Missing coolant

[DCerebrate]

Hi, the coolant level on my Speed Six Cerbera has dropped 2 - 3 inches without explanation. Local garage can’t find any leaks. Suggested possible cylinder head gasket, but is this possible if it has passed a hydrocarbon test? Car is running great, has covered about 500 miles over the past 3 months. Has a longstanding issue with heater suddenly turning off on the motorway then turning on later. As if there is an airlock or other blockage affecting the water flow to the heater. But that is probably a red herring....

[Hamish400]

Have had similar on my T350c (at 80k plus miles) Pressure testing cooling system (twice, including pressurised over a weekend) showed no water leakage when cold. But when engine was running and warm, coolant was leaking directly in to sump. (Water level going down and oil reservoir level going up.)
New head gasket sorted it.

Rgds Hamish

[Hamish400]

Would also say the problem initially was a small loss of coolant but this gradually got worse over a thousand miles of running, until finally running engine at idle for 30 minutes showed oil reservoir level had increased. Oil cooler had been temporarily bypassed for this test.
Slackening oil reservoir drain plug showed water present.

[Chim450]

Are you getting any white smoke from your exhaust? That is a sure sign that you are getting coolant entering the combustion chambers, either head gasket or porous block.

[DCerebrate]

Thanks guys. Checked for both white smoke and water at bottom of oil tank. No coolant pressure test or air leak down test as yet but for now I will just keep an eye on it.

[DCerebrate]

Update - all is well. This turned out to be a leak from a corroded coolant pipe. Then on another journey I was at fault for managing to get the coolant cap on the wrong thread - but all ok as I never hit any traffic. Mine is the set-up with the ancillary electric water pump by Davies Craig, temp controller and single large high flow fan. Local garage removed thermostat when coolant pipe replaced - and it ran too cool - 70 in the cold weather at the beginning of April. So I part covered radiator with cardboard! I have removed this now and want to see how it goes over the summer without the thermostat. Off to Cadwell Park on 25th May.