Bad sound on a fresh rebuild (video)

[Jake_IN]

Background (skip if you aren't interested): Some of you may have been following my rebuild thread over here. Didn't get any updates posted recently because i ended up kind of rushed on the last part of the build so i didn't get any pictures. Injector pump took longer to get than i expected. So it arrived just in time for harvest to start which means having no free time. Finally got harvest done and got the engine put together and installed this past Saturday.

Problem: Everything seemed fine on the startup, engine sounded good and i was happy. Today i decided to properly time the pump and as i was bringing up the RPM's to start checking it i started hearing this god awful sound out of the intake.

As you can hear it goes away at idle, and then over time at sustained high RPM's the sound gets louder and louder. Let it idle again and it clears up.

Any thoughts? First things first will be pulling the valve covers... (whenever i find time for that).

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[IDIBRONCO]

Does the engine start missing when that sound happens? To me, it almost sounds like a little bit of compression is coming back out of the intake. I'm not the best at diagnosing without being there in person. I'm thinking that maybe you have a weak valve spring or lifter.

 

[Jake_IN]

sounds like a little bit of compression is coming back out of the intake

That is exactly what it sounds like to me too. Exhaust doesn't change when it does it though. No smoke of any kind. Just that loud "chuffing" out of the intake.

ninja edit: so to answer your question. No it doesn't sound like a definite "miss" just a horrible chuff out of the intake.

 

[IDIBRONCO]

If that's what the sounds is, I'd guess that you have an exhaust valve that isn't opening all the way or maybe not at all. That's exactly what happened to me with my 7.3 build about 2 1/2 years back when I installed the Comp 910 valve springs. I had a weak lifter that wasn't opening the exhaust valve. If it happens to be an intake valve that isn't closing all of the way for some reason, then you've most likely got a bent valve now and some damage to the top of a piston. Hopefully, it's a weak lifter.

 

[Jake_IN]

I was on the fence about installing new lifters. Decided "When in Rome" and put all new lifters in.

Now i just need to find the time to tear this all back apart...

 

[Big Bart]

Jake,

1) Probably best to start with pulling the valve covers. See if you can find a bent push rod or loose rocker. Maybe reset the valve lash/pre-load.
2) Perhaps check for blow by before pulling your heads or motor. Maybe your rings have not seated yet and you are getting some blowby past your cdr valve. (Which wiggles and would potentially cause a similar noise right near the top of your intake manifold.). Pull the cdr or oil cap and see if you get blowby building up at higher rpms where the noise starts. If so let it idle, run it up a little, let it idle, run it up a little, and see if after 30 minutes if it clears up.
3) Perhaps you let it idle or run it below where it makes the noise. See if your lifters fill up and if it goes away. These engines don’t make much oil pressure at idle.
4) Likely if you bent a valve the noise would be constant not delayed like it is. But IDIBRONCO has seen more IDI’s than I have. If not blowby. Seems like a lifter is bleeding off and causing pressure to back draft on the intake stroke. IE when you run up the rpm it’s ok, then 5 seconds later it is not ok.

Either way that sucks, hope it’s something simple. You worked hard, you deserve better!

 

[IDIBRONCO]

Bart, you're right. A bent valve would make a constant noise. It won't unbend. I had forgotten about that part where the sound goes away sometimes so I doubt that it's a bent valve.

 

[Jake_IN]

Thanks Bart,

Yeah i think valve covers will be the first thing to dive into. I'm going to try and isolate which side the noise is coming from first.

 

[subway]

that sucks, a compression or leakdown test might help you narrow it down. I agree with what was mentioned above, it sounds really healthy overall but like it is leaking compression into the intake somehow.

 

[gnathv]

If you use an IR thermometer on each exhaust port of manifold the problem cylinder may be noticeably cooler in temperatpure.

 

[Jake_IN]

If you use an IR thermometer on each exhaust port of manifold the problem cylinder may be noticeably cooler in temperature.

I'll give that a try too.

 

[snicklas]

Jake,

How long has it run since you put it all back together?

I remember reading of more than one member who had bought a truck that has sat for a while, and it would chuff on the initial few start-ups but would clear up after some run time….. maybe you just have some schmoo in a lifter……

 

[Jake_IN]

Jake,

How long has it run since you put it all back together?

I remember reading of more than one member who had bought a truck that has sat for a while, and it would chuff on the initial few start-ups but would clear up after some run time….. maybe you just have some schmoo in a lifter……

Probably has less than 5min of total run time on it since getting the motor dropped back in Saturday. So nothing is broken in yet. Lifters were installed in the motor April 24th though.

Good to hear from you Scott, hope all is well!

 

[snicklas]

Good to hear from you Scott, hope all is well!

Yes, going well. Still just a bit South of you. Have the Excursion back in DD service but still have it…. 14 years and counting.

 

[subway]

I didn't realize it had so little run time on it. Not the same but when I rebuilt the top end of my Jetta it took longer than that for the lifters to refill and quiet down. I was starting to get really concerned but eventually it cleared and ran another 200k+ miles before retiring at 343K.