juno

Hey guys, my Audi started leaking cooland around 3 weeks ago.

it wasnt alot but every now and then i had to add. then it stopped leaking completly. after a week it started again and its leaking pretty bad now (only when engine off) it drains whole expansion bootle. for me it looks like the hose located under reservoir because its nothing connected to it and if i add some coolant it drips from there.


any idea?

G0to60

I am chasing a persistent coolant leak right now. Originally I thought it was the secondary coolant pump (common failure) and replaced that. It was leaking slightly so it was good that I replaced it but that didn't fix the overall problem.

Next I found that the coolant temp sensor on the PS was leaking due to a blown O-ring. Fixed that but still didn't fix the overall problem.

Now I have two other places. One is the rear cross over coolant pipe and one of the O-ring connections. The other is the expansion tank. I couldn't see any leaks around the cross over pipe when I dug down in there so I think that my expansion tank is leaking from the valve at the bottom of it.

So to make my long post even longer, I think that connection at the bottom could be your leak. I think that connection is a pressure relief of some sort but I'm not sure. My expansion tank is pretty sad looking and I found some stress cracks on the bottom so I'm going to replace the tank and the cap this weekend. I hope that this fixes my (and your) problem.

juno

first i need to know where that bottom.pipe is supposed to lead.
I was looking online, people are saying thst is some kind of fuel/emission pipe or something. i really dont know what to do and im at my friends house and i got access to all toola i need but dont know what to do...

jhart2.7t

Juno, that hose is just the overflow line. It's supposed to go to...nowhere. Just points down to direct coolant to the side/bottom of engine compartment. If you happen to pour a bit of coolant in the little space in between where the cap threads in, it will drain out that hose. Check your reservoir for hairline cracks. If its yellowed and old you might just want to replace it. There not that expensive.
I had a bad leak that only happened when I turned the car off. It turned out to be a hose on the rear of the engine that feeds the heater core. It only leaked while the system was cooling down and depressurizing. You need to do a pressure test to find out where the leak is coming from, or you will just be throwing away money on parts that may not have to be replaced.

GTA_Driver

You answered your own question, no? It leaks from under the reservoir. Take the hose off and inspect the reservoir itself. Either cracked reservoir, nipple, or hose.

cameltrophyallroad

they can crack underneath, once old they are brittle.

John535is

Juno, sadly it sounds like the aux pump. I had the same problem, the reason it only leaks sometimes is it only leaks if the aux pump needs to run (turbos still hot after turning off engine triggers the aux pump to run after a few minutes). You can check by (1) go for a 'spirited drive', turn engine off and wait for about 5 minutes, if it suddenly starts leaking on the garage floor, thats the aux pump leaking and (2) shine a light (penlight torch) down between the gaps in the inlet manifold. I used an LED book reading light on a flexible line to get in under the inlet manifold and there was pools of water/coolant in the bottom of the engine V as the tell-tale sign. There is a really good write up on the how to replace it, for a first time allow about 5-6 hours. It's a bosch pump originally and you can buy them without going to Audi parts. You also need 2 inlet manifold gaskets, a handfull of hose clamps, I decided to replace the hoses as well while I had it apart, and the two mounting brackets, I have the warm climate option (Australia) so there is a non return valve as well, cold climate model just has a bent pipe, which saves some money.

juno

I think it might be that aux water pump... its leaking like from the back of the engine, i can hear the water running, might be even dropping on the exhoust manifold, today i had to put a gallon of water thats how empty it was... ill have to be running on water for a little bit of time i canmot afford putting that G12 everyday ehh. Very sad

GTA_Driver

Just to double-check, you are using distilled water, right?

juno

I was in rush no tine to get it, i used a gallon of poland spring and some g13 ima flush the system upcoming weekend and fill it up with new coolant and distilled water.


Also could somebody give me right part # for that Aux Water pump? i see two different models and im confused.