Coolant leak near water pump

[isesoteric]

Hey guys I think I've got a leak on one of my coolant lines. I think it's the line from the pump, that T's with coolant reservoir, and the upper radiator hose.

Does anyone know the part number of that hose? Can I replace the o ring on that line, I'm fairly sure it's on there pump side. 20191229_133902.jpeg

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[whats77inaname]

That's most likely not the line, that's most likely the pump, unfortunately. They're known to fail pretty much where you see the moisture on your engine.

https://www.audizine.com/forum/showt...e-Coolant-leak

[19birel]

I had the same leak, had to replace water pump and thermostat

[elscotto80]

Replace the pump, t-statz etc. It's a known failure point.

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[kaz02a4]

Do a carbon clean while you're in there! You'll have much more access to the water pump with the intake manifold out of there.
https://www.audizine.com/forum/showt...Valve-Cleaning

[amulet1.8]

Hey guys I think I've got a leak on one of my coolant lines. I think it's the line from the pump, that T's with coolant reservoir, and the upper radiator hose.

Does anyone know the part number of that hose? Can I replace the o ring on that line, I'm fairly sure it's on there pump side. 20191229_133902.jpeg

Sent from my SM-G973U using Audizine mobile app

Had the same thing. Replaced water pump with OEM pump last June. It failed again in December. The first time it was the gasket. Probably could've just replaced that, but ended up putting in a whole new pump. In december, the new one failed and the hard plastic actually cracked. There's a class action lawsuit for this.

I now have a duralast pump on the car... we'll see how it does.

Also - totally doable without removing the intake manifold.

[SeniorFunky]

So it seems I am in the same boat. I have been trying to diagnose where the leak on my A4 is. But my symptoms are slightly different. The car seems to only lose coolant when its cooling down from proper operating temperature. And its especially strange, because it does not happen every day.

I have been trying to locate the source of the leak by means of looking from the engine bay, from underneath, with mirrors and by taking pictures and videos. Nothing clearly helped. So I ordered a bunch of parts and took of the IM. With the manifold of and the car still semi-warm (as warm as was possible to work on) I pressured the system to about 14psi and set out to find the leak. Didn't find any apparent leaks. When I was taking the pressure off the temp sensor seemed to be leaking. Inspecting it showed that is was rather loose and wobbly. So I replaced the O-ring and the clip holding it in place. The new assembly seemed much sturdier and so after many hours searching for dropped nuts and bits into the ... (I wont rant) ... reassembled the IM and hoped to have the issue fixed.

The next day my fiance took the car to work and it leaked :( ... After reading amulet1.8's post I am thinking it must be the housing/water pump. It was replaced roughly 10k miles by a shop specialized in German cars with an Audi part. Are there any other bits I might be missing? All the pipes look dry and the spots where water builds up are near the engine block, around the screws that hold the various black plastic covers in place.

I was hoping to diagnose properly before putting in another water pump, but it seems this might be the only way. I'd appreciate any second opinions.
Thanks

[Spawne32]

Everyone should be buying the aluminum version of the pump from here on out. Do not buy the plastic units.

[Slick_B8]

Everyone should be buying the aluminum version of the pump from here on out. Do not buy the plastic units.

X1. Just replaced mine at home without the need to remove the intake manifold. Took me about 2hrs considering it was my first one and I had also dropped one of my hose clips in the engine bay lol also, I recommend everyone buy the aluminum water pump kit from fcpeuro. Out the door was about 300 shipped but for the piece of mind knowing that it has lifetime warranty, well, it’s a no brainer.

[ericA6]

So it seems I am in the same boat. I have been trying to diagnose where the leak on my A4 is. But my symptoms are slightly different. The car seems to only lose coolant when its cooling down from proper operating temperature. And its especially strange, because it does not happen every day.

I have been trying to locate the source of the leak by means of looking from the engine bay, from underneath, with mirrors and by taking pictures and videos. Nothing clearly helped. So I ordered a bunch of parts and took of the IM. With the manifold of and the car still semi-warm (as warm as was possible to work on) I pressured the system to about 14psi and set out to find the leak. Didn't find any apparent leaks. When I was taking the pressure off the temp sensor seemed to be leaking. Inspecting it showed that is was rather loose and wobbly. So I replaced the O-ring and the clip holding it in place. The new assembly seemed much sturdier and so after many hours searching for dropped nuts and bits into the ... (I wont rant) ... reassembled the IM and hoped to have the issue fixed.

The next day my fiance took the car to work and it leaked :( ... After reading amulet1.8's post I am thinking it must be the housing/water pump. It was replaced roughly 10k miles by a shop specialized in German cars with an Audi part. Are there any other bits I might be missing? All the pipes look dry and the spots where water builds up are near the engine block, around the screws that hold the various black plastic covers in place.

I was hoping to diagnose properly before putting in another water pump, but it seems this might be the only way. I'd appreciate any second opinions.
Thanks

Try replacing the hour glass shaped plastic tube between the WP and oil cooler. This was my problem. I ordered the aluminum kit from ECS and they sent me an aftermarket part. It leaked for days with the new one. I couldn’t figure out this was the issue. I took it to an Indy shop and had them pressurize the system. When the engine was warm it would not leak at 17bar. When the engine was cold they found the leak immediately. I then ordered the genuine Audi part and no leaks since. It appears the aftermarket one is slightly smaller with the o-rings so when the engine is hot it swells and properly seals. When it cools down it shrinks and the pressure in the system pushes the coolant out.

If you didn’t replace the o-rings for the two large hoses that attach to the WP that’s also a cheap place to start. If the large hoses are old then replace the entire hose.

I also did WP removal and install without removing IM. Unless you want to deal with injector seals and carbon cleaning, don’t remove the IM. I also didn’t remove the reverse threaded bolt holding the sprocket that is attached to the crank for the WP belt. I slid the belt off and back on.

Good luck!


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[SeniorFunky]

Thanks for the hints ericA6, I just went in this weekend and checked again. Since the leak was not clearly from the pump, I ended up taking the IM off again.

This time with a different pressure kit it all worked a lot smoother. For anyone trying to identify a leak in the coolant system I can only recommend to pressurize and then wiggle all the components, because thats what finally revealed what the problem was. It was the O-Ring (WHT006407) for the hard-platic coolant pipe that comes directly out of the WP and is bolted into place in two locations (06H121065D, https://www.fcpeuro.com/products/vw-...-vw-06h121065d). When pressurized, I could wiggle the pipe up and down and see how the coolant would bubble out. This is with a cool engine only. I assume that the engine only leaked when it was cooling down after being properly heated, because the system had pressure and the out pipe would cool down faster than the engine, leaving more room for coolant to pass, especially with the bad O-Ring. I have had no leak since.

But now I am left with two more questions. First, I purchased the REIN replacement WP, which came with a metal clip for the temperature sensor (CTP). After replacing the CTP O-ring, the CTP would wiggle a lot with the original plastic clip. Trying the metal clip the CTP would be firmly in place. Does anyone know if a certain play with the CTP is normal? The was no leak even with pessure, even when moving the sensor, but it sure felt like it shouldn't move as much. Just some reassurance that the Audi clip allows for some play would be good for peace of mind.

And secondly the much bigger issue. When replacing the IM two of the bolt on the lower side seems to have eaten the tread in the block. They would only semi-lock and then click through when turning further. Now the IM goes on firmly with the remaining 7 points and the engine starts without issues and runs without showing a Check Engine Light. I take this as a sign that the gasket is sealing correctly and no over or under O2 is senses by the exhaust system. However, I would still like to make the bolts work again. Does anyone have experience with fitting a heli-coil (https://www.ezlok.com/ezcoil-kit-SK40610) into the block? This is currently the only thing I can think of that would repair the broken tread in the block... Or would you dismiss this issue until it becomes apparent that air is entering/exiting through the IM-gasket?

Thank in advance for the help!