Mystery running issues
I have frustrating problem. I have a 2004.5 lly with 219,000 miles. I bought it with 217,000. It is stick, a California emissions truck. When I got it it was losing coolant and had a hard upper hose. The coolant loss was a little at a time.
Last March I took the heads off, had the heads rebuilt, I sent the injectors off to california to be cleaned and checked and revalved if needed. I rebuilt the fuel filter head had the heads checked and shaved and rebuilt. I put OEM head bolts in,put it back together finally and started it the day after Christmas. The injectors were a bit out of balance, they seem to have significantly cleared up since.
I have put about 100 - 150 miles on it now. It has gone through three heat cycles. And it looks like I am losing coolant at the same rate as I was before. My oil is clean as if it came out if the bottle(I put a double filter system in it plus took the oil pan off and cleaned out the black and coolant I spilled when I took the heads off)
Several things started happening.
At first I was running doesn’t he interstate a few times at 75 to get the injectors going and to get heat into it to cycle the air out of the coolant. I did the air screw and all of that jazz, but just needed to cycle. When I pulled if the interstate at the first light it started to run rough, noticeably not terrible it was 33 degrees out.
On Tuesday, I took it down the highway and when I hit 50-55, under power,It started vibrating like a worn driveshaft. It went away when I left off. It would return under power. I parked it in my driveway and the engine will fluctuate between running smooth and running rough, enough that the engine shakes. It will eventually run smooth at some point, but it fluctuates back and forth.
Now, my upper hose is tighter? Not super hard but pressurized when the engine is hot, but it relaxes as the engine cools. It wasn’t tight like it was before I did head gaskets.
I drove it maybe 20 miles on Tuesday and my coolant dropped 1/4” in the tank.
Also, a day after I drove it, I checked my fuel filter for tightness and pressure, and I had to pump it up and I had no fuel come out the Schaffer valve before I pumped it. Some bubbles came out after I pumped it.
I am wondering if my EGR could be causing some pressure or coolant loss. I also have a wet looking spot on the lower corner of my radiator below the lower hose, but I think that is from the trans line being reinstalled.
From anyone s experience, can an EGR system leak, be tested for leaks? Can it cause any of these symptoms?
Any other suggestions as to where to look?
2004 LLY Duramax.
Silverado Crew Cab LT