1994 M998 Strange oil pressure

[AynorArmory]

I'm new to the site and just bought my first M998. I bought it from C&C Equipment. Since I have had it I replaced all of the guarded but still having issues with 2. The generator guage doesn't work at all. But no big deal. The oil pressure on the other hand shows 10 sometimes 5 psi. And holds at 10 psi while driving and sometimes goes to 20-25 at most. Truck sounds fine seems to run fine. Anyone have it ideas on what could be the issue? Bad filter? Clog? Or sender? Any help would be awesome

 

[Dock Rocker]

I'm new to the site and just bought my first M998. I bought it from C&C Equipment. Since I have had it I replaced all of the guarded but still having issues with 2. The generator guage doesn't work at all. But no big deal. The oil pressure on the other hand shows 10 sometimes 5 psi. And holds at 10 psi while driving and sometimes goes to 20-25 at most. Truck sounds fine seems to run fine. Anyone have it ideas on what could be the issue? Bad filter? Clog? Or sender? Any help would be awesome

Has the truck been serviced? Fluids and filters all the way around? If not start with that.

Never trust a military gauge. Ever. Replace the sending unit. That is likely your issued.

The volt gage really is a big deal. One of the biggest problem areas with these trucks is the charging system.

Do yourself a favor and get a grounding harness or make one and install it. It will prevent some of these problems.


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[3jacks]

Take the sending unit off and install a mechanical gauge to see what pressure you actually have in the engine. Plus what doc rocker said above.

 

[AynorArmory]

Thanks a ton. The air filter and transmission fluid look brand new. I'll get oil done Monday. What all should I have done?

 

[Dock Rocker]

Thanks a ton. The air filter and transmission fluid look brand new. I'll get oil done Monday. What all should I have done?

Download the TM’s and start reading. That will do more to help you than anything.

Service the hubs and check the seals, drop the trans pan and change the filter, change the fuel filter, instal a grounding harness to help keep your smart box alive. Drop and replace the fluid from the transfer case and diffs.Check the tire pressure. Air down to about 25 lbs for max comfort. Grease all of the points on the chassis outlined in the -24 manual.

If you do this you will at least have a baseline to keep up with your maintenance.


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[Bulldogger]

Do the entire lube order if you can. It could have been a decade since some of those fittings or systems saw fresh lube.

A new sending unit is a good idea. A cheap autometer gauge from the auto parts store will bring immediate piece of mind or tell you to stop driving at once. I did this same thing before diagnosing my sending unit.

The voltmeter issue is important! Put a multimeter on the batteries and at the generator ASAP and check your voltage. Watch it while driving if you can. You can overcharge and overload lot of stuff fast if your regulator is going bad. A good thing to do is follow all the positive and negative wires and cables and check each bolt and nut and clamp along the way. Loose connections can play havoc with equipment and with your regulator. Put "eyes on" every one of those connections, as yours may be the first eyes looking at some of them in a decade. My 998 hadn't any maintenance in 10 years if the date on the air filter is the last routine maintenance she had from the Guard.

Hope this helps

Bulldogger

 

[AynorArmory]

I checked the air filter, trans fluid, transfer case fluid, and greased fittings today I know it's not much but didn't have a ton of time today. Looks like c&c greased everything good fitting wise and the trans fluid looks brand new as well as the air filter. The transfer case was wet on the bottom side wish scares me and looks like I have a torn boot on on front left when axel. Also looks like I have a seal that needs replacing on the rear left side near rear brakes. I grabbed some dextron trans fluid today's so I'll drain the transfer case this week and refill. I also got the grounding kit in route. As far as oil guage how is it replacing a sending unit? I also ordered a trans filter and seal. I am pretty good at mechanical work but never done anything on a 998. Think it's something I can tackle or take it to my local lube shop? Thanks for halls input I'll post pics tonight of my rig.

 

[Bulldogger]

On my 998 the sending unit is on the rear of the engine just inside the doghouse.

Sounds like you're on the right path in terms of the maintenance you're doing. The repairs you describe, which might just turn out to be open / inspect are within the ability of a decent shadetree mechanic, especially one with help from this site.

The torn boot on the halfshaft can be replaced or simply a new half shaft put in. It's shorter in terms of time to replace the whole thing and save the torn one as a spare or sell it to someone who'd rather replace a boot than pay $150 for the whole assembly new. Having read the TM procedure for disassembling a half shaft I have no desire to do it.

Keep at it!

Bulldogger