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Thread: Engine knocking LDS-456

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    Default Engine knocking LDS-456

    I had kinda figured this noise was normal, as I've had some other diesels that made a similar noise, but after asking a few people who said that doesn't sound right for a deuce, I got a little concerned. I searched on here some and I found an old thread about somebody's LDS (my truck also has an LDS) with a very similar noise which ended up having a melted piston. My truck is a 68 that was rebuilt in 89 and had an LDS dropped in which according to the tags was also overhauled that same year, and only has about 25k on it now. I was poking around at it while it was cooling down after I got home, and I noticed that although you don't feel anyhting by touching the block, heads ect in various places, injector lines #2,3 and 5 feel like someone is tapping on them with a hammer, while 1,4 and 6 just vibrate and shake with the rest of the engine. The difference in feel is very noticable. The knock is definitely louder when cold, and as far as I can tell is present no matter what rpm the engine is at. Anyone ever heard of something like this before? And which set of tests do y'all think would help me most here? I was gonna start craking lines and try a compression test too but I don't wanna get too far in yet since I'm relying on this truck as my daily driver for the week while I pick up another car. I'll try to post up a video of the noise soon, I don't have great internet right now so my phone isn't too keen on loading a video into here

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    Use the heat temperature device thingie First to compare cylinder to cylinder.
    It is a huge internal compression engine.
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    As for the injector lines: They are all different lengths, so will vibrate differently. Are they all tied together in at least two places?

    I am with Frank...take a laser thermometer and check each cylinder (exhaust). Is there one cold one among all the hot ones?
    What does your blow by look like when you open the oil cap? If it is puffing smoke, it is an issue. If there is just a bit of lazy haze...not so much.

    Maybe you can shoot a short 10 second video with sound and share it?
    MVPA member. 1974 M35A2C w/w "Queen Lola", rebuilt LDS-465-1A, "D" turbo, Waterloo Overdrive upgrade. Med towbar, 11.00R20 Goodyear G286, flipped hubs, remote brake fluid reservoir, spin-on filters, bypassed FDC, LED taillights, LED headlights, LED turn signals, WESTACH EGT/boost gauge, AVM lockout hubs, LED convoy light, LED lollipop lights, HMMWV seat on air ride base, M211 dash passenger grab handle, hood lift kit, 24V solargizer/battery minder, ether start kit, flasher module mod, heavy duty dog bone ends, M35A3 aluminium fuel tank.

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    Ill try to get my hands on one of those thermometers tomorrow, along with a video. In regards to the injectors lines, I'm not sure I'll look tomorrow, I just found it strange how fierce the difference was. The blowby looked somehat heavy for what it should be, and I checked the oil again a little while ago and it looks like it's been slowly making oil so my hopes are pretty low already, really sucks.

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    Well, thinning out the oil because of one of the internal fuel leaks (well known....do a search....FDC, hydraulic head, flame heater are the most common culprits) would certainly make it get louder....less lubrication, less "cushioning", more blowby. If it is only that, it is a few O-rings and an oil and filter change, in the absence of any real damage! Better than a hole in a piston. You did not mention "milkshake" so I figure it aint coolant in the oil.
    MVPA member. 1974 M35A2C w/w "Queen Lola", rebuilt LDS-465-1A, "D" turbo, Waterloo Overdrive upgrade. Med towbar, 11.00R20 Goodyear G286, flipped hubs, remote brake fluid reservoir, spin-on filters, bypassed FDC, LED taillights, LED headlights, LED turn signals, WESTACH EGT/boost gauge, AVM lockout hubs, LED convoy light, LED lollipop lights, HMMWV seat on air ride base, M211 dash passenger grab handle, hood lift kit, 24V solargizer/battery minder, ether start kit, flasher module mod, heavy duty dog bone ends, M35A3 aluminium fuel tank.

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    Quote Originally Posted by cattlerepairman View Post
    As for the injector lines: They are all different lengths,
    Nope. Absolutely not. Dead Wrong.

    Every mechanical pumped Diesel engine has injection lines of the same length. Otherwise the injection timing would be off. Even most of the common rail diesels have similar length lines.

    To the OP: pull the oil fill cap while itís running, see if you can feel a definite ďchug chug chugĒ of air blowing. Also donít be scared to crack an injection line a 1/4 turn loose while itís running on each cylinder to see if any of them make a difference. Once you identify a problem cylinder diag gets easier from their.

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    Quote Originally Posted by Smokindodge View Post
    Nope. Absolutely not. Dead Wrong.
    Every mechanical pumped Diesel engine has injection lines of the same length. Otherwise the injection timing would be off. Even most of the common rail diesels have similar length lines.
    Duh on me, I never even thought about equal length and why but that is why some line are looped around a few times. And the multiple bracket fuel line keepers need to be there. Thanks.
    fuel system best picture.pdf
    Last edited by frank8003; 08-16-2019 at 00:57.
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    Oil is all clean, just a little dark. The FDC was already bypassed when I got it, so sadly I know it won't be that easy. The flame heater has also been disconnected. I'm gonna try cracking the lines later today when I get home, as well as checking the exhaust manifold temps. I'll try to get a video up here of the blowby as well as the noise. I had noticed too, but never really bought much of it, if the truck is cruising around 45-50mph, so around 2k rpm, it'll seem to kind of skip and hop around at times. The best way I can describe it is like when you got a real rough part of the road and your foot bounces around on the throttle and the engine gets kinda choppy until you smooth your foot out. It'll do the same kinda thing. As soon as I let off or give it more/put it under load however, it will immediately stop doing such. K was hoping it was maybe a HH related type issue but wouldn't that produce symptoms all around the rpm range as well as power loss issues too? The HH or a bad injector are kinda my last hopes here

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    Oerthedge21, your suspicions have not yet been proven wrong. Still on the rule-out list. Does your oil smell of diesel fuel and appear to have thinner viscosity? How does it drip off the stick? Motor oil should "stretch" and coat the dipstick. Oil with diesel in it tends to "bead" more (water-like), making big drops. Wow, super scientific....
    If your truck is "making oil", it does have fuel (less likely, coolant) leaking into the crankcase.
    MVPA member. 1974 M35A2C w/w "Queen Lola", rebuilt LDS-465-1A, "D" turbo, Waterloo Overdrive upgrade. Med towbar, 11.00R20 Goodyear G286, flipped hubs, remote brake fluid reservoir, spin-on filters, bypassed FDC, LED taillights, LED headlights, LED turn signals, WESTACH EGT/boost gauge, AVM lockout hubs, LED convoy light, LED lollipop lights, HMMWV seat on air ride base, M211 dash passenger grab handle, hood lift kit, 24V solargizer/battery minder, ether start kit, flasher module mod, heavy duty dog bone ends, M35A3 aluminium fuel tank.

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    It doesn't look too thin yet, but the level has definitely risen since I changed it. It doesn't smell either. For the exhaust manifold temp check, should I drive the truck around and get it hot before checking it, or should i just start it up and see which cylinder ports heat up quicker and reach a higher temp? And what exactly am I looking for as indication of an issue, a cylinder with a lower temp or one thats hotter than the others?

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