Low oil pressure?

[jjorgensen52]

Driving the Ty over my break this past week, third day I was home I noticed the oil pressure dropping. Drove the truck again, short distance to verify. I have about 50 - 55 psi at idle when the truck is cold, building to 60-65 psi with a little rev. Once it gets warm (right now I'm running around 170*F ), the pressure drops to 25-30 psi at throttle and 0-5 psi at idle (so low that the check gauges light flashes). The truck is not leaking anywhere, has a full pan of synthetic, and the oil doesn't look unusual in anyway, or smell burnt at all.

Any ideas ?

 

[ed hess]

Re: Low oil pressure?

Driving the Ty over my break this past week, third day I was home I noticed the oil pressure dropping. Drove the truck again, short distance to verify. I have about 50 - 55 psi at idle when the truck is cold, building to 60-65 psi with a little rev. Once it gets warm (right now I'm running around 170*F ), the pressure drops to 25-30 psi at throttle and 0-5 psi at idle (so low that the check gauges light flashes). The truck is not leaking anywhere, has a full pan of synthetic, and the oil doesn't look unusual in anyway, or smell burnt at all.

Any ideas ?

take the filter and cut it open, if the filter that was on there when this started is still around, cut that one open and look at it also.

ed

 

[AUSyTyIN]

Re: Low oil pressure?

I'm assuming you are using an aftermarket gauge? Aren't there two oil pressure sensors on these trucks (one for the stock gauge and one for the comp)? If so, I would say something is wrong inside you motor. Hopefully it's something small like the oil pump spring. :?

 

[jjorgensen52]

Re: Low oil pressure?

I'm assuming you are using an aftermarket gauge? Aren't there two oil pressure sensors on these trucks (one for the stock gauge and one for the comp)? If so, I would say something is wrong inside you motor. Hopefully it's something small like the oil pump spring. :?

Stock gauge, there is only the single sender (mine is about 600 miles old, new Delco part). It has been dead on ever since I put the new sender in, it just started doing this after sitting for 2 weeks. I have one of the high flow melling pumps, so that hopefully isn't it but we shall see.

Ed, I haven't changed the filter yet but an oil change and filter is on my list of troubleshooters

 

[4C FED]

Re: Low oil pressure?

Buy a mechanical gauge & stick it in the plugged port on the remote filter housing.
It adds a great deal to your piece of mind.

 

[jpalmer]

Re: Low oil pressure?

yeah same thing happened to me ........THEN MY MOTOR BLEW . do the guage but at the first sighn of trouble shut it down. check everything out something is wrong. good luck

 

[jjorgensen52]

Re: Low oil pressure?

Put a mechanical gauge on the truck yesterday and warmed it up... shut it down when the reading dropped below 20psi... same symptoms as before, the dash gauge is reading right on. Guess it's time to pull my oil pan

 

[jjorgensen52]

Re: Low oil pressure?

Well, after about 6 hours of labor my oil pan is out. 4k later the motor still looks pretty inside, no metal anywhere and everything looks intact. As it turns out, I have an M55 in the motor, so just as well that I took it apart. Of course, the GMPP high volume pump I just bought turns out to be a melling M55HV, so I'm in the same boat, looks like.

Anyway, the source of my oil woes was actually my pickup tube. As it turns out, the pickup was welded to the pump, and it developed a hairline fracture (probably 1/4" total) through the weld (thus, allowing loss of suction when the pump warms up and the crack expands). It's circled in the pic of the pump.

first, bad luck with my jack :roll:

Intake off and distributor out so I can prime the pump when it goes back together

Guts of motor, pan off

old M55 v. new M55HV

Crack in the old pump

And, the other thing I'm doing while I'm in there ... 2800 :tup:

 

[Windedv6]

Re: Low oil pressure?

The M55HV has a much stronger housing for those that are wanting someing stronger than the older original M55. The new M55 Select also has a stronger housing than the recent recast M55.

You need to know that the M55HV is longer than your stock pump. Check your pickup clearance whith the bottom of the pan.

John

 

[Windedv6]

Re: Low oil pressure?

When you put your pan on did you check your pickup clearance when using the HV pump? I was curious if it hits or comes close to the pan bottom.

John

 

[jjorgensen52]

Re: Low oil pressure?

Overall, it was 0.25" taller than the M55 was. I reshaped the pickup slightly to match the height of the assembly I removed

 

[Windedv6]

Re: Low oil pressure?

Thanks!:tup:

John

 

[4C FED]

Re: Low oil pressure?

I bet that crack in the weld was not the cause of your low pressure.
Regardless, you've made sure that you got rid of the crappy casting.

 

[sharkbait]

Re: Low oil pressure?

so is the truck running? If so, hows the pressure?

 

[Windedv6]

Re: Low oil pressure?

I bet that crack in the weld was not the cause of your low pressure.
Regardless, you've made sure that you got rid of the crappy casting.

The crack is on the inlet side. I agree...it probably is not a party to the low pressure.

 

[socalblue]

Re: Low oil pressure?

Im in the same boat, cant figure out why the oil pressure drops gradually on mine, keep us updated on the progress...I'll probably be following your lead lol

 

[jwaller]

Re: Low oil pressure?

you can see the additional rib on the HV casting. if you have that your fine.

 

[jjorgensen52]

Re: Low oil pressure?

Ran again, finally. about 40 psi cold at idle with the HV pump. More details to follow

 

[jjorgensen52]

Re: Low oil pressure?

That seems low.

Mine is 70+ PSI, cold (60deg F) W/ 15/50 Mobile 1. M55HV pump, large clearances. (.002-.0035 main, .0025 rods)

Did you pull some caps and check the bearings while the pan was down???

I did not pull any caps because there was no evidence whatsoever of metal in the oil or the pan, and it wasn't making noises. I never completely lost pressure, so I wasn't too worried.

I had 65psi idle before, but I also had a high pressure spring in the old pump, which I do not have in the new pump. oil is Synthetic Mobil 1, 10W30

 

[gkrcr882]

Re: Low oil pressure?

I have the same issues. It ran low on oil once, when the remote line gasket went, but I shut it down when the gauge dropped and the light came on. At warm idle, the pressure is really low, about 5 psi, but it jumps to about 20 when driving. Cold it starts out at about 40....BUT: I have reason to believe that my gauge is off, since 3 of my other gauges are off, along with the odo. Running Mobil 1 10W30, no odd noises or anything.