DIY: 1.8t Coolant Flange Removal and re-installation instructions on AEB others should be the same

BSK · 01-18-2006, 08:47 PM

So if you have been loosing coolant, had a coolant burning smell after a long drive or just happened to look down towards the back of the engine in between the firewall and noticed some pink crusting; then it's most likely time for a coolant flange job.

Picture by Andy TN showing some pink crust

The coolant flange holds the ECT (Engine Coolant Temperature Sensor) and is connect to the back of the engine head. It's a simple but semi hard to reach job but it's definitely DIY.

Let's get started:

Old vs. new. This side is the R side that will connect to the big black coolant pipe. Make sure you have a gasket in there

Coolant flange is semi installed. It's hanging in there loose

This side shown is the side that will attach to the engine, make sure that the gasket is installed and not torn... this is a leak area

The new flange with the temp sensor installed but no gasket between flange and engine

ETKA explosion diagram of the coolant flange and its connections

Some of the old coolant flanges will only have ONE port. The new ones that are sold come with a second port, that is seen PLUGGED in this picture. Make sure you have either an old temp sensor or the dummy plug from the dealer to fill the second port.

OK so now that you know how the coolant flange looks and where it connects to its time to get dirty:

You will loose some coolant during this procedure; it is also a good idea to replace the ECT as well while you are doing this.
You could either drain the engine coolant at the water pump or just leave whatever you have in there and see how much comes out.
I did the replacement on an engine that had all the coolant drained and replaced with brand new G12. Either way, make sure that the Engine is COLD or you will get burned.

Disconnect the cable leading to the ECT by squeezing the metal and pulling it off. You can leave the ECT in the flange or remove it. To remove it pull the small plastic U shaped clip out towards the firewall and then pull up on the ECT. You will have some coolant coming out right now.

I can't remember for sure if I had 6mm hex bolts of 8mm ones. But you need to remove 2 bolts that attach the coolant flange to the engine and another 2 that attach the flange on R side (looking from the front) to the black hose.

The picture to remind you. After you have those bolts loose you will have some more coolant come out. Pull the flange away from the engine block and also out of the black hose. The only connection that is left now will be the bottom hose.

In order to remove the bottom hose from the flange you will have to pull away a clip from the hose that will be on the flange. Make sure that you try to catch this clip as it will be flying away; it's very small and hard to find. After you have pulled the clip, hold the hose with one hand and pull on the flange with the other hand.
The flange will pop out with enough force.

Take your new flange and transfer the dummy plug and or new ECT from the old to new if needed.
You hopefully have 3 or 4 O-Rings depending on the flange. One O- Ring goes in between the flange and the engine, the other one goes between the flange and the black hose and the 2 other ones are for the ECT and the dummy plug.

Installation is in the reverse order. Make sure that when you tighten the bolts back up so just barely hand tighten them until everything is connected. Tighten them down a little bit at a time so the flange is not crocked installed.
Replenish the coolant lost, start the engine and check for leaks.

When i removed the old flange I didn't see any physical damage to it, so it might just be the O rings that are failing.

good luck

Nate (ETKA+Scumbag) · 01-18-2006, 08:53 PM

pointby · 01-18-2006, 09:17 PM

This should go into the tech section.

BSK · 01-18-2006, 09:22 PM

whenever i get the time and find the pics from back in the day when we did those. i dont think that there is a complete control arm article out there.

Andy_FL · 01-19-2006, 01:57 AM

...each additional, $1/click ;-)

Andy

BMORE_Ken · 01-19-2006, 03:33 AM

Sometime i get the whiff of G-12 from my engine but i can't find any leaks.

Ken

~~ModifiedA4~~ · 01-19-2006, 04:50 AM

Greyhound Guy · 01-19-2006, 05:38 AM

SilverStar · 01-19-2006, 05:53 AM

Rocket3004 · 01-19-2006, 06:38 AM

I know you mentioned you didn't see any physical damage, so that would lead me to beleive that just the seals are bad.

Any corrosion or anything else to suggest the replace the whole thing?

Nice writeup!

01-18-2006, 08:53 PM	#2
Nate (ETKA+Scumbag) Keeper of the Cash 1997 Audi A4 Join Date: Sep 2004 Location: Iowa Posts: 26,601	Horay! Just what I needed. __________________ "There might be intelligent beings created by God in outer space even if there are none here on Earth."

01-18-2006, 09:17 PM	#3
pointby AudiWorld Super User Garage is empty, add now Join Date: Apr 2000 Posts: 4,551	Good job. Something else to look forward to :( This should go into the tech section.

01-18-2006, 09:22 PM	#4
BSK AudiWorld Super User Garage is empty, add now Join Date: Apr 2003 Posts: 16,815	i will do a writeup for control arms as well whenever i get the time and find the pics from back in the day when we did those. i dont think that there is a complete control arm article out there. __________________ aim: afastgerman

01-19-2006, 01:57 AM	#5
Andy_FL AudiWorld Super User Garage is empty, add now Join Date: Nov 2000 Posts: 9,788	First pic is free.... ...each additional, $1/click ;-) Andy __________________

01-19-2006, 03:33 AM	#6
BMORE_Ken New Member Garage is empty, add now Join Date: Jul 2005 Posts: 399	Awesome, i might have to do that soon... Sometime i get the whiff of G-12 from my engine but i can't find any leaks. Ken __________________ Mod: Pure MS Snub Mount, More to come Recent Repairs: All Belts, Timing Belt Tensor, Water Pump Impellar \| Transmission Mounts \| New Engine Mounts \| Replaced Water Pump Housing B5 A4 FAQ Black 99.5 A4 1.8TMQ 103,000 and counting. Located in Baltimore, MD.

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01-19-2006, 04:50 AM	#7
~~ModifiedA4~~ Banned Garage is empty, add now Join Date: Mar 2000 Posts: 34,549	nice.

01-19-2006, 05:38 AM	#8
Greyhound Guy AudiWorld Super User 1999 Audi A6 My Garage Join Date: Jul 2000 Posts: 12,905	Hmmm, wonder if I should do that when i do the sensor just cuz. __________________ Current: 2001 Audi A4 Avant, Stage 3 (11 years, 99K) 1999 Audi A6 Avant, Worn (1 year, 138K) Sold: 1996 Audi A6 Avant (5 years, 155K) *(Owned, Odometer)

01-19-2006, 05:53 AM	#9
SilverStar AudiWorld Member Garage is empty, add now Join Date: Feb 2002 Posts: 519	Nice write up

01-19-2006, 06:38 AM	#10
Rocket3004 New Member Garage is empty, add now Join Date: May 2005 Posts: 218	You think the whole flange needs to be replaced or just the seals? I know you mentioned you didn't see any physical damage, so that would lead me to beleive that just the seals are bad. Any corrosion or anything else to suggest the replace the whole thing? Nice writeup!

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