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Cat Man
Cat Man, Caterpillar Engine Expert
Category: Heavy Equipment
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Experience:  23 Years Caterpillar Engine experience.
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My caterpillar 3406b is getting low oil pressure. Used to be

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My caterpillar 3406b is getting low oil pressure. Used to be hot 30 psi at 625 rpm. now 22 psi. used to be 60 psi at 1900 rpm now 54-55psi also hot. Think I need bearrings? If so will rod and mains do it? Or will I need to do the cam bearings to. Is the oil pump possabltay too> Larry

Hi. Thanks for using JA! I will try and help you out.

It is possible that you engine may need rod and main bearings. From my experience, cam bearing do not give much trouble on 3406B engines.

Are there alot of miles on this engine? Do you know when the last time it had a lower end overhaul?


Hey again,

The good news is your oil pressure is still within specifications. The minimum oil pressure spec for your engine is:


15 psi at idle




40 psi above 1200 RPM's.



Please let me know if you have any more questions.

Edited by Cat Man on 7/19/2010 at 10:43 PM EST
Customer: replied 6 years ago.

Thanks for getting back so quick. Motor has 1,180,000 miles on it (GO CAT!)

Verry little blow by out crank case vent. No smoke at all from stack.

Had rod and mains done, about 850,000 miles. About 270,000 miles on bearings now.

Seams the low psi came kind of quickly. Maybe 15,000 miles from normal to low now.

In review idle cold, 45 psi, hot 22 to 28, depents on water temp.

1900 rpm cold 80 psi, hot 54 to 56, " " " "

Thanks for the information.

Wow. That is great. You sure can't get over a million miles on todays engines.


I would probably monitor the oil pressure for a while. Like I said, the oil pressure is still within specs.


Did you have the oil pump replaced also when you had the main and rod bearings replaced?

Customer: replied 6 years ago.
No oil pump change at that time. Would not hurt, beings as we are already in there. What is the range on oil psi speck, and when should I worry, and hurry up the repair

Thanks for the information.

If you did not replace the oil pump last time, I would want to try an oil pump first.


Since 15 and 40 are the minimum oil pressure, I wouldn't worry until your engine hits one of these minimums.


Please let me know if you have any more questions.

Cat Man and other Heavy Equipment Specialists are ready to help you
Customer: replied 6 years ago.
Thank for your help. I ll change pump soon, and maybe wait awhile on bearings
Sounds good. Good luck!

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