Yeah thought about that but i already have two small leaks at the thermostat housing and the temp sensor near the driver side glow plugs so wouldn't that effect the test? Also I don't have the typical milky coolant or brown oil that I would expect to see from you average head gasket blow out. I'm starting to think about doing a compression test and then if all is good pop testing the injectors on the passenger side bank.
Any leak in the cooling system that isn't repaired can affect the pressure test of the cooling system. But, a pressure test can indicate other possible areas of leakage. I recommend repairing both leaks ASAP. Use a wire brush to clean the thermostat neck, especially where the upper rad hose connects and on the gasket surface. I run mine against a wire wheel attached to my bench grinder. Comes out nice and shiny. You also need to use a stiff brush on the gasket surface of the crossover. Get that nice and clean as well. Stuff a rag into the crossover to keep junk out, but don't forget to remove it before closing things up. Use a good quality gasket (FelPro #35271) and apply a gasket dressing to both sides
sparingly (I use permatex water pump & thermostat housing RTV silicone with good results). Might as well replace the thermostat while you have it open. If you've never removed the neck before, be ready to deal with a stuck bolt or two, especially the lower bolt. Worst case you will need to repair the threads in the crossover with a helicoil, M10 - 1.5 x 35 is the bolt size, but a 40 mm will work just fine (ask me how I know
). Anti-sieze is your friend on reassembly.
Since the clamps on these hoses are pretty old, and the engine side upper hose clamp serves a dual purpose of keeping the drivers side alt belt from destroying the upper hose, I put a second #32 clamp on the inboard side of the hose. There is plenty of room for it. Just a little insurance.
+1 on the compression test. This can indicate overall health of the engine. Understand you
can't squirt a little oil into the cylinder on these engines to determine if a compression issue is rings or not like you can a gasoline engine. Check the TM's for the procedure.
Milkshake in the oil or coolant would only occur if the leak allowed either/both to contact. You may be diagnosing a compression issue only, where cylinder pressure is back feeding through a tiny passage in the head gasket into a coolant passage. Check this out:
Headgasket Check - YouTube. The kit mentioned is available at A-Zone.
+1 on the injector pop test. The fuel injection system timing on these trucks is governed by the IP in conjunction with the injectors. The injector must pop at the correct pressure in order for the fuel to be injected at the proper time. Check this out:
http://www.thedieselfiles.com/Ford/Stanadyne%20DB2%20Operation%20and%20Instruction%20Manual%2099009.pdf
