Jay NE Ohio

No I am not running a winterfront. And it is long out of warrenty (1988 model). I tore off the fan clutch this afternoon. No wires, no air lines attached to it. I don't see any way to tear it apart. The hub turns by hand, so it is not locked up. I assume that it senses the temperature of the air by the little spiral thing (I have no idea of the technical name) and should lock it up at a certain temperature. Maybe I will stick it in the oven (when my wife leaves!) and see if it locks up???? I have attached a picture:

My 88 Mack tri-axle seems to be running warm. I've only been running it a month and the weather has been cold. Empty it stays around 190 degrees. When loaded it is running around 220. Red line is 230. The radiator is full and clean. However, I never hear the fan kick on and off like my freightliner does. With spring right around the corner, I want to get this fixed before the weather warms up. How does the clutch fan work on these 350 Macks? I took a quick look, but did not notice any wires or air lines in that general area. What is the most likely cause of failure? Thanks for any insight. BTW: A while back I posted about the fuel tanks pressurizing on this truck. I had a crack in the head which was pushing air into the return line which runs through the heads. I replaced the heads with rebuilt ones and all is fine now.

I think you might be onto something 'theakerstwo'. I have never drove a Mack before, so this is all new to me. It does seem to be a little low on power, as I had a hard time staying at 55mph empty up some hills in 5th gear high range. It is also idling slow (500 rpm). Thanks for the idea!

I still don't understand why it would build pressure. The engine is using fuel, which would create vaccum on the tanks over a period of time. Please help me understand. Here is the chain of events that I would think are logical: The pump draws fuel from the drivers side. This should create a vaccum on the drivers side. Gravity and vaccum should force fuel from the passenger side to the drivers side. Air should enter the vent on the passenger side as fuel level goes down to compensate. If the drivers side were to be vented, then no vaccum would be created by the use of fuel. Gravity should still level the tanks. The only explanation that I can think of is that the return fuel is heated as it is pumped and therefore takes up more space than the fuel that is being used. But this does not really make much sense as this would mean that the tank level would never go down as fuel is used??? Could air be getting into the system and being pumped back by the return line?? This would not make sense in a pressurized system though??? Or is my original logic flawed?

I bought a 88 Mack triaxle at auction and drove it home yesterday. It has a ~50 gallon fuel tank on each side. The fuel gauge is not working, so I checked each tank before I left and they both had about 9 inches. I went about 10 miles and ran out of fuel. At this point I went to unscrew the caps and found they were under considerable pressure (maybe 15 psi). The driver side tank was empty and the passenger tank now has about 12 inches of fuel. Of course it draws out of the drivers side and that is where the return line goes too. What would cause this? I put new fuel filters on and put some fuel in the drivers side to make it to the fuel station. The station was only a mile away and the tanks seemed to build up pressure again. I filled the driver side tank up to the top and drove it the rest of the way home with no problems. It was dark when I got home so I did not stick the tanks to see how much was left, but they were pressurized again. I looked in the tanks this morning and the drivers side is now half empty and the passenger side is full to the top. I did not put any fuel in the passenger side yesterday. The vent is on the passenger side. There is no vent on the drivers side. Just a suction line and a return line. The two tanks are plumbed together on the bottom. This thing really has me baffled. I thought that the tanks would have equalized overnight?????