Cummins 5.9HO and has a miss / blowby /blowby tube oil. Just purchased the truck and discovered the problem. One mechanis says injector issue amd another says valve issue but neither one explains blowby issue. Another mechanic says he thinks a burnt piston / cylinder wall and can be a result of being turned up to much. What should I do to diagnose the problem / what steps. Whay is the best way to identify which cylinder. HELP
Model: 2500 Mega Cab 4x4 automatic
Engine: 5.9HO diesel
Only asked for suggestions - and cry!!!!
Hi there, excessive blowby is caused be high head pressure. What happens in this case usually, combustion chamber pressure leaks past the piston rings. For checking for a dead cylinder you need to have it hooked up to a diagnostic computer and preform a cylinder cutout test. Since you have a high pressure fuel system you cannot crack the fuel lines going to each cylinder.
What is the best way to diagnose if it is a cylinder wall / piston problem or can it possibly be an injector or valves? How does the vent system operate on this engine and what steps should I take to identify the problem? Will the diagnostic machine pinpoint the problem such as bad injector? Can I use a borescope without disassembly.
Relist: Answer quality.
The most common reasons for blow by are Crankcase ventilation system is plugged,
Turbocharger oil seal is leaking or pushing boost back into the eng via the drain tube,
Valve stem clearance is excessive or the valve stem seals are damaged,
Cylinder head valve guides are excessively worn,Piston or piston rings are worn or damaged. In your case i would remove the injector and check the tip, if you can borescope the cylinder from above that is the easiest way to tell with out buying a new injector to find out you have a miss in the same cylinder. if you have to swap injectors take the bad one and swap it with a good one. see if the miss follows the injector to the cylinder. if not bad cylinder. if so bad injector. what blow by readings were you getting
Can I determine which cylinder is missing with temp stick on manifold or infared temp? Would it pay to go to the dealer and let him run a diagnosis before I go any further? Is there anything special about the 5.9HO engine vent system to look for and wheren is the best place to measure the pressure?
Yes now a days with the High pressure common rail you cannot just temp it or crack a line. you need the cummins software insite to cut the cylinders out. nothing special if you can see steam or "blow by" it's not plugged. the best place to measure is right out of the tube that you see the blow by ( the end of the breather) the spec is