Henry Boler

Ooh, Lots to reply to!! So to confirm, the cooling system is as far as I'm aware extremely clean. I've had everything off apart from the core plugs and nothing bad ever comes out and I've not got any blockages, I've checked the flow in every direction, including the block and head plugs. I even went to the trouble of rebuilding the water pump housing, cleaned out all the faces threads and tidied up the hose tails, chamfering the rough edges and checking the bypass works fine etc., the heater matrix is fine and the tap works perfectly too. Really thorough check! The radiator looks immaculate where visible internally... My gut feeling is definitely head gasket at the moment, the whole reason I have always had a sight glass fitted is from when I had my Spitfire and it would let me know when it was time to buy a new head gasket each time with a good couple of weeks pre warning of total failure! Air in the glass means problem... She is still running very well at the moment by the way. No signs of failure yet from that point of view... So Like you say Pete, a compression test probably wouldn't reveal a lot. I could try though. Re the air blowing coolant out thing, how long should I be able to run the engine with the cap off without coolant coming out? Obviously it's going to expand at some point and pour out, then boil as it's under pressure... When I do that it runs for a good 5 mins without more than a tablespoons worth coming out. It jets out on the motorway, give away is the coolant on the inside of the bonnet and over the chassis. How full should the overflow bottle be cold? How much water should come out of the rad when hot? I think that answered everything from you both! Henry ​

I think the thermostat is fine as the car maintains normal operating temperature, also I can see when it opens as I get a visible water jet coming in half way down the filler neck. Radiator wise, how would I know if the tubes are blocked? I've cleaned the radiator out very thoroughly numerous times over the last few years and it has always cooled very efficiently. Head Gasket I hope isn't the problem but who knows... The thing is all this only started when I decided to flush the cooling system the other day... Which implies something related to that has changed to cause the problem but I don't know... Last night after my post from Southampton, I just decided to get in the car and just drive it home it was fine, heating was back on and all... This morning is worked fine as well but was bubbling when I got to work. It seems that driving hard down a motorway, even for a short run like today which was about half a mile on the motorway gets the system bubbling... Head Gasket? Stupid Car!! ​

Okay, so unfortunately, no luck... I'm in Southampton now and the water fell out...

Okay, so I got home, backed all the nuts off and re torqued one by one. Then topped up the system and ran the engine with the cap off, bubbles came out and then I think they stopped. Went for a really quick drive round the block and there was air in the overflow pipe but it wasn't bubbling. So I let it cool down and have topped it up again and removed all the air in the overflow pipe and the cap so it will be obvious if there is any new air in there. Gonna drive down the motorway soon and see what happens.

Will do. I think you might be on to something there anyway as I ran it this morning for 5 mins with the cap off and every 10-15 seconds there was a small cluster of bubbles coming up, and the water level never went down at all which I guess if it was air locks escaping it would do... Just a quick question, I'm sure the answer is yes, but does the rocker shaft have to come off for this? I'll tighten them up tonight when I get home. Henry

That sounds like a plan. How safe is it to do that? Is there any chance of damaging the fire rings or anything? I seem to recall doing it on my spitfire years ago not long after a gasket change and it then blew, but that might just have been the unlucky spitfire engine that didn't like head gaskets...

Update, I couldn't get the cap off it's still got loads of pressure in it which is unusual for my car at the moment... And nothing but a bit of water came out when I turned the cap so thats a good sign I guess as well. I'm off to southampton for dinner now, 15+ miles each way, I'll let you all know how she goes later! I had a load of old spitfire ones I found! So I thought whilst I was at it I'd see if any or all worked! It's funny as all this started on the way home from my local ish meet in Petersfield, the Southern club! Actually rather a long way for me, almost an hours drive each way, but I like driving so that's fine!

I'm not sure if I'm losing water or not at the moment. I'll chech in a few minutes when the system has cooled and is below atmospheric pressure. I checked the heating on the way home from work, 2 minutes from startup and there is warm air coming out of the vents, the temperature gauge still reading cold at this point. I'd say that was a good sign of a functioning system. Still taking 5-6 miles to get to operating temp as you say. Yes thermostat is fine, I boiled a pan of 5 of them together on the hob this Sunday and they all functioned in the same way at the same time... I will try running the car tomorrow morning with the cap off from cold. I have done it for a little while whilst I was topping up the system and there was no sign of air coming out or any water being forced out either...

Are there any give aways that this could be head gasket related? Would there be any smells or colours in the coolant? The car has always made a few bubbles from the overflow, it's never caused me a problem and I do long journeys no problem, I have tried very hard to stop the bubble in the past, instead I have a sight glass halfway down the hose that shows me that it is still drawing water back in after a run. When my old spitfire bubbled it meant it wanted a new head gasket within about 50 miles but the GT6 has done a good 10,000 miles this year with no problems at all.

I changed the thermostat for one with a jiggle pin as I figured the old one wasn't helping... I'll keep trying things and let you know how it goes!

That's what my initial thoughts were/still are sort of... I ran the engine and kept filling it up until air stopped coming out, then I left it and did the process again and again. To be fair I did get more out every time. I drove her to work today 10 miles, and there were bubbles coming out again, but the heating remained on. When shes cool I'll see if there is room for more water. The water is definitely running as there is a massive water jet from the hose that enters halfway down the filler neck. I'll keep you posted!

Hi All, I know this is kinda similar to another thread on the go at the moment but I didn't want to hijack it so here goes... I have a problem with my cooling system at the moment, it wont keep the water in! This problem annoyed me enough to rebuild it all the last few days. So as far as I'm aware there are no leaks, there are also no blockages and it's all lovely and clean inside, always has been, which I guess would make it obvious if there were any contaminants getting into the coolant. What happens is I start with an empty system, I fill it up, fire the engine up run it for a few seconds which blows the trapped air out, I then top up with water and pop the cap on. Then from cold I go for a drive, within a minute I've got interior heating working just fine as you'd expect, I warm her up a bit more then as she gets hotter the heating fails, i.e. air in the matrix and then gradually everything comes out through the pin hole in the top of the expansion bottle at a very high rate, I then switch off and watch the expansion bottle sit there bubbling... I am stuck for ideas, I've tried everything I can think of, is there anything I might have missed? Or am I getting the fill procedure wrong? I've done this for years, my spitfire never had a problem, this GT6 has never been as easy to fill but I've never had this much grief... Henry

I'm half tempted to get the old girl on a rolling road to see what's coming out the wheels! My one always starts first time, even when it was -12'C outside! Doesn't pink, and has never run on, and this is the first time I've ever put anything other than 95 in her. Richard, what do you mean by 'no lean off'?

I used to fill up at a shell garage as I drove past one for my old job, maybe I'll see if there is another close one. I also don't know of a Tesco fuel station anywhere near by... I know a Morrisons one! What actual differences do you notice? Are we talking extra miles to a tank? Faster 0-60? Or just smooth running? My GT6 has always run like a dream on 95, never misses and it is pretty quick too!

I've now got a tank full of BP Ultimate 97, don't have any nearby shell garages here!

Me too! Dave Mac shaft on my GT6 MK3. Absolutely incredible now!

I did see the same comment you made on another thread Pete and it did make me think... I do drive a lot of miles in the GT6, would it be cost effective? I am tempted to try it... Would it increase the mileage by much? I used to run my old Spitfire on unleaded without the conversion and did about 50,000 miles with absolutely no trouble, I just decided I either do the conversion or see if it breaks as a result of not doing it and then to fix it, I would just do the conversion... It never broke... Ran fine, valve clearances were also fine!

I hadn't actually looked at the Forum before posting this. I guess this kind of answers the question. http://forum.tssc.org.uk/index.php?/topic/639-gt6-timing-question/

Hi All, I've been having a play with my ignition timing lately and was just wondering if anyone has any ideas about the topic. It's a MK3 GT6, All standard stuff, working perfectly. The centrifugal advance, vacuum advance work find and there is no wear on any parts etc... I run the car on 95 unleaded and I don't use any additives. Where should my engine fire? In the past it's been running at 6 BTDC, now it's on 13 BTDC... The engine runs like an absolute dream and I do drive it hard, nearly all the time, apart from when there are cops in close proximity! However, sometimes I do wonder how much of a difference it would make if I had the timing spot on... I've got a timing gun, I have also static timed it with a multimeter just to make sure the gun is working right. In the past I've found the tools to be useless and I've just fired her up and set the timing by ear. I know it's not actually a question as such, but any ideas appreciated. Also makes a change from my usual major mechanical failure posts! Henry

They are physically the same size so you could use either in either position, however, the prop shaft ones are hollow and have a grease nipple on them sometimes. The drive shaft ones generally need to be stronger as they take more load than the prop shaft, however many times your differential steps it up... I don't know if you need different ones on the spitfire though, but I definitely did on the GT6 as they kept breaking.