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heater goes luke warm on idle but hot when revving

3K views 5 replies 4 participants last post by  Turbo 2.4 
#1 ·
i have a 2002 t4 2.5 when on idle at full temp my heaters seem to go luke warm but if i rev a little they are nice and toasty..is this common as my mates does the same...neither of us have any air in system...:*
 
#4 ·
There are two temp sensors on the 2.5tdi. At some point in about '98 the function of each changed slightly. One of them costs about a tenner at VW and the other 30 quid ish.
I'm sure a grown up will come along soon and remind me which is which. One can fool the van into thinking it's hot enough, although the guage tells you other wise. in which case you temp gauge may fluctuate a little.
I think I need to change the one I didn't last year, as in the cold now on a run, espescially if cruising at 60 ish, my gauge drops whilst the van is moving and rises again if it's stationary. The thermostat is working fine having checked temps either side of it, both when cold and warming to the first "pop" of the thermostat and once up to temp.
As long as you water pump works, the thermostat works and your coolant is bled and levels correct, I'd suspect one of the sensors.
 
#6 ·
Mine does the same . It was a 1.9td it did it. Its now a 2.4 with turbo and it still does it. I was thinking it might have something to do with the electric coolant pump on the front cross member. Or does that only circulate when its turned off when hot..?
Investigation required.
 
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