Hi all. I haven't posted on here for quite a while but have always received good advice when I have. As always - apologies if covered fully by another thread …
My series 1 Elise is 20 years old now and survived just over 100k miles on its first engine before HGF ended its days and it was replaced with a reconditioned engine in 2014. After repairing I also got myself a little run around car to reduce the mileage on the Elise so have only done ~8k miles on the new engine, however the Elise is now my daily run around again.
A couple of years ago I noticed the temperature reading on the dash was low, down at mid 60s instead of the steady mid 80degC I've always had. I also started needing to top up with coolant on occasion. I had investigation work by numerous mechanics with sniffing for exhaust gases in coolant and pressure testing the coolant lines etc. with no obvious leak identified (there was no mayonnaise in the expansion tank but there are a few dark deposits!). There seemed to be no impact on performance and I continued to drive it, keeping a close eye on coolant levels and temperatures. Also the cooling system remained pressurised even when cold and not driven for days
At my service this year I was told they had now seen the first signs of coolant leakage through the head gasket. I had the head gasket replaced a couple of weeks ago and the mechanic said he could see no obvious fault with the gasket (other than that it was an unbranded part) and that from everything he could see the head was in good condition. There were clear signs that cylinder 2 had been washed clean with coolant flow as it was shiny compared to the carbonised other cylinders.
After a few days of very variable temperatures I enjoyed a couple of days of perfect temperatures for the first time in years, and the coolant system even seemed to depressurise when cold - happy days - but not for long and I'm now back in the mid 60s again and an expansion tank always at high pressure. I've not had to top up with coolant yet but fully expect to need to soon.
So to the point: what is going on? I'm not a mechanic (probably obvious). Is there anywhere else coolant can commonly leak other than the head gasket (if I assume both replaced and new gaskets are actually fine) to get into the engine? Any ideas why after working on the head all seemed fine but has now reverted? I'm completely at a loss and getting fed up with throwing money at the thing. Are the low temperatures and coolant leak linked or not? Any advice or ideas welcome (and apologies for the long story ….)