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Intermittent Rattle

Chevypoor

Chevypoor

Active Member
Messages
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Location
Mineral, Va
Larry started making a new noise about a month or so ago. It only happens when to the outside air temps are above 50. It sounds like the normal combustion/ diesel rattle sound just alot louder. It also seems to occur mostly when the truck sits in traffic and I go to accelerate. It will usually clear after I get moving and stay moving. If I accelerate harder it does get slightly louder. If I back of the fuel it will quiet down and almost go away. Usually occurs in the 17-2300 rpm range. No change in idle noises. No change in oil pressure and no real change in engine temps. New fuel filter and new Bosch injectors from Heath. New 93 Lift pump. Checked for codes and there are none. No smoke when accelerating and feels just as strong as it does it does not rattling/ making the noise. Checked timing and I advanced it thinking it might help. The noise is the same before and after setting the TDCO. IP is an unknown reman from the PO with less 20k on the IP. As soon as the air temp drops it goes away. I have never heard the rattle/ sound unless it is over 50 degrees outside and almost exclusively after sitting in traffic. It is also not consistent... sometimes I will not hear the noise for several days. Almost seems like a heat soak/ timing issue. Any thoughts?
 
Just guessing, but gut tells me timing. Take your lap top with you and watch what its doing next time.
 
I agree. Had a scary thought after I posted this... I used the upper intake from Gertie since it was modded for the att. I also used the map and iat from the Gertie since they were in the manifold. The problem is somewhat similar to Gerties 'rattle'. I never had the rattle until after the att install. I know in a gasser the iat and map have some control over the timing. Maybe one of those is bad. I may have yanked a good motor for a simple sensor..... I am thinking I am going to replace the iat and map one at a time with a known good iat and map and see if the problem goes away.
 
Scan what the sensors are telling the ECM. Are they in range? Possible you are going into the 'cold advance' range? (Thinking the low temp switch DB2's use for cold advance that must have a DS4 equivalent in the ECM.)

You got to remember on an IDI engine they rattle more until you get some heat in the precups. Idle cools down everything including the precups. Getting on the throttle will heat them up, but, will rattle louder until they do get heated up. Hot prechambers evaporate the diesel faster and it burns smoother with less rattle. More advanced timing will make the rattle from the 'idle cool down' louder - at least on my 1993 it does.
 
wiggle said:
Check live data on cooant temp sensor....dash guage may differ largely from ecm data
Click to expand...

Good idea.

Thanks for the help. I replaced the IAT on Sunday and drove her yesterday. No rattle and she seems to run noticeably different. Less boost for the same speed, lower EGTs and ECTs, smoother, and quieter. Seemed to have less cold start rattle as well... maybe I am being delusional but I was kinda surprised how different it felt after one simple sensor change. Fingers crossed at this point. I will keep you guys posted.
 
Well it was not the IAT... maybe it was the switch from winter fuel to summer fuel that made a difference. Maybe I am losing my mind. It did seem to run better... who knows. The rattle was better but still there. It also seemed to be running real hot, so hot you could not touch the motor.

Scared I was going to melt the motor down I took her down this weekend and swapped in the 2000 water pump from Gertie and the D Max fan and Hayden HD clutch. I also decided to swap out the injection pump for the brand new Standadyne pump from Gertie. It started up and seems to run much smoother. I am feeling like it was the pump... check out the video below. By my count 0-60 in just over 8 seconds... wow. It has never ran that strong and that was not foot to the carpet, she still had a bit left. The big snail hit 16 pounds and she now blows smoke when you get on her... it was not blowing any smoke before.

Fingers crossed I got the issue sorted.

Sorry.. having trouble with video...
 
Lets try this.

[video]http://s1358.photobucket.com/user/TinxToy/media/VID_20140406_163935681_zps15e83c67.mp4.html[/video]
 
You know what they say. .. They always run best right before they blow up. .. :hihi:

Sent from my SCH-I535
 
Burning oil said:
You sure you were in a truck and not a Corvette!!
Click to expand...

I knew was on to something when she barked a tire when I left the drive on the shift to second. The tires had a bit of antifreeze on them but the roads were dry.:D

btfarm said:
You know what they say. .. They always run best right before they blow up. .. :hihi:

Sent from my SCH-I535
Click to expand...

:hihi: yes I have experienced that before ;)
 
Update: On Monday no rattle at all. Ran smooth as silk. Definite difference in running. It is much quieter and smoother with the new IP. I also definitely feels like I am getting more fuel and the EGTS are a bit higher. It will also now roll the coal. At idle the scan tech shows 11.5mms of fuel vs 9.5-10mms on the old pump. Tuesday I did get a very brief rattle which cleared almost instantly. Yesterday nothing. ECTs are slightly higher now but more consistent. It also takes longer to warm up and it cools down quicker when you shut it off. So where to now if I continue to get the rattle? Could it be the tank sock? Will lack of fuel cause a rattle? Or could one of my brand new injectors be sticking? Or could have low fuel pressure caused the tip of the injector to foul? Any thoughts. Here is a video of the noise before the ip change. I meant to post this before and never did.

[video]http://s1358.photobucket.com/user/TinxToy/media/VID_20140404_135155676_zps6293682a.mp4.html[/video]
 
It is there. I have to max my speaker volume to hear. The strange thing it sounded like all cylinders. It was a change in the rattle in the tone and volume of the general combustion sound. I just tried the link and it did not come up. I will check it when I get back home later today.
 
Yep. With the volume maxed out 4 secs in and after the shift to second. It is much louder in the truck... did it again today. Got stuck in traffic for 15mins. After I got on the interstate it cleared up. It only happens after I sit idling for maybe 15mins or so on a warm day. Everything I have done to this point has made the problem better but it is still there. I will try to get a better video but it is tough since it is so damn unpredictable. I can go days without it and then there she is. Any thoughts?
 
Well the rattle is still with me and now I have discovered other issues and maybe some clues. Thurs last week went to start her up and she was hard to crank and then ran like crap. Opened the hood and checked the clear return line and sure enough lots of air. Drove it anyway and she cleared up after a bit. On Saturday had a chance to look into the leak. It was leaking from the heater element on the bottom of the FFM. Took the FFM apart and cleaned/ polished the flange lips with emory cloth as they were pretty corroded. I also replace the o-ring. No FFM leak, the valley is dry. However when I went to drive the truck on Sunday morning the clear return line was empty. It was empty on Monday morning as well. Today it was full of fuel with the exception of one small air bubble. The injectors are almost new from Heath. Last time I ordered them from him (two years ago) they were from Germany. These are from India. Heard mixed reviews on the Indian injectors. On a positive note the rattle is better with the air leak fixed but still present. Damn fickle 6.5! What the heck is going on? No cylinder imbalance codes, no codes period. If I had a bad injector she should be smoking. Also, can an injector drain down and then "fix" itself. Looking for some help or possible thoughts!
 
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