Pressure build up in cooling reservoir

[hungabunga]

I seem to be having a strange problem with pressure build up in the cooling reservoir. I started the car this morning and the red light in the temp guage was lit and temp guage stayed at zero. I checked the coolant level which was below minimum but once I unscrewed thr cap there was pressure release and the level jumped up to between the min and max lines.
I had a similar thing a few months ago and just put it down to it being a very hot day.

The car has never had the coolant topped up and is 5years old and there can't be a leak as the pressure wouldn't build up and oil level is fine so can't be head gasket.

Car is a 04 130 tdi with revo remap.

Just to add a few more things

1) the water pump was replaced about 10000 miles ago when the timing belt was done at 60K
Thanks in advance.
2) The car had been sat overnight and it still had pressure built up so was cold at the time.

Sully

 

[Markyboyt]

I'm not sure what causes this but the new Mini Cooper S' also do this although not to the extent of putting the light on though.

 

[finchy]

my lcr's done it a couple of times too.

 

[hungabunga]

I have topped up the coolant now, I guess it was too low to allow for the inch or so drop causing the light to come one.
I have seen a few threads on SCN but they all end without a conclusion as to the cause.
Will have to wait and see if it does it again, car is due a service so will have the garage take a look.

Thanks for your replies
Sully

 

[slim20vt]

dont panic my yellow old 210bhp lcr used to do this once or twice year.. all i did was put a cup full of water in the res tank. and it solved the problem...

just because there sealed and pressure rised up dosent mean the water dosent find some where to evaporate..........................

only panic when its doing it every day.....cheers

 

[hungabunga]

It has been fine for 5 years so had me a little spooked, will keep an eye on it and not worry too much. Worst of all is just bought a new car for the missus so can't afford for my car to break down as no money to spend.

Thanks for your replies, been a while since I was on the forum and forgot what a helpful bunch you lot are.

Sully

 

[platofan]

mine does it everyday.......

 

[LEE69]

mine does it everyday.......

Does what?

 

[platofan]

hisses at me in the morning, headgasket I think. Better get it tested.