Coolant filler cap

[Warren100uk]

Hi all, I have a really odd issue with my coolant system on my 2003 mini cooper. For a while coolant has been dropping from the expansion tank but no sign of any leaks after looking and no overheating issues. I decided to actually sit and look at the engine while it was running. I saw that after about 20 mins of the car running a leak came from the filler cap. So I ordered a new cap, once I had the new one on i watched again. Soon after starting the engine I saw that now there is a leak from the radiator which was never there before and only started after putting the new cap one.

Does anyone have any idea why it would do this? It's just very odd as now the amount leaking is a lot.

Any help would be appreciated. Thankks

[scrw.]

The old cap was leaking pressure, new one doesn't so the system leaked from elsewhere due to the system pressuring up now. Sure you don't have a leaking HG?

[Warren100uk]

Hi, thanks for your reply. What would be the indicator that I have a leaking head Gasket? Cheers

[ReverendCounter]

If I was you I'd replace the expansion tank as well, if the original is still on the car - they are notorious for leaking at the seam around the perimeter. If yours is leaking, it might be around the back or side where you can't see it so well. Could be allowing air in as the temp drops once you park up, if you've already had a bit of a leak.

[scrw.]

Warren100uk said:

Hi, thanks for your reply. What would be the indicator that I have a leaking head Gasket? Cheers

Using water, overheating, odd missfires, mayonaise oil in the oil filler cap, pressurising the coolant system....sure there are more I have missed, not always immediately apparent you have a HG failiure.

[Warren100uk]

From what you described, doesn't seems I have any of the head gaskets issues. Hoping it just the radiator, guess I will look into a new one and replace it. I had had the expansion tank off and can't see any evidence of leaks on it or on the heat cover underneath. What's anyone's thoughts on me doing the radiator myself? Looks straightforward from videos I've seen.

Cheers for the help