Fluctuating Coolant Levels in Header Tank K Series

[Kevin]

I hope the MLOC Team can advise!

The header tank cooling levels, on my 2002 S2 Elise, has started fluctuating 20mm below the min level, when cold, to just below the max level when warm. Images below (I hope)  I’ve had the car from new and the coolant level has stayed consistent between the min and max levels until now!!

There is no obvious coolant loss under the car and the oil dip stick and oil filler cap are just showing clean oil.

I have changed the pressure cap but this has not changed the situation.

Im not sure what my options are and PJS/Unit 4 are over an hours drive away and I’m reluctant to travel that distance!!

Any help and or advise is much appreciated

thanks Kevin

 

 

[timbo]

Is it losing fluid or only fluctuating level, ie. when it cools down has it dropped further? 

If you're not losing fluid then it's more likely to be pressure not holding when it's hot. 

[Lithopsian]

That much variation does suggest the tank isn't holding pressure.  If not the cap, then it might be a tiny crack.  Or possibly somewhere else in the system,  Most places other than the header tank would leak coolant, but then possibly you are losing coolant?  Do you get any hissing when you remove the cap when cold?  Could also be interesting to see if there is pressure when the system is hot, but there is some risk of burning your hands!

[Kevin]

Thanks Timbo and Lithopsian for your replies. I don’t get any hissing when I remove the pressure cap when cold and the header tank is dry on the outside and no coolant under the car. 
 

I will take it for a drive tomorrow and see if if have lost any further coolant when it cools down. Wish me luck!

Kevin

[MrWill]

Just adding my own thanks for the advice from you both. I'm getting exactly this is issue too on my early K.   (With the additional complication of an EWP which might be causing pressure fluctuations.)  

Will work through the advice step by step

All the best

MrWill 

[timbo]

On 08/08/2023 at 22:13, Kevin said:

Thanks Timbo and Lithopsian for your replies. I don’t get any hissing when I remove the pressure cap when cold and the header tank is dry on the outside and no coolant under the car. 
 

I will take it for a drive tomorrow and see if if have lost any further coolant when it cools down. Wish me luck!

Kevin

Any news?

I noticed you have some silicone hoses - make sure these are clamping down properly, also that one isn't scored internally as I recall some while ago an issue with DrH's Stratos replica where this happened to him and was showing up as an oil leak wicking along in the actual wall of the hose. 

[Kevin]

I’m happy to report that, following the conversation with Nick at PJS, I filled up the header tank to the minimum level line, and have driven the car on a number of occasions and I have not seen any loss of coolant!!

Thanks to all for your thoughts and advice and much appreciated 

Kevin

[Lithopsian]

Need to run the temperature up to the fan cutin a couple of times.  That will show if there is any coolant getting ejected when the pressure cap valve releases.  Or possibly if a weeping joint lets coolant out under pressure.  If the level is right, for your car then it will just rise to around the max line when it is warmed right through and the pressure cap will stay closed.  Can take 10 miles or more to heat the whole of the radiator circuit, or quite a few minutes idling.  After that the temperature will rise fairly quickly to 100C at idle and then the fan should cool it down.