Hi Locostbuilders. After a break to fix a wiring fault, I have my car back on the road (ZX12R powered). My engine has always run cool (I believe it has the hot weather thermostat in it), so it came as a surprise on Saturday when my water temperature started climbing. I turned the car off at 104C (normally 70-80C). When it had cooled, I checked my expansion tank, and found I was low on coolant. I topped back up, and it took 1 litre to bring it back up. It then drove normally a the right temperature.

Today, I went to take it out again, and I thought I better check the coolant, and it is low again. Not anywhere near as low, but it has dropped. On ramps last week, it made lots of glugging noises as the rear end was jacked up (I put it down to air coming out of the system due to the angle the car was sat at). Now I am thinking it is something more sinister....

I have no obvious leaks (certainly no sign of a litre of water on the floor). So that makes me worry it is a head gasket issue. Is there any way to check this theory? I will be checking my oil breather tank tonight, as if there is coolant getting into the oil, I would expect the catch tank to be full (it connects to the crank case/bottom end).

What else can I do to address this quickly, before the sun leaves us for another year!?

The two main tests you can do are
(1) Chemical test for combustion gas in the header tank.
(2) Pressure test the cooling system cold. (with or without using florescent dye and a UV lamp).

Thanks BT. I spoke to the garage today who had the car for the MOT. The owner (a BEC owner himself) said that at the MOT, they quite often just leave cars idling for ages. My car has never sat and idled for ages, and I am now wondering if this happened, and it spat out water last week. I did not see any sign of this, as my journey home was too short. Now I have done a longer journey, the low coolant level showed up as a hot engine. I topped up on saturday with a litre, but I wonder if more air has come out of the system since topping up, causing the drop I am now seeing. Just a theory, but I will explore it, as that sounds morel likely than a head gasket to me....