99 Tahoe oil pressure

[slingblade]

Recently I had Snappy Lube change the oil in my '99. Afterwards I checked it and they had overfilled it with 6 qts. My oil pressure gauge indicated very low oil pressure around 3-5 lbs. when idling and 10 at highway speeds. I drained the oil and replaced it with the correct amount. The gauge still indicated the same. Thinking they blew out my pressure switch I replaced it today. The gauge still reads the same usually at zero when idling and 5-10 driving. There has been no noises from the engine or smoke, and the oil level is correct. It has 160,000 and , maintained regularly.
I know that I need to obtain a reading from a mechanical gauge but I do not have one and probably replace the oil pump.
Now riddle me this......has anyone replaced an oil pump any what kind of pain in the ass is it going to be? I need to get a few more years out of her.
Any and all help is appreciated in advance

 

[994door]

try a delco oil filter, its cheap and worth a shot.

 

[AtomicHoe094]

yea usually if i run a fram filter, my truck will want to kill me. The oil pressures always wacked out with that fram, but once i change it to ac or mobil1, its fine. idk, but yours seems pretty intense. sorry

 

[slingblade]

Talked to a mechanic that told me to try and remove the oil filter and check the oil by-pass valve in the block where the filter fits. He said that sometime the spring loaded valve can get jammed and cause the by-pass to stay open and create low oil pressure.
Drained the oil, could not locate the valve which had shown me on a old block he had laying around so put a new purolator oil filter on and heavier oil. Still same problem, oh and did I mention I changed the pressure switch. Mechanic says unless it starts making lifter noises ignore it, but I'm **** and can;t have a gauge that does this crap.

 

[961500]

The pump is not hard to do it's the crap you need to remove to do it. On the vortec motors the timing cover has a lip that seals the oil pan so both have to come off along with accessories. It took me about four or five hours to do the pump and bs by myself. Now if someone here has a trick to the pan timing cover crud hopefully the will
rise up. Good luck on it you can by a new oil filter
plenum with the valve it's a simple bolt in to try first.

 

[retorq]

More then likely a gauge or wiring issue. If you TRULY had 0 pressure at idle and only 5 - 10 driving your engine would have had major issues ...

 

[96_2DRSPORT]

i love this forum because i am having the same problem !!!!!

 

[slingblade]

The pump is not hard to do it's the crap you need to remove to do it. On the vortec motors the timing cover has a lip that seals the oil pan so both have to come off along with accessories. It took me about four or five hours to do the pump and bs by myself. Now if someone here has a trick to the pan timing cover crud hopefully the will
rise up. Good luck on it you can by a new oil filter
plenum with the valve it's a simple bolt in to try first.

Does the harmonic balancer have to be removed? And did you have to drop the axle to get the oil pan off?

 

[Da90]

The pump is not hard to do it's the crap you need to remove to do it. On the vortec motors the timing cover has a lip that seals the oil pan so both have to come off along with accessories. It took me about four or five hours to do the pump and bs by myself. Now if someone here has a trick to the pan timing cover crud hopefully the will
rise up. Good luck on it you can by a new oil filter
plenum with the valve it's a simple bolt in to try first.

Not correct I changed the oil pump in mine about month ago hoping it would solve my knocking/low oil pressure problem. Ended up being a wrist pin anyway... All you have to do is take off the plastic part on the top of the motor that says vortec, take out motor mount bolts, jack up motor. There is a wire that runs along the crossmember that will need to be disconnected also. Then once jacked up just remove the oil pan. No removing the front accessories at all. Once off you will have 2 bolts on a pan if I'm remembering correctly and also 2 bolts also in the acutall pump. It's easy and takes about 2 hrs. Oh yea might as well replace the gasket while your there also. One more thing the oil pump has a 2 piece rod that has a plasic clip on it be sure and buy the replacement that has the metal clip.

 

[faze]

Were it me, before I dropped the pan, I'd pull the sending switch out and put a mech gauge on it to see what the real pressure is.

I've had the guage set go on a 95 and it started with the op guage and then went into the volt meter...both began reading incorrectly.

 

[slingblade]

Not correct I changed the oil pump in mine about month ago hoping it would solve my knocking/low oil pressure problem. Ended up being a wrist pin anyway... All you have to do is take off the plastic part on the top of the motor that says vortec, take out motor mount bolts, jack up motor. There is a wire that runs along the crossmember that will need to be disconnected also. Then once jacked up just remove the oil pan. No removing the front accessories at all. Once off you will have 2 bolts on a pan if I'm remembering correctly and also 2 bolts also in the acutall pump. It's easy and takes about 2 hrs. Oh yea might as well replace the gasket while your there also. One more thing the oil pump has a 2 piece rod that has a plasic clip on it be sure and buy the replacement that has the metal clip.

But did replacing the oil pump help out your low oil pressure? I will be hooking up a mechanical gauge this weekend to get a true reading

 

[slingblade]

UPDATE: Hooked up a mechanical gauge this AM and same results. At about 3000 rpm I got 20 lbs. then as it goes down to idle it slowly decreases until about 5 lbs then snaps to 0 lbs. I am going to try to remove the fitting that the oil pressure lines and sending unit screws into and see if it clogged. If not then Saturday I will be spending the afternoon replacing an oil pump. FYI: I talked to a co-worked that has a 1998 Z-71 and he says that the oil puimp in his truck is weak too. When he cranks it it rattles like hell until the pressure builds.He thinks its the oil pumps in the Vortec engine generally.

 

[T-Bagg]

yea usually if i run a fram filter, my truck will want to kill me. The oil pressures always wacked out with that fram, but once i change it to ac or mobil1, its fine. idk, but yours seems pretty intense. sorry

I've heard to much bad about Fram products. I use K&N filters. They're wrench off too, which is nice.



slingblade,
Keep us updated on the outcome. And good luck.

 

[slingblade]

I know I'm beating a dead horse bout this low oil pressure, but with vacation time rolling aorund I don't want my family stranded on the side of the road. Today I checked out the specs and oil pressure listed in a Haynes repair manual. The manual states the oil pressure as 6 psi at idling, and 20 pis at 2000 rpms on a 4.3L 5.0L. , 5.7L engones. Now going by that I checked the oil pressure with my $17.00 sunpro oil pressure gauge and got 0 psi at idle and 15-16 psi at 2000 rpms. Thas pretty close say for the 0 at idle, but considering I used a cheap gauge I amy be O.K.
Is there anyone that has knowledge of how a mechanicla guage actually works. I was thinking that the oil goes thru the tubing to the mechical gauge to register on the scale, but with this gauge the oil in the plastic tubingnever gets to the gauge. Also after taking out the fitting in the block that the sending unit screws into I started up the engine expecting to spray oil out of the hole, but nothing came out, I thought for sure oil would come out. Apparently oil is not making it to the top. Short of taking off a valve cover to see it the engine is oiling, what is the chararterisitc of a Vortec engine do they oil the same as a regular small block?? Still no noises,..... makes me wanna go hmmmmmmmmm
I am reluctant to start disasembly since we only a Mazda Miata as a back up and the three of us can't fit. I need to know for sure its a one day repair.

Also what effect will too much oil have on oil pressure


Any thoughts???

 

[dealer]

you are jurst delaying the engine overhaul.

 

[99_2door]

UPDATE: Hooked up a mechanical gauge this AM and same results. At about 3000 rpm I got 20 lbs. then as it goes down to idle it slowly decreases until about 5 lbs then snaps to 0 lbs. I am going to try to remove the fitting that the oil pressure lines and sending unit screws into and see if it clogged. If not then Saturday I will be spending the afternoon replacing an oil pump. FYI: I talked to a co-worked that has a 1998 Z-71 and he says that the oil puimp in his truck is weak too. When he cranks it it rattles like hell until the pressure builds.He thinks its the oil pumps in the Vortec engine generally.

how long would you say it rattles before the pressure builds? are we talking like a couple seconds? thanks

i'm noticing a new issue with my 99. hot or cold start, as soon as it cranks it will knock (at least thats what i think it sounds like) for about 3-4 seconds and then idle fine. no other odd noises come from the motor and it makes good power. not really sure what to do about this.

 

[Broken Truck]

I feel for you here.

235k miles on my hoe and the pressure is dropping and at least one lifter is making noise.

I may be doing an oil pump myself...

 

[Broken Truck]

on my way to the store to pick up a K&N filter....

 

[riviera rider]

wow im definitely only using delco or k&n filters from now on and may have to change my oil pump also, a while ago my truck was making bad lifter noise and i cant tell exactly what my oil pressure is at cuz i messed with my guages and not sure if the oil pressure one is on exactly correct

however i changed the oil/filter and dont think ive heard the noise since, but from now on im sticking with ac delco or kn filters i think

 

[Broken Truck]

I have the KN filter in.

So far so good. No lifter noise for two days. Oil pressure at idle and running is up about 5-10 psi. About 20-30 at idle, 40-50 running, sometimes up to 60.

I had also run some seafoam through the oil, gas tank and on top of the cylinders before the oil change and KN filter...