TD5 Temp gauge drops to 1/4

Hi,

This is my 2nd Disco2 Year 2004 TD5 (Disco owner 10 years).
Temp gauges have always behaved the same; Engine from cold after a few miles goes to 1/4, then few miles later up to mid point and stays there, regardless of outside temps, speed or distance run etc.

Until now....Was on A30 Cornwall Devon. The gauge would drop to 1/4 way and sit there, seemed to happen when going down hill, then back up to mid point on level or uphill. (But not all the time).

Stopped, checked level in reservoir low, so topped up. I unscrewed the bleed nut and ran the engine at tick over, a jet of just over a foot came out the bleed so refitted and topped reservoir.

The gauge continued to behave like this occasionally back home.

The Rave manual shows the V8 which has a different layout to mine. I've read through various threads but struggling to understand exactly how the coolant system works.

Would appreciate any advise, or if anyone has a layout with flow directions they could share.

Thanks
BugZ

Hi. This symptom is common when the thermostat is stuck open so replace that for start, when you refill the system unclip the reservoir and raise it above the bleed hole, poor coolant untill it flows through the bleed hole then put back partially the bleed screw as to still let fluid out and keep the revs above 2000rpm(for the mechanical bypass valve to open) untill no bubles are coming out then tighten it, fit back the tank, refill if necessary and tighten the cap to max... that's teh best way i attached the flow diagram but i share you the correct WSM here https://smallpdf.com/file#s=bf157087-0116-43ac-b05b-3be893d097b3

if with the new thermostat behaves the same we'll speak again

Hi sierrafery,
Thank you for your reply, you've been very helpful, and thanks for the manual, I have two but both different!
Will try the stat and let you know the outcome.
Cheers
BugZ