losing antifreeze

1/4 to 1/2 gallon per week isn't really that big of a leak...not enough to notice any puddles under the truck, anyway. You'll probably have to look hard at each end of every hose and put a screw driver on every hose clamp to make sure they are all tight. You MIGHT get lucky and see a drop that hasn't dripped yet....or perhaps just a little moisture. If the truck never gets shut off, the drops could be evaporating as fast as they are leaking out.

A few years ago, I was in a brand new 2006 Petercar and was having to add coolant every few days...not much, but enough to strike me as unusual seeing as how this was a brand new truck. I didn't find the loose hose clamp until I left the truck shut off overnight and had time to kill in the morning. I finally was able to see where the hose was wet on the end...tightened the clamp and the coolant loss stopped.

 

Ouch, I got to do that a couple months ago. At least mine was an external leak.

 

Peterbilt in Sioux City has checked every hose and clamp as have I, they didn't believe me, so I paid them to do it as well. I've left it in my shop with the heat off this winter, no leaks on the concrete floor after a three day weekend at 15*. Believe me when I say I have explored all the simple things......

 

My guess would be the head gasket since there is no visible external leaking.

 

Check transmission, could be tranny cooler leaking.

 

Finding these water leaks can be a bi#@!, but going along with the heater core post or any heater hoses to the cab and sleeper, I always install shutoff valves from the head to heater and the return line. This will eleminate that section from the list of possibilities. Someone mentioned the leakdown test, always one of the first things to do, get a radiator pressure test kit and pressurize the system and see how long it will hold the pressure. A radiator could have a pin hole or bad seam and only expanding and leaking when it's hot, alot of trashy radiators were installed on some of these trucks.

 

Oops, went back and reread the entire thread and realized I'd overlooked or forgot what you posted in post #12, maybe someone else can use the above info in another situation.

 

I change my headgasket in a shop in miami,totalbill was little more then $2100(the labor was only 850, the rest parts,oil,Filters, ,thermostat and more)

 

The very first thing you do when ever you are loosing coolant is get the Rad cap tested.
A bad cap will allow the water pump being it is a centrifical pump to draw in air.

When you get the bill for the head gasket change look to see if they put on a new Cap. You may have paid $2,090, to get a $10.00 rad cap

 

I've checked mine, new lube this weekend in fact. Looked good, it was just time from a mileage perspective. I've also checked the precooler, dry as a bone. New radiator cap when it was at Peterbilt(3rd one)! Like I said, I've done all the simple things including the pressure test on the radiator. I think it's either a head gasket or head, I just can't get Cat or Peterbilt to bite!