Coolant light is on, need help regarding adding coolant.

[paazan]

Recently my 2003 Audi A4 Quattro 1.8T keeps having its coolant light on for a few seconds every morning when I cold-start it.

Can't see any leaking.

Did a little online research, saw someone said that it should never goes down unless there's a leaking, but also other people said they had their coolant level went done and they topped it up back to required level.

Considering my card has over 150,000 miles on it already, it does make some sense that the coolant might have been consumed and gone done more or less over time, and might just need refilled.

I'm planning to add some and see if it fix the problem.

But here's the question:

Online research found most people said that I should only use G12. However there's a G13 in the market now which is said to be an upgrade one and supposed to work better. Also the G13 is safe to mix with G12, and G12 is safe to mix with G11. But now, Question 1, do I know what's left in the tank is G11 or G12? If it's G11 I won't be able to choose G13.

Question 2, should I flush the coolant system and add new coolant in to it or just add directly without flushing it?


Thanks in advance for your input.

[old guy]

Your B6 came with G12. Unless you know otherwise you should assume that your coolant has never been changed. I recommend flushing it and adding fresh coolant.

You can use G12, G12+, G12++ or G13. They are all compatable.

[Rubba]

Can't see any leaking? And the coolant level is decreasing?
Your engine is mixing the coolant with oil,
Is your engine idle abnormal?
Check the oil level to see if there is any water mixed with oil

[paazan]

That's right, I do not see any leaking, and the engine idle abnormal.
Engine burns oil though, just like many other A4s, so need to add oil once a while.

[Rubba]

Mine burns oil too, but yours is mixing oil and coolant and this is a serious thing!
Abnormal idle can be caused by spark plugs, coolant, not fully functional exhaust.
As i said check oil level to see if there is any coolant water mixed with the oil,
Mixing oil with water will make an acid that cause serious damage to engine.

[DarkoNova]

Definitely check your oil and make sure it's not a milky brown color. If it looks like regular oil, you should probably get a pressure tester. I'm almost positive AutoZone rents them. I have to add coolant every few days, and I couldn't see a leak anywhere.

Hooked up a pressure tester and magically there was a slow but steady stream of coolant coming from the back of the block.

[paazan]

That's right, I do not see any leaking, and the engine idle abnormal.
Engine burns oil though, just like many other A4s, so need to add oil once a while.

Sorry, I intended to say: engine idle normal, not abnormal.

[paazan]

In fact can't see anything abnormal, except all of a sudden the coolant light came on.
I kinda hope someone can confirm that it is "OK" to simply add some coolant in to the tank.
While understanding that it is recommended to flush, it is just too much work if I DIY, and for this hight mileage car I just try not to spend too much on maintenance by sending it to a shop. Of cause, only if adding coolant won't damage anything.

[teg2audi]

Yes, fill your reservoir with 50% distilled water 50% g12.

My guess is your have a leak somewhere, rear coolant flange, rear heater hose are good places to check

[paazan]

Yes, fill your reservoir with 50% distilled water 50% g12.

My guess is your have a leak somewhere, rear coolant flange, rear heater hose are good places to check

Will start from there. Thanks.

[MacFady]

That's right, I do not see any leaking, and the engine idle abnormal.
Engine burns oil though, just like many other A4s, so need to add oil once a while.

Firstly I'll just say my A4 has 248K on it an I have never had to top up oil or coolant between changes when things are operating normally. As suggested above about the rear coolant flange, standing on the passenger side look down on top of the transmission between the firewall and the back of the engine for any pink crust, assuming you are running the right coolant now.