Tapping sound on my 7.3 idi that gets louder as it gets hot.

mustangmalibu

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Hello all,
I've been working for months trying to find out what this knock in my engine is it starts as a tapping as it gets warmer it starts getting louder and louder and louder if you drive it long enough it sounds like it's going to throw a rod. I posted on this form before and I got the same usual answers. It's an injector bad injector, etc. It has a brand new injection pump, brand new injectors straight from stanadyne cost me five hundred bucks. And for the life of me I cannot find out what this tapping that turns into a knock is. I've been working on it for 3 months now it's about to put me out of business. Every time I take it to a shop they don't know either unless to I give them $500 to investigate. And drop my truck off for a couple of days which I cannot do because I have a business that revolves completely around this truck. I haul horses all over and facilitate horseback riding all over the place in Central California. I have read every posting every form everything you can possibly imagine. Over and over over but to no avail it starts as a small tap but that's only after it warms up when you first start it and it's cold it's runs perfectly. Like a brand new engine. Then after it reaches about a hundred eighty degrees it starts with a tap and gets louder and louder and louder. The engine has 48,000 miles on it but was sitting in a truck in a field for about 10 years but it is a brand new engine the truck was covered. Anyway I'm about at my Wit's End and I need this truck desperately so if anybody can help me I would certainly appreciate it thank you...
P.S. I tried to upload a file video and it doesn't work. Says the files too large. It's a 30 second video I will continue to try to upload one.
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Selahdoor

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The squirrel in the heart of the engine... You know, the one on a treadmill... Is getting old, and is not tolerant of the heat. So he's banging on the inside, with a push rod, to let you know to let the engine cool down some.

Hey, you said you'd heard all the answers. I just thought I'd try to give you a different one. ;):rotflmao
 

mustangmalibu

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Okay now I have videos I want to check those out the last one is the one you can really hear the tapping and it's it's not that I'm running it too hot cuz I'm not. I mean it it starts doing this may be a mile from the house so its theat normal operating temperature it's not hot.
 
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nostrokes

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Sounds like a collapsed lifter. Time to pull the valve covers off and find the loose push rod
 

Christian9112

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How do you confirm its a lifter? I have that same tick noise when i'm engine braking. no under throttle tho. I never touched the valve springs but i might just end up upgrading it if it is that.
 

Kyle Carter

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Pull the valve cover and shake/twist all the rockers while they should be under a load. If one isn’t just blatantly loose you can use a dial indicator to measure net lift and make sure there all in spec
 

mustangmalibu

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Thanks for replying. I have done that and they are all tight. Also I forgot to mention that it's only on acceleration that it makes that noise. When i first start it, it runs like a brand new engine. There are still paint marks on the rocker arms where whoever built was torqueing them down, I assume. When you come down a hill, and let off the gas, it purrs like a kitten, then acclerate it like a tap and turn to more of a knock. One other thing I noticed. When you first turn it over when it's cold, there is a slight twang that comes out of the intake manifold, but only once it doesn't do it anymore until it sit over night. I owned another 7 3 IDI before this one. And it didn't do that...I will post a video of it if it does it tomorrow and it running cold. Thanks man!
 

mustangmalibu

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I tore it apart already and I just don't know how to tell a bad lifter is all the rocker arms are still pretty tight I see two lifters in a rising position here's a pic.
What should I look for? Other than loose pushrods cuz they're all tight

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Thewespaul

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That looks fine to me, did the knocking start after you replaced the pump and injectors? Were the injectors pressure matched and the injection pump timed when installed? Do you have any smoke out the exhaust?

There’s three things that can cause a sound like that, a fuel knock, a bad lifter, and a rod knock. Rod knocks are very rare in these engines but I have seen bearings roll twice now, granted that is over many many IDIs I’ve had my hands in. Don’t think that just because parts came from stanadyne that they are going to be good. I rebuild these pumps and buy tons of parts from stanadyne, and the quality lately has been very poor. Out of the box, their new injectors do not fire well at all, I’ve had many of their “new” injectors completely seized out of the box and had to disassemble them to free up the pintles.
 

Selahdoor

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I would loosen the rockers one by one, and spin the push rods. I have found some that were so slightly bent that you couldn't tell it any other way. Yet they made noise.
 

mustangmalibu

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Right now I'm changing the lifters and I've been doing that with the push rods and I'll let you know how it goes I haven't found a bad lifter yet but I don't know what a bad lifter looks like...
 

IDIBRONCO

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If all of the lifter pieces are still in place, you may not be able to tell. The bad part could be a weak spring inside. You can't tell from just looking.
 

YJMike92

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In my experience, A lifter noise will not change in intensity under load. I would be more inclined to think bottom end? of course with new lifters, you will know soon.
 

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