now a diesel head..
AO Silver Member
Join Date: Sep 2014
Location: United Kingdom
coolant system loosing water is one of the main signs of HG failure.
in terms of the electrics stuff try an ecu reset it apparently cures 90% of the quirks on that side of things and the insructions are on available at the top of the GT forum page, start there before spending any more money.
re the sniff test, they can't give a false positive but have been known to give a false negative, resulting in more money spent on other parts to cure the problem.
I would pressure test the coolant system,
look up homemade pressure test kits online...one can be made for about £10...
and get some flourecent dye and a blacklight. dye goes in the rad cap..
with the engine off pressurise the system to around 25 psi, listen for leaks, with engine off you can hear them sometimes.
then use the blacklight to pinpoint where they are,dye in water will be v.easy to see.
if the coolant system has no leaks at 25 psi this implies the pressure is higher than that when the engine is running implying that there is indeed a breach btween the HG and water jacket.
the other thing you can do is a compression test on each cylinder, this will confirm things as one cylinder is likely to give a significantly lower reading.
IMO most people arrive at the headgasket diagnosis after replacing the water pump, thermostat and rad as it presents like a coolant system failure, also its normally the underlying cause anyway so going through this process is not a waste of time as its good practice to overhaul coolant components after a HG failure anyway.
if you are handy with a spanner the job is not hard, just time consuming so in order to save money I would do it yourself up until the camblet need fitting and timing done, get a good mobile indy to do this bit as if you mess it up the results can be expensive.
if you live anywhere near guildford i'm happy to look it over for you and can recommend a good mobile guy who has a block tester and compression tester in his mobile set up.
good luck and stick with it, the resut of this is you will end up with a car that your 100% certain is sound.
if you give up and go buy another there is no guarantee it will not have problems waiting to appear.