Alright. So I have read all of the threads and there is good speculation and information but nothing confirming anyone had solved their problem and are running and kicking ass. Here is a run down of my last 4-6 months dealing with this thing.

1. Truck ran and started awesome for me besides some minor tweaks here and there for the first six months but had an intermittent heat issue particularly when it was under a load. The gauge needle would reach an eighth of an inch below the top warning line.(white line not the red). I replaced these things.
A. Water pump.
B. Radiator hoses
C. Thermostat (went from 195 degrees to a 170 degrees)
D. Radiator cap (twice)
E. Reservoir hose and cap
F. Flushed the bejeesus out of the radiator every time I emptied it to replace something and a few times just for that.

2. After these measures the issue finally presented itself in full going up a hill after driving it for about an hour. While going up the hill the needle reached the top white warning line and I had to pull over after coasting the hill. The reservoir was spewing out air and coolant. Head breach. After reading the forum and from what I had seen on the one in the salvage, the head cracking isn’t uncommon, so I began my plans to replace the head.

3. In the process of preparing for the head swap I decided to have the radiator serviced and rodded, and had the turbo, injectors, and injection pump rebuilt.

4. I had a hard time finding a protruding valve head and the one I did find was sent to me with a stuck camshaft, so I decided to try the 4d56 head swap to flush valve. From reading on the forum it appeared others had done this and it had worked fine. The problem is that the threads usually end in advice given and the user with the error never gives conclusive evidence of the project turning out great for them. My assumption was that this meant they were rolling down the road, if they weren’t they would have been back for more advice. So I went for it.

5. I found out during the head swap my head seemed to be fine, but my issue was a misprinted gasket. The metal between pistons to seal the water channel was on the wrong side of the gasket, and it only goes on one way. That being said, my camshaft was junk, and I had mix matched caps from two engines. I still wanted to go with new stuff.

6. These are all the things that have changed or been replaced during this process.
A. Rebuilt Turbo. They used a TD-05 cartridge in place of the TC-05 cartridge because of part availability and to be easier to repair in the future.
B. Had radiator serviced and rodded.
C. Injectors rebuilt.
D. Injection pump rebuilt. (They replaced what needed it, really only the lift side appeared damage during operation, it was assisted by a 5-6psi 30gph electric inline pump)
E. MLS head gasket.
F. 4D56 flush valve head.
G. New oil and fuel filters (the water separator under the hood, and one I had before the electric pump, at this point with no electric pump and just the filter.
H. Flex a lite engine driven fan.

7. I had some issues getting it bled and started the first time, my primer handle doesn’t function, so I put the electric pump in the chain and bled it through the screw on top of the water separator and then to the timing plug on the injection pump. I had left injection lines cracked and spun the key a few minutes until diesel was spitting out of them, tightened them down, spinning the key between. Still not wanting to give it to me, so I used a squirt or two of ether. Started up rough, lots of white smoke, but eventually calmed down and sounded great. From then on it would start, albeit it rough, lots white smoke out of the exhaust, and lots of working the accelerator, then calm down.

8. During this I bullseyed an ear plug down an oil drain tube. Had to remove the pan and retrieve it. Wasn’t going to let that destroy my engine, and wasn’t going to be able to sleep knowing it was in there. Found it. Got the pan back on and took the opportunity to replace the steering components and the rubber on the stabilizer bar. Aggravating, but got something I needed to do done in the process.

9. Drove it the first time around the block and to the alignment shop. Cold start always sucks, lots of accelerator pedal to keep it going at first and high volumes of white remained. When warm, would start repeatedly on half key turn, right to 750 rpms idle and sounding great. In between warm and cold, the truck refuses to start. Glow plugs decide it is too warm to need their help, yet not warm enough to give me the half key turn start. If you unplug the temp sensor, glow plugs initiate and it fires right up, but rough and shitty as usual.

10. With the truck aligned, test driving truly began. Sometimes the thing would take off awesomely, and drive that way for 10-30 miles, then get incredibly bogged down and put out a lot of black smoke. More than I remembered it doing before, or what seems normal for it.

11. I found some leaking diesel around injector 1 at the return rail. Considering this and my compounded issues, I took these steps.
A. New return leaf washers.
B. Extra couple foot lbs torque on the injectors.
C. Replaced all fuel lines under the hood.
D. Put Teflon on the threads of the primer handle.
E. Adjusted down the throttle screw and the total fuel screw up until I was back at the idle I wanted. This time closer to 900 than 750 rpms.
12. I bleed the system of air again, and this time I leave the electric pump in line. Starts like crap, but smooths out. I drive it. Intermittent power loss. Will drive like a dream with more power than it has ever had, and then go limp and act completely starved.
A. Replace the fuel tank.
B. Warranty out the electric pump for one with 7-14psi 35.5 gph.
C. Another new filter before the electric pump.
13. Found out the tank had been coated with something on the bottom that looked like white paint. I assume some sort of rust treatment. Flakes a big as dimes of it floating around. Worth mentioning now, I had seen these flakes in the back filter (it’s clear) and in the plug for the water separator filter. Thinking I had my smoking gun, I start it, I drive it, same results. Lost at this point, I call in help from my mentor and diesel guru to come in person.

14. We check over some things, make sure the system is bled. We try some things.
A. Swapped the fuel cutoff solenoid with the one on the other pump. It is activating better.
B. Remove part of the exhaust and the muffler, inspect with flashlight, and test drive.
15. With the muffler off, there is an obvious noise when the power loss occurs, likely it is misfiring, but intermittent. I let the more knowledgeable and skilled mechanic load up the truck and take it with him. He tries these things.
A. Found the set screw missing and the screw backed all the way off on the 8th rocker arm. Replaced it. Poked around the head to find it, hopefully the drain pain. Never had any noise as if something was rattling and everything still looks cherry.
B. Had my spare injectors tested, they function great, so he swaps them. Finds the current injectors soaked and dripping of diesel. As of last night, we thought it fixed it, drove it around never made the noise, never lost power. He waits till morning and tries a cold start. Still sucky.
C. Trouble shoots the glow plug system and finds that the 6v relay is completely toasted not activating. The wires appear to be getting super hot going into it. He will be wiring a manual set up tomorrow.
D. Ran a compression test. 1-2-4 read 350psi, 3 reads 325 psi. That is in the pocket of what I want? Not cool 3 isn’t the same, but doesn’t seem likely to be the problem?
16. Next few days he will have the injectors he took out tested. Will wire manual control for the glow plugs. After double checking all the timing marks and the injection timing for the 100th time, remove the pump and take it back to the guy with the injectors and have the system ran on a table.


Any thoughts here? Anyone running a 4D55 block to flush valve 4d56 head with no problems? I feel like we should lock that down definitively and not speculatively. Maybe I missed something somewhere but all the threads on the subject tend to trail off and end before reaching no “maybes” answer. I’m going insane and honestly running out of things to check or replace it feels like. But I am also way to close to it and emotionally kind of thrown for a loop on this thing. Will drive great then suck, start shitty, then idle like a dream. Gets me up thinking I’ll be driving it to work again, then fails me in the morning when I try. Need more opinions that are further away from it.

I have some pictures and videos if you are wanting to see any of it. Unfortunately the truck is an hour+ away from me right now, but fortunately in more capable hands. For fresh photos, etc, will have to wait till Sunday at least when I could get over there.