Coolant flange

[B7A4 2.SLOW]

I’m going to replace my coolant flange been getting this coolant smell and having to refill every week or soo, is there anything else I should be replace while I’m doing it ?

[a4lownslow]

I’m going to replace my coolant flange been getting this coolant smell and having to refill every week or soo, is there anything else I should be replace while I’m doing it ?

All you need to remove is the vacuum pump to access the flange. I’d recommend re-sealing the pump when it’s off. Most likely it’s leaking anywAys


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[Willënskraft]

If you’re not planning on reusing the coolant hoses, I’d recommend getting new ones as the old hoses are a PITA to disconnect.


If I had to do it again I would just cut the hoses and replace with new ones.

[Low and Behold]

If you’re not planning on reusing the coolant hoses, I’d recommend getting new ones as the old hoses are a PITA to disconnect.


If I had to do it again I would just cut the hoses and replace with new ones.

This. I do this on any rear flange I replace. Trying to pry off the melted coolant hoses can take hours and it’s frustrating. Cut em and replace em.

[a4lownslow]

This. I do this on any rear flange I replace. Trying to pry off the melted coolant hoses can take hours and it’s frustrating. Cut em and replace em.

Seems unnecessary to cut the hose. Never gone this route. I will agree those hoses can glue to metal pipes, but it comes off much easier if you remove at the plastic flange side only. Radiator pick tool to loose it up, unbolt from the head and rotate out.


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[KJack]

I’m going to replace my coolant flange been getting this coolant smell and having to refill every week or soo, is there anything else I should be replace while I’m doing it ?

Consider buying an extra coolant flange bolt just in case you drop one and can’t find it (this happened to me). You’ll basically be working blind so anything can happen.

[Low and Behold]

Seems unnecessary to cut the hose. Never gone this route. I will agree those hoses can glue to metal pipes, but it comes off much easier if you remove at the plastic flange side only. Radiator pick tool to loose it up, unbolt from the head and rotate out.


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For sure. I’ve done it every which way you can think of.

It’s more about having the extra hose on hand in case it’s a frustrating PITA to get the old one off.

[Theiceman]

Which one is frustrating to get off ?
I did not have any problems without much frustration
I did remove vacuum pump and timing cover for ease of access though

There is a trick to this job. Leave the coolant line to the hard pipe on. Take everything else off including bolts
Now pull the coolant flange off and pull it above the engine. ( the rubber line to the hard pipe will just bend and allow this.
Then take the flange off the rubber hose in relative comfort.
Mark it so you put your new coolant flange in exactly the same position
Push it back down and the rubber hose will hold it in the perfect position.
Put bolts back on and reattach other lines


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[audiglenn]

Which one is frustrating to get off ?
I did not have any problems without much frustration
I did remove vacuum pump and timing cover for ease of access though

There is a trick to this job. Leave the coolant line to the hard pipe on. Take everything else off including bolts
Now pull the coolant flange off and pull it above the engine. ( the rubber line to the hard pipe will just bend and allow this.
Then take the flange off the rubber hose in relative comfort.
Mark it so you put your new coolant flange in exactly the same position
Push it back down and the rubber hose will hold it in the perfect position.
Put bolts back on and reattach other lines


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Hello Thieceman,

While I was tracking my coolant drip under the transmission, I noticed oil on the wiring harness below the vacuum pump as well as on top of the transmission. It looks like it is coming from the backside of the vacuum pump. I felt with my hand on the chain cover under the vacuum pump and did not notice any oil, but did feel oil at the bottom of the backside of the vacuum pump. Anyway, I am able to remove the top 2 30mm torx bolts at the top of the vacuum pump but having issues locating the third bolt. Is it also a torx bolt? The wiring harness sits almost right on top of it. This leak doesn't seem to occur while the car is running, much like the coolant drip, only during engine cool down.

I ran my hand underneath all the coolant flange connections and did not notice any wetness on them, not even any oil. I heard if oil gets on the flange connections, it could cause it to leak.

Just want to confirm the third bolt at the bottom of the vacuum pump is a torx bolt before I blindly try to remove it with my micro wrench. Since I have to drive the vehicle this week, I haven't messed with the hose connection going to the brake booster. Is this straight forward to remove with a vice grip without damaging it?

Thanks

[medrads2020]

Hello Thieceman,

While I was tracking my coolant drip under the transmission, I noticed oil on the wiring harness below the vacuum pump as well as on top of the transmission. It looks like it is coming from the backside of the vacuum pump. I felt with my hand on the chain cover under the vacuum pump and did not notice any oil, but did feel oil at the bottom of the backside of the vacuum pump. Anyway, I am able to remove the top 2 30mm torx bolts at the top of the vacuum pump but having issues locating the third bolt. Is it also a torx bolt? The wiring harness sits almost right on top of it. This leak doesn't seem to occur while the car is running, much like the coolant drip, only during engine cool down.

I ran my hand underneath all the coolant flange connections and did not notice any wetness on them, not even any oil. I heard if oil gets on the flange connections, it could cause it to leak.

Just want to confirm the third bolt at the bottom of the vacuum pump is a torx bolt before I blindly try to remove it with my micro wrench. Since I have to drive the vehicle this week, I haven't messed with the hose connection going to the brake booster. Is this straight forward to remove with a vice grip without damaging it?

Thanks

It is a T27 Torx located towards the middle of the engine. The vacuum pump has a bracket that angles down and out at around 45 degrees from it. Use the image below with my ratchet in place for landmarks to guide you.




Note that a bracket with one of the big 3 ground wires found in the engine is secured into place by this bolt. The T27 bolt goes through the hole circled. This needs to be reinstalled back into place or the car will not run right. You can see the bracket in the image below.


I hope this helps!

[Theiceman]

yes as pointed out above the last bolt is a torx. different style though as it holds the ground bracket also. take pic with your phone. so you can see how the bracket goes back on s its tricky.

Also the leaking oil pump us likely why your seal deteriorated in the first place

[audiglenn]

It is a T27 Torx located towards the middle of the engine. The vacuum pump has a bracket that angles down and out at around 45 degrees from it. Use the image below with my ratchet in place for landmarks to guide you.




Note that a bracket with one of the big 3 ground wires found in the engine is secured into place by this bolt. The T27 bolt goes through the hole circled. This needs to be reinstalled back into place or the car will not run right. You can see the bracket in the image below.


I hope this helps!

Appreciate the photos. I am trying to envision this bracket that is attached to the chain cover. I can feel the ground strap when I stick my hand underneath. I will take a closer look at the video I took with my phone. This bolt is likely harder to get back in then take out. Thanks.

[audiglenn]

yes as pointed out above the last bolt is a torx. different style though as it holds the ground bracket also. take pic with your phone. so you can see how the bracket goes back on s its tricky.

Also the leaking oil pump us likely why your seal deteriorated in the first place

I will take a closer look at the video I took. Thanks.

[forger]

I decided just to fix the oil leak from the vacuum pump by opening it up and replacing the back seal. Driven 50 miles and so far no more oil leak. Yes the re-installation of the ground strap required some manipulation. I had to rotate it counter-clockwise to get it to sit flush on the vacuum pump and at the same time get the torx bolt started on the thread.

My coolant leaks at night during engine cool down mainly on nights below 60 Fahrenheit. I am wondering if the hot oil dripping on the coolant hose connections is causing the leak and compromising/damaging the water tight seal. Anyway, will find out. I haven't determined which hose connection is leaking since the oil and coolant were leaking onto transmission at the same time. With no more oil leak, I may be able to trace the coolant leak if there is a compromise with any of the seals.

I don't look forward to fixing the coolant flange leak if it still exists. The hose connections are difficult to get to in the tight space.

[forger]

Thanks medrads. I was able to repair the leaking fuel pump.

[EvolutionArmory]

I decided just to fix the oil leak from the vacuum pump by opening it up and replacing the back seal. Driven 50 miles and so far no more oil leak. Yes the re-installation of the ground strap required some manipulation. I had to rotate it counter-clockwise to get it to sit flush on the vacuum pump and at the same time get the torx bolt started on the thread.

My coolant leaks at night during engine cool down mainly on nights below 60 Fahrenheit. I am wondering if the hot oil dripping on the coolant hose connections is causing the leak and compromising/damaging the water tight seal. Anyway, will find out. I haven't determined which hose connection is leaking since the oil and coolant were leaking onto transmission at the same time. With no more oil leak, I may be able to trace the coolant leak if there is a compromise with any of the seals.

I don't look forward to fixing the coolant flange leak if it still exists. The hose connections are difficult to get to in the tight space.

These coolant flanges leak because they are plastic and are subject to constant heat cycles and get brittle. Add that to constant stress of being attached to hoses that are connected to them and constant engine movement and they crack and leak.

9 times out of 10 the flange is cracked somewhere and the hoses are fine.

[Theiceman]

You are correct the hot oil breaks down the rubber oring in the coolant flange. It expands and breaks the flange apart

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[EvolutionArmory]

So being in one of the hottest parts of the engine next to the turbo and right near the fire wall with no airflow near it has nothing to do with it? 🤣 The flange gets heated above 200 degrees and cools down to at least half of that every day and sometimes cools to below zero depending on the season and sometimes multiple times in a day.

It’s a combo of constant heat cycles, vibration and being made out of plastic. I’m sure contamination doesn’t help but I wouldn’t say that’s the root cause.

Throw some dye in the coolant and see which part of the flange glows under UV light. That will tell you the source of the failure.

[Theiceman]

So being in one of the hottest parts of the engine next to the turbo and right near the fire wall with no airflow near it has nothing to do with it? 🤣 The flange gets heated above 200 degrees and cools down to at least half of that every day and sometimes cools to below zero depending on the season and sometimes multiple times in a day.

It’s a combo of constant heat cycles, vibration and being made out of plastic. I’m sure contamination doesn’t help but I wouldn’t say that’s the root cause.

Throw some dye in the coolant and see which part of the flange glows under UV light. That will tell you the source of the failure.

the rubber oring is just that , duro rubber and not designed to withstand oil. Its the same reason the water pump leaks on the b8, water pump that leak tends to be the ones that have a valve cover leak and oil runs down onto it.
of course nothing lasts forever, but I would say the flange and oring is designed to withstand heating and cooling, but is not designed to withstand oil contamination. I know the thermostat is not on the head but is on the block, but is made of the same composite and almost never leaks externally compared to the flange, and it sees similar heat swings, admittedly not as extreme though.

I do truly believe that if the oil pump was not such a problem and didn't leak at all, we would see far fewer coolant flange failures.

[EvolutionArmory]

But they are just as problematic on the 1.8T because they are near a 600 degree c turbocharger and wedged between the fire wall and head.

Think about this. You’ve got a 600+ degree turbocharger, 200+ degree coolant and varying ambient temps. Now think about what happens when people experience leaking coolant overnight. Your flange is cracked. Your coolant flange O ring expands when the car is used and stops the leak. When it starts to cool the O ring shrinks and boom, your flange leaks. Your flange temp can swing over 200 degrees in one day depending on ambient temp. That constant heat cycling is what causes them to become brittle and break.

The O ring isn’t the issue. The crack in your flange is. The O ring is the reason why it doesn’t leak when driving or warm.

[Ray1031]

dumb question here, why can't they make it out of aluminum instead...

[EvolutionArmory]

$$$


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[Charles.waite]

Correction from above, all the bolts back there are t30, none are t27.

Having just done this, and finding it impossible to get the clamp on the hose on the drivers side off, I undid the upper coolant pipe and left it attached, then lifted the entire flange out after disconnecting the coolant temp sensor and the heater core connector (the one sticking straight down).

I was planning on replacing just the o-ring but the flange was broken in half inside the head so I had to use my new flange that I was hoping to save for my new engine.

Also replaced the CTS since why the hell not. To get the best access without having to remove the timing cover, I removed the n205 as well as the vacuum pump and wrapped some exposed coolant clamps with electrical tape (at the brilliant suggestion of my wife) since the metal clamps were shredding my arms.

Glad to not be smelling coolant everywhere I go now...

[Charles.waite]

But they are just as problematic on the 1.8T because they are near a 600 degree c turbocharger and wedged between the fire wall and head.

Think about this. You’ve got a 600+ degree turbocharger, 200+ degree coolant and varying ambient temps. Now think about what happens when people experience leaking coolant overnight. Your flange is cracked. Your coolant flange O ring expands when the car is used and stops the leak. When it starts to cool the O ring shrinks and boom, your flange leaks. Your flange temp can swing over 200 degrees in one day depending on ambient temp. That constant heat cycling is what causes them to become brittle and break.

The O ring isn’t the issue. The crack in your flange is. The O ring is the reason why it doesn’t leak when driving or warm.

This. Mine was cracked off inside and would seal fine at operating temp, then cool and drip coolant everywhere. Rinse repeat for every drive cycle.

The reason they’re not metal is, as you said, $$$$. A FRP molded flange is soooo much cheaper than an aluminum one to manufacture, will last the length of the warranty, will be the same amount of labor to service for a tech.

Not defending the use of plastic but that’s why they did it.

Also a tip for reconnecting the lower hose, it can be a real bitch but I found that using the thin, flat edge of a large wrench and levering it off the bellhousing popped it in without too much fuss. Before that I nearly blew my back out reaching underneath and trying to force that sticky connector back on with my hands.

[Charles.waite]

Also also (third post!) I was shocked at how nasty it was back there with the coolant that’s been leaking for almost a year.



And here is the flange up and out (but still attached to the coolant pipe:

[Ray1031]

Just like most have said, this little "thing" it’s by far the most challenging I've encountered... Needless to say it's got to be done and once you get started there's no turning back... I can’t seem to get the bottom hose to attach firmly, the clip pops out , I've tried everything I can think off but nothing seems to work....


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[Theiceman]

Keep it attached to the coolant pipe as Charles did and just bend the rubber hose up to get it above the engine. Put the new flange on the rubber hose CLOCKED EXACTLY THE SAME. Drop it back below and the rubber hose to the coolant pipe will hold it in place perfectly while you bolt it up and reconnect

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[Charles.waite]

Just like most have said, this little "thing" I'd by far the most challenging I've encountered... Needless to say it's got to be done and once you get started there's no turning back... The bottom hose I can't seem to get it to attach firmly, I've tried everything I can think off but nothing seems to work....


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Use a long wrench as a lever and put upwards pressure on it from the transmission bellhousing onto the elbow of the connector.

[Ray1031]

Use a long wrench as a lever and put upwards pressure on it from the transmission bellhousing onto the elbow of the connector.

Thanks for the reply, should I leave the oring inside the hose or remove it and put it on the flange and try to get it on... I tried using a screw driver, a mallet's handle and nothing...


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[aluthman]

Smear the hose connector with some silicone grease and it’ll slide right on.

[Ray1031]

I went at it again this morning and it went in so easy that I started laughing to myself , I guess after 7 hours of dealing with the stupid thing last week I was tired and pissed off at it ... nothing like walking away taking a break and trying again at a later time ....


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