temp gauage/ heating issue

[groover1973]

Hi all
i would like to start by saying hello as this is my first post here.
i have a 2003 a4 1.9tdi sport and have an issue with the car temperature. the gauge was reading 88'ish and the temp would go down if i put the heater on. auto mode or not got the same result. i still have heat in the cab.
off the back of this i had the thermastat changed and seal. now the car hits 90 on the dot. problem i have is that when i run the heater it still drops ( as low as 45 ). turn the heater off and the temp will slowly go back to 90. as far as now, it has never gone over 90 :0)
can anyone suggest what is causing this problem.
if i dont use the heating its not an issue but i hate gremlins and need to solve this.
all your help and advice is most appreciated.
i will vag test it once i get the correct version of sotware for my after market cable as i have lost the disc and cant remember which revision i had with it.

 

[mattyb6]

Have you changed the temp sender unit? This is a common fault with these

also when you had the thermostat changed you may have created an air lock, and will need bleeding.

which I believe you can do it via the heater matrix pipe going through te bulkhead.

another thought it could be a blocked heater matrix, and might jut need flushing out.

 

[stu_m]

If tou leave the heating on does the temp rise back up slowly?

 

[groover1973]

i have had the issue with the previous stat so i dont think its an air lock. havent changed the sender yet!!
the temp dont rise until i knock off the heating.

curiously i had an extra 10 minutes on my way home from work tonight and the needle kept 90. heating full blast on auto,no drop. swithced to manual with fan on full max and the temp dropped a mm then went back up. i will watch it again in the morning.
TBF my jorney to work is usualy less than 15 mins but all the same the temp hits 90 after 6-7 mins.

 

[stu_m]

without heating on the temp will hit 90 soon enough

with the heating on it can take a lot longer in this weather

the missus goes 10 miles to work and can take a good 30 mins and only just gets to 90 if where lucky!

 

[groover1973]

I guess a good 30-60 min run would tell. I havent took it on a long run for a while.Just frustrating.Im sure somethings up but loath taking it to the stealer lol

 

[stu_m]

take it for a decent run with the heating on auto and see how long it takes to warm up and make sure it hits 90 and stays there

 

[groover1973]

I took it on a longer run to work this morning.5.5° outside.heating on auto it took 8 minutes to hit 90.
2 minutes later the outside temp dropped 1° and the gauge dropped 2 mm for 2 minutes then went back to 90.
I parked at work for about 3 minutes then started the engine again.temperature was 90 then started dropping again ::0(. I had to get started so I gave up at that point.

 

[RobMorris]

Id say Coolant temp sensor.

 

[VagCabby]

As said, stick a coolant temp sensor in it, see my post on strange problems with 2.5tdi, genuine CTS cured all my strange problems including a low reading temp guage

 

[stu_m]

sounds pretty normal to me

8 minutes to 90 is pretty good unless your gauge is erratic I doubt there is anything wrong with your coolant sensor

once you slow down if your coolant temp is only close to 90 it will soon drop again as the heating saps all the heat for the cabin once its fully warmed up it will sit at 90 all day long

take it for a longer drive to allow it to heat up properly and see how it is

 

[Mike B]

sounds pretty normal to me

8 minutes to 90 is pretty good unless your gauge is erratic I doubt there is anything wrong with your coolant sensor

once you slow down if your coolant temp is only close to 90 it will soon drop again as the heating saps all the heat for the cabin once its fully warmed up it will sit at 90 all day long

take it for a longer drive to allow it to heat up properly and see how it is

Spot on.The guage is only an indicator

 

[groover1973]

thanks guys. i think it may just be me and it needs more time to heat up.
i ran it on auto @21degrees and it heated up and didnt drop back.i usualy only do 20 minute drives to and from work.i guess to fully heat up it may take a good half hour or so.
first chance i get to go on a good hour or so trip i will check it again.
cheers again.

 

[stu_m]

The missus takes mine to work everyday which is a 25 min drive at 30's and 40's with a bit of stop start and it will only just get to 90 if where lucky she has the heating set at 24 too the cold ****!

It sounds normal

 

[Mike B]

I love my heated seats for short trips when its this weather

 

[Az]

My wife's 2.0 B6 avant is having engine temp issues at the mo too. I drove it last night for quite a while and although I know it's pretty damn cold outside at the minute the gauge barely lifted off of 50 degrees, it probably hit 60 degrees at one point for all of a few minutes then settled back down to 50. It was a good 20 minute journey with a 3 mile stretch of dual carriage way doing 70-80 so it should of easily warned upto 90 degrees. I take the same trip to work everyday in my 2.5 TDi and it's at 90 degrees after the first mile of that 3 mile dual carriage way stretch, even at 3.30am with outside temps of -4.

Her catt has had both coolant temps sensors replaced recently but still no change, so I'm guessing it's the thermostat staying closed? Can anyone confirm where the thermostat is on a 2.0 NA engine please? I'm hoping it's not behind the water pump like it is on my car as her cambelt was only replaced 10k miles ago! (previous owner had it replaced)

 

[stu_m]

Its the stat sticking open not closed if it was closed it would over heat its open and is over cooling

not sure where they are on the 2.0 to be honest it could also be a dodgy temp sensor but I would go with the stat first

 

[Mike B]

If the stat is working ie closed the rad will stay cold for some time .If it begins to get warm too early then the stat is stuck open which is what they are meant to do when the fail

 

[Az]

Yeah sorry that's what I meant, stuck open, I always get muddled up which way round it is. So of its stuck open will it not allow the engine to get up to operating temp then? I would of thought it would eventually get warm but just not as quick, but it doesn't seem to be getting warm at all. Like I said both sensors have already been changed (one at the front and one at the back of the engine) for genuine items from TPS, so I think it must be the thermostat.

 

[stu_m]

In this weather you have no chance of it warming up as the rad will just cool it quicker then it can heat it

 

[Az]

In this weather you have no chance of it warming up as the rad will just cool it quicker then it can heat it

Mao your saying it'll be the thermostat staying open for sure then?

 

[stu_m]

more then likely yes

 

[Az]

Well that's good enough for me as that's what I thought it would more than likely be myself from previous experience on other cars.

Thanks!

 

[Mike B]

Just feel the rad unless it stays cold the stat is stuck

 

[groover1973]

just a quick update.
i have run the car @ 21degrees on auto and it warms up fine now. no drop in temp :0)
i run the car for best part of an hour and run on HI. after a mm dip it ran fine. it was like being abroad lol.
guess the cold was just taking its toll.
thanks again for all your help.