Unexplained Coolant Loss

[Blindaviator]

Well I made the 2100 mile trip from northern California back to Texas. But along the way I started to have coolant loss issues.

 

I had the truck about 2 months before the trip and probably put about 1500 miles on it with no issues. During the trip I made it all the way out the south end of Cali and just hit I-40 when I stopped for some rest. In the morning I checked fluids and the coolant way dry in the top of the radiator. I ended up adding almost 1/2 of a gallon between the radiator and over flow. I also stopped at a Vatozone and picked up a new Radiator cap just in case.

 

During the rest of the trip I would stop about every 200 miles and let it cool down. I would have to end up topping it off but it was only about maybe 12-16 ounces each time. By the end of the trip I had just used the last of that gallon to top it off. So 1 gallon in 2100 miles of constant driving.

 

I have seen no obvious signs of a leak other than some coolant would be pushed out of the over flow when I dropped off the highway to get fuel or food and that was only a very small amount. That in it's self should not happen in a normal running system unless the system has built up a lot of heat and you slow too quickly.

 

Normally no leaks & coolant loss would mean a head gasket leak but I have seen none of the other classic signs of that. No foamy coolant, high pressures or rapid pressure loss when shut down. It would hold pressure for 3+ hours after being shut down which tells me there isn't a leak. I also dropped a bottle of the Bars Leak Liquid Copper when I first saw the low coolant. Normally if it was a leaky head gasket that stuff would temp seal it and stop the leak until you can replace the gaskets. It didn't make a difference. I finally figured out where the water pump weep hole is and as best I can tell I don't see any water coming out of it.

 

I started to notice on the last leg of the trip a growling noise. It is the classic sound a bearing makes in the water pump or idler pulley when it starts to go out. I will be taking the belts off later today and start it without them to see if the noise continues. If so it will be time for a water pump.

 

At no time during the trip did the water temp get much above 190 (I used my OBD2 scanner in live data mode to monitor it). Even when pulling up the steep mountains at 75mph.

 

No overheating. No obvious leaks.

So anyone have any suggestions on what to check to determine the problem?

[Cuong Nguyen]

Check the coolant elbow that feeds the lower intake plenum up front of the motor under the top coolant tube. Also check to make sure the hoses in the back for the heated throttle body.