itsstan

Hello all, I'm driving a 2002 A6 3.0L Avant Automatic with 140K mi. It leaks about a ¼ to ½ cup of coolant per minute when the heat is on. If the heat is off, it leaks nothing. After two months of summer driving it didn't leak anything, the reservoir stayed completely full. It doesn't leak with max A/C either, but it does leak if I ask it to hold a certain temperature like 70 degrees.

I'm guessing it's the aux or secondary coolant pump that is leaking? Does this sound right? I can't see exactly what it's leaking from, but it's on the passenger side pretty much where the aux pump is located.

I really don't want to change it, I don't feel like working that hard and I can't find a write up on the 3.0. I found one for the 2.7L but not the 3.0. Today I thought I had the answer, I'll just pull the fuse on it. So I found this and went at it. Audi Workshop Manuals > A6 Quattro Sedan V6-3.0L (AVK) (2002) > Relays and Modules > Relays and Modules - Cooling System > Auxiliary Water Pump Relay > Component Information > Locations > Page 276 Trouble is, my "Fold Relay Panel in E-Box Plenum Chamber" doesn't look like the one pictured in that link. Is the relay or fuse for the secondary pump some where else?

I'm worried about this now because it's freezing outside, and I've read that cars sold in cooler climates don't have the secondary pump which is why I thought I could get along without it.

I've been searching around for a couple of hours, thanks in advanced for your help, Stan

jcman

Short and simple reply, not the aux water pump to be to concerned about I'd be thinking heater core or the connections leaking because you did leave the clue.

crono35

Sure hope it's not the heater core... those are NOT fun to replace.

Do you notice any sort of wetness on the carpet inside? If it's leaking that badly it has to be going somewhere. If it's inside the cabin I'd expect a pretty distinct smell as well.

Check the lines running to and from the heater core as well as the heater control valve. If it's not leaking inside I'd suspect one of those. Be very careful when inspecting the lines running to the core, as looking at them angrily will cause them to break. If either of those are leaking you should see it end up on the ground.

Also, are you sure it's actually leaking? If you've done a coolant flush/refill lately and didn't run the heater when refilling it, there's a chance it's just filling up the core. Has it happened more than once?

devinsixtyseven

Check the bleed hole where the rubber coolant line attaches to the metal intake for the heater core, to the driver's side of the battery under the plastic cover.

If you don't see or smell leaks, refill and drive and check again. The first TB change I had done, the tech didn't bleed the heater core, so when I eventually needed heat, the coolant level dropped far enough to trigger a warning light on the dash.

itsstan

Crono, a bad heater control valve would fit my symptoms perfectly, trouble is, I don't think this thing has a heater control valve. After a 30 min drive with the heater off and it being 30 degrees out, both lines coming and going to the heater core are blazing hot. I burned my finger twice this morning. Besides that, I can't find anybody selling that control valve for my car. It's a quattro by the way.

Nothing is leaking inside, carpet is not wet and I get really good heat when I turn the heater on, but I would also get a really good coolant leak on the passenger side of the engine bay, running down the exhaust. I can't see anything from above, only below. That is, until I put a gallon of G13 in it. Now it seems to be leaking very little, if that. I found a quarter size drop of something under my car after it sat for at least an hour, and I'm not even sure it came from my car since the color really didn't match up.

Here's the whole story. My main water pump with less than 10K miles took a dump. So I changed it out, the whole process went extremely smooth until I filled it with water to check for leaks. As luck would have it, I found one. Prior to this, I didn't touch anything in that part of the engine bay and it didn't leak before. I noticed that the leak slowed when the heat was off, it was late, I was tired and said "F" it, slammed the hood shut and drove it 60 miles home. Two days later I eye balled the reservoir and the level looked good. Two months later, I toped off the reservoir, but could only get about an ounce in it till it over flowed. A couple of weeks after that the coolant ran low, I thought I was screwed but then I remembered I ran the defroster the day before, so topped it off and didn't run the defroster again, all was good. Then it got cold so I had to put the crazy expensive G13 in it so things won't freeze and mess more stuff up. After the 3rd day of driving with ice on the inside of the car, I once again said "F" it and turned the heater on. Now it seems as if very little if anything is leaking.

While pouring in the G13, I noticed that it's kind of thick. So the only thing I can figure, is that something is trying to take a crap under my hood, but the slightly thickened coolant is saving the day? Go ahead, call me crazy. Thanks for reading my novel and thanks for all the replies, Stan

devinsixtyseven

The fluid cooling the engine is a mix of water (preferably distilled--ie mineral free) plus whatever additive is used to expand the temperature range, improve wetting and heat transfer, inhibit corrosion, and so on.

In other words, always use the additive (G13 or whatever)...the stuff we colloquially refer to as coolant. I keep a mixed 50:50 jug in the garage just in case. If you're not exactly 50:50, it's not a big deal, but err on the side of too much G12/13 rather than too much distilled water.

itsstan

Ah come on Devin, I said call me crazy, not stupid.😉 I'm with you on everything you said. I actually filled it with mineral water when I discovered the leak, didn't want to put the money stuff in it, if it was just gonna leak back out, wouldn't be good for the environment either. This Audi was supposed to be my crutch car, I had a dude take out my other car by hanging a left in front of me. I'm waiting for the 2015 VW Sportwagen to come out, but the damn just won't show. Now it looks like it ain't coming out till April. I'm not sure if this A6 is gonna make it. Seems like get a different CEL code or warning light every other day.