Mother of all water leaks. Thermostat Gasket?

Hi all.
I've been having overheating problems with my 2003 Hijet 1.3 EFI.
I changed the thermostat, and when I tested the old one, it was indeed broken.
However, when I started filling it back up with coolant it started gushing out faster than I could put it in.
It seems to be coming from around about where the thermostat is, so I must have messed it up.
What I'm wondering is, was there supposed to be a gasket or something to go around the thermostat?
It did cross my mind while I was fitting it, but as there wasn't an old one there I just carried on.
There was no leak before I changed it.
Any advice would be greatly appreciated.

Stupid boy!!! Yes the proper, full size Factory Fitted Thermostat has a rubber seal around the disc. If you have bought one of the First Line cheapo Thermostats it doesn't usually come with the rubber edge seal.

The section through the seal is U shaped and fits tightly around the disc and fits snugly in the machined recess in the head and is compressed by the plastic Thermostat Housing.

Fit 3 NEW M6 thread set bolts (10mm socket HEAD, don't be tempted to put the old ones back in because they snap and if you do, quite often it is a cylinder head off or the whole inlet manifold to drill out the broken set bolt) and I also cover the base of the recess and the bottom of the Thermostat Housing with Hylomar. DO NOT OVER TIGHTEN THE SET BOLTS or you will be emailing me for another one because you have broken one of the 3 ears off the base of the housing.

I don't mind supplying you with another one for £25+ postage. I'm quite happy to do that for you.

But the problem you have now also is because you have bought a cheap and nasty First Line Thermostat, you have got to go back on Ebay or your local Motor Trade Wholesaler and get a decent full size Thermostat with the rubber seal already fitted. I don't think that Daihatsu sell just the rubber seal. Anyway good luck and have fun.

This is the cause of your problem - lack of rubber sealing ring. The decent Japanese Thermostat about £25 and the cheap and nasty about £3-50 First Line and other makes of Thermostat.

Hi Woodie, thanks for your reply.

It did come with the rubber seal, that I fitted, but it was a cheap ebay one. 8 pound i think.

Are the recess and the housing supposed to touch once the bolts are done up?
Mine has a small gap and you can see the rubber seal if you look from the side.
Which is why I thought maybe there was a gasket to close the gap or something.
Also, what kind of Hylomar did you use?

I've ordered another thermostat just incase, (can't hurt to have a spare).
Went for a more expensive Nipparts one this time after reading Highly Jetted's thread on overheating.

Thanks again for the advice.

Use Blue Hylomar. The housing usually sits flush on the head surface. But use your intuition when tightening up the three set bolts. You will need unquestionably a 1/4 drive socket set and extensions to do the job ideally.

Ok. I managed to only have to remove the plate that the handbrake sits on last time as I could reach the last bolt through the rear with a ring spanner, (tiny hands). But I think I'll try and make myself some more space this time so I can get a better look at it all.
Wish me luck.