Cat c15 Sdp air locking

I would look over the flow of the heater lines carefully. Is it possible that a bunk and cab hose got reversed accidentally sometime during the rebuild or repairs. It sounds as though you have no flow through the core. Trace out the flow path from the engine to the cores and back and make sure it all makes sense.

 

I would put a pressure gauge in the side of the block and watch the water pressure. What does it read and does it fluctuate? Some old cats run about 35 LBS.
I have seen a clear hose ran from the thermostat housing area to the suction side of the water pump. Bubbles indicate air in the system. I believe that is from an old Cummins book. However I would want to do the same test done on a sister engine before I did a lot of work based on those results.

 

Impeller can slip on the water pump. Usually they just totally fail but I have seen some come and go possibly with temperature. Cost some guys a lot of cash chasing it. Most I have found that way showed up in the shop but one had to be driven a few miles before the pressure started fluctuating wildly. Tie strapped gauge on mirror bracket.

 

Water pump outlet is to oil cooler. Piping from thermostat goes to suction side of water pump. When themostat is fully open, this pipe is under suction. Could be your air entry point. Fix those leaks!

 

1 drip a second is a lot. That would definitely lose pressure quick I would think?

 

Gotta remember too that liquids aren't compressible, so a few drops could lower the static pressure a lot quicker than if it were air.

 

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Illustration 1 g01321232
Cooling system for a warm engine

(1) Cylinder head

(2) Water temperature regulators

(3) Outlet hose

(4) Vent line

(5) Vent tube

(6) Shunt line

(7) Elbow

(8) Water pump

(9) Cylinder block

(10) Clean gas induction CGI cooler

(11) Precooler

(12) Oil cooler

(13) Radiator

During operation, water pump (8) sends most of the coolant from radiator (13) to oil cooler (12) .

The coolant from oil cooler (12) goes into cylinder block (9) through a bonnet and an elbow. The coolant flows around the cylinder liners into the cylinder head.

The flow of coolant into the head goes around the valves and the passages for exhaust gases in the cylinder head. The coolant then goes to the front of the cylinder head. At this point, the water temperature regulators (2) control the flow of the coolant into the radiator (13) .

Water temperature regulators (2) are closed when the engine is cold. The coolant flows through the regulator housing and elbow (7) back to water pump (8). This is done in order to increase the operating temperature of the engine coolant.

If the coolant is at normal operating temperature, water temperature regulators (2) open and the coolant flows to radiator (13) through the outlet hose (3). The coolant becomes cooler as the coolant moves through the radiator. When the coolant gets to the bottom of the radiator, the coolant goes through inlet hose and into water pump (8) .

Note: Water temperature regulators (2) are an important part of the cooling system. Water temperature regulator (2) divides the coolant flow between radiator (13) and bypass elbow (7). This will maintain the correct temperature.

Shunt line (6) gives several advantages to the cooling system. The shunt line gives a positive coolant pressure at the water pump inlet that prevents pump cavitation. A small flow of coolant constantly goes through shunt line (6) to the inlet of water pump (8). This causes a small amount of coolant to move constantly through vent tube (5). The flow through the vent tube is small and the volume of the upper compartment is large. Air in the coolant is removed as the coolant goes into the upper compartment.

The vent line is used to fill the cooling system with coolant for the first time. This will purge any air out of the top of a bottom filled system.

The OEM may supply a surge tank. The tank can be mounted on the radiator or the tank can be mounted on a remote location. The coolant that expands past the radiator cap is retained in the surge tank. The coolant contracts as the temperature drops and the coolant is drawn back into the radiator.