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Old 01-21-2018, 03:05 PM   #1
Mini-Skoolie
 
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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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Old 01-21-2018, 03:12 PM   #2
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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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Old 01-21-2018, 03:20 PM   #3
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Blue Smoke - Cat 3126

Quote:
Originally Posted by Twigg View Post
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?


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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Old 01-21-2018, 03:21 PM   #4
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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?

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Old 01-21-2018, 03:41 PM   #5
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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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Old 01-21-2018, 04:02 PM   #6
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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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Old 01-21-2018, 04:37 PM   #7
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Quote:
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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.


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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Old 01-21-2018, 04:38 PM   #8
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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.

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Old 01-21-2018, 04:42 PM   #9
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Quote:
Originally Posted by sean82206 View Post
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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Old 01-21-2018, 04:50 PM   #10
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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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Old 01-21-2018, 04:59 PM   #11
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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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I'm not the one to give advice on electrical issues. Bad electrical practices cause fires and piles of ashes.
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Old 01-21-2018, 05:00 PM   #12
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Quote:
Originally Posted by o1marc View Post
I'm not the one to give advice on electrical issues. Bad electrical practices cause fires and piles of ashes.


Lol, I understand.

I'm just trying to get everything right while I'm in the wiring stage right now.


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Old 01-21-2018, 05:03 PM   #13
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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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I'd listen to BlackJohn, he seems to have much electrical experience.
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Old 01-21-2018, 05:04 PM   #14
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Quote:
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I'd listen to BlackJohn, he seems to have much electrical experience.


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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Old 01-21-2018, 05:20 PM   #15
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Quote:
Originally Posted by sean82206 View Post
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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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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Old 01-21-2018, 05:25 PM   #16
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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!

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Old 01-21-2018, 05:47 PM   #17
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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.

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Old 01-21-2018, 06:26 PM   #18
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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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Old 01-21-2018, 06:33 PM   #19
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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.

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Old 01-21-2018, 07:16 PM   #20
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Quote:
Originally Posted by BlackJohn View Post
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
Agreed. The 125F is all it might achieve at idle or even high idle.
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