how often is it normal to fill expansion tank with water?

[rastiazul]

I have been having to fill the water bottle at least once every month, is that normal? I dont drive that much, I fill the fuel tank once a week, and its one of those smaller tanks.

 

[Homegrown]

No its not how it should be, but can have a lot of different reasons.
Check for external leak, water pump, hoses, radiator, heater core etc. If everything is in order I would lift oil filler cap and oil stick check so oil isnt contaminated with water (grey sludge). If oil also looks good you have an internal leak either head gasket or cylinder foot gaskets.
So after eliminating external leaks and car dont smoke white while driving (water enters combustion chamber) and oil looks good I would keep filling bottle and check oil filler cap/ dipstick every fuel fill.

 

[rastiazul]

Thank you @Homegrown, now that you mention oil, it might be worth mentioning that I got a new bottle recently and it has quickly become dark with a greasy substance

 

[JdeW]

As a start change the head gasket it's an reasonable easy diy

 

[Piet]

I have a car with an old Billancourt engine, and at one point in a fit of enthusiasm I fitted a new plastic expansion bottle and valve from the latest b1b version- however it regularly started losing water/coolant from various places including the water pump bearing (which was on a newish water pump). Prior to this it had never lost any water. In the end I went back to the old glass expansion bottle and it’s valve and all was fine again. I only ever changed because the Haynes book said if you ever boil, replace the valve. I had the radiator recored and couldn’t get an old type valve hence the new bottle. In retrospect I wonder if that was just Renault up selling. I assume the later bottles probably have a higher pressure expansion valve setting and enough little tweaks on the B1B water pump seals etc to carry that off.

 

[malcolm]

I have a similar problem on my Billancourt engine. My first step is fitting a temperature gauge to see what the temperature gets to before overheating. If it only gets to less than 100 degrees the system isn't pressurising. If it gets to maybe 105 or 110 degrees the system is pressurising OK. If it gets to 120 degrees the pressure release isn't working.

Although if it isn't overheating with the glass expansion bottle then leave it as it is.

 

[Piet]

I agree, I assume the later bottle has a higher blowoff pressure. With the old bottle and valve never a problem even in Australian summers, so I believe the valve works, just set to a lower pressure. I should try measuring it one day.