1998 ram van overheating...

Hello all and thanks for helping me out in advance. I am working on a 98 ram van with a 3.9 for a friend of mine. the problem is that when he runs down the highway at about 70 mph he starts to over heat. But when he slows down to 55 mph the van cools down to normal again. Then he can run around all day at 55. I just replaced water pump, thermostat and radiator cap. Everything I could think of for overheating. Besides radiator. I looked at the oil dipstick drained oil and all no sign of a head gasket leak. So what else so I look at and all. He claimed he did a flush on the cooling system before I did any of my work. Any thoughts would be apprecitated.....thanks again

1. A bad sender.
2. A bad gauge.
3. A restricted radiator.

First you will need to verify that it is really overheating by using a thermometer. You can check the radiator by feeling it from top to bottom and see if it's evenly hot. If you find a cool section then it's likely the tubes in that area are plugged. A back-flush might solve it, but more than likely a new radiator will be in order.

Hello all and thanks for helping me out in advance. I am working on a 98 ram van with a 3.9 for a friend of mine. the problem is that when he runs down the highway at about 70 mph he starts to over heat. But when he slows down to 55 mph the van cools down to normal again. Then he can run around all day at 55. I just replaced water pump, thermostat and radiator cap. Everything I could think of for overheating. Besides radiator. I looked at the oil dipstick drained oil and all no sign of a head gasket leak. So what else so I look at and all. He claimed he did a flush on the cooling system before I did any of my work. Any thoughts would be apprecitated.....thanks again


does it leak? after it overheats do you check the amount of water in the radiator?