I had a small coolant leak so decided to correct the issue. It was leaking form the cylinder head coolant flange. I ordered a new coolant flange and temp sensor off ecs tuning. I installed everything back on the car, now it doesn't leak, but after about 15 minutes of driving the coolant temp starts going up on my gauge in the car and then it starts leaking from where the coolant flange meets the block. It won't leak at all for about 15 minutes or so. I don't get it, and when it starts to overheat it looks like my coolant reservoir is empty but as soon as I open the cap the coolant starts to bubble and like magic all the coolant is back up in the reservoir. I don't understand. Please help, my slow leak over time was much better than this. The weirdest part to me is that it won't leak till after a while.

 

Lots of people say that the aftermarket cooling flanges are junk and that you need to get an OE replacement.

But first things first - did you clean off the sealing surface on the block after removing the old piece? Did you remember the o-ring?

 

didn't clean the block no, and yes I remembered the o-ring. The one form ecs tuning looks exactly like my oem one.

http://www.ecstuning.com/Audi-B5_A4-...langes/ES5904/

It doesn't leak till after I drive it for a while and the temp gauge starts to go up a little bit.

 

I read that people were having problems with like Meyle and other aftermarket ones not sealing correctly. You can try cleaning the sealing surface. Worst comes to worst, RTV should take care of the problem.

 

I think my radiator may have a clog, not sure, last time it happened one side of the rad was super hot the other was warm to the touch

 

It's possible, but do keep in mind the whole point of the radiator is for one side to be cooler than the other.

 

Did you burp the cooling system when you finished the parts changeover? You broke into the system at a point other than the highest point in the cooling system, so there's a likelihood you developed air bubbles in there, and those will jam the thermostat shut. That's not a problem until the car is warmed up to the point that the thermostat would open. With air bubbles trapped behind it, and the system sealed and under pressure, the t-stat can't open and you overheat.

Jack the front of the car up, so that the thermostat points upward at an angle. Start the car and let it idle. Give it some revs if need be (in neutral of course) to get it to start overheating. Watch the gauge and when you get 3/4 of the way to an overheat, you know you've got the bubbles stuck behind the t-stat. Shut down the car, let it cool enough that you can open the reservoir cap, and you should hear the air bubbles burp up into the reservoir. When you open the cap, you break the pressure in the system, so the t-stat can open. With it pointed upward, the bubbles flow through, up, and out of the system, into the reservoir, where they burp into the air. Top off your coolant if needed, and repeat as needed until the car refuses to overheat (should only take a few tries).

It's easy to do, and necessary. I would bet that this fixes the overheating issue.

 

thanks all fixed, burped it back to health

 

I would recommend checking the thermostat as well. Whens the last time you changed it out?
Event hough you need to bleed the cooling system, I don't think you should have coolant leaking out from there. It should flow to the tank.
Keep an eye on it and if it heats up again, check the thermostat.

 

Good call ITD...