A6 running cold but temp warning ??

**sumbuddy** · 13-11-2006,12:15 PM

Hi,

I hope I have found the right place.

We have an A6 (that has a gas conversion which I just disabled to get to the root of our problem.)

The head was refurbished 14 months ago (and the car drives a dream.)

But. It never warms up (so it never turns the gas on) and the red temp warning comes on immediately you start the car (its full of coolant) and beeps often (doh)

The heater matrix has been tested OK (during head fix) but this winter the heater doesn't do jack. (it did work last year - dont remember if the coolant gauge showed a temp though)

The gas stopped working a couple months ago. As its now bypassed/non-working it is not an issue imho.

I know its probably the thermostat but...

1)wouldn't the garage have dealt with this during refit?
2)where the heck does it live? where is it situated?

I am not afraid of fixing things, but I have to find them first.

Thanks in advance (I have searched high and low before joining this forum)

;-)

**salty** · 13-11-2006,09:03 PM

Originally Posted by sumbuddy

Hi,

I hope I have found the right place.

We have an A6 (that has a gas conversion which I just disabled to get to the root of our problem.)

The head was refurbished 14 months ago (and the car drives a dream.)

But. It never warms up (so it never turns the gas on) and the red temp warning comes on immediately you start the car (its full of coolant) and beeps often (doh)

The heater matrix has been tested OK (during head fix) but this winter the heater doesn't do jack. (it did work last year - dont remember if the coolant gauge showed a temp though)

The gas stopped working a couple months ago. As its now bypassed/non-working it is not an issue imho.

I know its probably the thermostat but...

1)wouldn't the garage have dealt with this during refit?
2)where the heck does it live? where is it situated?

I am not afraid of fixing things, but I have to find them first.

Thanks in advance (I have searched high and low before joining this forum)

;-)

SOUNDS LIKE THE THERMOSTAT IT WOULD NOT BE DONE WITH A TOP OVERHAUL AS THE THERMOSTAT IS IN THE BLOCK BEHIND THE WATER PUMP NOT TO BAD TO CHANGE BUT YOU DO GET TO IT FROM UNDERNEATH THE CAR IF YOU RELEASE THE POWER STEERING PUMP FROM THE BLOCK NO NEED TO UNDO THE PIPES FROM PUMP THEN YOU CAN SEE THE HOUSING REMOVE WATER PIPES FROM HOUSING REMOVE 2 FIXING BOLTS THEN YOU CAN REMOVE THE THERMOSTAT BE CARFULL TO REPLACE THE RUBBER SEAL
SALTY

**sumbuddy** · 14-11-2006,06:47 PM

Thanks Salty - I will check it at the weekend and get back.

Thanks again.

**sumbuddy** · 19-11-2006,05:56 PM

OK - changed the thermo - looks like I ain't cured the prob.

Temp gauge still sits at 55/60 - the fans cut in not very often.

The heater ain't heating.

The temp warning light is permanent.

The bottom heater hose is hot - top is cold. There is coolant flow in the heater but not much. Couldn't find a bleed point (anywhere actually)

Matrix was checked when head done.

The system loses zero coolant. Pressure is still present an hour after shutting down.

Stumped now - any help/suggestions gratefully received.

**adamss24** · 20-11-2006,01:05 AM

Hi, you may wanna change the coolant temp sensor(its a dual item and its used by the ECU and instruments temp gauge(each share 2 pins), the coolant header tank and you may wanna check the air temp control flap/positioning motor. You did not say what year, model and engine type and if it has a normal heater or A/C or Climate control. Also you may need to run some diagnostics. The header tank incorporates the low level sensor and after engine overheats the system gets pressurised and eventually the coolant drips inside the conector and will lead to corosion/duff signals(try cleaning it first). Also check if the wires have continuity and they are not brocken. Post the fault definitions if you get someone to scan the car for you. Hope this helps.

**Marc97** · 20-11-2006,12:18 PM

Could be a partially blocked radiator (if the temp sensor is at the top of the engine it would explain the low temp reading). Does the heater get hot if it is left idling for a while or if you get stuck in traffic then cool down again?
You said the fans come in but not very often, how is the heater temp when the fans come in?

Marc.

**adamss24** · 21-11-2006,09:18 AM

Originally Posted by Marc97

Could be a partially blocked radiator (if the temp sensor is at the top of the engine it would explain the low temp reading). Does the heater get hot if it is left idling for a while or if you get stuck in traffic then cool down again?
You said the fans come in but not very often, how is the heater temp when the fans come in?

Marc.

Hi, a tdi its soo efficient it wont get hot at idle(the cylinders cool down and the diesel condenses on the wals dripping and washing the oil film off the cyl wals) so its not reccomended to idle for extended periods. The fans comming on occasionally indicates that the engine behaves normally(i personally never heard my fans comming on on my car and the temp wont read more than 90 celsius). If it was a blocked radiator, engine will overheat. The temp sensor its on the metal pipe comming from the engine block to rad and has 4 pins. Clean the pins/wiring as its important that it works -2 pins supply signal to temp gauge, the other 2 are used by the ECU to optimise fuel delivery. I suspect a stuck/faulty flap positioning motor from the heating system as there is no hot coolant flowing inside the cabin trough the heater matrix(that's why 1 hose its hot and the other cold. Have someone scan the car for electrical faults inside the AC. If it does not have AC/Climate control, check for broken mechanism(they used to break if 2 were turned in the same time on Golf/passats). Good luck.

**Marc97** · 21-11-2006,02:28 PM

Cheers, told I don't know much lol.
Probably just a thermostat but that doesn't explain a cold heater.

**sumbuddy** · 21-11-2006,07:53 PM

Thanks for the answers guys it will give me something to work with.

I replaced the thermostat - nothing I hate more than swapping out a working part - especially when its a pig to get at :-(

Right. the engine is 2 litre petrol 1994 refurbed head 12 months ago runs (ran until 2 months ago anyway ) on LPG Prins conversion never serviced in two years hence first thing I bypassed.

No AC.

Heater matrix was pressure tested and flow tested no problems.

I only know the fans come on because I have spent so much time under the bonnet hahaha.

Thanks for pointing out the flap - didn't know it existed. I will check and clean the sender also.

Thanks again - I will post results after I do those jobs.

**adamss24** · 21-11-2006,08:23 PM

Cars without AC have no flap, but they should have a electrical valve controlled by the heater control switch or by a rod/mechanism in older cars. I would look for that first. The best thing to do is buy a Haynes repair manual as its describes in detail how to get to the bottom of the problem. If it was a diesel i bet you will not hear the fans kicking in unless on tow on a hot day or by turning the AC(they meant to kick in and cool the compressor and not the engine). I would look on the heater matrix hoses inside the bulkhead for the stop valve. Hope this helps.