Lude Generation

Lude having a bit of a problem.. Sometimes it heats up to half way pretty quick and is fine. Other times in the cold it could not heat up half way at all (I've driven to London and still not heated up)
My radiator burst a few weeks ago so all the water was changed etc and heated up much better.
Then today I was driving most of the day and on a few occasions its heated up half way and then dropped back down again so no vtec?!
Checked oil and its all ok. Did top it up as it was a little under. I do have a sump leak and ordered a new gasket but surely that can't the problem? Some mates have said it could be the thermostat?

Any ideas?

sounds like either the thermostat or rad cap to me

My uneducated guess is the thermostat.Have you checked you still have coolant in it? Some cars and I don't know about Preludes when they overheat will show it working fine and then drop away as no water is getting to the thermostat due to an airlock.

Yeah water and rad all fine brand new. Hoses are fine, have no leaks. Must be the thermo then. Would it be best to buy one brand new or get a 2nd hand one from here?

Buy a new one, they aren't expensive

Seriously I would buy a new one and if that does not fix it you can rule it out as the problem.

Yeah my thinking too.

Any other ideas?

More likely Thermostat (take it out and give it a clean, maybe something is blocking it?) but what about the electrical connections on the gauge sender unit (or the sender unit itself), could they be playing up? Don't know how easy it is to get to on the 4th Gen prelude to check though.

Just sounds like thermostat stays open all the time, when i was driving without thermostat it never got good temperature
So take it off , give a clean and then test it in boiling water maybe it needs to be changed

Ok will try that first. I don't know where it is found. I know they are fairly cheap, some come without the seals which is pointless... Might aswell get the kit for a couple quid more!