Sound coming from airbox.

Delta.Speed

Member
Mar 26, 2022
49
5
8
Good afternoon everyone. Has anyone ever ran into a similar sound coming from the intake? Its barely noticeable from a distance but if you put your ear up to the intake box you can clearly hear it. Some kind of deep, steady, thumping sound. I dont hear any knocking or noise coming from the sides of the engine itself, and I have no loss of power or any other symptoms. Just the sound.


I've been working on my truck for several months now, and when I bought it this is one of the issues that it came with.

On disassembly I found a lifted injector, and as part of some upgrades I was planning on doing on the truck anyway, I installed a fresh set of Industrial Injection heads with pre-installed screw-in injector cups, and some new SAC style injectors. I also went back with SoCal billet injector hold downs. Everything seemed to indicate that the sound was compression passing up through the failed injector washer, so I thought that everythingI was upgrading wouldalso take care of the noise. Well apparently not.

Another suggestion I've gotten as a source for this sound is incorrect valve adjustment, but I triple checked my valve adjustment and did it by the book. I adjusted all valves on one TDC, checked them all a second time before moving to the next TDC, adjusted those, checked them a second time, and then spun the engine over 360° and checked all the adjustments again.

I've also heard bent or bad valve as a possibility, but the sound was there before, and its the exact same sound going back with all new loaded heads.

At this point I have no idea what this sound could be, and my local diesel shop took a listen and said they couldn't diag without a tear down which of course would suck after dumping over $13k on this truck.

Any help would be greatly appreciated.
adcf8edb7a1440d21458ed894dad5ffb.jpg


Sent from my SM-S908U using Tapatalk
 

2004LB7

Well-known member
Dec 15, 2010
4,246
504
113
Norcal
sounds normal to me. it's been a while since I've had an LB7 but I think it sounded the same through the intake

does it run and drive good? no excessive blow by?
 

Delta.Speed

Member
Mar 26, 2022
49
5
8
sounds normal to me. it's been a while since I've had an LB7 but I think it sounded the same through the intake

does it run and drive good? no excessive blow by?
It runs and drives great. It was tuned by Starlite, doesn't smoke and doesnt have any blow by as far as I can tell.

Sent from my SM-S908U using Tapatalk
 

Delta.Speed

Member
Mar 26, 2022
49
5
8
My LB7 makes the same sound out the exhaust. I think it's just resonance and completely harmless.

Sent from my FlashScan V2 using Tapatalk
Well good to know that about the intake sound. This is my first diesel truck and maybe it's making normal noises I'm just not used to with gas engines. I just wouldn't want to leave an abnormal noise go and end up with a valve smacking a piston or something like that.

Sent from my SM-S908U using Tapatalk
 

Delta.Speed

Member
Mar 26, 2022
49
5
8
I hope I'm not being paranoid. But I took the truck for a drive and brought it back to a second sound, this time I can hear it by cylinder 7 and unlike the first sound thats still there, this one I can hear from a couple of feet away. If y'all could take a listen and tell me your thoughts.


I dont want to take the truck back apart hunting for a problem that doesnt exist.

I've got a friend down the steet with an LLY powered motorhome... I'm thinking I'm gonna drive down there and take a listen at his engine to see if it sounds the same.

Sent from my SM-S908U using Tapatalk
 

Delta.Speed

Member
Mar 26, 2022
49
5
8
maybe lifting or leaking injector? what's the balance rates look like?
The injectors are literally brand new. 30% over SAC injectors from Lincoln Diesel Specialties. I also went back with SoCal billet injector hold downs and torqued those to spec. Naturally they have all new crush washers and o-rings. Not only that but as I mentioned I also ordered a set of new loaded Industrial Injection heads with the threaded injector cups and they came pre installed. The combination of threaded cups and billet holds downs makes it damn near impossible for a cup or injector to lift. I'd be shocked if it was a lifted injector.

I haven't checked the balance rates because I'm sorta trusting the LDS quality, but I'll definitely check them.

Sent from my SM-S908U using Tapatalk
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
19,381
1,933
113
Phoenix Az
do a compression test on cyl 7 and 5. id also check exhaust gaskets very well for leaks.
 

2004LB7

Well-known member
Dec 15, 2010
4,246
504
113
Norcal
compression looks low along with more then 10% difference. was this done cold or hot? charger on the battery? how long of a crank?
 

Delta.Speed

Member
Mar 26, 2022
49
5
8
As Brad mentioned above, I'm out to get a better gauge. I checked balance rates yesterday and I'm attaching a photo of what I got.

I called Lincoln Diesel Specialties and they were adamant that their injectors rarely ever fail and that my issue must be elsewhere. The guy I spoke to asked me if I had checked compression and I gave him the same results I mentioned above from the crappy gauge and he quickly blamed the injector balance on the lack of compression.

He said that sometimes the engine will compensate for lack of compression on all cylinders by overworking just one injector. I dont know enough about these engines to refute him, so I'm buying a better gauge to double check compression. Really hoping I dont have a low compression motor at only 217k miles.

So if I check compression and I'm low on all cylinders I know what that means... engine out, full tear down and rebuild, but if my compression is good, what should I be looking for next?

LDS didn't really give me alot of reassurement that they would help, seemed like they are gonna give me the runaround on this. The guy I spoke to said that if I still think the injector is bad I gotta pay $50 for them to test it, if its bad they reimburse me and send me a new injector, if not they keep the test fee naturally.

Couple of thoughts on that.

1) If I have a bad injector right out of the box, I want to return them all and go to another manufacturer like DDP or Exergy. I would no longer trust these injectors to not fail one by one and end up being a pain in my @$$. The LDS guy said they wouldn't do that. They would only replace the one.

2) If I determine I have a bad injector, I'm not sending an LDS injector to LDS for testing. I would want to have it tested by someone local and provide LDS with documentation that its bad.

Anyone ever ran into a situation like this that has any advice for me?? Super crap situation to be in after spending over $13k on this not cutting any corners and getting new vs reman injectors.
fe5d1e9c97d4d1e3f084bdf0b4f69aba.jpg


Sent from my SM-S908U using Tapatalk
 

2004LB7

Well-known member
Dec 15, 2010
4,246
504
113
Norcal
number 7 is high for sure. what's the main rate? was the engine up to temp? looks like it's -30°c

I wouldn't be too worried about the compression unless you have some kind of issue related to it. if you get the injectors sorted out and the engine runs good without excessive blow-by then drive it. I wouldn't do a rebuild just because the compression numbers alone

when I had some of my LDS injectors go out I had to take it to the dealership to get a report from them on injector health. then they sent me replacements
 

Delta.Speed

Member
Mar 26, 2022
49
5
8
number 7 is high for sure. what's the main rate? was the engine up to temp? looks like it's -30°c

I wouldn't be too worried about the compression unless you have some kind of issue related to it. if you get the injectors sorted out and the engine runs good without excessive blow-by then drive it. I wouldn't do a rebuild just because the compression numbers alone

when I had some of my LDS injectors go out I had to take it to the dealership to get a report from them on injector health. then they sent me replacements
-30 C on the coolant temp has to be some kind of mistake.... I'm in Florida, our thermostats dont go down that far.

The truck was not up to operating temp because I was working on sorting out some leaks that were present after I put everything together. I've fixed 2 of the 3 leaks I found when it first started.

Last leak I have is coming from the turbo oil drain I believe. It shows up as oil leaking around both sides of the trans bellhousing and my inspection camera showed me a puddle of oil in the valley. That drain was kind of uncomfortable to install so I wouldn't be surprised if one of the two new gaskets shifted while I was getting the bolts in. Im gonna work on fixing that leak so I can warm the engine all the way without having oil pour out of it and check balance rates again.

Sent from my SM-S908U using Tapatalk
 

Delta.Speed

Member
Mar 26, 2022
49
5
8
number 7 is high for sure. what's the main rate? was the engine up to temp? looks like it's -30°c

I wouldn't be too worried about the compression unless you have some kind of issue related to it. if you get the injectors sorted out and the engine runs good without excessive blow-by then drive it. I wouldn't do a rebuild just because the compression numbers alone

when I had some of my LDS injectors go out I had to take it to the dealership to get a report from them on injector health. then they sent me replacements
Number 7 is also where I was hearing that loud tapping noise from. Not the intake one, but the one that started after it running for a bit.

Sent from my SM-S908U using Tapatalk
 

2004LB7

Well-known member
Dec 15, 2010
4,246
504
113
Norcal
make sure you get the new balance rates with an upto temp engine and let us know what they are