Passat tdi engine cooling - rob5
Starting from cold my '98 Passat tdi 110 hp engine temperature gauge stays in the cool zone .The top of the radiator is also cool.However after stopping for 15 minutes and restarting, the temperature gets to normal (90 degrees C) and stays there. Can anyone suggest a reason for this?
Passat tdi engine cooling - GrahamF1
Hard to be sure what's going on, but mine did play up in a similar manner to this a while ago.

Could be an airlock in the cooling system, or a sticking thermostat. Check the coolant level and that there are no leaks. Squeeze the radiator top hose a bit with the expansion tank cap off - see if it displaces any air.

If you still can't figure it out, drain the coolant and replace the thermostat. Refill the cooling system (slowly, with lots of hose squeezing to expel the air) and you should be ok.

If it's still problematic after this, then it's probably something more serious like a blockage in the radiator or the heater matrix.
Passat tdi engine cooling - gingerwizard
could be coolant temp sensor playing up, its a common fault on most VAG motors
Passat tdi engine cooling - Civic8
Temp sender is located after thermostat.ie stat has to open before it registers through sender..I would go for stuck thermostat first.Temp sender fault would show up as engine hot/radiator.But not registering on temp guage?
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Steve
Passat tdi engine cooling - DL
Sounds like a normal VAG Tdi engine to me; very fuel efficient=small amounts of heat. If I drive my A4 TDi from cold and have the heater on full chat the temp gauge behaves in the same manner. With the heater on normal settings, it can take 10 miles for 90 degress to be reached, driven sedately.

I'd be tempted to replace the temperature sensor and thermostat, just for good measure.
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groups.msn.com/honestjohn - Pictures say a thousand words.....
Passat tdi engine cooling - rob5
I think DL has a point with his cool running VAG engine idea, because the radiator doesn't seem to get hot. Perhaps the position of the sensor in the cicuit is also a factor, in that it's not exposed to the hot water until the 'stat opens with the residual heat from the engine during the stop.I'll change the thermostat for good measure though. Thanks for your inputs.
Passat tdi engine cooling - gingerwizard
steve and rob 5
temp sender is located in a plastic housing which bolts onto the cyl head and is subjected to engine heated coolant straight away and it is no where near the stat. the temp sender also sends temp info to the engine ecu so the fueling is altered as the engine heats up.it would be pointless to fit the temp sensor after the stat!!!!!!!!
get your facts right before posting.
Passat tdi engine cooling - Civic8
>>>>get your facts right before posting.

As rob 5 asked the question.I wonder why you said that.Point about sensor being bolted to head.Yes it may well send to ECU.Temp guage sender should be located as I mentioned. after thermostat..Same as fan switch.Unless their is another way of doing it now???
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Steve