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97mack1

Cat 3406 Low Oil Pressure

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I have a 94 model cat 3406c peek motor which has been converted to full manual , anyways I have a couple of questions first one is I did an inframe on it less than 2000 miles and my oil pressure once its at 180 degrees is about 25 psi low enough for the buzzer to go off. would replacing thwe oil pump bring my oil pressure back up. when the motor is cold its at about65 psi at around 1200rpm. second queI have an oil leak behins the front structure plate by the top of the block deck. what all is involved in fixing this leak? any help is greatly appreciated.

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WHAT WAS THE OIL PRESSURE BEFORE THE INFRAME? DID YOU HAVE THE CRANK MICED FOR WEAR? IF YOU DID AN INFRAME YOU SHOULD PUT A CAT REMAN OIL PUMP IN. WHAT SIDE OF THE MOTOR IS THE OIL LEAK? IS IT ON THE GEAR HOUSING SIDE?

BULLHUSK

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If this just happened at the time it was rebuilt, something was not put back right.

Check the oil pressure at the front and back of the block. Are they the same? Different?

Does it have Jakes? A cracked or inproper installation of the jakes can cause low pressure.

Did some one change oilpumps? The E and C oil pumps are the same but the E motor releaf spring and hold down are different. The E runs a lower pressure, but not that low. A good E will run 50-55 at 1800, a C should run 65.

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Thanks for the responses. I am not sure if the crank was checked dropped it off with the so called mechanic. The oil pressure has always been low, before the inframe once it was to operating temp it would drop to about 35psi but the temp would not go over 160 I replaced the thermostat when it gets to 180 that's when it drops down.The front structure is leaking on the drivers side up top runs down behind the pump down the side of the block.

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97 Mack1'

I would check the Jakes an the oil pressure (front an back of block as peterj suggested).But it sounds to me like there is tollerence issues either in your oil pump or your crank. Did the guy know you had oil pressure issues before he did the overhaul? If so why didn't he put a new oil pump in when he did the motor? How did the bearing inserts look when he pulled them, were they showing copper? I'm not trying to be a Monday Morning Quaterback I'm just trying to help. Now with that being said if we do a motor job either in shop or sending it out, if there is an oil pressure prob. we check all of these things including micing the crank for oil clearance. I would call the guy who did the motor job for you an run some of these questions that peterj & myself asked. As far as the oil leak? I would clean up the block where you see the oil an try to pin point where the leak is

Good Luck Ernie

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If you are losing oil at the jake brake housing, it would be easy to find. Pull the valve covers and watch while an assistant starts the engine. Why an assistant? They could also shut it off before it makes too big of a mess. Any oil loss at the jake housing is unacceptable. I once had to do a roadside repair for a friend, whose jake had come apart under pressure and blew a hole as big as a golf ball in the top of the valve cover. A 3406 has rocker arm stands like an FE Ford. The jake oils through a ported alignment stud which is press fitted into the top of the stand. It is sealed by an o ring. Take the cover off and look, and you wont have to guess.

I just noticed your address. West Texas Peterbilt is the place to go , in your area.

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If you are losing oil at the jake brake housing, it would be easy to find. Pull the valve covers and watch while an assistant starts the engine. Why an assistant? They could also shut it off before it makes too big of a mess.

And don't let the Jake come on with the valve covers off!!! BIG MESS!!!

-John

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At this momentthe jakes aint hooked up, when the truck was converted to manual we did not hook them up. It was set up as a 2 stage is there a problem hooking it up as 1 stage?

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Also if not already done you should check for fuel in the oil. Take a samlpe and send in for the check.

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Also if not already done you should check for fuel in the oil. Take a samlpe and send in for the check.

I did take a sample of oil to get checked out there was no oil in fuel.

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Hi I had a 3406B in a 1989 freightliner oil samples came back high in copper. Cat dealer could'nt figure it out and about the same time I noticed my oil pressure down about 5 lbs. Finally after much disscusion with cat they agreed to do a bearing roll in. When they had the pan off they found the bushings shot in the oil pump. So rebuilt oil pump and my problem was solved. Not sure if this will be your problem but I 'd check the pump out.

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Well I have an update. Pulled the pan and replaced the the oil pump. Noticed that the old pump had some wear on the shaft bushings, I was sure this was my problem,put the new pump put fresh oil and filter turned her on and ran it for a while till the temp got to about 180. It has good pressure when truck is cold but once it gets to operating temp it drops to about 25#'s. any other suggestions? I am going to get the front stucture redone as it is leaking oil would it be wise to replace cam bearings in it? this has me stumped. :pat:

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Well I have an update. Pulled the pan and replaced the the oil pump. Noticed that the old pump had some wear on the shaft bushings, I was sure this was my problem,put the new pump put fresh oil and filter turned her on and ran it for a while till the temp got to about 180. It has good pressure when truck is cold but once it gets to operating temp it drops to about 25#'s. any other suggestions? I am going to get the front stucture redone as it is leaking oil would it be wise to replace cam bearings in it? this has me stumped. :pat:

When the pan was down would have been a good opportunity to roll new bearing shells in. Did you mic the bearings for clearance at all? A lot of aged engines lose oil pressure internally due to bearing clearance which is a factor of wear from operation.

Rob

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