Where does your needle sit (seen this question lots of times

[lloydy]

this is the same part number as mine. it has a few engines types listed there, but the part number is pretty much the same across the vw range
https://www.vwheritage.com/shop/0441211 ... lf-t25-t4/" onclick="window.open(this.href);return false;

[kevtherev]

I have argued this with Martin before.
I assumed that if you could maintain 87 deg the stat would open partially, if the temp increased a degree then the stat would open a degree more.
Wax melts at 62-65 deg so this is clearly not wax from a candle
To quote the wikipedia

The thermostat stays closed until the coolant temperature reaches the nominal thermostat opening temperature. The thermostat then progressively opens as the coolant temperature increases to the optimum operating temperature, increasing the coolant flow to the radiator. Once the optimum operating temperature is reached, the thermostat progressively increases or decreases its opening in response to temperature changes

I can only relate to this, however Martins experience says different.

[lloydy]

i had a google on the tdi forums, and it does say start to open at 87, fully open at 102. I've never looked at the wbx ones, so can't really comment on that

[California Dreamin]

WIKI's are written by people like us ...

If we agree on the basic function of how the stat works..that the changing of the wax from a solid to a liquid creates the expansion that forces the pin out and the valve open? yes
Are we suggesting that the wax goes from partially melted state to fully melted state over that wide temp range?
Or
Melts completely at 87C but then continues to exponentially expand at it heats further...this I could except..if it wasn't for the many practical observations I've done with my students.
And you guys have all felt the sudden and extreme heat change of a top hose when the stat opens....not a gradual heating but a rush of heat?
You have me doubting myself though....when I do this next time I will try and video it, either way, I'm happy to admit if I'm wrong.

Martin

[kevtherev]

To quote a supplier of automotive waxes..

Each thermostat contains a plug or pellet of wax, designed to melt at a particular temperature or over a specific temperature range. On melting, the volume expansion in the enclosed system works against and finally overcomes the spring loaded seal, effectively introducing coolant into the engine and regulating operating temperature. This rate of expansion can be regulated with the introduction of Alkanes, thus smoothing the range of movement

Yes the wax melts but as I believed the expansion opens the valve

[eagle]

turn engine on red light flashes goes off as normal then starts again needle goes right over to max hot ,this all happens within 6 seconds.
changed sensor under engine ,changed sensor in expansion tank still same,i have a red sensor I think it is by thermo housing but no one seems to have one
its been on for 11years no trouble ,started as soon as it got cold problem that is,steve

[kevtherev]

There are no coolant senders under the engine.
You don't state your engine type... For the correct temp sender.

If you look in the wiki, the coolant level sender and relay 43 is responsible for the light flashing.
The wiki explains how to check what's causing the flash, assuming you have a full to the brim header.

The coolant temp sender is responsible for the gauge.

[danmetallic]

turn engine on red light flashes goes off as normal then starts again needle goes right over to max hot ,this all happens within 6 seconds.
changed sensor under engine ,changed sensor in expansion tank still same,i have a red sensor I think it is by thermo housing but no one seems to have one
its been on for 11years no trouble ,started as soon as it got cold problem that is,steve

The Temp sender on the Thermo housing which sends signal to your gauge should be the black/green sender.
https://www.brickwerks.co.uk/coolant-te ... green.html" onclick="window.open(this.href);return false;

[bmouthboyo]

Sorry to fog this thread up but wondered if anyone can recommend how or where I use this infrared gun to test my Mk1 GTI temperatures and what they should be.

After 40mins idle I aimed it at the temp sender housing and it was reading 75.5c with the temp needle just to the right of the warning light.