Thermostat

Well it's gone from not budging of cold to needle sitting just on the edge of red for past 100 mile ,what I've I done wrong .when I changed thermostat I only disconnected the pipe that goes into top of radiator ,could I have got an air lock?

DISCOVERY1-DAZ said:

Needle should be 1/2 way on the gauge at normal running temp if the gauge and sender are good. Have a search on how to bleed the coolant - if you're not 100% sure how to do it properly.

Daz

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As above - you might have an air lock - you will need to bleed the system

Daz

Well its been checked and there's no air lock ,I can only think either partially blocked rad or water pump .thing I don't understand is before I put thermostat in it didn't get hot and now it constantly runs hot ,I've even got to thinking viscous fans not working properly .is there anyone up this way who would be willing to come and have a look as I'm at end of my tether with it

Check the rad gets hot at the top and warm at the bottom - some people run with their fans removed at this time of year - fan check: rolled up news paper you should be able to stop the fan with the engine cold, with it hot you should not be able to stop it turning.

Pump check: with the engine running and cold undo the bleed cap on the thermostat housing - water should squirt out with cap removed!!

Daz

Well done the fan test and I think that's the culprit ,it'll stop with a bit of cardboard when engine is hot .are the "bolt on bits " fans any good?. Will test the water pump later just in case that's also on it's way out

its the viscous coupling you need to replace, afaik you can buy them separately, or stick a screw in the one you've got to lock it in place as a test.
TBH though, this time of year, especially on a run you shouldn't need the fan at all, the air flow through the rad should be sufficient on the move.