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View Full Version : Cool Runnings (A6 2.5tdi 1996)



tut_gareth
19-11-2007, 01:19 PM
OK,

I have Replaced the thermostat (twice), flushed the cooling system, and changed the temp sender, but my I5 2.5tdi engine still runs very cool. eg: never goes above 60-70 degrees C even after a good long drive. The thermostat doesnt appear to be operating either. and the oil temp guage doesnt read either.

And the heater inside the car doesnt get particurlarly warm although when i flushed the system it didnt seem to be blocked.

Any ideas?

tut_gareth
22-11-2007, 01:48 PM
just thinking could the viscous fan affect the low temperatures i'm seeing?

jubbly
27-11-2007, 08:26 PM
I have exactly the same problem!!

Have you tried to blead the heater matrix?

Under the black plastic cover in the engine bay is the heater matrix, I haven't had chance to blead mine yet as the thermostat was changed but now I have to drain the system again to get to the bottom pully!!

tut_gareth
28-11-2007, 08:23 AM
No, haven't tried that yet. is the matrix behind the bulkhead where the battery lives?

I have blocked off the radiator with some card to see what happened and the temp did go up, but only to just below 90 in traffic then dropped back down again in clean air.

i have a look for the matrix at lunch time.

jubbly
28-11-2007, 10:34 AM
Yes it's by the battery, a knurled knob on the heater matrix pipe.

JimSharp39
28-11-2007, 11:02 AM
Hi,
As I understand it, because diesels are much more efficient, they take longer to heat up (hence the heater booster feature on many diesels) - when the weather is cooler this manifests itself in cooler running. In "ye olden days" you used to be able to buy grill covers to restrict the flow of air to ensure a quicker warm up...Mk 1 and 2 discoveries had them as an option I think. So it may be nothing to worry about. Your heater booster feature may be disabled -I have a 97 v6TDi quattro and it's factory fitted with a device which senses cold temps and separately burns diesel to heat up the cabin heater more quickly.
Also, the gearbox oil gauge uses a different scale to the coolant temp, so compared to the coolant gauge its always going to be towards the left stop, its unlikely they'll point at the same "angle" and look the same. (unless its being thrashed or low on oil or the oil's too thin etc!).

Jim

jubbly
28-11-2007, 11:37 AM
Hi,

Mine does now creep over to 70, before I changed the thermostat the temp gauge didn't hardly move, I do get warm air after a few minutes drive and it does warm up on a longer journey.

My car is the 1997 2.5 5 cyl Tdi Quattro C4 model, I've only had it two weeks, quite impressed so far :)

Peter D
28-11-2007, 12:21 PM
Check the viscous couple fan is free to rotate when cold. it may be ceased. Regards Peter

jubbly
28-11-2007, 12:26 PM
Mine must be, it rotates as soon as the car is started.

I have to change the bottom pully this weekend so all the front is coming off, I will see if I can free it up at some point.

Thanks

Paul

tut_gareth
28-11-2007, 01:59 PM
It will rotate with the engine but can you stop it when the engine is cold.

My viscous fan spins freely both ways when cold.....so think that is ok.

Just tried to bleed the heater matrix and, no air or water came out so i'm thinking the matrix may be blocked. but would that cause the engine to run cold?

Could the water pump impellor be knackered maybe? ( i would have thought the engine would get too hot though if it was......)

Peter D
28-11-2007, 02:05 PM
Jubbly. It does rotate at start up but once settled it is turning much slower than the drive shaft. Does it turn when the engine is off. ??

If the impellor had failed it would boil and chuck out the contents via the pressure relief on the filler cap or blow a hose off.

Regards Peter

tut_gareth
29-11-2007, 08:34 AM
thought the water pump was ok.

Well, lastnight i flushed the heater matrix and engine block with the trusty hosepipe and a fair bit of limescale errupted from them but they weren't by any means blocked. filled the system back up with coolant but with more water this time, and..... still the same. The heaters did get warmer though so thats good.
But why does the engine still not run over 65-70 degC?

jubbly
30-11-2007, 10:25 PM
Changed the temp sensor on mine today, only the cheap 2 pin plug not the four pin, made no difference.

jubbly
01-12-2007, 01:15 PM
Ok the 2 pin temp sensor is for the Glow plugs so thats made no difference.

I have now changed the 4 ping temp sensor, the lower one on the top hose, took the car out for a spin and hey presto the temp gauge is working 90Degrees about time!!

Trouble is the price!!

£90 from audi ouch!

£47 from euro car parts. Euro's car parts part number is 460440430

Now my car has climate control so I assume the car thinkint the water temp was 50-60 was only blowing luke warm air, now it thinks water temp is 90 it's blowing hot air.

Hope this helps, my brother has the aat engine and has the same problem, trouble is he is away till next weekend so I can't test it.

spink
01-12-2007, 06:54 PM
Mine takes ages to get upto temperature,although it never reaches 90'c.Eventually you do get a good amount of hot air through the c/control.
Is the sensor you replaced look like this?

http://i22.ebayimg.com/05/i/000/be/17/b4f0_1.JPG

http://i13.ebayimg.com/04/i/000/b8/5f/e962_1.JPG

a8 tech
01-12-2007, 06:59 PM
common issue for this is the heater matrix fins blocking up.the coolant just goes in and out instead of the filling the matrix.Flush the coolant and replace the matrix, poor antifreeze causes corrosion in the cast iron engine block which ends up in the matrix.

spink
01-12-2007, 07:01 PM
changing the matrix isnt something i fancy doing again,just changed one today on a 80 V6 of a mates.Took 3 of us about 3 1/2 hours

a8 tech
01-12-2007, 07:17 PM
3 of you,so thats 3 cups of tea and three sets of cut knuckles.Not the nicest are they

spink
01-12-2007, 07:20 PM
wouldnt attempt it on my own thats for sure,was expecting it to take all day so i suppose it wasnt so bad.

jubbly
01-12-2007, 07:24 PM
Mine takes ages to get upto temperature,although it never reaches 90'c.Eventually you do get a good amount of hot air through the c/control.
Is the sensor you replaced look like this?

http://i22.ebayimg.com/05/i/000/be/17/b4f0_1.JPG

http://i13.ebayimg.com/04/i/000/b8/5f/e962_1.JPG


Yeap thats the one only it only had 3 connectors :)

spink
01-12-2007, 07:28 PM
excellent,ive got a couple of spare ones off S2's as they are the same according to etka,really dont fancy spending 40 quid on a sensor if it isnt faulty,bought a thermostat today for my ael and that was £15,compared to a A4 1.9 tdi one which is £4!, conning gits.Do you happen to know if a knackered mtfs temp sensor shows up on vagcom or not?

jubbly
01-12-2007, 07:55 PM
I didn't have any faults on vag com so I don't think so.

Cheers

Paul

spink
02-12-2007, 05:05 PM
ok so i changed the sensor for a known good one,no difference!.Then i noticed that the electric fan to the left of the viscous fan is on all the time when the engine runs,checked the rad switch at the bottom of the rad near the aircon pump but it isnt showing a fault,although even if i disconnect the rad switch it still runs all the time! i had to disconnect the power cable to the fan to stop it.Anyone know if it is actually the rad switch that is the activator for the fan?

ps i looked at the viscous fan,it does go round when the engine runs which i think is correct? but it can be stopped if a piece of wood is held against it so presume thats ok?

jubbly
02-12-2007, 06:59 PM
I'm stumped you are sure those old sensors definatly worked?

spink
02-12-2007, 07:04 PM
yeah it was on a car that was running fine,i havnt actually taken it out for proper drive to see if the temp goes up now the the fan is disconnected.What does yours sit at in normal day to day driving?mine has always struggled to get passed 55'c-60'c.

jubbly
02-12-2007, 07:13 PM
The diesel will take ages to warm up just ticking over, in fact some say it won't get up to temp unless you drive round.

Mine reaches 90 now driving around before i changed the sensor it only got to 70 max after about 30 minutes driving!

tut_gareth
03-12-2007, 08:45 AM
think i'll be getting myself down to Euro car parts then.

spink
03-12-2007, 11:06 AM
Ok the 2 pin temp sensor is for the Glow plugs so thats made no difference.


is that the one that sits above the expensive sensor in the aluminium housing?

number 19 in the picture.

jubbly
03-12-2007, 11:35 AM
is that the one that sits above the expensive sensor in the aluminium housing?

number 19 in the picture.


Thats right Number 19 is the glow plug temp sensor, the lower one number 20 is for the temp gauge.

Cheers

Paul