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01-21-2018, 03:05 PM
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#1
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Mini-Skoolie
Join Date: Oct 2017
Location: Fernandina Beach
Posts: 21
Year: 2002
Coachwork: Thomas
Chassis: Freightliner
Engine: Caterpillar 3126
Rated Cap: 25
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Blue Smoke - Cat 3126
It's me again, lol
I've done some research into on the web trying to figure out why my bus is exhausting blue smoke while running or pressing the accelerator, however I've not come to a conclusion that would help me fix it. I have no diesel mechanics in my area to mention this to either, so I'm asking here.
While the bus is running, after about 5 minutes, a light blue smoke will begin to exhaust and continue for the time the bus is running, and it happens when you depress the accelerator too. Can anyone make any comments as to what the most logical things are the check and replace?
I am considering flushing the oil with a higher quality oil and see if that changes anything. I want this fixed so it doesn't come to have bigger more $$$ problems.
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01-21-2018, 03:12 PM
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#2
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Bus Geek
Join Date: Sep 2017
Location: Owasso, OK
Posts: 2,627
Year: 1999
Coachwork: Thomas
Chassis: Saf-T-Liner MVP ER
Engine: Cummins 6CTA8.3 Mechanical MD3060
Rated Cap: 46 Coach Seats, 40 foot
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You might have a rebuild in your future:
https://www.perkins.com/en_GB/resour...lue-smoke.html
Blue smoke indicates burning oil. Usually related to top end or ring/bore wear.
How many hours on the engine?
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01-21-2018, 03:20 PM
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#3
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Mini-Skoolie
Join Date: Oct 2017
Location: Fernandina Beach
Posts: 21
Year: 2002
Coachwork: Thomas
Chassis: Freightliner
Engine: Caterpillar 3126
Rated Cap: 25
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Blue Smoke - Cat 3126
Quote:
Originally Posted by Twigg
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Not sure how many hours on the engine, as mine doesn't tell me that info, unfortunately. I just know it has 194k miles and was maintained every month and a half by a school district.
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01-21-2018, 03:21 PM
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#4
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Bus Crazy
Join Date: Jun 2013
Location: Picton,Ont, Can.
Posts: 1,956
Year: 1997
Coachwork: Bluebird
Chassis: GMC
Engine: Cat 3116
Rated Cap: 72
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Ok, a shot in the dark first.
What is the engine temp when warmed up during a good run? Normal on the guage?
Do you have a grid heater on that bus for the intake air? They cycle on and off depending on the temp the engine develops running normal and may kick back on when at low idle to help with combustion. Usually they shut off when the engine has reached the optimum operating temp and you have a clean burning, low smoke exhaust. Makes me wonder if it is working.
Could be low battery power too if the grid isn't heating up or just not working at all. usually a relay feeds the grid and they do expire over time.
Do you see black smoke under load?
John
__________________
Question everything!
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01-21-2018, 03:41 PM
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#5
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Mini-Skoolie
Join Date: Oct 2017
Location: Fernandina Beach
Posts: 21
Year: 2002
Coachwork: Thomas
Chassis: Freightliner
Engine: Caterpillar 3126
Rated Cap: 25
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I don't have any black smoke, and my dad and I both have checked the batteries and they're all charged.
The temp is something else to note. It doesn't go above 125° after running about 30 minutes with high RPM. We did remove the rear heater completely, and refilled the coolant and nothing changed. But the entire bus runs so flawlessly. The exhaust is just a little worrisome to me.
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01-21-2018, 04:02 PM
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#6
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Bus Geek
Join Date: Dec 2017
Location: Dawsonville, Ga.
Posts: 10,482
Year: 1999
Coachwork: Genesis
Chassis: International
Engine: DT466/3060
Rated Cap: 77
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Normal operating temps should be 190-195°, concern if over 210. I would be checking the reliability of gauges that read only 125 after running for 30 minutes.
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01-21-2018, 04:37 PM
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#7
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Mini-Skoolie
Join Date: Oct 2017
Location: Fernandina Beach
Posts: 21
Year: 2002
Coachwork: Thomas
Chassis: Freightliner
Engine: Caterpillar 3126
Rated Cap: 25
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Quote:
Originally Posted by o1marc
Normal operating temps should be 190-195°, concern if over 210. I would be checking the reliability of gauges that read only 125 after running for 30 minutes.
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I am looking into getting a newer gauge cluster, but am unsure how because of the difference in connectors. I made another post about that but am still unsure how to approach it. It doesn't seem to run hot though. Everything is so smooth
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01-21-2018, 04:38 PM
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#8
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Bus Crazy
Join Date: Jun 2013
Location: Picton,Ont, Can.
Posts: 1,956
Year: 1997
Coachwork: Bluebird
Chassis: GMC
Engine: Cat 3116
Rated Cap: 72
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125 is way low.
The thermostat might be done or stuck in an open condition. Try tapping around the housing. Wouldn't hurt to put a new one in and compare results.
John
__________________
Question everything!
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01-21-2018, 04:42 PM
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#9
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Bus Geek
Join Date: Dec 2017
Location: Dawsonville, Ga.
Posts: 10,482
Year: 1999
Coachwork: Genesis
Chassis: International
Engine: DT466/3060
Rated Cap: 77
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Quote:
Originally Posted by sean82206
I am looking into getting a newer gauge cluster, but am unsure how because of the difference in connectors. I made another post about that but am still unsure how to approach it. It doesn't seem to run hot though. Everything is so smooth
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That gauge would concern me, if it is off by 70° now, if it were to read 190, it would really be 260 and possibly leave you in a false comfort zone.
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01-21-2018, 04:50 PM
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#10
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Mini-Skoolie
Join Date: Oct 2017
Location: Fernandina Beach
Posts: 21
Year: 2002
Coachwork: Thomas
Chassis: Freightliner
Engine: Caterpillar 3126
Rated Cap: 25
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Could you look at my other thread and see if you could explain how I'd go about upgrading the guage cluster?
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01-21-2018, 04:59 PM
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#11
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Bus Geek
Join Date: Dec 2017
Location: Dawsonville, Ga.
Posts: 10,482
Year: 1999
Coachwork: Genesis
Chassis: International
Engine: DT466/3060
Rated Cap: 77
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Quote:
Originally Posted by sean82206
Could you look at my other thread and see if you could explain how I'd go about upgrading the guage cluster?
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I'm not the one to give advice on electrical issues. Bad electrical practices cause fires and piles of ashes.
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01-21-2018, 05:00 PM
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#12
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Mini-Skoolie
Join Date: Oct 2017
Location: Fernandina Beach
Posts: 21
Year: 2002
Coachwork: Thomas
Chassis: Freightliner
Engine: Caterpillar 3126
Rated Cap: 25
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Quote:
Originally Posted by o1marc
I'm not the one to give advice on electrical issues. Bad electrical practices cause fires and piles of ashes.
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Lol, I understand.
I'm just trying to get everything right while I'm in the wiring stage right now.
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01-21-2018, 05:03 PM
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#13
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Bus Geek
Join Date: Dec 2017
Location: Dawsonville, Ga.
Posts: 10,482
Year: 1999
Coachwork: Genesis
Chassis: International
Engine: DT466/3060
Rated Cap: 77
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Quote:
Originally Posted by sean82206
Lol, I understand.
I'm just trying to get everything right while I'm in the wiring stage right now.
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I'd listen to BlackJohn, he seems to have much electrical experience.
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01-21-2018, 05:04 PM
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#14
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Mini-Skoolie
Join Date: Oct 2017
Location: Fernandina Beach
Posts: 21
Year: 2002
Coachwork: Thomas
Chassis: Freightliner
Engine: Caterpillar 3126
Rated Cap: 25
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Quote:
Originally Posted by o1marc
I'd listen to BlackJohn, he seems to have much electrical experience.
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Alright cool. I'll send him a message about the instrument cluster and find out how to diagnose the blue smoke in the meantime. Thanks!
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01-21-2018, 05:20 PM
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#15
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Bus Geek
Join Date: Sep 2017
Location: Owasso, OK
Posts: 2,627
Year: 1999
Coachwork: Thomas
Chassis: Saf-T-Liner MVP ER
Engine: Cummins 6CTA8.3 Mechanical MD3060
Rated Cap: 46 Coach Seats, 40 foot
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Quote:
Originally Posted by sean82206
Alright cool. I'll send him a message about the instrument cluster and find out how to diagnose the blue smoke in the meantime. Thanks!
Sent from my iPhone using Tapatalk
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For your peace of mind I'd have a local diesel shop do a "blow-by" test. It's easy to do and the cost should be minimal.
If the result isn't good, you'll have your answer.
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01-21-2018, 05:25 PM
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#16
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Bus Crazy
Join Date: Jun 2016
Location: Orange County, CA
Posts: 1,356
Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
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A few gauges are critically important, i.e if they do not work reliably you shouldn't drive the bus until they're fixed. The coolant temperature and oil pressure gauges are arguably the most important of them all. Can the individual gauges be replaced, or is the instrument cluster one of those newer displays without separate gauges? Check all the wiring and contacts (especially the grounds) for the sender first, and if it's still reading wrong you will need to replace it. Sorry!
I changed some of my original Teleflex gauges for Speedhut gauges - they are full sweep, use stepper motors, and give me far better resolution than the original quarter-sweep gauges. I don't want a gauge that says coolant is sort-of about at between 180-ish and 200-ish degrees - I need to know exactly what temperature it is!
John
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01-21-2018, 05:47 PM
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#17
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Bus Crazy
Join Date: Jun 2013
Location: Picton,Ont, Can.
Posts: 1,956
Year: 1997
Coachwork: Bluebird
Chassis: GMC
Engine: Cat 3116
Rated Cap: 72
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The 125 reading is in degrees F correct? Not Celsius or you would be overheating.
Before diving to deep into gauge issues check the t'stat out as I mentioned, get the air out of the system totally by removing rad cap and running the engine till no bubbles at all. Might take a while but open all valves related to the heaters. Then you have a good idea what is happening within causing blue smoke.
You never did say grid or glow plugs , I'm not that familiar with the 3126 but all systems operate on the same basis.
John
__________________
Question everything!
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01-21-2018, 06:26 PM
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#18
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Mini-Skoolie
Join Date: Oct 2017
Location: Fernandina Beach
Posts: 21
Year: 2002
Coachwork: Thomas
Chassis: Freightliner
Engine: Caterpillar 3126
Rated Cap: 25
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I have a 3126 engine with glow plugs. I do wait until that light goes out to start the bus, as well as a few other diagnostic checks mine does. It is in degrees Fahrenheit, and I don't any a local diesel shop anywhere near by, not to mention the bus isn't insured, and can't be driven because the driver seat has been removed to do flooring and wiring.
My cluster is an older model, but the gauges aren't replaceable. I would like to switch to a tablet display with a connection to the engine if possible, but I'm very unsure about reliability, so I'm looking into the newer Freightliner clusters, and am completely unsure how to make the transition since mine has 4 connectors and a mechanical oil pressure sending unit instead of electronic. All wiring is connected firmly to the back of the cluster.
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01-21-2018, 06:33 PM
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#19
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Bus Crazy
Join Date: Jun 2013
Location: Picton,Ont, Can.
Posts: 1,956
Year: 1997
Coachwork: Bluebird
Chassis: GMC
Engine: Cat 3116
Rated Cap: 72
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So, if you aren't driving the bus, it isn't going to warm up fully.
Glow plugs might be the issue too but do as in post 17 then get back.
Google how to test glow plugs also then check them out.
No sense thinking about guage conversion till it runs properly.
John
__________________
Question everything!
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01-21-2018, 07:16 PM
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#20
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Bus Geek
Join Date: Sep 2017
Location: Owasso, OK
Posts: 2,627
Year: 1999
Coachwork: Thomas
Chassis: Saf-T-Liner MVP ER
Engine: Cummins 6CTA8.3 Mechanical MD3060
Rated Cap: 46 Coach Seats, 40 foot
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Quote:
Originally Posted by BlackJohn
So, if you aren't driving the bus, it isn't going to warm up fully.
Glow plugs might be the issue too but do as in post 17 then get back.
Google how to test glow plugs also then check them out.
No sense thinking about guage conversion till it runs properly.
John
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Agreed. The 125F is all it might achieve at idle or even high idle.
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