Cdti top hose mod ...
 

Cheap test for this mod.
I have fitted three oem replacement stats over the last three years and last week I noticed that even over a longer distance the OBD was only showing 78 degrees, it didn't go up any higher in traffic.
So after reading about the top hose mod I decided to fit one and try it, Eurocarparts had the thermostat I wanted (Circoli Part number 209745041) for a Renault 5 1.4, the diameter is 43mm.
Priced at £9.29 but with a blackfriday code used the total cost was £6.04.
2 degrees outside this morning and one hour later and I am running around with 86 degrees showing, normal roads, I ran around for about 10 miles or so and it only moved up or down by 1 degree, left her idling on my drive for about 15 minutes and the temp dropped to 84/85.
I will keep an eye on the temperature but if it stays like this for the winter I will be happy.

https://i.postimg.cc/kX9q4xH9/Euro.jpg

Thanks.Just ordered mine,same problem as you,the one i put in some months ago never gets up to 80.

I do have a new version OEM thermostat in my garage from Mat (DMGRS) but fitting these isn't a 20 minute job whereas in reality the top hose mod job is.

The inline modification is a very easy way forward - and I know I'm likely to get some flak for this, but I'd advise members away from Circoli as we had issues with (quite literally) half of the batch we bought from them not sealing properly and running at mid-60s instead of 80+ degrees.

There's plenty of brands out there that do work - First Line, Gates, Waxstat etc have all been fine. Mostly available for a similar price too :)

Again, just my 2p. Not meaning to cause a ruckus... :D

No worries Mat, for six quid and 20 minutes work if it plays up its an easy fix, I get what your saying though. :}