Coolant leak on V6 driver side under intake

I walked out of work today to find a big puddle under my car so I popped the hood and saw the top of my transmission was covered in coolant. I tried to look under the manifold to see if I could find the leak but I couldn't get the proper angle. There's a lot of coolant relate hoses in this area so it's tough to determine which one it is for me without seeing. I was wondering if there was a common hose/gasket in this area that I should try first before tearing everything apart. The leak is coming down onto the transmission and rolling off towards the back of the car, I know that doesn't give much help to diagnose the problem, but if anyone has any ideas that would be help that would be great. It doesn't appear to be coming from the upper or lower hoses as I can see both are completely dry and have no drips on the underneath.

Your more then likely gonna have to take it apart to dianose.

have you pulled off the intake yet? That is where the water-neck is located. There's several holes in the block that connect to the water neck where it could be leaking. If you go in there with a flashlight, and try to follow the stream of coolant upward, you should be able to find the spot that it's leaking from. It could even be your upper or lower coolant hoses are tight enough. The coolant would run down the water-neck then start dripping down onto the transmission.

I tried recreating the problem last night to get a better look but couldn't get a leak out of anywhere. Then this morning after the long trip to work when I went to lunch I found the puddle again. This time I had a flashlight handy and I could see that the leak is coming from somewhere under the manifold, there was coolant visible when looking between each runner. I put my hand up and under each connection on the upper and lower hoses and there's no leaks there, and I couldn't feel any around the rest of the water lines that they feed into. I'm feeling pretty certain that the issue might be a bad head gasket as I was loosing coolant slowly before the leak happened, maybe every 2 months I would need to refill the radiator, but now it's been every day this week since the leak started. :(

Check the oil and see if there is coolant in the head gasket. If not, then you can rule the HG out.

Your thermostat housing is also in that same area, I would check that outand make sure it is sealed properly.

Check the two Throttle body coolant lines as well.

Last but not least, make sure the water pump is not leaking. If the water pipe is wet, and you can see coolant in between all the runners, the water pump might be leaking from the top, which explains why you dont see the coolant as soon as you park it.

yup.. check by the thermostat.

As mentioned already check the oil for coolant mixed in.

If oil is fine then I would suggest taking off the coolant crossover pipe (cast piece that connects to the front and rear heads). You will want to replace these gaskets, as well as pulling out the water pipe that connects the crossover pipe to the water pump. On this specific pipe each end has a rubber o-ring, if these "dry out" they can crack or shrink up and can allow coolant to pass by the sealing edges and allow coolant into the valley of the block (same can happen if one of the other crossover pipe gaskets fail).

The oil isn't milky at all so I'm going to have to say that the pipe running from the water pump to the cross over pipe is probably the culprit and is leaking on the water pump side. Everything on the driver side is completely dry to the touch when I can see the leak, so it must be coming from the only other area that I can't inspect which would be the water pump side. What's the normal process for replacing these o-rings? Is it as simple as unbolting the crossover pipe connecting the two heads and pulling the pipe out of the water pump, or does the whole intake manifold need to come off first?

the intake manifold can stay on. With the coolant crossover removed, the tube slides right out. Also, there is one bolt on the tube holding it in place before you start pulling. Luckily it's easy to see and remove.

Awesome, I'll try and get to that this weekend then. Thanks for all the help!

So, I've called a few dealerships and they can't tell me the size of the o-rings for the tube under the manifold, does anyone know so I don't have to pull this tube and find a ride to the store and I can get it before I tear into this?

I would suggest just getting them from the dealer. They are thicker than the typical o-ring of that diameter. I installed a standard sized Victor-Reinz o-ring and it has a slow leak since installed in May. I ordered the correct one from Mitsubishi this morning as a matter of fact. It cost $7 dollars, but that's what it takes to properly seal it.

You wouldn't happen to have that PN from when you ordered it do you? The dealership couldn't even provide it to me. Their answer was "we just take the pipe over and find the o-ring that matches right."

Just an FYI, after replacing the o-rings and having the same exact issues I ran out of time to try and diagnose this myself and took the car to a local shop. Turns out the leak was coming from the water pump, wish I had the time to replace it myself, not liking the bill that I'm going to see for this replacement... Thanks for everyone with their help on this one though.

Oh man wish I would have seen this earlier. Same thing was just happening to my car. The water pump was leaking and the stream was traveling across to the drivers side making it look like it was something on that side of the car. Finally after it got to the point of me pouring in coolant and hearing it pour right back out we were able to fix it. Expensive fix hope you knew the guy.

omg your wallet is gunna get raped...

The mechanic is my old land lord and my brother worked for him for years, so hopefully it won't be too bad. I'm supposed to get it back tomorrow so we'll see. Either way it's better than buying a new car.