What should the oil pressure be on the 6.5L?

[Mogman]

Barring a problem with oil viscosity I have never heard of "too much oil pressure" unless you have some other indication of problems (IE noisy lifters etc.) I suspect you are overthinking this...

 

[mgFray]

Barring a problem with oil viscosity I have never heard of "too much oil pressure" unless you have some other indication of problems (IE noisy lifters etc.) I suspect you are overthinking this...

It's a diesel, it's noisy compared to any of the gasoline or rotary engines I have.

But it's way above the range in the service manual, and that makes me nervous. The fact that it's not high across the entire range (like I would expect if something was clogged/pressure relief was bad) confuses me greatly.

 

[Mullaney]

It's a diesel, it's noisy compared to any of the gasoline or rotary engines I have.

But it's way above the range in the service manual, and that makes me nervous. The fact that it's not high across the entire range (like I would expect if something was clogged/pressure relief was bad) confuses me greatly.

.
I was pretty happy to see somebody else voice the opinion that I had. I don't think you have an oil pressure problem. Those numbers look good on paper (screen) for that truck. While I am selling opinions here, you mentioned the oil. If you haven't already changed the oil and filter on the truck, that might be a wise investment in time and parts. Getting your motor to a known state would be a good thing. Wouldn't hurt to change out the fuel filters too while you are at it. Might even be good to drain and maybe flush the radiator. You mentioned cold. Where you are, I would think you might do that anti-freeze thing while it isn't miserable cold outside.

All just some opinions, but if you had numbers 20 psi or so higher it might be a concern. AND if you don't have oil seeping from every seal in the motor, I don't think I would be concerned.

 

[Mogman]

It's a diesel, it's noisy compared to any of the gasoline or rotary engines I have.

But it's way above the range in the service manual, and that makes me nervous. The fact that it's not high across the entire range (like I would expect if something was clogged/pressure relief was bad) confuses me greatly.

All engine oil pumps have relief valves, if yours is say at 58LB then that is as high as it is going to get, hot or cold
I say change the oil and drive the damn thing rather than sitting in your driveway looking for problems.

 

[Mogman]

I would change all the fluids on ANY vehicle I get used, unless the "dealer" gave me brands and specs on the fluids.
Heck Tractor supply "all fleet" meets all the required specs but I would not run that stuff, the dealer on the other hand really only needs to meet minimum specs to have a clear conscience.

 

[Maxjeep1]

I got 60psi cold and 40psi at 210 degrees. I’m fine with that. Im happy with it. I would not want less.

 

[Action]

A plugged CDR valve will cause higher pressures, too. I don't know how high that would go.

 

[Maxjeep1]

A plugged CDR valve will cause higher pressures, too. I don't know how high that would go.

Mine stayed the same when it didn’t have CDR and with new CDR. Gov planet just removed CDR and stuck hose inside of hose.

 

[mgFray]

Ya, I've not checked the CDR at all. I'll add that to the list of things to check.

 

[Maxjeep1]

Ya, I've not checked the CDR at all. I'll add that to the list of things to check.

I think the best thing to do is check/ change fluids and drive the piss out of them. Mine has been sitting forever and the more I drive it better it gets.

 

[Milcommoguy]

I think the best thing to do is check/ change fluids and drive the piss out of them. Mine has been sitting forever and the more I drive it better it gets.

How is it these stories ALWAYS have some goofy back story??

Oil, reference the LUBE ORDER. Diesel engine, Yes a bit noisy. Wait till winter. Clanky - clonky till it warms up. Pressure... be HAPPY with the pressure. Might just have a tight built engine, good output pump. The couple I have rebuilt had 70 + PSI on first start. Two weeks later figures like you're seeing. Black oil, YEP. Change it, drive around the block. NOW coal black.

Call when you are seeing less than 10 PSI HOT HOT Mojave desert HOT and at idle. That's the time to check it, LOL

Take it back to the dealer, CAMO

 

[Bulldogger]

I don't know. I've messaged the dealership I bought it from to ask. If I had to GUESS it would be 10W30 or 15W40.

I know with winter coming soon, I need to move to 10W30.

Dealership? Whuh?

 

[papakb]

Dealership? We don't got no stinkin' dealership!!

 

[mgFray]

Dealership? Whuh?

local specialty car used-car dealership. They normally sell classics (pre 1980) cars. Their usual mode is repair the seats, service the vehicle, repair/replace mechanical components that need it, repaint if necessary, etc..

They bought the M998 from someone as a trade-in, were going to 'hummer' it and then realized that made no sense financially. They did change all the fluids (I know both the mechanic and upholsterer that work for them.). All of the fluids and filters came from NAPA. But, they don't remember the oil weight they used in the engine.

But I do know the coolant was flushed and replaced with 50/50 green. The brake lines were flushed and replaced with fresh DOT 5. Fuel filter [under the hood] was replaced, air filter was replaced, all back in May. Differential oils replaced, hub oil replaced, ...etc...

As far as driving it, my housemate who is former Army and does a lot with the local American Legion had been driving it weekly since then to various parades. So I know it wasn't just 'sitting there'. (I got to drive it a few times before I bought it to/from parades...)

My intention is to drive it periodically come winter, probably once a week or so. Which is why I'm going over the vehicle system by system. Anything that doesn't look in spec (like the oil pressure at idle) I am questioning and trying to figure out if it's going to harm the vehicle, leave me stranded somewhere, etc.

 

[Action]

local specialty car used-car dealership. They normally sell classics (pre 1980) cars. Their usual mode is repair the seats, service the vehicle, repair/replace mechanical components that need it, repaint if necessary, etc..

They bought the M998 from someone as a trade-in, were going to 'hummer' it and then realized that made no sense financially. They did change all the fluids (I know both the mechanic and upholsterer that work for them.). All of the fluids and filters came from NAPA. But, they don't remember the oil weight they used in the engine.

But I do know the coolant was flushed and replaced with 50/50 green. The brake lines were flushed and replaced with fresh DOT 5. Fuel filter [under the hood] was replaced, air filter was replaced, all back in May. Differential oils replaced, hub oil replaced, ...etc...

As far as driving it, my housemate who is former Army and does a lot with the local American Legion had been driving it weekly since then to various parades. So I know it wasn't just 'sitting there'. (I got to drive it a few times before I bought it to/from parades...)

My intention is to drive it periodically come winter, probably once a week or so. Which is why I'm going over the vehicle system by system. Anything that doesn't look in spec (like the oil pressure at idle) I am questioning and trying to figure out if it's going to harm the vehicle, leave me stranded somewhere, etc.

Seems odd that the dealership would flush the brake lines.
And, they got an air filter at Napa?
This sounds like the dealership that wanted to charge me for a cabin air filter replacement in a Trailblazer. It doesn’t use one. Lol

 

[mgFray]

So it had been driven to/from parades and such and all over the place with a smashed oil pan?
Seems odd that the dealership would flush the brake lines but not fix the pan...
And, they got an air filter at Napa?
This sounds like the dealership that wanted to charge me for a cabin air filter replacement in a Trailblazer. It doesn’t use one. Lol

I think you are confusing me with someone else. No smashed pan on this thing.

Underside of my M998 only shows some minor rust on the transmission oil pan, and a whole lot of dirty from off-roading in my pasture. . But there are no dents in any of the pans, and the pan surfaces are "original to the engine". (This was something I've looked at, alas no pictures though.)

 

[Action]

I think you are confusing me with someone else. No smashed pan on this thing.

Underside of my M998 only shows some minor rust on the transmission oil pan, and a whole lot of dirty from off-roading in my pasture. . But there are no dents in any of the pans, and the pan surfaces are "original to the engine". (This was something I've looked at, alas no pictures though.)

Yes. You are right on the pan. I got these mixed upp. I will edit that. Thanks.

 

[Bulldogger]

But I do know the coolant was flushed and replaced with 50/50 green. The brake lines were flushed and replaced with fresh DOT 5. Fuel filter [under the hood] was replaced, air filter was replaced, all back in May. Differential oils replaced, hub oil replaced, ...etc...

Gotcha.

Regarding green coolant, I've read that is will work but most swear by SCA versions that fight corrosion. Peak makes the one I use, and it is Pink.
Green won't harm the engine, but won't protect it from internal corrosion, as I understand it.

Bulldogger

 

[Milcommoguy]

TO BE sure go over it again. I would be a bit of work for a "quickie flip car dealer" to work that out IMO. The "lipstick on a pig" might not work in your favor.

There's a lot to know & learn on these rigs. If you get the free 10,000 mile, 28 point check with oil change without something going wrong... I want to know that dealership.

Said this before, my moto. The HMMWV "A driving experience coupled to a mechanical nightmare". This is something the dealer forgot to mention.

You did say Winter is coming?? Get familiar with the starting system and sequence. Driving techniques, stopping, stuck and braking. Check those tires for date codes and cracking if military issue. Trying to be helpful...But there's a ton of checks and inspections not necessarily main stream auto shop.

Here's a list for those all APPed up. Would be neat to have one worked out for the hobbiest. Let's go IT department.

Good Luck. You (all) can do this. Read, inspect, repair, replace, wrench, money and Band-aids. Beer too.

Know your rig, TM's and bring your tools, or run in convoy, CAMO

PS...... TM's is not Technical Manual. Trouble Manual. That's why there's so many. LOL

FLOW CHART to FOLLOW.

 

[TNDRIVER]

Ok, I've got a manual gauge, and also was able to hook up the tack. So I've got some "real" numbers.

6.5L (2004)

Cold idle - 600 RPMs - 35-40 PSI

Warm idle 650-700 RPMs - 30-40 PSI

55 MPH - 2800 RPMS - 55-57 PSI

55+ MPH - 3000 RPMS (roughly) - 57-58 PSI

The engine never exceeded 60 PSI.

In neutral (no load) at 2800 RPMs was about 52 PSI.

So at a _MINIMUM_ it appears to me that the idle oil pressure is WAY too high. I have no idea what could cause this. Any suggestions?

At speed/load the vehicle seems to match what others have told me to slightly high.

I know very little about Diesel engines, especially this type of problem. I'm looking for any idea what I should look at/investigate next.

I'm tempted to simply do an oil change/filter replacement. (The oil in the engine is _very_ black. I was told it was changed about 1000 miles ago when I bought it, but if it was a gasoline engine I'd certainly be doubting that based on how black the oil is.)

Edit:

Found this in the service manual:

STOP 6.2L IDLE (650 ± 25) 6.5L IDLE (700 ± 25) 6.5L DETUNED IDLE (700 ± 25) 2000	0 PSI 10-15 PSI 10-15 PSI 10-15 PSI 40-50 PSI

So stop and 2000 RPM are about right, but idle is _way_ off.

The oil is black becauses of soot, common with diesel engines. My two cents is use Shell Rotella 15/40 with the Wix 51060 or NAPA 1060 (same filter) . You should see what the stuff looks like at 20000 or 25000 miles, and the oil analysis says its still good! Your pressure numbers look good. If its a new or rebuilt the idle numbers may come down but looks good to me. It's got PRESSURE, enjoy! No PRESSURE no joy!