As you've got your digital temp gauge you could while away your time while waiting, checking exactly how effectively your old thermostat works. See what temp it starts to open and at what temp it's fully open when heating. Make sure that when fully open the secondary port is fully closed off as well- sometimes they don't open enough to close that port.<br>
It's not easy to see- a glass saucepan helps (but don't tell the other half)<br>
Monitor movements as the water cools as well, to see when it starts closing and is fully closed.

It starts opening at 93 and fully open at 104 but assuming the secondary port is the top it doesnt look like its fully closing but its very difficult to see as you say.

ok, really really stupid question, I know.
If you suspect the thermostat, why you'll waiting for a new one, isn't it possible to put the cover back on and run it without one? I know in the old days, it was possible to do this but of course, cars have got far more techno these days. If it didn't overheat, you'd know for sure it was the thermostat then.

Unfortunately its not like a traditional car thermostat. Its an external heart with the thermostat inside that connects to 4 hoses.

It starts opening at 93 and fully open at 104 but assuming the secondary port is the top it doesnt look like its fully closing but its very difficult to see as you say <br>

Assuming you're quoting degrees c there's a problem then. My known good one started to open at 82 degrees and was fully open at 93 degrees, which pretty much agrees with the RAVE numbers. <br>
In addition if the top port is not fully closed off when the stat is fully open, coolant will partially bypass the radiator completely. <br>
IIRC to test that bypass port I lifted the stat, when up to temp, up enough so I could pour hot water into it. If the water vanishes, the port's not sealed and the stat is defective. <br>
If you're really anal (like me) test the new one when you get it. They've been known to be defective out of the box.

Thats kinda reassuring as I really hope this is the problem.

Fitted new thermostat today, only took 11 days of waiting for it to arrive,tut.

Its looking hopeful though the proof is in the driving which I havent done yet.

I ran it for 30 mins with a lot of high revs, No overheating and the needle sat nicely in the middle, soft top hoses BUT it did drip from the overflow pipe then slowed down and eventually stopped overflowing so I'm hoping that was just it settling in or something with the correct amount of coolant.

As usual fix one and another appears or it maybe related.

As soon as I turned the engine on I heard a fast whooshing sound , it was coming from the passenger side blower area and a fast pressurised jet of water was pissing on to the carpet, probably half a cup full. It then stopped.
The only thing that Ive read it might be is the A/C drip tube is blocked and is backing up but would that cause a high pressure jet or is theer anything else behind there?

But there isn't any coolant or AC pipes in the area of the passenger blower and the AC drains are in the centre, either side of the transmission tunnel and just dribble? You sure that's where it came from?

Its shot out of the top r/h corner of the passengers footwell, I havent managed a closer inspection yet as its been chucking it down for days here.

Not the Thermostat, just took for a spin and quickly overheated. The bottom hose was still cold so I guess its a radiator change.

My MPG has dramatically dropped to 8/10 mph though the rear exhaust is corroded according to my last MOT.

Had a closer look at the passenger leak and the OBD is soaked but its water and not coolant and the same thing happened could here the whining wooshing noise and a jet of water.

Rain water getting in through the pollen filter housing and being sprayed around by the heater fan? If your heater ducts are anything like mine the foam in the joins has fallen out long ago so only about half the blower output gets as far as the heater box, the rest comes out and blows on the passengers feet (which causes my passenger to complain so I really should get under there with some duct tape). That could explain the whoosing noise and jet of water as it gets blasted through the gaps.

Sounds highly probable.
Its been cats n dogs for weeks here now. My sunroof drain also needs doing.

Just removed the radiator as my new one should be arriving today.

You were probably right Gilbert, The only label I can find on its is BTP53695 or something like that so its probably a Britpart, it also has a lot of damaged fins which would have been there from installation. Yet again French cowboys at their best.

Still not feeling confident this is the end of the problem though, hopefully the new one will be here soon.

Well so far I have changed:
Radiator. Water pump.
Thermostat.
Hoses.
Expansion cap.

It seems even worse now. It now overflows with the cap off , It only did it with it on before. Ive bled and bled and bled.

Still no indicator of gas in the coolant using the sniff tester or mixture of coolant with oil.

Its time to strip the engine as Ive probably spent near £800 on replacing other stuff the past few months otherwise I would probably just give up.

It's up to you of course, but I don't think its time to strip the engine yet. Are any of plugs 1,2,7,8 shiny and steam cleaned looking? Compression test and Leakdown test? <br>
I still think its air. I know you've bled and re-bled many times, but... <br>
Let's try something slightly different with bleeding: <br>
Unbolt/ clip the expansion tank from its mounts and lift it as high as the hoses will allow. Jury rig something to hold it up there. You need it to be the highest point in the system. Doesn't need to be elegant, you won't be driving. <br>
Take off little hose from rad to expansion tank at rad end and blow until nothing comes out the tank end but air <br>
Pour coolant into expansion tank until a steady stream comes out of top of rad, squeezing the large top hose until you can't hear any gurgling anywhere and your hose squeezing is directly reflected in the flow out of the top of the rad pulsing with your squeezes. <br>
Put small hose back onto rad <br>
Keep expansion tank as full as you can (to just below where the small hose squirts into the tank) at all times during this. You'll get coolant coming out over the top when you hose squeeze as well. <br>
Start engine- keep squeezing large hose as it warms up. You'll still get coolant coming up and down in the expansion tank, maybe even overflowing. It's important that you don't let the level fall in the tank so it doesn't suck air <br>
Keep squeezing that bloody hose until the stat opens <br>
Stop engine, keep squeezing the hose but now be more gentle and avoid forcing coolant out of the tank. There should be no air bubbles at all coming back into tank as you squeeze<br>
Let it cool <br>
Suck coolant out of tank (not by mouth!)- soak it up with clean rag or something until coolant level is on the line <br>
Put cap back on <br>
Put tank back in its mounts <br>
Job done...

Thanks OB for keeping me going. The plugs if anything where sooty probably because the O2 sensor needed changing.

I have pretty much done that routine with raising the tank etc. I thought I'd cracked it the other day as I ran it for ages even with the cap on without it overflowing but 5 mins driving and it overheated.
I did have it on ramps when it was ok, it seems to be when its on the flat or maybe just driving I got the problems apart from today where its constantly overflowing without the cap on even.
I will give it one more go tomorrow but this has been going on for weeks if not months now.

If the plugs are sooty, it's unlikely to be burning coolant- not impossible, but unlikely. <br>
Stick with the bleeding and burping for now <br>
Just for clarity, is it overheating or just pressurising the coolant, blowing it out, then overheating?

It usually blows out and overheats when driving.

Whilst sat outside with the cap off its just blowing out but I probably also dont give it time to overheat as I turn it off straight away.

The other day when I thought it was fine, whilst sat outside with the cap on it dribbled out the overflow but didnt overheat until I drove it.
I also have had the engine revved between 2-4k whilst outside without blowing out therefore thinking it was good until driving again.
On the odd occasion whilst overheating the needle dropped back down which made me think maybe it was a doggy thermostat before .

When I hear the engine gurgling once its blown out its gurgling from the Inlet manifold ( from 99my) or the bunch of bananas as someone else calls them. Is that where youd expect to hear it . I'm wondering if air is being sucked in through the gasket. I replaced the gasket last year and it was a bit tricky seating it, just wondering if that could have anything to do with it. You can tell I'm not afraid to look stupid :)

riddlemethis wrote:

Whilst sat outside with the cap off its just blowing out but I probably also dont give it time to overheat as I turn it off straight away.

If there are no combustion gases in the coolant, it's air. If you have a leak near the top of the engine, it will be drawing air in rather than leaking coolant out (especially if the cap is off so there is no pressure in the system), which will cause an airlock which will expand and blow the coolant out.

So could I be right about the inlet manifold gasket, maybe sucking air in?