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Discussion Starter · #1 ·
If anyone has any suggestions other than what I've gathered from reading the archives here, please let me know. I have a 1999 Audi A6 2.8L AHA Tiptronic AWD.

Summary: Coolant is leaking from somewhere that dribbles down around the oil pan. I hope it isn't the water pump but I didn't have an opportunity to pull the timing belt cover and check before getting the car towed from the Costco gas station to a mechanic who's closed all weekend. What else should I check for leaks if I pull the timing belt cover and it isn't the water pump/thermostat?

I saw wisps of steam coming out the front grille when I was in line at Costco gas today and found the coolant reservoir empty. Moved over to a parking space and found that coolant was dripping from the low spot on the oil pan. (This is an A6 and it doesn't need a belly pan to hold the fender liners off the tires, btw. Previous owner did a coolant reservoir sensor delete so no warning light when I lost coolant. Will be getting that reinstalled for sure.) After checking the forum and seeing "bad water pump" as a high probability cause, I got it towed to the mechanic by my apartment. (I killed my first Passat engine driving it till the water pump failed because I didn't recognize the symptoms, so I'm not doing that again.)

I really hope it's just a hose, because I don't want to pay a shop to change the water pump, thermostat, timing belt, etc. I helped my friend do that when I got it 5 years ago and having to pay $180/hr is going to cost a fortune. (And this is the shop that still hasn't gotten the transmission pan to stop leaking so do I want them working on stuff I can't see with the car up on ramps?)

After reviewing the forum more closely, apparently I could've pulled the timing belt cover to check the water pump area. I haven't dropped off the keys and I can probably do that while they're closed tomorrow. This is NOT a good area to try to do it at night.

The leak doesn't seem to be related to the radiator or the reservoir (which is fairly new). Some time during the pandemic, I replaced the coolant lines to the oil cooler and it's possible it was a bad idea to replace crimp clamps with screw clamps. I checked the oil and there were no signs of coolant in the oil, so it's not the head gasket. I replaced the coolant temp sensor a few months ago and haven't driven much since. I replaced the heater hoses Spring 2020.

I have been concerned about intermittent slow warmup to operating temperature--but I've rationalized it as "it was really cold last night and apparently even the parking garage got cold." Or "Maybe a piece of junk from rotted hoses sticks in the thermostat sometimes so it's only mostly closed?" Because some days, it's fully warmed up by the freeway onramp about 1/3 mile away. (This is San Jose so our night temps are typically 45-55F with a few "super cold nights" 35-40F. Cold days are 50-55F, lately it's been 60-65F. It's in a basement parking garage and the building's water boilers seem to keep the basement warmer than outdoors.)

Thanks!
 

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Likely several issues going on. Sounds like you have a bad thermostat which is stuck open (or partially so). Your geographic location doesn’t experience cold enough weather to drastically affect the engines ability to warm up. It should be coming up to temp (needle centered in the gauge) within a few minutes of driving around. If not, the stat will need to be replaced.

The easiest way to identify where your leak is coming from is to purchase a coolant pressure tester, and use it to pressurize the system when cold. You’ll then be able to spend time poking around a cold engine to see where the leak is originating. The fact that you’ve dropped this off at a mechanic however leads me to believe this step might be a little out of your comfort zone? You can try poking around the engine bay searching for the leak, but it will be difficult without the system pressurized.
 

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Agreed.
I also believe you've got a faulty thermostat.

I've currently got one as well in my 1998 GLS V6 AHA. I'm about 13 miles to work and the needle never gets above those three white lines that are bunched together. I'm guessing mine is stuck wide open.

Trying to diagnose a small coolant leak with engine running and while it's hot can be extremely difficult.
I would try the pressurizing method and see what that produces.

Nothing wrong with replacing those spring style clamps with screw type clamps.

Your weather is very similar to over here in Phoenix right now. Your car should be up to 190° within minutes in our weather, especially being parked in an underground parking structure.
 

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Discussion Starter · #4 · (Edited)
Thanks, good ideas. I have a vacuum/pressure thingy and just found it while cleaning my mess in my friend's garage. I can bike over there in the morning. Got 3 jugs of distilled water in my earthquake supplies 10 feet from where I'm sitting and it needs to be rotated out anyway.

I forgot to mention the leak dripped unpressurized when I added half a jug of water after the engine cooled. That's part of why I decided it needed a tow.

Unfortunately, AAA won't drop off cars at a private residence anymore and I didn't want to risk the water pump failing trying to drive it back to my friend's house where I work on it. There's a shop that rents lift space to DIYers, but the working conditions were sufficiently unsafe last time that I don't want to go back till they're sorted. In any case, they typically need a reservation in advance on the weekend and I would end up having to pay storage fees while I wait for a slot on the calendar. And my local shop needs to sort out the transmission pan leak anyway. I don't know what his tech did wrong, but it's seeping around the edges.

Thank goodness this coolant leak didn't happen going over the Santa Cruz Mountains to my workshop.
 

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I don't know what his tech did wrong, but it's seeping around the edges.
Could be a cheesy gasket or tightening the oil pan bolts way to tight.
There's this misconception that trans pan bolts need to be tight. There's a reason for those torque specs on the pan bolts.
 

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Trans pan: I've never had a pan leak, but I do apply Permatex Silicone gasket sealant to the clean pan flange, stick the gasket on, then apply a coat of sealant to the top of the gasket. Install right away, and as AndreasPassat says, go easy on those 27 screws (stubby ratchet wrist-tight if not using a torque wrench).

Your A6 has the 12-valve 2.8, which I had in my '96 A4. A leak that is so large that water runs right out when filling the reservoir won't be the pump or pump gasket, in my opinion. I wouldn't be surprised if you pull the passenger-side belt cover and find the thermostat housing loose or the O-ring failed.
 

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A leak that is so large that water runs right out when filling the reservoir won't be the pump or pump gasket, in my opinion. I wouldn't be surprised if you pull the passenger-side belt cover and find the thermostat housing loose or the O-ring failed.
If that is the case I would expect some kind of strange noises. But then again, stranger things happen.
 

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Really!!? Wow. That's awful!

Good luck with the pressure testing kit. Hopefully its pretty obvious.
Yeah, that's horrible about AAA if true. I was about to look into getting it once the kids start driving, but not now. I usually do all the car repairs. This would only be useful if you are on the road a lot away from home and can't work on it yourself. Luckily my insurance will tow mine home for me if needed up to 15-20 miles for free.
 

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Discussion Starter · #10 ·
Trans pan: I've never had a pan leak, but I do apply Permatex Silicone gasket sealant to the clean pan flange, stick the gasket on, then apply a coat of sealant to the top of the gasket. Install right away, and as AndreasPassat says, go easy on those 27 screws (stubby ratchet wrist-tight if not using a torque wrench).

Your A6 has the 12-valve 2.8, which I had in my '96 A4. A leak that is so large that water runs right out when filling the reservoir won't be the pump or pump gasket, in my opinion. I wouldn't be surprised if you pull the passenger-side belt cover and find the thermostat housing loose or the O-ring failed.
The '99 has the 30V 2.8 but everything else is similar.
I pulled the wrong cover (d'oh!) but I can go back and check. It's still dripping 18 hours after I added water and I got pics of where the drips fall on a level surface. My car isn't really bleeding, it's just on a red painted surface where most of it is dusty and the water shows the real color. (It's a cash vampire, though.)
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Discussion Starter · #11 ·
Yeah, that's horrible about AAA if true. I was about to look into getting it once the kids start driving, but not now. I usually do all the car repairs. This would only be useful if you are on the road a lot away from home and can't work on it yourself. Luckily my insurance will tow mine home for me if needed up to 15-20 miles for free.
I hadn't thought about adding towing to my insurance policy, but that would be great for these short local tows. I don't know if all AAA districts have the "only to a mechanic" policy, or if I could get around it now that the dispatch is automated. I wouldn't rule them out till you check with your local district office. I know they made a fuss in spring 2020 when the heater hose failed and I still talked to a human dispatcher. DIY or Die has a full service German repair in the same shop, so I can tow there. (Turns out my friends don't really want me working in their driveway again anyway.)

When I originally subscribed to AAA Premier Plus, I lived in the boonies in a small town where I usually walked. I drove an aging Nissan Sentra that I didn't work on myself. My boss had to get his B5.5 Passat wagon towed hundreds of miles to a VW mechanic when he hit a fallen tree branch on 101 in Mendocino County. I realized that this could've been me, making the same trip several times a year. Up there, people think you're un-American to drive a Japanese car, so I didn't want to depend on whatever rural mechanic was handy. After I moved to the Bay Area, I was still driving the Sentra and got it high-centered on an exit ramp in the rain one night. Took two tow trucks to get me on all four wheels again. (I misjudged the poor traction with old tires and muddy pavement. Oops!)

I still (want to) do road trips, and until the pandemic, I didn't have an issue going to DIY or Die.
 

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Discussion Starter · #12 ·
Really!!? Wow. Thats awful!

Good luck with the pressure testing kit. Hopefully its pretty obvious.
I didn't test it last night, but the last time I talked to a human dispatcher and not just the automated system, that's what they told me. I don't know if it's a universal policy or if the automated system will let you select a residential address.

I don't know how much work I should do in the garage drop-off area. I know for sure it has a bad thermostat after AndreasPassat's feedback. Ugh timing belt area work...
 

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Discussion Starter · #13 ·
Could be a cheesy gasket or tightening the oil pan bolts way to tight.
There's this misconception that trans pan bolts need to be tight. There's a reason for those torque specs on the pan bolts.
It's a ZF gasket, so my money's on the tech overtightening the bolts after I complained about the filler plug leaking.

Which is the kind of thing that makes me uneasy about them messing with stuff behind the timing belt.
 

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Oh yeah, that's got the tell-tale signs of coolant leaking out the front of the motor somewhere. More than likely the water pump or the thermostat housing.

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Discussion Starter · #15 ·
I'm pretty disappointed in the last replacement parts only lasting about 35k miles. It has 195k and we did it at 160k back in 2017.
 

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I hear you. For the amount of work / labor involved with that kind of repair, anything less than the expected life cycle is a major bummer.
Not saying you bought inferior parts, but that's exactly why I preach to everyone on this site to use quality parts related to the timing belt kit.
 

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Discussion Starter · #17 ·
We got the ECS kit, assuming they'd curate good quality. Now I'm not so sure.

One of the reasons I wish I could do this myself is that I can get a good deal on the parts at the closest VW parts department. (Unless we need a new thermostat housing, because the only new ones I can find are UroParts and that concerns me.) They're discounting 30-40% for the same part number as the Audi stealership says will fit this engine. (It's just a really chonky Passat.) $31 for a VAG thermostat vs. $16 aftermarket won't break my budget. The rest of the parts are pricier but the difference would only buy about an hour of labor combined, if that. Water pump, $213. Timing belt, $125.

Thermostat housings: anything I should know before ordering or authorizing the shop to order?
 

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ECS Tuning has in the past used some lesser quality roller bearings, but I can't say for sure what they've done for the water pumps.

All of the timing belt service jobs I've done, I've sourced all the parts individually to make up the complete water pump kit for reasons stated above.

My wife's 2002 GLX and my 2004 GLX both had the plastic housing originally and they both had leaked at some point in time. As evident of the pink residue build up on the front of the motor.
The aluminum housing doesn't distort or crack. Subsequentially I've converted all of the V6's I've owned (4 of them) over to the aluminum type housing.

Aluminum housing part# 078 121 121 J
ECS Tuning sells them for around $120.
The brand is URO which I'm not a big fan of, but the one my wife's V6 is a URO and it's good. It's not as refined as the Genuine Audi/VW version but it functions just fine, no issues.

I'm not telling you that you have to make the switch, I'm just offering up my personal experience.
 

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Discussion Starter · #19 · (Edited)
Thanks for the positive review. Edited: The local parts stores can order it; they don't stock it. When I was researching online, it looked like the B5 had the aluminum part and the B5.5 switched to plastic. I don't remember what mine looked like 5 years ago when I worked on that with my friend. I didn't get my tools from my friend's house so I don't have a mirror on a stick to get a good look down there.
 

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That's correct, the B5 had the aluminum housing from the factory and the B5.5's had the plastic housing.

Also, if you do decide to order it, it'll say the part does not fit the B5.5.
It does, I can assure you that it does. Of the 4 I've converted, 3 of them were the ATQ - B5.5.

Note: the aluminum housing part# 078 121 121 J also has the provision for the coolant after run pump.

I was also going to add, the plastic housing has 3 bolt holes to secure it to the engine block. The aluminum housing only has 2 holes. It still works and is not a problem.

I just checked ECS Tuning, the aftermarket brand plastic housings are only $35-$40 cheaper. The Genuine Audi/VW is $133.72 :oops:
 
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