Engine knock when cold

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My truck has developed an engine knock that goes away after it warms up. I only notice it first thing in the morning while shifting gears. The temps here in the morning have been about 35 degrees. The circumstance is shifting from 4th to 5th with about 20 psi boost getting on the freeway. It knocks as the engine speed decelerates between shifts. It sounds a lot like a collapsed piston (happened once to me on a gasser). Has anyone had anything like this occur on their truck?

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98 2500 Quad Cab, 12V, 5spd, 4x4, HD Transfer Case, 370HP Diamond B Injectors, #4 TST, 16cm2 Housing, AFC Spring Kit, Governor "Modified", Walker Muffler, 285/75-16 BFG AT's, SS Tube Steps, Fifth Whl Hitch, Leather, CD, LSD Dana 80 Rear, 60 Front, Centerforce Dual Friction Clutch, Rancho RS9000 Shocks, Rancho Steering Stabilizer

 

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Hope its just a bad injector fouling out on ya. Have them pressure checked.

 

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It happened to me and it was coming from the injection pump. I replaced the fuel return valve on the pump and the noise went away. What it was doing was over-pressurizing the pump and the transfer pump was slamming away at the high pressure.

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Chris Timochko
1997 5sp 4X4, HX40, BD 4" Brake, Marine Compression, Custom Tuned Injection Pump, 370B Injection Nozzles, Delivery Valves, Governor & AFC Spring Kit, Psychotty Air, Water Injection, NOS Diesel Kit, 6" Chrome Exhaust System, No Smoke Valet Switch, McLeod Dual Disc Clutch, Mag-Hytec Rear Cover, Cummins Chrome Kit, Optima Red Tops, Hadley Bully Horns, Hurst Line Loc, Goodyear Wrangler AT/S 305/70/16s. Test mule for Auto Wurks Diesel race program

 

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Thanks for the replies. I modified the relief valve about 1 year ago when I placed a small Buna N O-ring under the spring on the overflow valve. The pressure was at the low end of spec and that brought it up to 30psig at 2500rpm. The noise just appeared a couple of days ago. I got under it tonight and had my wife run the truck to about 1500 rpm and I could hear something pounding away but can't locate it with all of the racket. It is possible that it is coming from the top of the engine as well.

[This message has been edited by dieselburner (edited 11-17-2000). ]

[This message has been edited by dieselburner (edited 11-17-2000). ]

[This message has been edited by dieselburner (edited 11-21-2000). ]

 

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I too had modified the spring to a higher than spec value of 35 psi. Mine started rapping about 7-8 months after I did the initial adjustment. The rapping seemed most pronounced when listening in the wheel well. Acquire a new one and keep the one you have in the truck in the event of an emergency. It's worth the test. I'll bet that is what yours is doing.

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Chris Timochko
1997 5sp 4X4, HX40, BD 4" Brake, Marine Compression, Custom Tuned Injection Pump, 370B Injection Nozzles, Delivery Valves, Governor & AFC Spring Kit, Psychotty Air, Water Injection, NOS Diesel Kit, 6" Chrome Exhaust System, No Smoke Valet Switch, McLeod Dual Disc Clutch, Mag-Hytec Rear Cover, Cummins Chrome Kit, Optima Red Tops, Hadley Bully Horns, Hurst Line Loc, Goodyear Wrangler AT/S 305/70/16s. Test mule for Auto Wurks Diesel race program

 

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I removed the O ring spacer from under the spring on my overflow valve but the knock is still there. It's not real bad but it is worse when the truck is cold. I can hear it at certain rpms after it warms up. It's really buggin me but other people can't hear it or think that maybe they do. Has anyone had to replace the lower end on their engine yet? How about a source for bearings and pistons (marine?). This one is making noise and I'm afraid that it's just a matter of time before I need to tear into it.

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1998 2500 Quad Cab, 12V, 5spd, 4x4, HD Transfer Case, 370HP Diamond B Injectors, #4 TST, 16cm2 Housing, AFC Spring Kit, BD Governor Spring Kit and other modifications, Walker Muffler, 285/75-16 BFG AT's, Stainless Steel Tube Steps, Reese Fifth Wheel Hitch, Leather, CD, LSD Dana 80 Rear, 60 Front, Centerforce Dual Friction Clutch, Rancho RS9000 Shocks, Rancho Steering Stabilizer

 

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Mechanic taught me this trick. Get a piece of wood(wood poles for clothes hangers or wood dowling). Put one end to your ear the other to different areas of engine. You should be able to pin point area on engine where you here knock.

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Missouri Mule 96 White 4X4 ST club cab,(grey int. ),5 spd, 3. 54 reg dif, 8 ft bed, 1 ft high cheater boards, front and side of bed,Pofile V bug shield,
99 Freight liner FL60 blue Cummins 24v 215 hp, 520 torgue,6 spd 3. 59 no spin rear, 16 ft dry box (white) 19. 5 low profile tires,Weight 11,000, gvw 23000, 11 to 12 mpg
Bill Thomas (Wild Bill)