Temperature Gauge Sender

vincematthews · Apr 14, 2014

Getting no movement whatsoever on the water temperature gauge. I've cleaned the spade connectors but still no joy.

Looks like I need to change the Temperature Gauge Sender, the rearmost of the two, the one with one large and one small spade connector on the top.
Does any kind person have any tips on the best way of getting this out, it looks like I will need to disconnect the throttle body from the inlet manifold for access or is there an easier way?

Also is the Sender pocket blind or does it go into the water jacket (1987 2.5L Lux).

robwright · Apr 14, 2014

It sits im the head. You will need to drain coolant. Then just dismantle what you need for access.

vitesse · Apr 14, 2014

If it's loose enough to unscrew by hand once you've untightened it,if the new one is ready & handy I just do the "finger in dyke" job & quickly screw the new one in--just release the pressure cap & unscrew the bleed screw a smidgeon-shouldn't lose much coolant.

vincematthews · Apr 14, 2014

ORIGINAL: VITESSE If it's loose enough to unscrew by hand once you've untightened it, if the new one is ready & handy I just do the "finger in dyke" job & quickly screw the new one in--just release the pressure cap & unscrew the bleed screw a smidgeon-shouldn't lose much coolant.

Yes I was going for the Dutch approach . . . I assume you're saying release the pressure cap/bleed screw before unscrewing the sender? Sorry haven't got my head round the problem yet! That throttle body to inlet manifold hose is something else to remove! - need to move it in four different directions at once - whoever 'designed' that should be sacked. [

] The good news is I managed to find a potentiometer and test the temperature gauge - which appears to work.

vitesse · Apr 15, 2014

Vince, Yes just to remove any pressure in the system-I also have one of those Â£1 plastic squeeze pumps which provides a simple less messy way to drop the coolant level to minimum in the header tank thus reducing head of water pressure as well. You can warm up the rubber duct with a electric paint stripper to make it more flexible.

vincematthews · Apr 15, 2014

ORIGINAL: VITESSE Vince, Yes just to remove any pressure in the system-I also have one of those Â£1 plastic squeeze pumps which provides a simple less messy way to drop the coolant level to minimum in the header tank thus reducing head of water pressure as well. You can warm up the rubber duct with a electric paint stripper to make it more flexible.

Thanks for that - I suppose a bit of positive pressure though would be a good thing to stop air getting in? Good idea about the heat gun - I've used one before on the 924 on that oval plastic inlet duct to get it back out to shape when it collapsed inwards on the manufacturing joint under negative pressure and engine heat on a hot day.

vincematthews · Apr 20, 2014

Well I've changed the Temperature gauge sender OK and the gauge now registers. I ended up taking the throttle body off to give myself more room - cleaned it up at the same time. HOWEVER - I started the engine and ran it for 5+ minutes to see what temperature the gauge levelled out at but I never found out because the engine just died when the car started warming up. It coughed a couple of times when I tried re-starting it but after that it will only turn over but not fire. Bl@@dy amazing - you fix one thing and something else goes wrong!! [

] I don't believe in coincidences so I must have disturbed something, just can't think what - any ideas?

Frenchy · Apr 20, 2014

Check the wiring on the water temp sensor for the ECU, front of the head on the right, around the thermostat area.

vincematthews · Apr 22, 2014

ORIGINAL: Frenchy Check the wiring on the water temp sensor for the ECU, front of the head on the right, around the thermostat area.

Merci Monsieur . . . I think you got it right. I say 'think' because it wouldn't start to begin with. I took the inlet hose off again and had a look at the blue plug and wires. The spring on the plug was missing so I borrowed one from a spare loom, and I generally cleaned up the plug and connections. I measured the resistance (like Clarkes suggests) which was lower than it should apparently be at 1.03 Kohms. I don't know what this value will effect on the car though? I then tried starting and although it turned over it refused to fire - still. I put the battery on slow charge and it completed in a couple of hours. It then started but was reluctant to idle and even when it idled OK after a few minutes it didn't inspire confidence that it wouldn't cut out. I think it was probably a mistake cleaning inside the throttle valve!! I'll probably have to get it set up again - what do you think? BTW is it normal for the Temperature Gauge to be showing engine temp. after turning the ignition is off? .

Frenchy · Apr 22, 2014

Is it running rich ? black sooty smoke from the exhaust, the sender you were looking at measures the water temp and feeds back to the ECU, tickety boo when cold but if not working correctly does not send the required resistance back to the ECU which in turn does not alter the fuel to suit the temperature. Mine ran rich then cut out when warmed after a couple of minutes, bloody thing had only been fitted 12 months had one on the shelf so i changed it wilst in there one day. Stuck the old one back in, all was good again. Another one which let the car run for a while then cut out was some pitting and corrosion on the distributer cap coil lead contact.........................don't ask me how i know [&:]

vincematthews · Apr 23, 2014

ORIGINAL: Frenchy Is it running rich ? black sooty smoke from the exhaust, the sender you were looking at measures the water temp and feeds back to the ECU, tickety boo when cold but if not working correctly does not send the required resistance back to the ECU which in turn does not alter the fuel to suit the temperature. Mine ran rich then cut out when warmed after a couple of minutes, bloody thing had only been fitted 12 months had one on the shelf so i changed it wilst in there one day. Stuck the old one back in, all was good again. Another one which let the car run for a while then cut out was some pitting and corrosion on the distributor cap coil lead contact.........................don't ask me how i know [&:]

' Thanks for those suggestions. Started it again today and it ran OK at idle (1000rpm ish), and that's leaving it running until the fan kicked in. It doesn't seem to be running rich, so I think I might leave 'as is' for the moment but bear in mind your two suggestions above, both of which may well apply - I was thinking of renewing the cap and leads anyway. Now I've got it running, I might test the DME sensor again and see if it complies with Clarke's listed values. I've checked the block temperature when the fan kicks in and that's about 85C. Also the temperature gauge (with its new sender) suggests the temperature is about 90C - so that seems about right for the starting point for the DME test. .

ChasR · Apr 23, 2014

I'd invest in a good temp sender. A friend of mine on his GF's Polo had plenty of fun diagnosing a running issue. After going through what seemed like a plethora of temp sensors (from GSF) a genuine VAG item seems to have cured all of the issues, even if the sensor did cost Â£40 (Christ!).