99 C3500 overheating

[Joemcwhorter]

My 99 C3500 keeps overheating, I have performed 2 coolant flushes, replacement of t-stat and now even removed it. Nothing blocking airflow. I’ve tried burping the system using a leak proof funnel and it will overflow the funnel when I try this. I have a new radiator cap and radiator is fairly new. I rented the system test and it held pressure just fine, also didn’t fluctuate when reving engine. I am at a loss and any advice is greatly appreciated!

[Ferrnt]

Don't like replacing parts to troubleshoot... Have you checked your temp bulb?

[CadillacLuke24]

Have you tried a block test to check the head gaskets?

[Joemcwhorter]

I have done the block test and it checks out, I haven’t done anything with the temp sensor but I know that it is getting hot. My coolant is boiling and can’t drive for 15 minutes before red line. I don’t know if I just haven’t gotten all the air out of the system or water pump is bad or what. I do know that after the short drive there is so much pressure built up in the system that I can not hardly squeeze any of the hoses even the ones coming from the heater core. Once it cools down and bleeds the coolant back out of the overflow I can add about a quart of coolant and still get the same results.