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A 4b-390 cummins suddenly started to smoke and drop oil

Customer Question
A 4b-390 cummins suddenly...

A 4b-390 cummins suddenly started to smoke and drop oil pressure. engine starts and runs normal. oil pressure is normal until engine warm then drops and starts smoking. suggestions? thanks

Mechanic's Assistant: What is the complete model and serial number of your machine?

Case 450c gbe 1680

Mechanic's Assistant: Are you fixing this yourself? What have you tried so far?

Yes. the equipment is lightly used 50 hours a year. the engine has had regular service oil, filter, antifreeze once every 3 years. current fluids look normal (no water, diesel in the oil). about to check compression. is there anything common to smoking and oil pressure loss?

Mechanic's Assistant: Anything else you want the construction mechanic to know before I connect you?

No. thank you.

Submitted: 11 months ago.Category: Agriculture and Farm Equipment
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Customer reply replied 11 months ago
compression test. all cylinders around 300 to 320 psi.
Answered in 44 minutes by:
9/18/2017
Mechanic: Wayne, Journeyman replied 11 months ago
Wayne
Wayne, Journeyman
Category: Agriculture and Farm Equipment
Satisfied Customers: 11,324
Experience: 34 + years as a mechanic
Verified

Hi I'm Wayne

I will help you with this

Oil pressure drop can be caused by fuel dilution

and smoking can be caused from faulty injectors

I suggest to smell the oil ,see if it smells like diesel fuel

injectors will cause both issues

I hope this helps you

Hi. If this helped you

Please rate my answer 4 or more stars.

That is the only way I get credit for the question

or the money you paid stays at JA and I get nothing for my time.

If you need more info use the REPLY button

Not the Poor/Bad service.

Wayne

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Customer reply replied 11 months ago
these questions should be directed to an experienced cummins mechanic.
is there anything common to sudden smoking and oil pressure loss?
engine starts and runs normal until warms up.
Mechanic: Dan, Technician replied 11 months ago
Dan
Dan, Technician
Category: Agriculture and Farm Equipment
Satisfied Customers: 6,889
Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment, trucks and farm equipment - 1995 WyoTech graduate.
Verified

Hi my name is***** see you requested a new professional. I agree with the other professionals answers and would also add that a worn oil pump, rod and main bearings, or a faulty oil pressure regulator can effect oil pressure as well as a faulty oil pressure bypass valve.

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Mechanic: Dan, Technician replied 11 months ago

What color smoke?

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Customer reply replied 11 months ago
is there anything common to SUDDEN smoking and oil pressure loss? the change from normal to smoking happened within 5 minutes. engine starts right up and runs normal except for smoke and low oil pressure.
current fluids look normal (no water, diesel in the oil), radiator was a little low.
oil pressure is normal when cold until engine warm then pressure drops and starts smoking a lot.
smoke color : i would call it blueish. the engine is a cummins 4b-390. are they know for a crack head or other sudden failure?
are you experienced with cummins?
thanks
Mechanic: Dan, Technician replied 11 months ago

Im very experienced with Cummins and these engines have different fuel systems depending on application. Do you have the rotary injection pump or inline robert bosch? Smoke can be fuel system related or oil consumption related due to wear....

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Mechanic: Dan, Technician replied 11 months ago

These heads are known for cracking between the valves and injector seating area

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Customer reply replied 11 months ago
i dont know the difference between the rotary injection pump or inline robert bosch. the injector lines are at the rear of the injector pump, opposite end from the gear drive, (not on top).
could an oil leak in the injector pump cause low oil pressure?
is it likely a cracked head could cause the smoking and oil pressure loss?
from your experience:
the smoking and oil pressure loss happened 'suddenly', can you explain what may have happened?
is this likely to be an inframe or engine remove fix?
thanks
Mechanic: Dan, Technician replied 11 months ago

Thanks for the update. Blue smoke can be both oil and fuel. So let me ask. The oil pressure was it verified with a separate mechanical gauge? If so what is the actual oil pressure?

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Customer reply replied 11 months ago
the oil pressure gauge is a case (red/green) no psi numbers, i dont know the actual psi. i have had the dozer for 12 years, the oil gauge always was 2/3 in the green until this happened.
could an oil leak in the injector pump cause low oil pressure and oil in the diesel?is there anything common to SUDDEN smoking and oil pressure loss? the change from normal to smoking happened within 5 minutes. engine starts right up and runs normal except for smoke and low oil pressure.
current fluids look normal (no water, diesel in the oil).
oil pressure is normal when cold until engine warm then pressure drops and starts smoking a lot.
the question i am asking is: the smoking and oil pressure loss happened 'suddenly', can you explain what may have happened?
thanks
Mechanic: Dan, Technician replied 11 months ago

We need to get a mechanical guage on it to see what the actual pressure is before and after this occurs for accuracy.

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Mechanic: Dan, Technician replied 11 months ago

You are getting diesel in the oil? yes the fuel will thin out and dilute the oil causing low oil pressure. The injection pump drive seal can leak in through the front timing cover. Your injection pump will need to be rebuilt. You need to pin the timing pin on #1 TDC under the injection pump. Push in and bar the engine over until the plastic pin plunger drops into the gear slot before removing the pump. Remove the first valve cover and be sure both rocker arms are loose on #1 cylinder. If so and the pin is engaged in the hole you are okay to remove the injection pump.

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Customer reply replied 11 months ago
hi,
your question: You are getting diesel in the oil?
from my earlier response: 'current fluids look normal (no water, diesel in the oil).'... you are not reading the info i sent, neither did the first mechanic.
thanks for the description on injector pump replacement and i agree i need to get accurate oil psi, but the current oil gauge is acting like it has for 12 years, 570 machine hours.
thank you, ***** ***** are not answering the question: is there anything common to SUDDEN smoking and oil pressure loss?
Thank you again. there is no need to respond.
Customer reply replied 11 months ago
hi,
are you experienced with a cummins 4b-390 engine? it is in a case 450c dozer, 1986 vintage.
i assume you can read the previous messages.
the question is there anything common to SUDDEN smoking and oil pressure loss?
current fluids look normal (no water, diesel in the oil)
compression test. all cylinders around 300 to 320 psi.
the change from normal to smoking and oil pressure loss happened within 5 minutes.
the engine currently starts right up and runs normal except for smoke and low oil pressure.
the question i am asking is: the smoking and oil pressure loss happened 'suddenly', can you explain what may have happened?
thanks
Mechanic: Curtis B., Technician replied 11 months ago
Curtis B.
Curtis B., Technician
Category: Agriculture and Farm Equipment
Satisfied Customers: 31,876
Experience: Technican turned service manager on multiple lines of equipment and rental equipment.
Verified

This is the natural engine and not the turbo charged BT3.9 that is also listed with the 450C? Form the Cummins service manual, it states smoke and loss of oil pressure is caused by oil thinned from diesel intrusion, or turbo charger bearing out, which shows a smoke.

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