on my 1.4mpi fabby only for it to throw a wobbler. Firstly the hoses were all cold,then the top hose & only one of the heater hoses got hot.The gauge at that point had reached the middle. I assumed I had an airlock so squeezed the hoses to no avail. The temperature gauge then started to creep towards the red so I switched off & left t for about 10 minutes. After that I took it for a short drive & it overheated chucking coolant everywhere.

I grumpily drove home after it had cooled down & it overheated on the way back.

After grizzling to the Mrs for about half an hour that I would have to bite the bullet & get the car to a garage, I decided to check one more time. No coolant in the header tank so a litre of coolant & about the same of water was added & I went for a drive of around 8 miles. Gauge stayed in the middle & the heater is now back to it's usual searing level of heat.

I am confused as to what on earth happened & why (fingers crossed) is all O.K.

My only theory is that when it boiled over it purged all the air from the system, but is that even possible?

Hi Folks,not sure if anyone can answer this, but today I changed the thermostat on my 1.4mpi fabby only for it to throw a wobbler. Firstly the hoses were all cold,then the top hose & only one of the heater hoses got hot.The gauge at that point had reached the middle. I assumed I had an airlock so squeezed the hoses to no avail. The temperature gauge then started to creep towards the red so I switched off & left t for about 10 minutes. After that I took it for a short drive & it overheated chucking coolant everywhere.

I grumpily drove home after it had cooled down & it overheated on the way back.

After grizzling to the Mrs for about half an hour that I would have to bite the bullet & get the car to a garage, I decided to check one more time. No coolant in the header tank so a litre of coolant & about the same of water was added & I went for a drive of around 8 miles. Gauge stayed in the middle & the heater is now back to it's usual searing level of heat.

I am confused as to what on earth happened & why (fingers crossed) is all O.K.

My only theory is that when it boiled over it purged all the air from the system, but is that even possible?

 

Yes.

Thanks for the swift & concise answer sepulchrave apologies for posting twice.

I've always fill those with the temp sender removed it's just about the highest point do if you fill slowly the air gets purged out.

I've always fill those with the temp sender removed it's just about the highest point do if you fill slowly the air gets purged out.

This.

I've never had an issue. Just fill it up with coolant and run it with the cap off until it's up to operating temp. The air will come out of the return into the header tank.

All seems fine now. Went to work today, sat in traffic for a while, temp needle stayed in the middle, heater piping hot. The car now reaches full operating temperature within about a mile rather than ten with the old 'stat. All good.