Hey guys...

I have a mysterious coolant leak I am trying to locate/fix and was wondering if you guys had any input. It has only done this 4 times now; the day I brought it home, twice after using the air condition, and today (didn't use the air condition).

It only seems to do it when the engine is COMPLETELY warmed up (Oil Temperature indicator is between 200 and 225 degrees) and the engine has been running for at least a half hour. It has yet to do this in an area I can lift the car and see where it leaking from. I took the belly pan off and went for a drive last week hoping to duplicate it but wasn't able. However I have left the belly pan off since and it seems to be leaking on the driver's side of the engine. I'd say if you were looking at the puddle from the top of the engine you'd be looking in between the engine and the wall that separates the battery/computer compartment from the engine compartment. This is just an estimate too, so keep that in mind.

It does form a puddle, but it doesn't leak a lot. It makes a noticeable drop in the reservoir but I'd say no more than 1/4th of the reservoir height diminishes. Now someone before me had flushed the coolant system and put regular green coolant in. I have G12++ to put in after flushing again but I want to fix the leak before flushing. The car is stock. Any help or suggestions would be greatly appreciated!

Thanks,
Brett

 

Auxiliary water pump? Try looking under the intake with a flashlight and see if you can see any dry G12.

 

I tried looking in there from the back of the engine but didn't see anything. I'm gonna take off the Y-Pipe tomorrow and see if I can't see anything from the front.

 

I'd put money on it being one of the following:
- aux water pump;
- one of the 2 x coolant temp sensors or their o-rings; or
- cracked coolant reservoir.

 

really sounds like the aux water pump. I had the same exact thing (leaking from the same location roughly, and leaking the same amount after running it similar amount of time). You can look between the spaces on the intake manifold and probably see a bunch of dried up pink coolant around a small black pump with two 1" hoses and a sensor wire coming away from it toward the back of the car. You can also look down from the hole by the drivers side diverter valve that dissapears into the top middle of the engine. Good Luck!

 

Already replaced the Coolant Temp Sensor and the Coolant Reservoir, leaving the Auxillary Water Pump and the After-Run Thermo Switch.

I looked in from the back of the engine with a flashlight last night but couldn't really see anything. I was going to take the Y-Pipe off today but it's raining so I'll try and do that tomorrow.

 

Check if its coming from the bell housing. s4 has a water cooles rear main seal. those go bad every now and than and start leaking. if you under the car check the area where transmission bolts to the engine.