Inconsistant Water Tempreture

[gavsteryoung]

For a couple of weeks now I have been getting inconsistent water temperature on the gauge. Infact, ever since the car went into Audi to have the auxiliary water pump changed.

I always remember the car getting to 90degrees and staying there all the time. Now sometimes it only heats to the bar below, 80degrees and moves back to 90.

The car is running fine, I don’t appear to lose any water, I can find no evidence of water in the oil (no mayo on the cap) and no drips from under the car.

I occasionally smell a water, oily smell when I park the car but thats it?

What do other S4 owner’s water temps do? Is there anything I should check?

[Nige_RS4]

Mine goes up to 90 and stays there (once went upto 100 on the track!) - you have a problem somewhere - have you got access to VAG-COM to see if a sensor is playing up?

[gavsteryoung]

Wow super fast response. I have no VAG-Com and dont know anyone near me (East Kent) that has one I can try!

Maybe I should bite the bullet and get one!

Mine used to goto 90 and stick there like glue!

[SimonS4MTM]

Maybe the thermostat has gone, if it is constantly open then the water temp will struggle to get to 90

[Morpheous]

More likely to be the temp sensor down the back of cyl 1~3 head, its called G62 and has been modified.
Old ones have a black body, new ones have a green body.
The reason they stay around 90 Deg is due to a temp window between 83 and 105 Deg C. the dash is set up to show 90 between these temp readings.

[gavsteryoung]

Cheers Morpheous and Simon, I'm pretty sure I have the old black sensor. So if there not expensive I may as well replace this!

The thermostat also sounds possible as the gauge will go straight to 90, I will get fuel and then pull out the garage and it will sit at 80.... and struggle to reach 90! Where are these located?

cheers

[Morpheous]

Ok, engine cold, remove air mass meter convoluted pipe. (Dont lose rubber seal down the Y pipe or your turbos WILL DIE the first time you boot it down the road!! Ask sitas3 for details of this, late cars wont have a separate rubber seal as its part of the pipe).
look down the back and you can see a cross pipe with a sensor sitting vertically with a four wire connector plug.(If you see a two wire connector plug, you are looking at the turbo after run thermo switch).
To remove the connector you have to put a downward pressure on the plug (push it on further) then at the same time depress the plugs retaining clip and pull up on the plug. DONT force it, there is a knack to it.
Release pressure in the cooling system by undoing header tank cap, then tighten again, this will reduce the coolant loss when the sensor is removed.
Remove plastic clip retaining the sensor then gently remove the sensor.
Discard the O ring seal which usually stays in the bottom of the pipe, and dont worry if the coolant spills, it will stabilise as long as the expansion cap is screwed down.
Fit new O ring seal to the sensor then smear G12 coolant around the seal to act as a lubricant.
Fit the sensor into the pipe, making sure the seal does not drop off and refit the plastic clip.
Fit the four pin plug to the sensor listening for an audible click from the retaining clip.
Refit the convoluted pipe making sure the little arrow lines up with the seam, and any seals are correctly seated.
Top up the header tank with G12 coolant. Job done. Pat yourself on the back.
Older cars may have a siezed in sensor. Use patience not braun and you will remove it.

Seal Part No...............N 903 168 02.
G62 Part No...............059 919 501 A
On older cars also you might want to change the plastic retaining clip as these are pence but could break due to exposure to engine heat.
Dont have part No of that to hand sorry.

[gavsteryoung]

Ok have my VAG Com now and checked the engine module and there was no errors for the Temp Sender..... I have taken a look and found the old black type, so will probably just replace this anyway if there not to expensive.

Now the thermostat also sounds interesting, where abouts is this. I can get a replacement from German and Swedish for £6.50 I would asume this is a more mechanical device?

[DJG]

For a couple of weeks now I have been getting inconsistent water temperature on the gauge. Infact, ever since the car went into Audi to have the auxiliary water pump changed.

I always remember the car getting to 90degrees and staying there all the time. Now sometimes it only heats to the bar below, 80degrees and moves back to 90.

Strange I have the same feeling that my car is running a bit cooler since I had my cambelt and water pump changed. Both oil and water temperatures about 10 degrees cooler than I remember.

Now I am getting paranoid that the heater does not get as hot as it used to.....

[gavsteryoung]

Dear all,

well I finally changed the sensor and the car still struggles to get to 80degrees unless driven really hard.

The vagcom says that the car coolant settles at 75degrees at idle.....

So what else should I check, do these cars have a thermostat? If so where the hell is it!

thanks

Gav