Coolant system woes - 1.9 130

[Lil_Tammy]

After driving round with a failing coolant temp sensor for the last six months, I finally got sick of the high pitched warning noise every time I started the car and decided to change it. The EGR valve was also starting to leak a bit of oil. So genuis idea - whip this off which will make access to the CTS easier and change the gaskets whilst I'm at it. And since I'm doing all that, why not replace the thermostat too?

Everything has now gone back together, coolant system drained using the plug on the bottom of the radiator, refilled and bled through the heater pipes. This is where the fun starts. The heater is now warm but not hot, engine temp doesn't reach 90 on the gauge and the radiator fan is running constantly.

Any ideas as to what I've done wrong here? It seems to point to air in the coolant, but I'm getting straight coolant out of the bleed hole? Any help would be appreciated - this is driving me mad

Edit: So having just driven the car for a second time today the engine management light has now come on. Two errors:

P0401 EGR flow insufficient detected
P0299 Generic turbocharger/supercharger under boost.

[ianhayter]

Have never owned the diesel B5's/B5.5's so can't help with EGR issues, but on the petrol ones (of which I've owned/own a few) there are 2 water temperature sensors. One at the rear of the engine underneath the piping to the throttle body and one at the bottom of the radiator. They are different, but most motor factors don't seem to recognise this, and fitting the wrong one can give some interesting problems. If I remember correctly the one at the rear of the engine should be either blue or green and the one at the bottom of the radiator should be grey. Not sure if the diesels are the same, but perhaps worth checking.
If you need to find part numbers try this link: Volkswagen Parts catalog - ETKA Online, Volkswagen EUROPA, original Catalog Volkswagen EUROPA

[Lil_Tammy]

Have never owned the diesel B5's/B5.5's so can't help with EGR issues, but on the petrol ones (of which I've owned/own a few) there are 2 water temperature sensors. One at the rear of the engine underneath the piping to the throttle body and one at the bottom of the radiator. They are different, but most motor factors don't seem to recognise this, and fitting the wrong one can give some interesting problems. If I remember correctly the one at the rear of the engine should be either blue or green and the one at the bottom of the radiator should be grey. Not sure if the diesels are the same, but perhaps worth checking.
If you need to find part numbers try this link: Volkswagen Parts catalog - ETKA Online, Volkswagen EUROPA, original Catalog Volkswagen EUROPA

Hi Ian, thanks for the reply. The EGR/turbo issue turned out to be a tiny disconected pipe at the back of the engine bay which leads to a solenoid down by the turbo. I must have knocked it when removing the EGR which threw the fault codes and prevented the turbo from spooling.

Think you're right about the temp sensor too. When I was under the car draining the coolant I noticed a switch/sensor at the bottom of the rad as you describe which looked worse for wear. Massive thianks for the link too. Using it I've discovered that what I was looking at was the "Temperature Switch, radiator fan" I reckon the coolant drain and flush has pushed it over the edge and it's failed. I've also got a part number from the same link so ordering a replacement was simple.