where is the coolant going?? no signs of leak on the ground, but level slowly drops

[achilleas101]

the past couple weeks, i've noticed that my coolant level has dropped slowly slowly to below the min level in the reservoir. Didn't see anything on the garage floor though other than water that was carried in from rainy days. Topped it off with a little water (about 10oz), and after a couple of weeks, it was down below min again. And again, no sign of coolant on the floor.

what the heck? when a friend's water pump was going and had his 3.0 at my house, there was noticeable drip of coolant on my floor within a couple hours. So i'd expect if that were the case, i'd see something (and my water pump was replaced ~20k miles ago w/ the TB, so doubit it's that).

any thoughts?

[JolePatrol]

I'm in the same boat, but I have a feeling its the rear coolant flange cause I can smell the coolant burning somewhere. I am just waiting to do it with my t-stat replacement in a week or two.

[achilleas101]

i saw a thread about the coolant flange for the 1.8s causing problems, but don't know if the same applies for the 3.0s or the location of it..

[NyteEscape]

this summer i replaced pretty much my entire coolant system on my 1.8t except for the radiator, and i still have an ever so slight leak. this includes waterpump, rear flange, t-stat, j-plug. i mean everything, and the leak is still there, and i do get that coolant burning smell.

i don't know, i think i'm going to give up looking until spring.

[achilleas101]

this summer i replaced pretty much my entire coolant system on my 1.8t except for the radiator, and i still have an ever so slight leak. this includes waterpump, rear flange, t-stat, j-plug. i mean everything, and the leak is still there, and i do get that coolant burning smell.

i don't know, i think i'm going to give up looking until spring.

coolant burning smell huh? don't suppose you can describe it? i recently smelled something that smelled kinda like oil, but different, so you just made me think...

[diagnosticator]

Coolant will be lost at a vey slow rate, slow enough to not puddle on the floor under the car, when the radiator is leaking at the end tank tube sheet starts to seep a little bit when up to temp. Close inspection with the engine hot and idling, will reveal wisps of steam or liquid coolant leaking out and evaporating quickly. Slow leaks will have a pick crusty deposit around and below the leak.

[Pingu]

it could be an internal leak? Dont know much about them though.

[zer0cool]

I had exactly the same issue, and as other people have said its the rear coolant flange.

It doesn't leak until its starts to get a good flow going through it, and at low speeds and idling it doesn't leak.

From reading the actual repair itself is pretty simple, the hard part is getting to it. If you are not familiar with engines its probably beyond a DIY repair.

I got mine replaced at a UK Audi main dealer and it cost me £313. But they did replace all the hoses, seals and gaskets as well.

[BARRY]

this summer i replaced pretty much my entire coolant system on my 1.8t except for the radiator, and i still have an ever so slight leak. this includes waterpump, rear flange, t-stat, j-plug. i mean everything, and the leak is still there, and i do get that coolant burning smell.

i don't know, i think i'm going to give up looking until spring.

i was in the same boat, but located the leak. the junction points for my heater hoses slowly seep out coolant at times. most often when its VERY cold outside and the O-ring shrinks enough. when i go snowboarding i lose probably 1 cup of coolant overnight due to this. i have about 214k miles on my car.

[Timtheguru]

Have a look at the pressure relief valve on the expansion tank cap. I bet you it's going through that and then out the overflow on the tank, then it's dripping on the exhaust piping below eventually (maybe). You should be able to see white specs, if you're driving in rain, it would probably wash it all away.

Edit: Also, I had a leak not to long ago and it was the damn water pump that the PO had installed at a shitty shop. They didn't even clean the scale build up on the engine block for the o-ring. $240 later to 034, $20 in G12, and $1.78 in distilled water, I had my timing belt changed by me. Oh and it took me about 8 hours with all of the random bolts and screws holding the front end on (shop must of lost some bolts/screws), some were torx, hex, and allen..(not all the stock bolts, these were all random sized screws/bolts that aren't stock.)


Anyway, I took the cover off to look down with a flashlight, it would only start to leak coolant once the engine was cold (as metal expands when heated so the seal was better). You can see in the pic where it was running down.

[EUROaleksey]

+1.. i just keep refilling when it goes under.. no harm done :)

[achilleas101]

i guess i'll have to check my hoses with the car on at some point and see. Can anybody point me to where the coolant flange is located on the 3.0?

Have a look at the pressure relief valve on the expansion tank cap. I bet you it's going through that and then out the overflow on the tank, then it's dripping on the exhaust piping below eventually (maybe). You should be able to see white specs, if you're driving in rain, it would probably wash it all away.

there's a pressure relief valve on there? Where? So are you saying it may be coming out of the cap? not sure where the overflow on the tank would be... i'll check around there though either way.

[achilleas101]

+1.. i just keep refilling when it goes under.. no harm done :)

Yeah if i can't find anything with all the hoses and what not, i'll probably keep doing that. i just ordered a 1.5L bottle of pentosin to hopefully last me a while.

[Timtheguru]

i guess i'll have to check my hoses with the car on at some point and see. Can anybody point me to where the coolant flange is located on the 3.0?



there's a pressure relief valve on there? Where? So are you saying it may be coming out of the cap? not sure where the overflow on the tank would be... i'll check around there though either way.

The cap itself has a pressure relief valve, it is also intended to keep a certain amount of pressure on the system. The overflow is on the outside of the threads where the cap screws on, it's a little hole. Then under the expansion tank (not sure if the 3.0 has a hose like my 2.7t) there should be a hose that goes to the right of a heat shield. If no hose is there it will just be a little nipple on the bottom. (for some reason I thought you had a 1.8t)

[A4_Mike]

If the rear coolant flange is leaking, you should be able to see at least coolant residue at the back of the engine.

[JolePatrol]

coolant burning smell huh? don't suppose you can describe it? i recently smelled something that smelled kinda like oil, but different, so you just made me think...

Kinda smells sweet, definitely a different smell. Sometimes at night I can see a TINY bit of smoke coming from my front grille area if I stop and get off really quick before it dies down.

[old guy]

Kinda smells sweet, definitely a different smell. Sometimes at night I can see a TINY bit of smoke coming from my front grille area if I stop and get off really quick before it dies down.

Probably coming from the radiator end caps. Same thing happened to mine and I noticed the steam around the front grille.

[achilleas101]

well, haven't checked all the hoses yet, will do that when i change the oil this weekend, but opened the hood up to see if there was any steam/smoke coming out of anywhere and didn't see anything. Nothing by the radiator or engine. Looked around the reservoir, no residue. I checked both after my drive home when it was nice and hot, and this morning when it was nice and cold. So we'll see if i can find anything by any of the hoses.

Does anybody have a good diagram of the flow of the coolant? where all the hoses go from/to? this is again, for the 3.0...

[mr_gp4e]

Having the same issues here....My audi 3.0 loses around 200g of coolant every 1.5 months. Now I really dont think its a big deal and would top it off and drive like this, but question for you guys...

....Since its winter and I dont wanna use water only, should I put antifreeze only or mix it 50/50 - 100g coolant and 100g water?

Thanks

[achilleas101]

i think i may have found the culprit. Can anybody tell me if this hose transports coolant? or are these for the p/s fluid? it had some greasy grime on it (it's a bit cleaned off in this pic), and on the belly pan, there was a stain in that area. I can't tell where it run to/from, it's so packed in there tracing it is difficult. Again, this is on a 3.0.

[b6Hate4]

Found my coolant leak by just grabbing and squeezing the rubber coolant lines, in my case it was the coolant flange. God that sucked.

[JolePatrol]

Probably coming from the radiator end caps. Same thing happened to mine and I noticed the steam around the front grille.

Thanks! I'll definitely be checking that out next time I get a day off.

[woofster]

Just bumping this thread to see if anyone's arrived at any concrete conclusions for this strange disappearing coolant phenomenon. I just had to re-fill my engine coolant reservoir again. The last time I had to do it was quite a few months ago and the time before that was another month or so. What I did notice was that the level of heat has diminished quite a bit (feels as if air is trapped in the coolant system or a clogged heater core). From what I've been reading, most of the cases involving air in the system or clogged heater cores don't involve slowly disappearing coolant, which is why I'm wondering whether I'm having 2 separate issues occuring over here.

[mobilesuit818]

I would apply the troubleshooting methods.

Depending on the tools available....this is what I did.

1. Pressure check coolant system with uv kit. Any exterior leaks would be visible. This includes the cap.
2. No leaks from test 1, then proceed to do a leak down test.

Mine ended up being cracked head..no white smoke on startup either.

[woofster]

I would apply the troubleshooting methods.

Depending on the tools available....this is what I did.

1. Pressure check coolant system with uv kit. Any exterior leaks would be visible. This includes the cap.
2. No leaks from test 1, then proceed to do a leak down test.

Mine ended up being cracked head..no white smoke on startup either.

Hmmm...the last time I had my car in the shop (probably about 2-3 months ago), they did a pressure test on the cooling system and everything came out fine. It's rather mind-boggling because I don't see any leaks on my garage floor anywhere.

What did you end up doing about the cracked head?

[vlad]

I had the slow coolant leak problem as well. Same symptoms, never saw any drips, never smelled anything, just a slowly diminishing level of coolant. It was the rear flange in my case. Thankfully I was still under CPO warranty so dealer replaced.

[woofster]

I had the slow coolant leak problem as well. Same symptoms, never saw any drips, never smelled anything, just a slowly diminishing level of coolant. It was the rear flange in my case. Thankfully I was still under CPO warranty so dealer replaced.

Rear coolant flange? Thanks for the tip. I'll have to take a peek at it next time. The thing about the rear coolant flange is that once it cracks fully, everything is going to be gushing out. On one hand I hope it's not the rear coolant flange 'cause it's a pain to access but on the other hand, it sure would be nice to know where all the coolant is disappearing to!

[woofster]

Just wanted to provide an update (if anyone was still following this thread and for those who may do a search in the future) that I had my shop take a look at this slowly disappearing coolant issue and it turned out to be the water pump!

[diagnosticator]

Thanks for the update!

[mihali]

https://lh5.googleusercontent.com/-O...1000/hoses.jpg
Almost positive that that carries power steering fluid