A4 TDi running cold ?

[spaarky]

1998 A4 1.9TDi

my old man's TDi has started running cold - temp gauge never goes above 70, regardless of driving on motorway, town, idling etc & sod all heat coming out of heater. not ideal at this time of year for an old man with buggered post-chemo circulation. was thinking thermostat knackered i.e. if stat is open all the time, motor never gets up to full temp, hence cold on gauge & rubbish heater

saw a test to check stat, involving a long run then idling until temp comes up & then running again to watch temp go back down. did this, but temp still don't get above 70 - always used to be 90 as normal, & with a decent heater too

does anyone reckon there's anything else I should be looking at other than replacing the thermostat ? car has done nearly 160k miles, so wouldn't be surprised if it's due a replacement . . .

[20vcqdriver]

Originally Posted by spaarky

1998 A4 1.9TDi

my old man's TDi has started running cold - temp gauge never goes above 70, regardless of driving on motorway, town, idling etc & sod all heat coming out of heater. not ideal at this time of year for an old man with buggered post-chemo circulation. was thinking thermostat knackered i.e. if stat is open all the time, motor never gets up to full temp, hence cold on gauge & rubbish heater

saw a test to check stat, involving a long run then idling until temp comes up & then running again to watch temp go back down. did this, but temp still don't get above 70 - always used to be 90 as normal, & with a decent heater too

does anyone reckon there's anything else I should be looking at other than replacing the thermostat ? car has done nearly 160k miles, so wouldn't be surprised if it's due a replacement . . .

Sounds like stat to me, or possibly pump. Depends how the hoses to rad feel after a run.
My Passat ran at about 80 all the time, but always got heat into the car

[spaarky]

thanks 20vcqdriver - you reckon maybe the water pump? I would have thought a dodgy pump would make it run hotter though lower circulation rate . . ?

[spaarky]

finally got to have a quick look at the the old man's car today, it has 2 rad fans & the large radiator fan is spinning even when the engine starts from cold - is this normal on a TDi? with the engine off & cold, the fan spins freely in either direction by hand. am wondering that if the fan should be stopped when motor cold, but in fact is always spinning, then the rad is getting overcooled, hence low running temp & no heat in the car. anyone got any experience with TDi ? I know nothing about these oil burners, but it has done lots of miles with no problem so must be a pretty good motor

[steveb]

Does it have air con ? if it does and the temp is above 5deg one fan will run all the time

No Air con.... the sender switch in the rad has prob failed

[spaarky]

yes m8 - it has climate control - again summat new to me (my 'new' car is 22yrs old!); the fan does look like it is supposed to run all the time due to all the pulleys etc, viscous coupling I think. the car used to have some heat, but now it's rubbish & cold all the time. & the engine temp gauge also only hits 72C max, when it used to be 90C all the time. thought about rad temp sender too, but having climate control has confused the issue even more for me. think there's one single problem causing the low engine temps & low heater output, since my understanding is that the heat part of climate control is 'conventional' i.e. thru matrix & it's only the cooling bit that has any input from the climate control stuff. really confused. electronics ? buggered if I know, gimme some carbs & basic electrics !

if you reckon an aircon a4 fan should run all the time above 5C, that makes me think that maybe not a fan problem, but poss watercooling thermostat again. have got a new stat for it, but reluctant to fit it if also needing to change rad thermo switches etc since not a 5min job & coolant etc ain't cheap - old man lives a long way away, so need to do the whole job at the same time if poss. any thoughts really appreciated, can't afford garage prices, but I really wanna get the old boy warm

[Puglife]

I've got a 97' A4 Tdi 110 and mines not got climate control but one fan runs constantly.... thats normal.

As for no heaters that sounds classic Airlock symptoms, theres an airlock in the coolant system... You'll most likely need to bleed system to get the air out but may be worth fitting a new thermostat whilst your at it.

[Puglife]

Also notably.... Mine doesnt get above 80degrees much whilst driving around... when i standstill it will sit at 90degrees and fluctuate slightly when 2nd fan comes on and off.

[spaarky]

cheers puglife - tried the idling test, but temp still don't get above 70ish, in any situation i.e. idling/town driving/motorway etc, which is why I was wondering about excess fan action or knackered stat - haven't touched the coolant or water system for a long while, so doubting it's an airlock unless it's sprung a leak somewhere, tho it don't seem to be leaking at all. I guess best bet so far is probly a knackered stat that's open all the time, though still not convinced, just a bit confused; this modern stuff (even anything watercoooled) leaves me scratching my head like an idiot. scrap the FInj, water, electronics etc & gimme a basic engine & I'll make it scream & run like a dream, but all this modern shit leaves me feeling stupid. I can literally climb into my 80Q engine bay & play about, but with an A4 it seems you need lotsa diagnostics, a whole day to do real simple stuff & 1" arms like an alien . . .

[dandan]

just had this on mine pipe to and from the rad stone cold, needed thermostat and also found i needed a new fan switch, didnt realise fan wasnt working until investigation into thermostat problem