5.3 gm oil pressure sending unit

[Vaquero]

I have a '05 Avalanche and my oil pressure shows pegged at 80 pounds under normal conditions and drops to zero under moderately heavy acceleration. No in between readings. Would this be the sending unit? If so, where is the unit located on the engine? Thanks for your consideration of this subject.
on the phone

 

[dreyes89]

Should be near the intake manifold, take the plastic cover off( one bolt in middle), sending unit will be in rear near firewall

 

[Vaquero]

Danged if I can find it! That "Vortec" intake manifold is really crammed in there. I'll keep looking.

 

[dreyes89]

If this don't help you, I have failed lol...

http://ww2.justanswer.com/uploads/ggrote1/2010-12-26_165614_oil.gif

 

[M. Sage]

You're sure it's full of oil?

 

[Vaquero]

Well, that'll pull me off the right hand side. Thanks! Soon as I finish supper I'll take another look.

 

[Vaquero]

You're sure it's full of oil?

Oh yeah. Been this way through the last 15k or so. Many oil changes.

 

[dreyes89]

I'd go ahead of disconnecting it then connecting, and see if it stops, clean the connections, it was probably just loose.

 

[shortround]

At normal idle, the oil pressure gauge should be at the low end, since the oil pump is mechanically driven and the higher the RPMs, the higher the oil pressure.

If there is no "check engine light" and if you have no oil leaks, the oil on the dipstick is not black, and the oil level is good, then you probably don't have to worry about it.

Before you replace any parts, do a full engine oil flush. Dump a quart of oil and add a quart of engine oil flush. Run the engine as directed on the product's container.

Dump all the oil, replace the oil filter, and refill with fresh oil, and see what happens.

You did not say how many miles on your burro, or how often you change the motor oil.

If vehicle mileage is less than 50K, consider full synthetic oil. You can safely go 15K miles without an oil change. Just dump the oil filter at 7.5K miles, and top off the oil.

 

[M. Sage]

At normal idle, the oil pressure gauge should be at the low end, since the oil pump is mechanically driven and the higher the RPMs, the higher the oil pressure.

If there is no "check engine light" and if you have no oil leaks, the oil on the dipstick is not black, and the oil level is good, then you probably don't have to worry about it.

Before you replace any parts, do a full engine oil flush. Dump a quart of oil and add a quart of engine oil flush. Run the engine as directed on the product's container.

Dump all the oil, replace the oil filter, and refill with fresh oil, and see what happens.

You did not say how many miles on your burro, or how often you change the motor oil.

If vehicle mileage is less than 50K, consider full synthetic oil. You can safely go 15K miles without an oil change. Just dump the oil filter at 7.5K miles, and top off the oil.

Hell no.

First, the computer on that truck doesn't care about oil pressure. It won't trip a check engine light for it. I can't think of any that actually will (directly - the closest I can come are cars with variable cam timing that set cam position codes because of low oil pressure).

Second, don't flush your engine unless you want to pull the oil pan off and change the pickup tube. If an engine's gunked up to need a flush, the screen on that pickup tube is going to get plugged when all that stuff comes loose. Most times, the gunk stays stuck in places that don't get a good flow of oil anyway, so your oil galleries are clear.

Last, the synthetic oil/low miles cars thing is a mix of urban legend and outdated info. You can switch over any time.

 

[Vaquero]

220,000 miles so far. Oil change @ 5000 or less since I've owned it. I give up on finding the sending unit, I'm cut up like a butchered hog and aint got close. lol!
No "check engine" light and no leaks, no knocks. No change at idle or highway cruising speed, pegged at 80 pounds until I pass on a two lane then it drops to zero, back to 80 after out of passing gear.
Just odd. (need one of those "head scratcher smileys)

 

[Vaquero]

Instrument cluster failure? (I hope not)

 

[M. Sage]

Looking at that diagram, it's going to be toward the driver side of the engine, just behind the intake manifold. Not real easy to get to, and you "need" (yes, I'm sure there are other ways, but it'll make life easier) a specialty socket to change it.

 

[dreyes89]

look for anything that has a connection towards the rear right(driver side), and that is screwed on vertically. lol, and i doubt it is instrument failure, due to the fact that the oil pressure gauge is the only one acting up, if it was cluster, then i believe all it would be acting froggy.

 

[shortround]

Interesting view point.

My lawn mower shuts off if it detects low oil pressure.

Reputable engine cleaners will dissolve all solids and sludge without having to drop the oil pan.

Synthetic oils will attack the seals of high mileage vehicles.

Just like ethanol rips through fuel lines.

Not to disagree, just to provide another way for a fellow to save money without having to find a shop.

 

[M. Sage]

Interesting view point.

My lawn mower shuts off if it detects low oil pressure.

GM cars used to do that, the fuel pump was wired for power through the oil pressure switch.

Reputable engine cleaners will dissolve all solids and sludge without having to drop the oil pan.

I've yet to find one that will. I know something about sludged engines, seeing as I work at a European shop and VW/Audi is my area.

Synthetic oils will attack the seals of high mileage vehicles.

Exactly what I was talking about. Back in the day, synthetics didn't have seal conditioners added like regular oils, so engines with higher mileage would wind up leaking.

Synthetic oil will not attack seals in any way.

Just like ethanol rips through fuel lines.

The water the ethanol attracts...

Not to disagree, just to provide another way for a fellow to save money without having to find a shop.

Not to disagree, but I've been wrenching for money (and ammo from time to time) for the last 13 years, and I'm one of the guys that other shops will send their problems to. I kinda know a thing or two about cars.

 

[Vaquero]

M.Sage,
Please go ahead and lock this thread. I've poked around under the hood all I'm going to and honestly don't wish to further the "discussion" between you and Shortround.
I'll go visit Mr. Goodwrench at my earliest convenience.
Thanks to all for your help, the failure is on me.

 

[1slow01Z71]

A lot of misinformation in this thread. The computer does monitor oil pressure, you cannot log it vie HPT or EFI but the BCM does register it. The sending unit for your year model is at the back of the block right behind the intake manifold. All that is for nothing though, your problem is the stepper motor in the gauge cluster. Very common problem and you can buy a complete used cluster for a $100 or so. The actual sending units rarely go bad, when they do its due to the actual plastic cracking and you will have an oil leak as the hard plastic is what retains the actual sensor membrane that the oil presses against.

If need be I can run out to the garage and take a picture for you of where on the block it sits. I build LS motors and do performance work on the side, if youve got any other questions and dont want to deal with the internet warriors shoot me a PM.

 

[jocat54]

A lot of misinformation in this thread. The computer does monitor oil pressure, you cannot log it vie HPT or EFI but the BCM does register it. The sending unit for your year model is at the back of the block right behind the intake manifold. All that is for nothing though, your problem is the stepper motor in the gauge cluster. Very common problem and you can buy a complete used cluster for a $100 or so. The actual sending units rarely go bad, when they do its due to the actual plastic cracking and you will have an oil leak as the hard plastic is what retains the actual sensor membrane that the oil presses against.

If need be I can run out to the garage and take a picture for you of where on the block it sits. I build LS motors and do performance work on the side, if youve got any other questions and dont want to deal with the internet warriors shoot me a PM.

You can buy the "new design" stepper motors off fleabay and pull the cluster and de-solder the old ones and solder in the new ones...it's really a pretty easy job, did it on my 2004 crewcab. Probably less than an hour to do.

 

[1slow01Z71]

Yeah, just figured for the average Joe it would be easier to buy a used cluster. The soldering route with the new design steppers is definitely the way to go unless you get a cluster thats an 06 or newer as the 03-05 clusters seem to have teh bulk of stepper motor problems.