I am assuming that your question is "how to increase the flow rate" and that your pump is a centrifugal pump.
For centrifugal pumps, the flow rate out of the pump is dependent on the pressure at the exit of the pump. If the pressure is high, the flow rate will be lower. If the pressure is low, the flow rate will be higher. That dependency is typically illustrated for each pump in a graph of flow vs pressure which is called the pump's "pump curve".
For fluid systems with a centrifugal pump, the flow rate will be reduced by each element (tubing, fittings, valves, etc.) in the system. Each element added to the system increases the pressure and reduces the flow.
My first step would be to find the pump curve for your pump and measure the pressure at the exit of the pump. This will tell you two things:
- is the pump operating correctly?
- is the pump operating against a
relatively significant pressure?
If the pump is not achieving the flow rate indicated on the pump curve from the pressure you are measuring, it may need to be rebuilt or replaced. If the pump is generating its maximum flow rate already, it will need to be upgraded.
If the pump is working correctly but not at maximum flow, you next step depends on the complexity of the system. It may be easiest and cheapest to upgrade the pump to one which will generate a higher flow rate against the pressure you are seeing. Or, it may be easiest and cheapest to investigate the other elements in the system and replace the problematic ones.
If upgrading the pump is not an option, you will need to determine where the restrictions are in your system. The ideal way to do this is to place pressure gauges in between each element and look for the highest pressure difference. I would start with one between pump and radiator, between radiator and intercooler, and between intercooler and pump. Whichever element has the highest pressure drop will be the one which is causing the most restriction to the flow.
- I expect the interior loop is not reducing the flow rate substantially.
- If the tubing is a significant restriction, increasing the inner diameter of the tubing can increase the flow rate dramatically. Reducing the length will increase the flow rate but may not have as dramatic an effect.
- Each valve and fitting reduces the flow rate. If you suspect the fittings or valves, you might replace them with higher Cv (https://en.wikipedia.org/wiki/Flow_coefficient) versions.