Gen3 '04 suburban Oil pressure low
10-07-2023, 12:59 PM
#1
Gen3 '04 suburban Oil pressure low Will try to cram as much into as few words so I respect everyone's time. and I'm not an expert at any of the below, so looking to listen and learn
'04 suburban 250k miles...always changed oil and filter every 5k. ran fine until my son had oil changed recently by Jiffy Lube, oil filter was not secured at the time, worked its was loose, bled oil, son called me from a gas station, I heard the ticking, told him to put oil in ticking went away, drove home, I noticed oil pressure down to 20, changed oil and filter (no flush or trans fluid), put in new oil sending unit, pressure dropped further (Assume the old one had aged tolerance), pulled pan and front end, put in new timing chain/gear, cam thrust plate, new melling pump and pickup tube (red o-ring), torqued all as spec'd, primed oil pump via side galley orifice, fired up....same result. Note: these is absolutely no ticking/tapping/etc. Sounds perfect. Drove 150 miles with the only issue being when I would stop, the oil pressure goes to almost nothing and low oil pressure warning comes on (but again no ticking or noise). Oil pressure at 2k rpm is about 25, but at 4k still below 40. I did not replace oil bypass valve as I didn't know what that was at the time (newby). I also have not rigged a manual oil pressure gauge to fit in the priming port as I need to figure out what parts I need (any help on that is appreciated).
observations during the install....I could tell the engine was hot from the oil varnish on in the pan and on the tube (250k miles without ever dropping the pan....so it had its issues). also, when installing the new oil pressure sending unit (with intake on), I searched for a sending port screen per references in on line search but could not determine if this model year motor had one (granted I was fishing for it with the intake on)...did notice the oil dabs on my pic tool from the sending unit passage were very black even though oil had been changed and oil is so clean in the pan at this point its hard to see where it registers on the stick. from cold start up pressure is low at idle (20). Once oil heats, it drops off to trigger the low oil pressure warning.
So stumped. I almost feels like there is no downstream (engine topside) restriction to keep the oil pressure up and I know zero about issues with lifters, walked cam bearings, etc but would think if there is a pressure issue topside, I would be hearing the tap dance because of no oil...but engine sounds perfect......so fully stumped but rightfully so as I don't really know what I'm doing. Guess it could be an open oil filter bypass valve so I will replace that...but have my doubts.
appreciate any guiding lights and education. Not sure I can tackle at this point but would like to know how to communicate what likely is going on to whomever I can find to tackle.
Thanks folks
Bob
'04 suburban 250k miles...always changed oil and filter every 5k. ran fine until my son had oil changed recently by Jiffy Lube, oil filter was not secured at the time, worked its was loose, bled oil, son called me from a gas station, I heard the ticking, told him to put oil in ticking went away, drove home, I noticed oil pressure down to 20, changed oil and filter (no flush or trans fluid), put in new oil sending unit, pressure dropped further (Assume the old one had aged tolerance), pulled pan and front end, put in new timing chain/gear, cam thrust plate, new melling pump and pickup tube (red o-ring), torqued all as spec'd, primed oil pump via side galley orifice, fired up....same result. Note: these is absolutely no ticking/tapping/etc. Sounds perfect. Drove 150 miles with the only issue being when I would stop, the oil pressure goes to almost nothing and low oil pressure warning comes on (but again no ticking or noise). Oil pressure at 2k rpm is about 25, but at 4k still below 40. I did not replace oil bypass valve as I didn't know what that was at the time (newby). I also have not rigged a manual oil pressure gauge to fit in the priming port as I need to figure out what parts I need (any help on that is appreciated).
observations during the install....I could tell the engine was hot from the oil varnish on in the pan and on the tube (250k miles without ever dropping the pan....so it had its issues). also, when installing the new oil pressure sending unit (with intake on), I searched for a sending port screen per references in on line search but could not determine if this model year motor had one (granted I was fishing for it with the intake on)...did notice the oil dabs on my pic tool from the sending unit passage were very black even though oil had been changed and oil is so clean in the pan at this point its hard to see where it registers on the stick. from cold start up pressure is low at idle (20). Once oil heats, it drops off to trigger the low oil pressure warning.
So stumped. I almost feels like there is no downstream (engine topside) restriction to keep the oil pressure up and I know zero about issues with lifters, walked cam bearings, etc but would think if there is a pressure issue topside, I would be hearing the tap dance because of no oil...but engine sounds perfect......so fully stumped but rightfully so as I don't really know what I'm doing. Guess it could be an open oil filter bypass valve so I will replace that...but have my doubts.
appreciate any guiding lights and education. Not sure I can tackle at this point but would like to know how to communicate what likely is going on to whomever I can find to tackle.
Thanks folks
Bob
10-07-2023, 11:13 PM
#2
TECH Enthusiast
Will try to cram as much into as few words so I respect everyone's time. and I'm not an expert at any of the below, so looking to listen and learn
'04 suburban 250k miles...always changed oil and filter every 5k. ran fine until my son had oil changed recently by Jiffy Lube, oil filter was not secured at the time, worked its was loose, bled oil, son called me from a gas station, I heard the ticking, told him to put oil in ticking went away, drove home, I noticed oil pressure down to 20, changed oil and filter (no flush or trans fluid), put in new oil sending unit, pressure dropped further (Assume the old one had aged tolerance), pulled pan and front end, put in new timing chain/gear, cam thrust plate, new melling pump and pickup tube (red o-ring), torqued all as spec'd, primed oil pump via side galley orifice, fired up....same result. Note: these is absolutely no ticking/tapping/etc. Sounds perfect. Drove 150 miles with the only issue being when I would stop, the oil pressure goes to almost nothing and low oil pressure warning comes on (but again no ticking or noise). Oil pressure at 2k rpm is about 25, but at 4k still below 40. I did not replace oil bypass valve as I didn't know what that was at the time (newby). I also have not rigged a manual oil pressure gauge to fit in the priming port as I need to figure out what parts I need (any help on that is appreciated).
observations during the install....I could tell the engine was hot from the oil varnish on in the pan and on the tube (250k miles without ever dropping the pan....so it had its issues). also, when installing the new oil pressure sending unit (with intake on), I searched for a sending port screen per references in on line search but could not determine if this model year motor had one (granted I was fishing for it with the intake on)...did notice the oil dabs on my pic tool from the sending unit passage were very black even though oil had been changed and oil is so clean in the pan at this point its hard to see where it registers on the stick. from cold start up pressure is low at idle (20). Once oil heats, it drops off to trigger the low oil pressure warning.
So stumped. I almost feels like there is no downstream (engine topside) restriction to keep the oil pressure up and I know zero about issues with lifters, walked cam bearings, etc but would think if there is a pressure issue topside, I would be hearing the tap dance because of no oil...but engine sounds perfect......so fully stumped but rightfully so as I don't really know what I'm doing. Guess it could be an open oil filter bypass valve so I will replace that...but have my doubts.
appreciate any guiding lights and education. Not sure I can tackle at this point but would like to know how to communicate what likely is going on to whomever I can find to tackle.
Thanks folks
Bob
'04 suburban 250k miles...always changed oil and filter every 5k. ran fine until my son had oil changed recently by Jiffy Lube, oil filter was not secured at the time, worked its was loose, bled oil, son called me from a gas station, I heard the ticking, told him to put oil in ticking went away, drove home, I noticed oil pressure down to 20, changed oil and filter (no flush or trans fluid), put in new oil sending unit, pressure dropped further (Assume the old one had aged tolerance), pulled pan and front end, put in new timing chain/gear, cam thrust plate, new melling pump and pickup tube (red o-ring), torqued all as spec'd, primed oil pump via side galley orifice, fired up....same result. Note: these is absolutely no ticking/tapping/etc. Sounds perfect. Drove 150 miles with the only issue being when I would stop, the oil pressure goes to almost nothing and low oil pressure warning comes on (but again no ticking or noise). Oil pressure at 2k rpm is about 25, but at 4k still below 40. I did not replace oil bypass valve as I didn't know what that was at the time (newby). I also have not rigged a manual oil pressure gauge to fit in the priming port as I need to figure out what parts I need (any help on that is appreciated).
observations during the install....I could tell the engine was hot from the oil varnish on in the pan and on the tube (250k miles without ever dropping the pan....so it had its issues). also, when installing the new oil pressure sending unit (with intake on), I searched for a sending port screen per references in on line search but could not determine if this model year motor had one (granted I was fishing for it with the intake on)...did notice the oil dabs on my pic tool from the sending unit passage were very black even though oil had been changed and oil is so clean in the pan at this point its hard to see where it registers on the stick. from cold start up pressure is low at idle (20). Once oil heats, it drops off to trigger the low oil pressure warning.
So stumped. I almost feels like there is no downstream (engine topside) restriction to keep the oil pressure up and I know zero about issues with lifters, walked cam bearings, etc but would think if there is a pressure issue topside, I would be hearing the tap dance because of no oil...but engine sounds perfect......so fully stumped but rightfully so as I don't really know what I'm doing. Guess it could be an open oil filter bypass valve so I will replace that...but have my doubts.
appreciate any guiding lights and education. Not sure I can tackle at this point but would like to know how to communicate what likely is going on to whomever I can find to tackle.
Thanks folks
Bob
I'm not trying to be rude, but you only have one post to your history, and your post is riddled with capitalization errors. We see that a lot with bot accounts.
If you aren't a bot, then I think it's entirely possible that your 250K bearings got wiped out after that low oil pressure event.
You can change oil pumps all you want, but if the bearings (crank or cam) are worn out, you will never get good oil pressure.
The bottom line is to put a mechanical gauge on the engine and know what the pressure really is. And be sure to check it when the engine is at operating temperature.
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G Atsma (10-07-2023)
10-07-2023, 11:34 PM
#3
Fair enough, as I get the new world order and no, I'm not a bot (mid 50s dad trying to keep his kids handed down rigs running)
Appreciate the candor on what is likely wrong. In so far as mechanical gage, I assume you mean connecting to the priming port to check pressure there, correct? Any heads up on what I'm looking for....eg, if its 40 there and 20 at the sending unit...what does that indicate? if its's 20 and 20, does that point to the bearing issues you mentioned? Not planning on digging into this if its downstream...but would like a good sense of where to go (new engine vs rebuild, etc). Again, apologies for the prosaic writing style. appreciate the help.
Appreciate the candor on what is likely wrong. In so far as mechanical gage, I assume you mean connecting to the priming port to check pressure there, correct? Any heads up on what I'm looking for....eg, if its 40 there and 20 at the sending unit...what does that indicate? if its's 20 and 20, does that point to the bearing issues you mentioned? Not planning on digging into this if its downstream...but would like a good sense of where to go (new engine vs rebuild, etc). Again, apologies for the prosaic writing style. appreciate the help.
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G Atsma (10-07-2023)
10-08-2023, 07:49 AM
#4
Launching!
I have always used the green o-ring from melling for that application. I think red was OEM.
anyway, sounds like too much bearing to journal clearance, as stated.
There is no screen below the oil pressure sensor on your year model.
anyway, sounds like too much bearing to journal clearance, as stated.
There is no screen below the oil pressure sensor on your year model.
10-08-2023, 09:01 AM
#5
Thanks Jake. I thought about the red vs green but red was on the Melling pickup tube I bought so went with that (they looked identical). Thought about going back in and replacing but starting to bump up against cost/benefit of nursing the 250k engine. Given that I just (a month ago) put in a new tranny, I need to start planning on a new engine install. The truck is in very good shape so thinking it may be worth it. thoughts on reputable remans?
10-09-2023, 10:14 AM
#6
Launching!
Not sure if you have the means but, I would freshen up your current engine.
The bores are usually still in spec if it has been serviced regularly. If the crank journals are still good, do rings, bearings, gaskets, seals, lifters and trays and you will be good to go.
these engines are super simple.
The bores are usually still in spec if it has been serviced regularly. If the crank journals are still good, do rings, bearings, gaskets, seals, lifters and trays and you will be good to go.
these engines are super simple.
10-09-2023, 10:34 AM
#7
Weighing the condition of the vehicle (which is very very good) vs buying a used with an unknown history. So tempted to go the route you suggest but it would definitely be a new adventure and would need to find someone with that skill as that is most likely out of my wheelhouse. I've tackled my issues on my old Rover Classic and Discovery but the work has always been front end (timing, oil, etc)....not internal (cam, crank, valves, lifters, etc)....not sure what special tools/etc needed but assume this is not something i could tackle at home.
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10-12-2023, 06:15 PM
#8
studied the roll in of main/crank bearings...first, having a shop take mech pressure at the sender port to rule out defective sender which has yet to be done.
As the oil pressure starts at 25, then when hot, will roll down next to nothing at 500rpm, I assume DixieBandit69s assessment of cam/crank bearing leakage is the culprit. As I have perfect engine sound (per the shop I took it to), does that point to leakage at the crank bearings more so than other areas? If so, was thinking of having them roll in main bearings to see if that addresses the issue. I know nothing is guaranteed but wondering if that's a reasonable step or not.
As the oil pressure starts at 25, then when hot, will roll down next to nothing at 500rpm, I assume DixieBandit69s assessment of cam/crank bearing leakage is the culprit. As I have perfect engine sound (per the shop I took it to), does that point to leakage at the crank bearings more so than other areas? If so, was thinking of having them roll in main bearings to see if that addresses the issue. I know nothing is guaranteed but wondering if that's a reasonable step or not.