Water Pump?

[bagge72]

I have a 2004 V8 LS with 112,000 on the car, and 82,000 on the motor (I know I drive a lot I have 2 jobs, and a girl that doesn't live so close) Just the other day I noticed that when my car was up to temperature that it was still blowing out cold air no matter what the heat setting was on, until I had been driving for about 5 minutes or so. At first I thought maybe it was the T-stat, and it was just stuck open so it was taking a while to heat up. Then last night on my way home my car actually overheated, so I let my car cool down, and found out that my car was down about a gallon of anti-freeze which explains why it was blowing the cold air for so long. Now obviously I must have a leak some where, but I have not left any puddles any where that I park, even when the car is running and in park so I'm guessing it isn't one of the hose's, the radiator, or the degas bottle. So I was wondering if anyone had a way to find out what was making it leak while I was driving?

Thanks for any help anyone can give me.

 

[02LincLS]

I would start by assuming air in the system (from a cracked expansion tank) caused everything. In extreme cases, this can prevent proper flow and boil the coolant locally. The over pressure from this then causes the expansion tank cap to vent. This can certainly happen while you're driving so you won't notice a puddle. I bet if you look under the hood, you'll see or even smell coolant. It also likes to drip down the topside of your plastic fender shield (peek under the car as you can usually see drips coming off of the top side of it).
Still, inspect the expansion tank as it is usually cracked (hairline and difficult to see) in blind locations. I think this causes a slow coolant loss over time, or at least allows the water to evaporate out. As the car cools back down from being hot, it pulls air in through these cracks. I posted pics of my junk expansion tank in this thread.

 

[bagge72]

Thanks for all of that info, I will be pressure testing the system this weekend to see if I can spot where the leak is, and I will definitely make sure to check the expansion tank.

 

[02LincLS]

Of course there's a bunch of other potential causes, but that is a good place to start before throwing parts at it.

 

[Lincoln Jealous]

if you lost that much fluid i would say its your degas bottle, you overheating probally evaporated the spilled coolant, next time when your overheating check under the hood while the temp is rising, youll find the leak, the degas bottle leak would happen around the driver side wheel well