Coolant leak mystery

[996C4SC]

Just drove home last week and steam was coming out from the rear of my 99 996 C4. Opened the trunk lid and verified it was a coolant leak. Search and read bunch of leak related issues and found the #1 cause is expansion tank so figure that it probably expansion tank. Got around this weekend to take a closer look. I disassembled down to the tank but without taking it out since it looks like a b**ch to snake it out so just started inspecting and looking at the coolant expansion tank where it is sitting. It did not looks like has any crack on it. I feel around the bottom of the tank and it also doesn't has any moisture or water outside the tank itself. By now almost all coolant in the expansion tank has leak out. I filled the tank up with some fresh coolant and trace the leak again; looks like the leak location is just below the water pump pulley but can not tell it directly leaking from the pump since there are belts and other stuff blocking the view. So my question is, should I take out the coolant expansion tank out and look further or strip down the belts and get down and dirty on the water pump? Has anyone has leak coming out of the water pump? Bad gasket? I hate to take out stuff and later find out it something else and I have already spent 8 hours on it. Any advise will be appreciated. Thanks in advance! :help:

Edited February 2, 2009 by 996C4SC

[Loren]

Coolant tank, hoses (especially on a 10 year old car), and water pump are all known problem areas.

You will need to let it cool down and then try to find the leak source.

[KevinMac]

I had a coolant tank leak, and I could not find the leak no matter how much I felt around. I removed my tank and it was on the very back side up where the tank gets welded together. I would see coolant on the floor after using the car in the size of a quarter. The coolant actually dripped off the header when parked. The tank would only leak when under higher pressure.

To get the tank out support the engine with a jack at the jacking location, not oil pan. Remove the rear left motor mounting nut, drop the engine and it will drop on the left side making it a much easier job! Gives you the necessary clearence. After i removed the tank sure enough there was an orange residue at the two leakng locations, but dry as a bone. I also replaced the hose clamps to all connecting hoses with full SS ( home depot, car parts stores are not full SS) ones that can be tightened via a crew.

If you remove the tank be careful of the coolant level switch located in the bottom of the tank.

Edited February 2, 2009 by KevinMac

[996C4SC]

Ok, Loren has a point so I decide to change out both the water pump and the coolant expansion tank while I am at it. Hopefully that will fix the cause since I can not find the leak so far and both item will fail eventually. I am alittle price shock comparing my coolant expansion tank (99-01) cost vs. the later 996 tanks(2002+). Does anyone know a good price for a coolant expansion tank? Is it possible to swap a later tank(2002+) on a 99 996? Currently, I almost got the water pump out; all 6 10mm are out except one 10mm nut next to a pulley that is taking forever to get it out-I can only do one or two clicks at a time on my rachet due to the limited space. Thanks again!

Edited February 2, 2009 by 996C4SC

[Loren]

Ok, Loren has a point so I decide to change out both the water pump and the coolant expansion tank while I am at it. Hopefully that will fix the cause since I can not find the leak so far and both item will fail eventually. I am alittle price shock comparing my coolant expansion tank (99-01) cost vs. the later 996 tanks(2002+). Does anyone know a good price for a coolant expansion tank? Is it possible to swap a later tank(2002+) on a 99 996? Currently, I almost got the water pump out; all 6 10mm are out except one 10mm nut next to a pulley that is taking forever to get it out-I can only do one or two clicks at a time on my rachet due to the limited space. Thanks again!

I wasn't suggesting changing everything out - I was suggesting finding the real source of the leak.

[996C4SC]

Loren, I know. Since I am taking it out anyway I might as well replace it with new parts. The car has 82K on it and the tank and the water pump has not been replacement since new. I rather replace it now while it's in the garage then it break down on the road. It's just for my peace of mind ....No blame on you. :) However I will inspect both parts carefully and find the root cause of the leakage. As long as it's not something serious like a crack block or something like that...cross my finger...

[996C4SC]

Just wanted to post my reason update on the coolant leak problem. I replaced the water pump and it solved my leakage problem. Thanks to the writeup on the water pump replacement post! I did have to take out 2 extra hoses (not mentioned in the writeup) next to the water pump to completely free the pump out-maybe my was a C4S instead of a C2. Anyway, when I pull out the pump, I spinned the pump manually and hear a squeekie sound coming out of the old pump; and the resistance of the pump is at least 3 times more than the replacement pump. This gave me some assurance that the leak was coming out of the pump or the worn bearings. No leak after the installation! I still want to replace the expansion tank since there are bunch of people here that have problem with it later when I have free time. I just want to thank all the advise I got here. :renntech: