water tanks

[sneakyalien]

Hi,
Are there two water tanks in the cooling system of a T25?
I have read on one forum that there is only one watertank and on other forums people mention a water tank behind the flap.
Where is the flap on a T25 and the secondary water tank?

My T25 is a 1.9 petrol, C reg hightop.

Thanks

[lloydy]

yes there are two...
The flap is where your rear numberplate is, pull it down and you will see it and the dipstick, and the oil filler

[sneakyalien]

yes there are two...
The flap is where your rear numberplate is, pull it down and you will see it and the dipstick, and the oil filler

Thanks for the reply.
Is the one behind the flap, the tank that is on the left hand side of the engine bay, with the blue cap? or is it a different tank to the one in the engine bay?
I'm just trying to find which tanks to fill up to try and stop temp light from flashing continually even though engine is cold.
Thanks

[lloydy]

its in the engine bay, but is a different tank the hose attached to the blue cap leads to it. best if you just pull the numberplate down and look

[sneakyalien]

Thanks for the help
Will check it out in the morning.
Cheers.

[CovKid]

You only need (normally) to top up one behind number plate. Oil filler and dipstick can also be found there.

[sneakyalien]

I filled up the water tank (behind the flap) which was low on water and also topped up the tank in the engine bay(on the left) and the problem still persists -I still have the problem of a flashing temp light on the dash and the temp needle climbs to the very right position(even when the engine is cold and I have only just switched the engine on). I removed the sensor on the water tank and shorted the connections out to bypass the sensor, but still no joy.
One thing I noticed is if I remove the connections to the sensor that is on the engine, the temp gauge just falls quickly to the most left position(and just stays there) and the red light stops blinking - The sensor has been replaced with a new one, but this did not fix the problem. If I connect the cables from the sensor together (bypassing the sensor)the red light flashes and the temp gauge moves to the right again....don't know what else to try. Is it maybe something behind the dashboard that has gone wrong?
May be best if I take this to a garage who knows what they are doing - Does any one know any good VW camper garages in Preston, Lancashire arear?

Thanks for any advise.
Cheers.

[123-jn]

You need to check the continuity with a multimeter between the two pins on the temp sender, Just because it's new doesn't always mean it's good!!! You should have no continuity at all (no current should pass when cold, resistance is high) as the water warms the resistance falls to zero at about 105-115 degrees C. If this checks out then you must have a short in your wiring but this would not explain why all is well with the wires pulled off? The dash board appears to be behaving as it should.

[marlinowner]

The fact that the gauge is showing hot when the light flashes means that the fault is in the temperature, not coolant level, circuitry. Your tests on the temp sender mean that the rest of the circuit is OK, the fault is at the sender. Possibly one of the wires is shorting to ground somewhere when connected to the sender, when you disconnect it for testing, the movement means it is no longer shorting.

[sneakyalien]

Spent some more time with the temp light/needle problem today and put a continuity tester on the two pins of the temp sensor - The tester just bleeped, indicating continuity regardless of the engine being cold and hot??? Does this mean the sensor is faulty or the incorrect part for my van?
Thanks

[pirate-pete]

Hmmm - not got the manual handy right now but does the low coolant sensor not cause the needle to go to max and bring the light on too? Try shorting the two cables to the the expansion tank lid.

[sneakyalien]

Hmmm - not got the manual handy right now but does the low coolant sensor not cause the needle to go to max and bring the light on too? Try shorting the two cables to the the expansion tank lid.

Thanks for the reply.
Tried that earlier(see below)

I filled up the water tank (behind the flap) which was low on water and also topped up the tank in the engine bay(on the left) and the problem still persists -I still have the problem of a flashing temp light on the dash and the temp needle climbs to the very right position(even when the engine is cold and I have only just switched the engine on). I removed the sensor on the water tank and shorted the connections out to bypass the sensor, but still no joy.

Cheers.

[MidLifeCrisis]

The tester just bleeped, indicating continuity regardless of the engine being cold and hot??? Does this mean the sensor is faulty or the incorrect part for my van?

This would suggest that the temp sensor is not working correctly - as someone has already said it should show a high resistance when the engine (and therefore coolant) is cold, and a low resistance when the engine/coolant is hot.

What were you using as your tester? Is it able to measure resistance?

FYI - The resistance of the temp sensor should be 255-265 ohms when cold and 30-40 ohms when hot.

[pirate-pete]

Thanks for the reply.
Tried that earlier

uh - sorry for missing that.

The tester just bleeped, indicating continuity regardless of the engine being cold and hot??? Does this mean the sensor is faulty or the incorrect part for my van?

This would suggest that the temp sensor is not working correctly - as someone has already said it should show a high resistance when the engine (and therefore coolant) is cold, and a low resistance when the engine/coolant is hot.

What were you using as your tester? Is it able to measure resistance?

FYI - The resistance of the temp sensor should be 255-265 ohms when cold and 30-40 ohms when hot.

If it helps I have just measured resistance of brand new T25 sensor from VW dealer (black 2 pin) and it is showing 1520 ohms at room temp (17 deg) coming down to about 900 ohm perhaps lower if I stick my tongue on it for a minute or so. (this is a clean unused one so does not taste of antifreeze )

That is a bit higher than the 255 - 265 ohms so I wonder if that is the resistance to use when testing for cold position on the gauge. Googled for T25 sensor value and the ones JK are selling have this bit of text.

Suitable for Type 25 engine codes DF, DG, SS, MV and DJ.
T4 engine codes 1X, ABL, AJA, AAB, AES.
Temperature Range 25 degree C to 80 degree C
Resistance [Ohm] = 1000
Resistance [Ohm] = 148

[sneakyalien]

The tester just bleeped, indicating continuity regardless of the engine being cold and hot??? Does this mean the sensor is faulty or the incorrect part for my van?

This would suggest that the temp sensor is not working correctly - as someone has already said it should show a high resistance when the engine (and therefore coolant) is cold, and a low resistance when the engine/coolant is hot.

What were you using as your tester? Is it able to measure resistance?

FYI - The resistance of the temp sensor should be 255-265 ohms when cold and 30-40 ohms when hot.

I used a Multi Meter set to continuity tester and it bleeped as soon as I connected it to the two pins on the sensor - I will try it with a resistance setting to see what ohms is at the sensor.
Cheers.