Engine overheating! Please help!!!

[Rydog]

Hello, im new to this, so please bare with me.

I've got an 2006 Audi A3 2.0 TFSI, s line special edition (not sure if you need half of that )

Been driving the car with no problems, but was driving home from work today, and I got a low coolant message pop up on my dash, then the temperature gauge shot from its normal 90 position, straight into the red. I pulled over, turned the car off, checked my coolant which is absolutely fine. I left the car off for a bit, started it back up and drove home, and it didn't do it again, so not sure if its nothing, but I'd rather not take any risks, and hopefully get some advice on what to try. I have read somewhere that it could be a theromostat that is stuck shut. Is there a way of confirming if it is this without taking it out? I've had a little look, and it looks a bit of a pain to get to, but if it is likely to be that, then I certainly don't mind doing so.

Any help will be greatly appreciated! Apologies if I've posted in the wrong place. Thank you!

 

[nluk100]

Unlikely to be a thermostat, more likely the sensor for the coolant level. Did you check the wires for that (try cleaning the contacts etc.)

 

[Rydog]

Thank you for your reply mate!

I have had a look this morning, gave the contacts a clean but all looks fine.

I took the car for a drive this morning, and within 20 minutes, the temperature started to rise again, so I stuck the heating on full whack, the temperature came down, and I got it home ASAP.

I checked the coolant, and I dont see any oil in the coolant, in fact it looks pretty fresh, so im assuming the previous owner has changed it, so I may do a flush, in case any air has been left in the system.

If its not that ...

I'm sorry if I sound stupid or way off here, but could it possibly be a failing waterpump? I've got no leaks that I can see, and no unusual noises or steam coming from the radiator, but I can't think off the top of my head anything else that it could be.

 

[abmat]

Look in the expansion tank with the engine running, you should see the flow of coolant. If not then the pump could be the culprit.

also have you checked the belt is taught and driving the pump correctly.

 

[Rydog]

Hello,

Just an update. I've checked the waterpump and that is working fine, so I have ruled out, air in the system, head gasket, waterpump. I did notice when the car got up to temp, the fans didn't kick in at all, and me and my old man had a look and it could be as nluk100 said with the sensor, or thermostat, or something to do with the fans of some sort. My mechanic seems to think its either a sensor or the thermostat, so going to have someone come out and have a look.

Thank you for your advice and help so far! I will let you know what the outcome is when I know

 

[Rydog]

Just in case anyone comes across this with a similar issue, it turns out my issue was a faulty coolant temperature sensor. I thought I had checked the right sensor (turns out I didnt) with mine, the o ring had snapped.

I read somewhere you would need to take the battery and its casing out to get to it - this definitely isn't the case. For me, I have an upgraded air filter, I took this off and the engine cover and I had plenty of space to get my hands down and take it out. If you're not planning on doing a coolant flush with it, I would probably have the sensor ready to put in when you take the other out, as you will lose some coolant when you take the sensor out, and although I would imagine its common sense, make sure the engine is cool before you try and do it or youre going to get burnt.

Thank you for the help and advice! Really appreciate it!

 

[mr_pepps]

Hi @Rydog

I read your post with interest; my A4 B6 is showing the same symptoms. After about 15 mins driving the coolant warning symbol and alarm does off - under the bonnet the coolant is all present and correct and the engine bay not hot.

Which sensor did you replace? Was it one of the green ones with the brass end held in place with a little sliding clip?

Julian

 

[Rydog]

Hello @mr_pepps.

I'm not too sure if they're the same on the A4 B6, however mine was grey, and it was the sensor just underneath the air flow box next to the battery. You should also have one on the opposite side, next to the radiator/fans. If in doubt, I'd probably change both, I believe you can pick them up for about £10 each at wilco.

When changing this sensor although it is easy, just make sure you let the car cool down before trying it because coolant will come flying out when you remove the sensor, also, make sure the old O ring comes out, I made the mistake of not checking, and the old broken O ring was stuck inside, so when I put the new sensor in it bent the new O ring, which caused a leak.

What I would recommend is after changing wipe around the area for any loose coolant dripping off any pipes or sensors, run the car and just keep and eye around the sensor for about 5 minutes after for any drips or leaks (a tiny leak will drain your coolant and cause it to overheat again alot quicker than you would think)

If this doesn't solve your problem I would definitely take a look at your thermostat, as they would cause very similar symptoms.

Hope you manage to get it sorted

 

[mr_pepps]

Thanks @Rydog much appreciated.
I have the 3.0 V6 in my A4 (2004).
I'll check out getting replacement sensors.

Weird thing is that on this morning's commute the temp rose up to 130° but then hopped quickly down again to about 110° but then bounced back up to 130° again. And then did that again!

When I pulled up at work the temp was 130° and the radiator fan was on. I turned the ignition off. Then back on. Normal temp reading.
I started the engine again. Temp normal!
Weird!!!!

 

[Rydog]

@mr_pepps definitely sounds like a sensor issue to me especially if the coolant isn't overheating and the engine bay is staying cool. The fans sound like they're doing its job.

Is your coolant bubbling or can you see any steam coming from that direction at all when you notice the temperature rising?

 

[mr_pepps]

Yeah it's odd. The coolant stays cool, the expansion tank is warm but by no means scalding to the touch.
No steam. no boiling sounds (had that before on my old 1.8T agu - the metal coolant pipe split around the back of the engine. Tiny crack but yeah it lost all the coolant fast.

Trouble is I'm driving every day tense that I might be damaging the engine.
I can't work on the car after work 'cause it's freezing cold, dark and sodding wet (no garage).

 

[mr_pepps]

@mr_pepps definitely sounds like a sensor issue to me especially if the coolant isn't overheating and the engine bay is staying cool. The fans sound like they're doing its job.

Is your coolant bubbling or can you see any steam coming from that direction at all when you notice the temperature rising?

Hi @Rydog - sorry for the delay in replying.

I've done some more checking:
Coolant doesn't bubble at all and no steam. When the car is up to temperature (dashboard gauge showing 90 degrees) I used a kitchen meat thermometer to test the coolant temp in the expansion tank. Reading showed 13 degrees!

The big fat hose going from the expansion tank to the top of the radiator was warm to touch with an outside temp of 30 degrees. The stubby fat rubber hose from the metal up pie to the thermostat housing was the same, just warm. The metal up pie to that same stubby hose to the thermostat was cold!

Around the back of the engine where the green coolant temp sensor is was hot. The metal pipe that green sensor sits in was too hot to touch.

So I'm now thinking I have a thermostat fail.

I shall drain the system and try to wrestle the thermostat out to test it in a saucepan of water on the stove. This is going to be a faff I know. The thermostat housing is pretty well buried in just under the inlet manifold.

I'll write up what I find.

 

[mr_pepps]

Worst morning possible:

Today I attempted swapping out my thermostat.
I shouldn't have. But I did.

To gain (cheaters) access the first thing I did was undo the x2 T35 bolts which hold that weird plastic thing on to the front of the inlet manifold. These things are something to do with the little breather hoses. Anyway, I undid the bolts and went to gently pull off the plastic housing.
I should have left it.
I should have not done anymore when I felt a little resistance.
I should have just put the bolts back in and tried to remove the inlet manifold instead.

Anyway, so I gently tugged at this plastic thingy. Then I heard an awful 'breaky plastic' type noise. Then I realised if I gently squeeze the two piston things on the front of this weird velve thing together it would probably have just come out. As it is I think I knackered it.

I put it back in. Did up the bolts.

Started the car.

Ohhhhhhh.
Some knocking was audible from the engine bay.
Then some more nasty 'breaky plastic' type noise.
So I shut the engine off.

I plugged my diagnostic gadget into the obd2 socket and ran a test. No codes reported.

I started the engine again. It ran sweet. Sounded fab. Ran for about 3 minutes. Then a big judder and it started misfiring lots. So I switched it off.

Now I feel gutted. And it's ****** freezing and raining out here in Kent.

So I need some help please. I'll post a photo of the bit I think I've busted. And hopefully it's just a case of buying a replacement part.

 

[mr_pepps]

This is the bit I think I've knackered. The bit with the long white label on.
What is it and can it be replaced?

(Apologies for sort of hijacking this thread - help would be amazing thanks everyone)

 

[abmat]

They look like vacuum operate actuators.

what is that on as it’s not a A38p. Perhaps post in the relevant section for better advice.

 

[mr_pepps]

They look like vacuum operate actuators.

what is that on as it’s not a A38p. Perhaps post in the relevant section for better advice.

Hi @abmat - thanks for writing. You're correct it's the inlet manifold actuator. I think I've sussed out the problem now - I need to find a new unit.
I didn't realise I was posting in the A3 forum too.
I've started another thread in the A4 B6 forum.

Thanks for pointing that out