Mk2 golf overheating

[buzmuzguz]

Hi, I've got a mk2 golf 1.6 driver, I've finally, after about 2 years fixed my temp gauge in my clocks by fitting a new temp sensor. Now the gauge is telling me the engine is overheating. The needle sticks around the 3/4 of the way mark with water light flashing when at this point. Could the new temp sensor be giving a wrong reading? The radiator fan kicks in but is only on for a about 30 seconds and comes on every few minutes. I would have thought if the car was overheating the fan would be on all the time until is is cool enough to switch off.

Any ideas, is the engine actually overheating?

cheers

[Crasher]

It does not sound like it is actually overheating. The gauge should go just past half way. What colour was the sensor you fitted?

[buzmuzguz]

thanks for the quick reply, the sensor is black, i've attached a pic of what i'm seeing. The needle just sits at that point with the water light flashing.

[Crasher]

I would attach a separate K type thermocouple inserted into the top hose to see what the temp actually was; you will not have access to one of these so it is difficult to say if the gauge is over reading or if the fan is not reacting correctly. The fan will be a two speed unit and I would be able to tell if it was on speed one or two, but for you to tell this for us here you would have to identify the colour of the wire going positive when the fan is running, the red/white (1) or the red/black (2).

[buzmuzguz]

Cheers Crasher, I''l get it up to my local garage and see if they can tell me what the actual temp of the water is.

I"m not sure if this could effect it however, When changing the temp sensor i always thought it was the one on top of the flange nearest to head. It turns out that mine is directly beneath. When the temp gauge first stopped working i changed the top one nearest the head and since this didnt fix it at the time i don't recall changing it back so the chances are i.ve got to the wrong sensor at the top. If my temp gauge sensor is at the bottom whats the one at the top nearest the head? and could the effect the reading? I've attached some pics if it helps.

cheers

[Crasher]

The important thing is that the correct sensor is connected to the relevant wiring and the plugs are all colour coded to the sensors. The actual position in the housing does not matter but as far as I remember the black and white are on top and the red below. The black (251 919 501 D) is for the coolant temperature gauge and the red (251 919 369 B) for the inlet manifold air pre heat unit and the grey (191 919 369 B) for overrun cut off control. The specific wiring I have at work, not at home.

[buzmuzguz]

I've been playing around with the car to make it over heat and noticed the bottom rad pipe doesn't get hot at all until the water light starts to flash and the needle is at 3/4s. Also every time i got the car to over heart the rad fan didn't come on once! So do you reckon i should change both the thermostat and Radiator fan switch?

cheers

[Crasher]

Change the thermostat.