Help, diagnosing sound. (1 Viewer)

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Joined
Jul 20, 2014
Threads
115
Messages
503
Location
Costa Rica & Texas
Bj40 b engine:

Before I begin I do understand diesels make pings, Knocks and all sorts of sounds normally. Up until a few weeks ago when I crank my bj40 b engine it was quite in the cab and sounded smooth.
This sound recently started a few weeks back and I am stumped. i know many of you that drive these regularly can tell when something is not right.

You can only hear it from inside the cab near the tranny hump and firewall. The sound is not a hard knock or a pinging sound like a lifter or rod but more like an exhaust leak. When I step out side the LC it sounds fine.

I have inspected the header gaskets, exhaust flange and exhaust pipe for leaks and nothing.
It gets more quite as I gain revs and travel at highway speeds to point it almost is not heard. I tried to capture this sound on video but very hard to get a clear recording. Will try again in the morning to get a better recording.

At idle it's very pronounced (even after I warm her up) I cannot isolate under the hood due the engine noise or maybe not the source of the problem???
So maybe I can get some ideas on a step by step diagnosis?

1. Possible bad injector at cylinder 4 (nearest firewall)
2. Any chance it can be coming from the transmission? If so what would cause this noise.
3. Possible IP and needs a purge?
4. I assume if it was a lifter I would hear it at the valve cover.

I need to reiterate this is a new sound and not normal.
 
It's really hard to get a distinct sound with the iPhone:

It is very loud compared to a week ago inside the cab.

Inside the cab by the tranny hump and firewall:


Inside engine bay. Cold start:
 
To me the engine sounds good, however, I did hear a high pitched metallic sound in the first video. You might want to check if there's anything loose around the rear of the engine or possibly the tranny, and clutch area.
 
I think that could be the sound of a loose exhaust valve slap. Seems similar to an old VW thing I used to drive.
 
While the engine is running depress the clutch pedal and let me know if it sounds better or worse.

No difference in sound. Thought at one point it was the clutch plate but I think those may "whine" more than what I'm hearing
 
I think that could be the sound of a loose exhaust valve slap. Seems similar to an old VW thing I used to drive.

I thought if it was a a loose exhaust valve slap I for sure would hear it in the engine bay around the valve cover. Given how loud the sound is in the cab it would be much worse at the valve cover???
 
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I took off the valve cover and checked all the clearances. All good. Next, I removed the #4 cylinder injector and the noise seemed to decrease a lot. Since I could hear in the cab I decided that maybe this injector is clogged or possible bad. Going to remove this injector and see if that is indeed the problem. Can these be cleaned or should they all be replaced?
 
My understanding is that you would just have injectors rebuilt instead of replaced. You're definitely narrowing this down.
 
Figured it out. The #4 injector is bad. I switched #3 in its place and the sound defiantly decreased. So, I will have the local shop rebuild all 4 for me now. Sure to experience more power and fuel economy. No telling how old these injectors are. Thanks for all the input.

#4 injector

image.jpeg
 
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Glad you found the source of your noise Jimmie.

When reconditioning them, they should replace all the nozzles to restore the spray pattern back to normal and then adjust the shim thickness on each one to get the opening pressures correct and matched.

Your experience here has made me remember the source of strange noise that occurred on my B-engine.... The bracket holding my breather/blow-by pipe broke allowing that pipe to dance to the beat of my engine and bash the broken ends of the bracket together. So I now have a much beefier bracket in place there...

You can just see it in the dark murky background of this photo (arrowed in blue):

OilCooler.jpg


:beer:
 
Thanks Tom. After driving these diesels long enough I feel you can tell when a noise occurs that will indicate something is not right. I am half tempted to do a diesel purge before dropping the $$ on rebuilt injectors. It's a long shot but with the horrible diesel we get in Costa Rica maybe it's worth a shot.
I have ran bio diesel on multiple occasions and feel it may have cleaned some gunk out. After a long road trip to the beach a month ago I had to fill up in small beach towns that are natourious for bad fuel but was better than pushing her home.
Luckily I can get these rebuilt in this country for a fraction of the cost as others but purging is a cheap way to test.

PS: you ever get a small amount if oil build up at the opening if your blow by pipe? I don't have a drip but more like a ring of oil there. You caused me to go look at my bracket to make sure it was secure and notices this small deposit of oil.
 
Figured it out. The #4 injector is bad. I switched #3 in its place and the sound defiantly decreased. So, I will have the local shop rebuild all 4 for me now. Sure to experience more power and fuel economy. No telling how old these injectors are. Thanks for all the input.

#4 injector

View attachment 1291757

Very good diagnosing Jimmie!
It sounds like you'll be up and running without any more gremlin sounds soon! I'm the same way with new sounds, I have to find and defeat immediately, otherwise I cannot get any rest while thinking about it.
 
Very good diagnosing Jimmie!
It sounds like you'll be up and running without any more gremlin sounds soon! I'm the same way with new sounds, I have to find and defeat immediately, otherwise I cannot get any rest while thinking about it.

Thanks! I been dealing with this noise for several weeks and know the feeling. Plan on a good night sleep with this issued resolved for now...damn gremlins.
 
T....you ever get a small amount if oil build up at the opening if your blow by pipe? I don't have a drip but more like a ring of oil there. You caused me to go look at my bracket to make sure it was secure and notices this small deposit of oil.

That pipe never drips enough oil to make any sort of stain on my concrete driveway .. but it does drip enough to keep my front driveshaft (directly below the opening) continually wet with an oil film.

It has always done this though ... right from when I first bought my BJ40 with just 40,000kms on the clock.. so I accept some drips there as being normal.

:beer:
 
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