Coolant burping ok or is my head gasket on the way?

[Gunnersellit]

Hello experts
Please help me. I have a 2004 cooper which has always been great. I prepared for a long journey in nov by checking my levels. I recognise its daft now but i did add about 500ml of coolant to my expansion tank before we went. It hardly ever has coolant in the tank, unless hot. I now know i shouldnt have added to the exp tank, but done now...

We then went on a long journey in November and on the way home we stopped at a junction and just then heard a horrid noise that sounded like something crazy down a drain. I stopped at the next turn, opened the bonnet and all looked well. We carried on and all has seemed fine since. I do a 30 min journey through traffic each morning and just yesterday morning I noticed the heater not pumping hot air unless driving over 50mph.

So I got her home last night and opened the bonnet only to see no cap on my expansion tank. Could this have popped off in November?

Anyway, today I opened the coolant cap and the main bleed valve by the rad and at idle began to add some coolant. All fine. So I trundled off to work picking up a new expansion cap from BMW on the way. I got to work and the pipe to the rad was very pressurised so I left it to cool. Started it again, bleed open, cap off and topped up A little more.

No major flow of water from bleed valve and a little appeared in the exp tank. I was now thinking that I may have got all air out.

It seems I hadn't as I got home and it was still pretty pressurised. So I thought I'd open the bleed and main rad cap again and watch for bubbles. A few burps here and there for a few mins. Then it started really whirling and eventually gushing coolant out of the top.

What does this mean??

[Gunnersellit]

Forgot to add, engine temp always seems fine.

[mab01uk]

I think you have got air in the heater and cooling system by allowing the coolant level in the expansion tank to drop below Minimum. You can add coolant to the expansion tank when engine is cold.........it should never be empty as that is when air gets in and overheating of engine occurs and the heater goes cold because it is full of air.

Renewing the pressure cap on the engine should stop the expansion tank flip cap blowing open due to excess pressure reaching the ex tank. Continue to bleed system and watch level carefully over next few days and see how it goes. also check first stage speed of radiator fan is cutting in.

More useful info here:
Solving MINI Cooling Problems.......... - Forums

Note: The pressure cap presurises the system to raise the boiling point of the coolant, without the cap on the coolant will eventually boil like a kettle at a lower temp.......only leave the pressure cap off for short periods to allow air to escape when bleeding, etc. (The plain exp tank cap is much less important on R50 One and Cooper models but on the R53 Cooper S it is also the pressure cap).

[Gunnersellit]

Hiya, been trying hard to bleed, burp and refil. What's worrying me is that it's burps like mad!! I can't turn the bleed by the head, just can't get to it. It sprays steam from the one by the rad and if I let it burp with the coolant cap off it's goes for ages and literally jumps out. Till I lose my bottle and cap it back off.

I then ensured the expansion tank was full, it sucked more in when I stopped the engine, then I went out for a drive and expansion tank was empty in 1mile. But i am getting hot air from the heaters now. So ive Got home, refilled it again and will let it cool completely and keep topping up the expansion tank this weekend.

Or am I in danger of doing damage to the engine? Should I get a professional to empty, fill and test the whole coolant system?

[mab01uk]

Hot air from the heater is a good sign it means the heater matrix rad now has coolant circulating through it rather than air.

I would give it a few more tries at topping up over the weekend but as said don't let the level in the expansion tank drop too low or it will draw air in again and you will be back where you started. The bleed valve by the head/thermostat needs a long nut driver for access........details here:
http://www.mini2.com/forum/maintenan...screw-plz.html

[Cooper S Jon]

Quote: Originally Posted by Gunnersellit (original)

I then ensured the expansion tank was full

Nooooooo.You done fill the expansion tank,you only half fill it.

it should have a mark on it that says max,thats where the level should be when the engine is cold..