cbarn

Hello friends!

I have a 2004 Suburban 1500 4WD LT with 5.3L Vortec, 307,500 miles on it. A few weeks ago when driving the oil pressure dropped nearly to zero and the low pressure warning came up on the DIC. I pulled as soon as possible, checked the oil, and saw it was quite low - it's always burned a bit (maybe a quart or two between oil changes) but I think the summer heat accelerated that; no visible leaks anywhere, it's not piddling in the driveway. Dropped about 1.5 quarts in, and while it bumped the pressure a bit it was low enough to give me jitters. Got home, did a full oil change + new filter, and pressure was pretty much normal after that. For a short while, anyway - but now I'm paranoid and watching the gauge, and still seeing it drop as low as 20 at idle, and just hitting up at 40 when driving harder. My recollection is that 30-50 is more my normal range, so I started digging for possible solutions.

Today I replaced the oil pressure sensor to make sure I'm getting an actual accurate reading. Many of the threads mention that the lifter filter basket below the sender can clog up - however, mine doesn't have that filter. I believe I read that only the later model (like, later in 2004 and after, I just missed it!) engines with the automatic fuel management lifters have the filter, is that correct?

Unfortunately, the new oil pressure sensor reports the same as the old one, so I think my next step is the O-ring on the oil pickup tube. Not sure how I feel about doing that in the driveway (no access to a lift, plenty of jack stands and ramps though), but it looks like it might be manageable!

Rednucleus

At 300k miles, if your idle (hot idle?) is as low as 20, that is pretty darn good. You will read alot of posts with hi mileage motors (>250k) are running idles closer to 5-10 psi.

cbarn

Thanks Rednucleus, in that case for now I'll just keep an eye on it and leave well enough alone! It's entirely possible that it's slowly dropped to this level over time and I just didn't notice until it plummeted when level went low and I started watching it like a hawk. Was watching yesterday and starting (cold) idle with ambient temp 85F was 20, hot idle dropped a hair (maybe 18) and pressure was up to nearly 40 when accelerating. Cruising seems to settle at about 25, not much above idle.

I do notice more oil burn in the summers (tend to drive harder in the summers also), and after a hard drive I'll sometimes get a decent sized puff of blue smoke at startup, thinking that the hot oil is slipping past rings in one or more pistons. Might just bump up to a higher viscosity to compensate for the age & wear on the engine. I'm still running 5W-30 as recommended, but the manual says 10W-30 is OK also. Will also put in a new level sensor when I do the change since the old one failed to notify when I was down 1.5 quarts.

Cusser

We had similar issue on our 2005 Yukon Denali with 6.0 Vortec engine for like 3 years. Our trusted mechanic said no filter screen under the sensor and advised NOT to replace the sender, trust the pressure gauge, just ignore the DIC "warning" and chimes at start up.

Yes, if really no oil pressure while driving, engine would've died long ago. Anyway, we recently sold this 2005, and advised the new owner about the issue. 235K miles on the 2005 was starting to concern Mrs. Cusser. So we updated to a 2011 with 73K on it.

cbarn

Thanks Cusser, I appreciate the response. Fortunately I've got DIC warnings or chimes at startup and it seems to be holding at about 20 at idle right now, just gotta watch and make sure the level catch me by surprise again. No chimes at all, actually, since the factory Bose stereo amp appears to have died a few months ago - time to refocus on that project!

cbarn

Just a follow-up on this - I treated the oil with Seafoam, drove it about 200 miles, and did another oil change on it today replacing the specified 5W-30 with 10W-40 (at 17 years old and nearly 308,000 miles we're way out of factory spec by now!) After the change, sitting at nearly 40PSI at cold-ish idle (car was still at about 170F, normal run temp is 210F); revving to 3000RPM pushed it up to about 60PSI, both values pretty much spot on for what it was when new. I also replaced the oil level sensor, which let me down a few weeks ago - pretty easy change-out except that when it was installed they managed to align it at exactly the right angle to prevent releasing the wiring connector.

Cusser

"Love" those required "squeeze this as you try to pull back" connectors !!!