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6.5 oil pressure issue.... still!

ranchtruck

ranchtruck

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Location
Central Oregon
Hey hoping for some help. I have 1993 one ton 4X4 with a 6.5 that started to lose oil pressure. I read that it could be the camshaft and bearings. Sure enough I pulled the camshaft and it was shot. Long story short, I replace cam and bearings, new crank, and new rod, main bearings, new heads, new oil pump, new timing. I turned the truck over without the glow plugs in til I built oil pressure, then started the motor. Sounds awesome, runs great, but still I am running what I think is low oil pressure. I am running about 20-25 lbs warm at an idle. Could the oil cooler be plugged or the oil filter housing/ adapter be plugged?? Why could I be still running so low oil pressure? Thanks in advance for the help.
 
Mechanical oil pressure gauge hooked up? I mean a 25 year old sender and gauge still works?

Long story, what is it? Was there a bunch of metal from bearings going out? Did you check for mains cracks? Oil cooler hoses kinked/condition?

What oil and weight you using?
 
WarWagon said:
Mechanical oil pressure gauge hooked up? I mean a 25 year old sender and gauge still works?

Long story, what is it? Was there a bunch of metal from bearings going out? Did you check for mains cracks? Oil cooler hoses kinked/condition?

What oil and weight you using?
Click to expand...
Both stock and mechanical gauge hooked up, new oil cooler lines, new sending unit, mechanical gauge with copper line is new, no kinks in any of the lines. there were no metal fragments in anything all was clean. Using Delo 15W 40 oil.
 
20-25 psi warm idle isn’t bad at all. When you did new cam and bearings, did you take clearance measurements?
What are they?
What about main and rod clearances? New or old?
What are the specs?
Did you check lifter and lifter bore clearances?
Again, what are they?
And the biggest one WW mentioned- is your main webs crack free?

When I am chasing an oil pressure question, I will make a bypass hose that skips the long oil hoses and cooler. It takes a little time and $30, but eliminates questions. Obviously after making all volume flow and pressure improvements, reinstall the cooler into the loop.

As Chris mentioned the bypass valves are often overlooked and cannot be removed and inspected do to damage incurred while removing. Simply buy new ones and replace.

What filter (s) are you using?

With all this, keep in mind- oil pressure isn’t what keeps the engine alive. Volume of flow does. doing oil sample and testing for metals wear can show if bearing contact/ wear is occurring. I have seen 6.5 engines wipe out rod bearings with 50 psi idle and other engines live well into the 300’s when thay never hit 50 at any rpm and idled at 12 psi. Not saying lower is better- but there is a reason gm said 8psi is ok on this design.
 
Don't remember what the specs were exactly but I do know they were well within the specs listed in the GM service manual.
Will L. said:
20-25 psi warm idle isn’t bad at all. When you did new cam and bearings, did you take clearance measurements?
What are they?
What about main and rod clearances? New or old?
What are the specs?
Did you check lifter and lifter bore clearances?
Again, what are they?
And the biggest one WW mentioned- is your main webs crack free?

When I am chasing an oil pressure question, I will make a bypass hose that skips the long oil hoses and cooler. It takes a little time and $30, but eliminates questions. Obviously after making all volume flow and pressure improvements, reinstall the cooler into the loop.

As Chris mentioned the bypass valves are often overlooked and cannot be removed and inspected do to damage incurred while removing. Simply buy new ones and replace.

What filter (s) are you using?

With all this, keep in mind- oil pressure isn’t what keeps the engine alive. Volume of flow does. doing oil sample and testing for metals wear can show if bearing contact/ wear is occurring. I have seen 6.5 engines wipe out rod bearings with 50 psi idle and other engines live well into the 300’s when thay never hit 50 at any rpm and idled at 12 psi. Not saying lower is better- but there is a reason gm said 8psi is ok on this design.
Click to expand...
ok this may sound like a total novice, but then again, in a lot of ways I am a novice in diesel repair. What is the main web? I have never heard that term before.
 
If you can't find the issue and still want higher PSI you can use the oil pump for the squiter blocks and gain some psi. If you are already using it then you have an issue somewhere
 
ranchtruck said:
Don't remember what the specs were exactly but I do know they were well within the specs listed in the GM service manual.

ok this may sound like a total novice, but then again, in a lot of ways I am a novice in diesel repair. What is the main web? I have never heard that term before.
Click to expand...

Shorthand on this site I guess. Main bearing block webbing for crankshaft. Exploded view (literally) here with common crack examples. http://www.thetruckstop.us/forum/threads/6-5-carnage.39865/
 
So you lost oil pressure, rebuild, and... Is the oil pressure the same or better, but, just not pointing the needle straight up at 40 for hot idle? These don't idle at 40 psi: GM diesels move the oil pressure guage a lot.
 
Bought the truck and it ran down the road at about 45psi idled at about 35psi. on both stock and mechanical gauge. Over the course of 65000 miles the oil pressure dropped more and more till the warning light would come on when it idled and it was only running about 10 at 2500 rpms. Took the motor out went through it like described above and turned it over with the glow plugs out to build oil pressure and then fired it. When it starts cold it idles at 42 psi then as it warms up it drops to about 20 psi and runs 35 at 2500 rpms. This just seems very low. I had a 7.3 that at 475,000 was still idling at 45 and running was up around 60, and I have an Isuzu 5.8 that idles at 45 and runs about 70. I am just wanting to make sure this thing is good before I really start driving it cause I don't have the money to do this again. I love the truck and love these 6.5 diesels. The block was in good shape and the crank was brand new along with the cam and heads. Bought most the parts from Rockauto, and Northern parts.
 
Just a thought - what about the turbo health/age?

Is it using any oil? That can vary a little according to usage.

Just for a reference point, I change my oil after burning about ~ 200 gallons of fuel. Fresh oil seems to slow the loss. If I drive a lot on the interstate with sustained boost I'll have to add a quart near 150 gallons of fuel. Seems to use more as the oil gets older.
 
Turbo is good, no use of excess oil. But I took the filter adaptor off and saw the bypass valve. It is about 1/2 inch up in the hole and I can't seem to get it to budge. Was wondering how to get it out. A machine shop I use has a new one for me but I want to get the old one out to take with me. Any help would be great. Thanks
 
ranchtruck said:
Turbo is good, no use of excess oil. But I took the filter adaptor off and saw the bypass valve. It is about 1/2 inch up in the hole and I can't seem to get it to budge. Was wondering how to get it out. A machine shop I use has a new one for me but I want to get the old one out to take with me. Any help would be great. Thanks
Click to expand...
I just took another look. So there is a silver plug with a very small hole in it that is jammed way up there. The valve on the other hand, I can push it up and down with a piece of wire. Seems to push very free and easy.
 
I could be wrong- but think the melling M55I is a low volume oil pump.

We need julian date code & cast number on rear of block to see if this is correct pump for that engine. About 80% chance it is wrong.
 
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