Should it be still?

KrisKrk

KrisKrk

A6 C6 4F 2010 LeMans Avant
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Guys, had something like that in the past and sick worried now, if it's the same.

This morning noticed temperature gauge from still 90 dropping slightly, while stationary at traffic lights. When driving, it's going back up. Movement isn't big, within 90 number.
I think cold or cooler air is being blown at the same time although temperature is set to 20 on drivers feet's and 19.5 windscreen from the passenger.

Made about 6 miles when noticed it and after another 10 miles, roughly.

Anything you can think of that might be causing it?
 
It looks like it was a sticky thermostat.
MPG's have increased with that fault also over two full tanks of diesel.
Bobby Singh took care of it for me and so far all is good.
 
I'm getting similar readings again
Driving is fine and brings the temp gauge to 90 after 15-20 minutes. But then, it drops every time when stationary/idle on traffic light or something.
Goes back up again once off.

Had a stat changed about a month ago and it was fine, untill yesterday.
Noticed also coolant level dropped.
Been to top it up after stat job, 2-3 weeks ago. Now its right at the min level and was above max, back then.
How many time the stat can go?
Can it be temp sensor?

Have the heating on all the time throughout, if this matters.
 
The temp gauge never moves, the temp will fluctuate in the engine but the instrument cluster has software to take account of this, so the gauge just sticks at 90, it must be a large drop in engine temp for the gauge to move. Do you know if the thermostat fitted was a genuine Audi branded stat, I've had aftermarket stats fitted before and they caused temp issues. It could be a sensor fault but I would monitor the engine temp using VCDS during a drive to see what actually is going on.

If you loosing coolant then you must have a leak somewhere, remove the undertray and stick some cardboard under the car to see where you are loosing coolant.
 
Thanx B5Nut.

Will try with the cardboard.

I'll ask about the stat.

I drove to work just now and as soon as the temp reached 90, it started to drop whenever stationary for more than 10-15 seconds. Looked around the internet and some vag users say to try to drive without heating on, so I did. As soon as I've switched the heating off, the gauge has reached 90 and stood still for the rest of the journey, another 13-15 miles.
Can this have any impact if the heaters are on?
 
I've had a lot of Audi's over the years and you could have the heating on with any of them without the temp dropping, I would say you still have an issue with your thermostat, or it could be an issue with the engine fans. VCDS may give you a clue to the issues.
 
Ok. Will get him to scan the while car.

Stat he used is genuine, he said.

According to the people over other vag user forums, it is a common issue in vag cars.
I didn't had any of that since own it, 1.5 year. Got the stat done and the issue came back after few weeks.

I'm going to see the guy on Friday so will report back.

Appreciate your input
 
In 20 years of owning Audi cars I've only had fluctuating temperatures on three occasions, head gasket failure, thermostat failure and water pump failure. It not a common issue on the C6 A6 and the engine you have. I know some people in the US have suffered faulty stat issues, but it's more on the petrol side than the TDI engines.
 
Water pump was changed 16k ago with whole timing kit. Stat just recently.
I'm in fear now about the gasket, tho.
There is loosing coolant associated with this issue as had it at max level few weeks back. Now is at minimum level.
Either there is a leak or ... rather not say.
Had same symptoms with head gasket fault on the A4 previously owned. But then, even while driving in the city and motorway, cold air was blown inside the cabin and temperature was going above 90, than dropping below and again up and so on.

There is no other way to determine head gasket fault without taking it apart, right?


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Coolant level may have dropped due to an air lock after the stat was changed. When did you last check it?
I think that you can get a sniff test done to check for combustion gasses in the header tank, but I've never had one done.
Sounds to me like your thermostat may not be shutting properly.
 
Last edited:
About 4 weeks after stat job it was topped up to over max level.
This was roughly 3 weeks ago and now it's at min.

Driving now, it's not happening.

Maybe cold starts add on to it?


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Sniff test on TDI can be inaccurate, had one done on my A4 with a HG failure and it did not pick up anything. The question is where are you losing the coolant. One of the tests I would do is to tape some paper towel to the over flow on the coolant bottle see if coolant is escaping from there, if it is then the coolant system is being over pressurised, which could be signs of a failed HG.

Other that remove the undertray take the car out for a quick blast to get the engine up to temp and then leave some cardboard under the engine and see where the leak is coming from.

Also check the oil cap for mayo....
 
audi upgrades
Arrived home late today so didn't checked much with it.
No mayo under the oil cap but noticed coolant splutter all over the steering reservoir and even back of the headlamp.
Will try to do the paper towel test but already sh...tting my pants for the worst.

Could a remap caused it?

Will be seeing the guy who did the remap and all, tomorrow evening so should have some results on vcds scan also.


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Issue hasn't returned since Monday.
Was driving with and without heating and there was no difference, temperature was dead on 90 once reached.

Today evening it reached 90 within 3.5 miles city drive.

Coolant level hasn't dropped any further so good sign there. But splatter marks are atually all over the front of the engine also. Been told, it could be leaking radiator and coolant hitting fan.
Bonnet underpart is clean, not a single spot.
Coolant expansion tank has few on and around it also so decided to clean it all off and place tissue over it, tapes to whatever it can be taped to. Hopefully it will not show anything but worst case scenario it could be expansion tank cap leaking.
If this will not work, will try to place some paper towels around that area and see.

Car was scanned for any errors and there isn't anything. Fault free.
Happy for that.
 
This is getting silly, now.

Drive to work today and after 5 miles 90 temp hasn't been reached yet. Driving continuously (Saturday so no traffic) with heating on. As soon as I switch it off, temp goes up to 90 and stayed there throughout the rest of journey. Managed to switch the heating back on during the drive and temp gauge didn't move.

Done 20 miles this morning and paper towel on the coolant tank cap is still dry. No other visible splatters around

:sob:

Worth to mention that the guy I've seen yesterday, pressure tested the cooling system for any leaks and there was no obvious signs of leaks.
 
Perhaps it was just an airlock and now that the car has "relieved" itself, everything will be back to normal.
 
Hopefully, Simon as it's getting on my constrictor muscles
 
Got a warning on the dash yesterday that my coolant level is low.
Checked it and it was low. Paper towel installed days ago was still dry. Doubt it would be the cap leaking.
Topped up coolant to level between max and min and will check once back home.

Noticed that the temp gauge arm drop down only with heating on. If I cold start the car with heating on, engine will not reach the 90 temp as quick as without heating. Not only that, if I allow engine to reach right temperature (no heating on start) and switch the heating on later, it is fine. No drops.

It is very intermittent and drives me crazy now with coolant disappearance.

If I open the coolant tank cap, there is no pressure, coolant does not come back up, coolant is always clean.
With HG fault in previous car, coolant was coming back up, at pressure and wasn't clean. Also cold air was pumped in to the car while driving what is not happening now, in this car.

Feel hopeless ...
 
Try a new cap. If it doesn't hold pressure, the coolant will boil and evaporate off.
 
You can see trough the plastic that on the walls inside the tank there are drips and drops of liquid steamed up.
Is that normal or already a bad sign?

Cap would not leak as there are no signs of splatter underneath the bonnet but they are visible as far as drivers side head lamp.
Was thinking to replace the whole tank as there are more dipping signs underneath it.


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Had a quick read through the thread. These kind of things are difficult to find but the fact that you can see coolant spatters all around the bay I wouldn't have thought it was leaking from the cap on the bottle.
When coolant is spattered around the bay quite often it is because it's found it's way onto a belt and been sprayed around.
There is a bleed point at the back of the engine under the plenum cover, has the air been bled from the system.

Upload 2017 3 23 13 56 10


I would have thought the problem is a leaking hose joint or some other leak in the system allowing coolant to leak and air into the system.You have to look at the spatter marks from coolant that has leaked to try and work out where it's come from.
 
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Ok. thank you for that, DS. Will check tonight when back home.
The whole coolant piping system been pressure tested but no visible leaks or marks has been detected.

Will try also the water pump as you've recommended on the other thread and report back.

Cheers
 
Got out of the parking space today morning and noticed two leak spots on the floor

2acab299b86c3f883f2169e8c9aec23b.jpg


I park my car front facing the wall now as had some difficulties to get out of it when park backwards to the wall (****** pillar!).
Liquid is definitely coolant as it's pink-ish and level from the tank has dropped

1f4d32075cdcda9d0cf5e5a6a8f4a295.jpg


Been to see the mechanic and the car is booked for next week for an inspection and thorough pressure test.
Pointed out possible faults (i.e. water pump or hose connections) but will see what they'll say.

Till now have/had no problem with the car. Temperature is fine, even with heating on but only when started without heating and allowed to reached 90 first.

Was driving yesterday a bit more than usual and don't know if it could cause mo spillage.
Recent back pain did not allowed me to get under the car to take the engine underbody off to trace the leaks but pattern on the floor indicated two spots. It could well could be one separated by under tray.

Will report back later once more info gathered


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Had to rebook the garage for tomorrow morning but wondered if I should try one of those rad leak formula? Maybe it would've work if there is a hole or something.
How would've water pump reacted to it, as Desertstorm says?
Hmmm ...:sorry::blink:
 
Find the leak, don't for god sake stick that crud in the system. With that much coolant coming out a good mechanic will find the leak, as there should be traces of coolant dripping down where the failure is.

If you start sticking rad leak in the car, you could end up changing radiators, heater matrix & thermostat. Only time you use that stuff, is if you have an old crap car and need to sell it on to some unexpected punter...
 
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Thanx B5NUt.

Just dropped off the car to the mechanic and await for the results.

Will update
 
Got the car back the same day as dropped off but couldn't see the results till next day or so.

Engine has been warmed up, cooling system pressured and whole car been lifted off the ground.
After few minutes of engine cooling down, guys at the garage has noticed a small puddle and dripping point. Coolant was leaking on the seal connecting two rubber hoses inline of cooling system.

f633a4ff851f517e5636da4e97ba4773.jpg


Seal of a size of 5p that costed 3p (!)

It was buried there

86586199d7019c13383eb270934b4df2.jpg


You can still see the pressure cap attached on the expansion tank.

All pipeline on the way had to be taken out, including throttle body.

After reassembly, car is heating up properly and hold temperature without any problems.
No drip marks on the parking spot either.

Didn't had much occasions to drive it as have some health issues but hope will just need to top up a bit of water to the tank at some point as air lock could've gulp'ed it down.

Thanx guys for all the input and advice.


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audi upgrades
Glad you got there in the end. Coolant leaks can be difficult to track down on newer engines due to all the complexity of extra hoses and emissions stuff.
 
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