draining coolant necessary ?- rear coolant flange replacement

[dirtyserby]

should I drain the coolant when replacing the rear coolant flange.

id rather not jack up my car and crawl underneath to do it...

How big of a mess is it if I just try and replace it?

[dougyfresh]

I would drain your coolant. If your rear coolant flange is leaking already you more than likely don't have much coolant left in the system.

Easiest way to drain is to put a clean pan under the lower radiator hose. There is a drain petcock next to the coolant sensor on that lower radiator hose connection with the radiator. Open up the drain petcock and also open up the coolant reservoir and let it drain. Unless you're significantly lowered you can do this without jacking up the car.

If your pan is clean, you can filter the coolant with a nice painter's funnel/filter into a new container and re-use it. (thanks Jake)

The rear coolant flange is held in with an allen bolt (5mm) on the bottom and a stud on top (10mm socket). The stud on top is an attachment point for the EVAP hard line that comes up from the block breather (under intake mani) and to the rear fitting on the valve cover. I recommend 1/4" drive tools for they are small and can get back there. I also recommend removing the EVAP hard lines that connect to the back of the valve cover to gain you some access to the coolant flange.

There is a connection to the heater core coming off the back down on the bottom. It is connected like your radiator hoses (pull that clip up and pull the hose off). There is also a line coming out on the intake side that connects to the coolant hard line that runs across your intake manifold. I recommend either removing the upper coolant hard line with the rear coolant flange or removing the connection of the flange to the hard line (up on the hard line, not on the coolant flange) because there is very little room back there to disconnect the hard line clamps.

When reinstalling the heater core hose (or radiator hoses) I've found that just a small dab of silicon grease on the connector helps it slide on easier (effortless). It cuts down on the friction of the O-ring.

Go with an OEM coolant flange. I've seen the ones from ECS break.

[dirtyserby]

I would drain your coolant. If your rear coolant flange is leaking already you more than likely don't have much coolant left in the system.

Easiest way to drain is to put a clean pan under the lower radiator hose. There is a drain petcock next to the coolant sensor on that lower radiator hose connection with the radiator. Open up the drain petcock and also open up the coolant reservoir and let it drain. Unless you're significantly lowered you can do this without jacking up the car.

If your pan is clean, you can filter the coolant with a nice painter's funnel/filter into a new container and re-use it. (thanks Jake)

The rear coolant flange is held in with an allen bolt (5mm) on the bottom and a stud on top (10mm socket). The stud on top is an attachment point for the EVAP hard line that comes up from the block breather (under intake mani) and to the rear fitting on the valve cover. I recommend 1/4" drive tools for they are small and can get back there. I also recommend removing the EVAP hard lines that connect to the back of the valve cover to gain you some access to the coolant flange.

There is a connection to the heater core coming off the back down on the bottom. It is connected like your radiator hoses (pull that clip up and pull the hose off). There is also a line coming out on the intake side that connects to the coolant hard line that runs across your intake manifold. I recommend either removing the upper coolant hard line with the rear coolant flange or removing the connection of the flange to the hard line (up on the hard line, not on the coolant flange) because there is very little room back there to disconnect the hard line clamps.

When reinstalling the heater core hose (or radiator hoses) I've found that just a small dab of silicon grease on the connector helps it slide on easier (effortless). It cuts down on the friction of the O-ring.

Go with an OEM coolant flange. I've seen the ones from ECS break.

great advice! thanks

going to work on it now

[n7plus1]

should we be doing a 50/50 mix with water or straight g12?

[dougyfresh]

should we be doing a 50/50 mix with water or straight g12?

straight g12 is overkill and you actually get better temperature properties with some water mix in there.

50/50 at best. I'm probably around 80/20 or 90/10 right now (water/g12). I'll probably go back to 50/50 come winter-time.

[n7plus1]

this is most likely somewhere here...but how much do we need, 2 liters?

[dirtyserby]

god what a pain in the ass job!

glad its done, dont ever want to do that again.

[dougyfresh]

god what a pain in the ass job!

glad its done, dont ever want to do that again.

Excellent! So you got that stripped SAI bolt off. Good job!

[CO AVANT]

straight g12 is overkill and you actually get better temperature properties with some water mix in there.

50/50 at best. I'm probably around 80/20 or 90/10 right now (water/g12). I'll probably go back to 50/50 come winter-time.

Jeff drove around lake Tahoe in the freezing winter with an 80/20 mix and had 0 problems. I think 30% G12 is all you'll ever need unless it stays 20 below 0 for days on end... I'm running a 80 water to 20 G12/engine ice mix right now. Works great in the summer months. Water has better cooling properties over coolant (for the masses, I know you know Doug).

[dougyfresh]

/\
I know. Took no offense and read with an open mind.

[lookaught]

I just want to add a little to this thread for the archives:

I changed my leaking flange last night. I was lazy and did not drain the coolant, but in retrospect it would have been a good idea as when I popped the lower hose it did go everywhere as expected but more drained than I though would (pre cat littered the floor to catch it all though). It took about a 1/2 gallon of g12/water mix to bring back to normal level once I was finished, so if you drain it, drain out a little more than 1/2 gallon (provided your car is at the correct level to start with) and you should have minimal falling on the ground.

Thanks for the tips about that hellish little flange Doug, it was a real PITA to change! The whole time I was just cursing the PCV and SAI systems that make it so much harder to access. I did fix the vacuum leak, it was broken right on the combi valve. I think Im going to order a bunch of silicon hose and go to town replacing it all, as many of them are frayed and brittle from 86,000 miles.



To anyone who fixes a flange in the future, I wish you good luck! It's not a fun fix.

[dougyfresh]

Jon,
Good to hear you got it done. My rear coolant flange broke back in the summer of 2005. Way before I did any performance mods to my car so I still had SAI and all that other crap on my engine. It wasn't fun to swap out. As you saw, its so easy on my car now with the SAI and crap removed.

Here is that post I had on the McMaster Carr vacuum line connections (with the appropriate tool) and one source for silicon vacuum lines.
http://audizine.com/forum/showthread...52#post2400452

I just recently bought silicon vacuum lines from ATP. The lines they sell have a thicker wall than the ones Baker Precision sells. Therefore they are a bit more durable but harder to connect onto the fittings. Here is a link to ATP's silicon lines: http://www.atpturbo.com/Merchant2/me...egory_Code=VCM

I recommend black lines throughout. Fancy colors just look ghey.

If you are having trouble connecting the lines to the fittings, spray a dab of WD40 onto the fitting and it'll slide on with ease.

Enjoy!
Doug

[wolfdog]

I attempted it but realized I was one hose clamp short and had to quit 1/2 way through. I'm in a bad spot because now I know too much and realize what's ahead of me but it has to be done!

[dougyfresh]

I attempted it but realized I was one hose clamp short and had to quit 1/2 way through. I'm in a bad spot because now I know too much and realize what's ahead of me but it has to be done!

You know what to do. Hose your engine down with White Lightning to clean it off. Then run the lines. Just gotta force yourself to do it rather than procrastinate

[wolfdog]

Well, that job is done and I will never do that again. About 1/2 way through when the flange was unbolted and I had to remove the hoses I thought "this is why I work, so I can pay people to do annoying jobs like this".

There's no room to work back there with all that secondary air crap. I kept dropping allen keys and bolts and other small stuff. By the way, I lost a small torx screw. In the picture below, there is a plug you remove by pressing down the wire thing (in center of picture, labeled unplug). Whatever it is that the plug actually plugs into is held on by two small torx screws. I lost one of them and am not sure what this piece is or does. I've got one holding it on at the moment but need to get another to prevent it from moving.


Yep, next time I'm paying someone to do that job. By the way, I'd say about a 1/2 gallon as well.

[dougyfresh]

that is your VVT adjuster. no need to unbolt it. want a bolt? call me tonight. I'll be in nj tomorrow morn

[2003Qu4ttr0]

My 2003 A4 just started leaking real bad. She pissed out a lot a coolant in the parking lot at work. Southgate Audi is just a 3 minute drive away. As soon as I parked, I popped the hood, walked over to the passenger side of the car and took a peek behind the engine where it meets the transmission bell housing. Sure thing, there was a leak coming from above, the coolant flange. While I was at Audi, I asked how much the flange would cost to replace. $400-$500 Canadian. Yeah right, he was quick to provide the number too, so this is a common one.

I called Karmac and Autobahn Performance. Both have the coolant flange for $24 which is cool. Performing the job, not cool. So I booked a time with Karmac, and they'll do it for under $200. Sounds good to me.

What else could be leaking back there if it's not the coolant flange?