Ongoing issue with coolant

[murdera6]

Now it’s been a month now battling an issue with a coolant leak, I’ve replaced the pcv some hard pipes under the supercharger that connects to the thermostat, also replaced the thermostat, one of the intercooler bricks because I knew it was going bad, What are some other things that can it be? I have a new water pump but mine isn’t making any sounds or leaking that I can see, I checked around the water pump as well and don’t see any dripping, car seems fine normally driving soon as you do a wot pull that’s when it seems to loose coolant, maybe other intercooler brick going bad? Coolant cap? I really need some help figuring this out before I go drop it off and have someone else look at it

[GilliamOS]

Check the coolant solenoid valve under the car that connects to the ATF cooler. Lots of threads on it failing. When it does, it leaks into the wiring and ruins harnesses and controllers.

[murdera6]

I’ll check this out, no signs of it dripping out or beneath the car and I know it’s not the head gasket, pcv was bad and leaking coolant into engine fixed that now dealing with this last issue

[WatchMeSpend]

My coolant is slowly disappearing too. I think it is from the radiator or HX because I can smell it, but only when the car is very hot and the fans are on high. So walking towards the car from the back to the front, I can smell it, but when the fans are off the smell goes away. Right in front of the car the smell is being blown backwards. Face in the engine bay, the smell is coming from the rad side, not the engine.

The hotter it is and the more frequent I drive in hot weather, the faster it goes.

A sensor was replaced last year that was at the back top of the engine. That particular leak you could smell, engine off or on and easily locate it.

[murdera6]

I will get a coolant system failure sometimes and I read with vcds it says coolant pump, secondary pump is fine and pumping only thing I doubt is the waterpump I squeeze the pipe and I don’t really feel a flow or anything so I’m gonna change out the waterpump but does that explain the loss of coolant on wot? Evaporated? Not sure hopefully this helps

[murdera6]

Just drove normal for 30 mins just fine soon as wot get coolant fault at end of pull and coolant loss

[gav28uk]

I've just got my 3.0 V6 TDI back from the garage for coolant leak. There was no coolant on the floor, but pooling in the bottom of the engine tray. Apparently it's a very common fault over here in the UK. £950 later, 6 hours of labour (a very good independant garage) it's sorted. Transpired my 3.0 V6 had two leaks at the bottom of the "V". A replacement thermostatic housing and a coolant regulating valve were to blame. They are both common failure points apparently but a bitch to get to, hence the engine strip and large labour cost.

[murdera6]

Checked the coolant solenoid for the trans not leaking checked everything on the coolant system no visual leaks no drips, car doesn’t loose coolant when driving very moderate soon as you get on it that’s when it’s having issues, replaced waterpump today no fix, I did replace the thermostat and crossover pipes no luck, I have one intercooler brick I didn’t change because I thought it was good maybe it is bad I tried to pressure test it but it seemed fine, maybe should test again. Making me feel like it’s a head gasket now I hope not any other suggestions on what I should do to test the system? Pressure held when I tested it, get home from a drive and the system is pressurized and holds pressure I don’t hear any leaks or hissing nor see any. I’m stumped

[MattyMarkey]

If you are getting an error message on your display, have you pulled the fault codes to determine what it actually is? You mention you read online what the error message is, but the fault codes through VCDS should give you more info.

With everything you’ve replaced, I may suspect air in the system. When I had my 3.0T, I was told it was a self-burping system (local Audi dealer). Maybe try a coolant flush and vacuum bleed.


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[FirstAudiA6]

Coolant pump and thermostat replaced at 38k miles. It's a fairly common issue.

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[MattyMarkey]

Coolant pump and thermostat replaced at 38k miles. It's a fairly common issue.

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Fairly certain her already said he did… didn’t solve the issue


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[AudiC7Owners]

Stupid question but are you checking your coolant levels when the car is warm and on level ground?

Might not need to be said, but make sure you are always checking & topping off your coolant at operating temp.

That being said, the common leak points are:

-Thermostat
-coolant pipe that goes from heater core to the t-stat
-where the rubber coolant hoses connect to your sc crossover pipes
-trans cooler valve under the car
-water pump

If none of those are showing visible signs of leaks then you need to do a pressure test on your coolant system to find the leak.

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[gk1]

This likely has nothing to do with your issue, but FYI from the service manual:

• The coolant level must be at that MAX marking when the engine is cold.
• Coolant level may be above MAX marking with engine at operating temperature.

[murdera6]

Yes I checked vcds the code hasn’t came back in a bit but I did replace waterpump pcv thermostat and the crossover pipe that breaks that’s goes into the thermostat car is fine when I drive under 2400 rpm if I get on it and at the end of the pull there is hardly any coolant left in the tank and the temps spike up I replaced the coolant tank cap as well no visual leaks outside or under the car, I did a vacuum fill as well didn’t seem to help

[murdera6]

Just found out something I want to try with the “n489” valve the vacuum port on the waterpump it could be bad I can’t feel water pumping thru the hose at idle maybe that’s how it’s suppose to be but I’m use to feeling pressure at idle, also I got a code for intake flaps stuck not opening which could be the issue with the control valve I have a couple laying around the house I’m gonna try to replace it, and I know the flaps aren’t stuck because I’ve undone the blower 70 times by now pretty experienced in my book on Audi to a point but this has me stumped

[choy188]

Just found out something I want to try with the “n489” valve the vacuum port on the waterpump it could be bad I can’t feel water pumping thru the hose at idle maybe that’s how it’s suppose to be but I’m use to feeling pressure at idle, also I got a code for intake flaps stuck not opening which could be the issue with the control valve I have a couple laying around the house I’m gonna try to replace it, and I know the flaps aren’t stuck because I’ve undone the blower 70 times by now pretty experienced in my book on Audi to a point but this has me stumped

I would try that color changing fluid stuff that changes color when It contacts exhaust gases on your coolant reservoir and pray it's not a head gasket leak, I think it's called block tester combustion leak or something, i think they have it on amazon

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[TheBlackMarvel]

If you’re going through the whole tank of coolant in a single run and you don’t see any signs of coolant in the engine bay, it’s likely either head gasket or the other inter cooler bank leaking. In either scenario I’m surprised you don’t see any smoke out the tail pipe, but you did say you can smell it.


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[MattyMarkey]

If you’re going through the whole tank of coolant in a single run and you don’t see any signs of coolant in the engine bay, it’s likely either head gasket or the other inter cooler bank leaking. In either scenario I’m surprised you don’t see any smoke out there tail pipe, but you did say you can smell it.


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Or poor, muddy looking oil… fairly easy/common checks for a head gasket leak.


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[Burkeomatic]

Thing that sucks, is that if it is a leak from a coolant passage to the cylinder, none of that stuff will show. Those leaks can come and go. Though typically when those manifest themselves intermittently like that, the combustion goes into the cooling system forcing air in. I had an issue like that, it would pressurize the system with air, then it would look like the coolant went down. If you carefully unscrewed the reservoir, the coolant would magically return to normal level after the combustion gasses exited the cooling system.

[AudiC7Owners]

Thing that sucks, is that if it is a leak from a coolant passage to the cylinder, none of that stuff will show. Those leaks can come and go. Though typically when those manifest themselves intermittently like that, the combustion goes into the cooling system forcing air in. I had an issue like that, it would pressurize the system with air, then it would look like the coolant went down. If you carefully unscrewed the reservoir, the coolant would magically return to normal level after the combustion gasses exited the cooling system.

What did you do to fix it? What was causing the system to pressurize?

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[murdera6]

What did you do to fix this?

[DelayedFlight]

I myself had a coolant leak, and took it to in for service with that complaint. They said it had a failed motor mount, and subsequently replaced it. It was such a slow leak that I thought that maybe I misdiagnosed the fluid that was pooling in my garage. After the car sat for a few days, come to find out it had the same slow leak of the same fluid. I take it in, and they decide it is a coolant leak this time. (Gee, thanks.) Mine was from near the center of the engine block, requiring enough disassembly that the car required a full re-calibration of the parking sensors, radar, and so forth for the ACC, Brake Guard, and something else I can't remember. Thankfully, my extended warranty covered it all. Still sucks though.

[Burkeomatic]

What did you do to fix it? What was causing the system to pressurize?

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It wasn't on this car. Combustion was getting into the cooling passages, leak detector die would not pick it up. Turned out to be a bad HG and the head was warped. He could look in the cylinders to see if one of the pistons has been "steam cleaned." Most cars with a leak like that, the coolant cleans all of the carbon and gunk off the piston, and it looks brand new.

[AudiC7Owners]

It wasn't on this car. Combustion was getting into the cooling passages, leak detector die would not pick it up. Turned out to be a bad HG and the head was warped. He could look in the cylinders to see if one of the pistons has been "steam cleaned." Most cars with a leak like that, the coolant cleans all of the carbon and gunk off the piston, and it looks brand new.

Damn. You have me worried bc my coolant has dropped when warm and once I unscrew the cap it comes back after depressurizing.

But I would assume there would be white smoke if I was burning coolant like that

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[Burkeomatic]

Damn. You have me worried bc my coolant has dropped when warm and once I unscrew the cap it comes back after depressurizing.

But I would assume there would be white smoke if I was burning coolant like that

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NO, it was on a Chrysler Cordoba with a 4.8 LS motor. lol. A little is normal. Funny thing, is no coolant was leaving the car, it was just building huge amounts of pressure in the cooling system which wouldn't vent. My cousin drove it for another year with the radiator cap cracked until we finally pulled that head off.

[AudiC7Owners]

NO, it was on a Chrysler Cordoba with a 4.8 LS motor. lol. A little is normal. Funny thing, is no coolant was leaving the car, it was just building huge amounts of pressure in the cooling system which wouldn't vent. My cousin drove it for another year with the radiator cap cracked until we finally pulled that head off.

Lol gotcha. My coolant levels are staying the same so I think I'm good haha

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