beforeyougo

After doing a head gasket change, I noticed i have a coolant leak. Diagnosed it to be coming from the bypass hose/pipe behind the thermostat under the intake manifold where the coolant is pooling around the valley pan. Lifted the intake manifold (again...) and I'm trying to figure out how to get it stop leaking. I tried moving the pipe around but its solid metal and not the easiest thing to move. In addition, its connected to the back of the cylinder heads. Has anybody else encountered this? If so, how did you get to stop leaking. Any other suggestions are much appreciated as well.

I'm including a picture of the cooling system diagram and the area i'm talking is shaded in gray right behind the thermostat.

Thanks in advance. Cheers!

beforeyougo

Scratch it. Saw the post from earlier. O-rings it is.

jkerton

Doing mine as well. Just got the four O rings from the dealer. The two at the back of head are the same size O ring and the two at the front block are different sizes.

ezveedub

Change all those o-rings for the pipe and IF the pipe is really corroded, you might want to replace it also.

hubturn

If you have the pipe out, loosen the bleeder plug. It can be difficult to open it with just the allen socket.

jkerton

ah...good point!

jkerton

Would changing the O2 sensors be a good idea too?
Car has 200,000 miles on it. Seems hard to access after all the plastic components are in place.
V6 12v

hubturn

They are suppossedly good for a about 100,000 miles. Depending on your year, you have two or four. Two in front of the cat and if four, two behind the cat. They can be pricey, particularly if you get exact match wiring. Without a Vag-Com, you don't really know how they are functioning. I've never checked mine. You can do basic tests with a multimeter, such as testing the sensor heater for continuity. Without a code or a MIL light, you would be doing preventative maintenance. Probably not a bad idea, and much easier with the exhaust manifold on the workbench. Bentleys Cautions: use anti-sieze on the threads but use care to not get any in the sensor slots. Do not use any silicon products in the intake system as the vapors do not combust and will damage the O2 sensor. Do not use cleaners on the wires as they will draw the cleaner into the sensor through capillary action around the wires. So, no RTV in the intake system, such as the gasket that splits the IM in half. Be sparing with the anti-sieze. Just a bit will do.

jkerton

I'm doing the IM work because of the EGR code P0104. While everything is out of the way, I figured I would see what I could replace while I had the room to work. As far as I remember, I had not had any O2 codes but was being proactive with the thought of changing them with everything open. O2 and its wires/connectors seem to be buried at the back of the engine area. Not easily accessible later.

hubturn

It could be my imagination, but I think doing the EGR port polish procedure and changing numerous vacuum lines (as suggested by many experienced posters) affected my engine operation significantly. The ECM has a learning function and the newer ones have more learning capability. New O2 sensors will affect that. I'd do it. Clean the MAF wire. Double check the attach point for the EGR tube on the back left side. It can be loose.