Over heating at higher speeds

[jethro 03]

Hello all, newer member here. It's even my first post. I have a 2003 4.7 qcsb. It's running very hot at highway speeds, especially under load (higher rpms, not towing). It gets up to 3/4 to 7/8 up the gauge. If I back off to 65 or less, it goes down to half way. I changed the clutch fan and doing the tstat tomorrow. Has a new radiator from before I bought it.

The top radiator hose was hot but I could still grab it. The bottom hose was cold. Shouldn't the lower hose be hot also?

Not sure if this is related, but I can move the belt tensioner by pulling on the belt with hardly any effort. Shouldn't it be tighter?

Sorry for the book first post lol. Thanks

Sent from my SAMSUNG-SGH-I747 using Tapatalk

 

[MegaMouseGW]

First welcome to RamForums.

Now for your problem: If the belt is easy to move then the tensioner needs replaced. DO that first. Now check under your truck after driving for a bit and stopping in a clean spot I a parking lot (ok good luck finding a clean spot), or before you go to bed stick a piece of cardboard under the front of the engine. What you will be looking for is what may look like water on the ground at the front of the engine or a wet piece of cardboard. If that happens then the water pump is out and needs replaced. Now another check for proper water pump function is to take the radiator cap off, start your engine, and look for coolant flow where the cap goes. No flow bad water pump.
It sounds like the water pump is out and should be replaced, while you have the time replace the thermostat also to eliminate it failing in the near future.

 

[NYCruiser]

Definitely not enough tension if you can flex it easily by hand. Change the tensioner. The belt is probably slipping at high RPM's. Also inspect any idler pulleys and the belt at this point and change them while you're there. Sounds like it will be easy to get the old belt off..LOL

Also - your truck is old enough to warrant an antifreeze change if that hasn't been done.

Water pump has a weep hole that works as a tattletale to tell you the bearing/seal is shot. The pumps still pump fine when that starts failing. Unless you are seeing leakage, or having to add coolant, I wouldn't worry about the pump yet as mentioned above.

 

[jethro 03]

Thanks for the replies. I planned on flushing the system with the thermostat change anyway. I'll have to look into a tensioner as well. I didn't think it should have been that easy to move. I'm a strong guy, but I barely had to try lol.

I will definitely be inspecting the water pump while I'm at it.

Sent from my SAMSUNG-SGH-I747 using Tapatalk

 

[jethro 03]

For anyone that sees this, I changed the tstat and the belt tensioner and all is good now. Not sure which one did the trick or a combo of both, but the temp stays just below half all the time.

Sent from my SAMSUNG-SGH-I747 using Tapatalk

 

[ercmesser]

Did you check the water pump for play? my pump failed but didn't put out a drop. The bearings had so much play that it would move about a quarter inch each way, but my truck never over heated.