ice trip; had some issues (oil pressure / charging)

[steiny93]

2008 Tahoe LTZ, 217k on tracks; was up on Lake Winnipeg last weekend.

I don't have a lot of time in this rig, bought the Tahoe and installed the lift / tracks right away, maybe 100 miles on it.

First issue:
Noticed that the oil pressure was staying about 25 psi. Seems to be a candidate for an o-ring.
But... once when I came to idle after pulling the ice house for a couple miles (4-low, hard pulling) the gauge went to 10psi and the low oil alarm came on. Rev'ing the engine changed the pressure very little, maybe up to 15 psi. I shut off the engine, checked levels, restarted and all was back to the 25psi range (at times up to 40psi, but typically 25psi). Stayed in the 25psi range the rest of the week.

Initially I was thinking o-ring; but now I'm wondering o-ring (for the low pressure) and maybe check valve (for the sudden loss then return (10psi then back). Thoughts? Plan was to double check the sensor / screen, validate pressure with a manual gauge first.

Second issue:
After 3 days on the ice; charging system quit charging. After the engine dying twice due to low voltage (I'd swap out a different battery); the charging system started working normally again. So now I don't have a way to diagnois the issue.

Any thoughts on this one, all connections were/are tight. I'm assuming alternator but don't have a lead on this one. I kind of need this to work, I'm leaning towards just swapping the alternator, anything else to check? Kind of difficult with it working again.

any intel much appreciated

 

[Marky Dissod]

Even though you should DEFINITELY check the oil pressure externally, it may be a good idea to just go ahead and buy new replacements for the most likely culprits after 16 years?

As for the alternator, see my previous suggestion.

 

[steiny93]

Even though you should DEFINITELY check the oil pressure externally, it may be a good idea to just go ahead and buy new replacements for the most likely culprits after 16 years?

As for the alternator, see my previous suggestion.

on a 16 year old rig the parts list will never end

 

[Geotrash]

2008 Tahoe LTZ, 217k on tracks; was up on Lake Winnipeg last weekend.
View attachment 423496

I don't have a lot of time in this rig, bought the Tahoe and installed the lift / tracks right away, maybe 100 miles on it.

First issue:
Noticed that the oil pressure was staying about 25 psi. Seems to be a candidate for an o-ring.
But... once when I came to idle after pulling the ice house for a couple miles (4-low, hard pulling) the gauge went to 10psi and the low oil alarm came on. Rev'ing the engine changed the pressure very little, maybe up to 15 psi. I shut off the engine, checked levels, restarted and all was back to the 25psi range (at times up to 40psi, but typically 25psi). Stayed in the 25psi range the rest of the week.

Initially I was thinking o-ring; but now I'm wondering o-ring (for the low pressure) and maybe check valve (for the sudden loss then return (10psi then back). Thoughts? Plan was to double check the sensor / screen, validate pressure with a manual gauge first.

Second issue:
After 3 days on the ice; charging system quit charging. After the engine dying twice due to low voltage (I'd swap out a different battery); the charging system started working normally again. So now I don't have a way to diagnois the issue.

Any thoughts on this one, all connections were/are tight. I'm assuming alternator but don't have a lead on this one. I kind of need this to work, I'm leaning towards just swapping the alternator, anything else to check? Kind of difficult with it working again.

any intel much appreciated

Start with the oil pressure sender and screen. It's the easiest of the likely culprits to change, but still can be a pita if you have big hands. It solved the same problem on my '12 when I bought it.

 

[Dustin Jackson]

@steiny93 What was your indication that the charging system quit working?

 

[steiny93]

@steiny93 What was your indication that the charging system quit working?

Service charging system message on dash, volt gauge on dash dropped to 12volt then continued to decline to 9volt (verified via multimeter), dash went dark then the engine quit. Swapped battery; voltage started at 12 then declined to 9 and quit. Used jump pack; engine restarted, voltage was dropping 12 to 9, but before the engine quit a 3rd time the voltage jumped to just over 14 volts and the system was operating as normal.

On restart no service charging system message, voltage above 14 on dash.

 

[Dustin Jackson]

Interesting, I am wondering if it was the alternator, battery, or battery cables

 

[j91z28d1]

only use gm oil sensor and not from Amazon. I've seen a few threads with oil pressure drop till light comes on, pull over check stuff. restart and fine for a while. honestly don't know why, and not confident to say your o'ring is going to fix it.
can't hurt to do it, but it's a lot of work and I lean towards it's probably not it.
most people end up replacing everything before they are happy. o'ring, high volume pump, full vlom delete, cam and tuned out.

the alt, at least use the time to upgrade to the newer 220amp one. there's a thread about it here by iamdub that details the install. he goes a bit overboard for me. it's a direct bolt on and it's fine. but the numbers and stuff are there.

why it stopped charging and started again.. no clue.

 

[steiny93]

Interesting, I am wondering if it was the alternator, battery, or battery cables

The first battery was fully charged prior to the issue (as well as the swapped battery); additionally they were enough to start the engine. Not sure how bad batteries could start an engine then pull enough off the alternator to indicate below 9 volts then work normally (take a charge, indicate being charged).

The battery cables look great and are not corroded; they were cycled a lot during this mess. When the voltage came back up it was while the engine was running, hood closed, driving down the river. I don't know how cables could cause this behavior. Unless you are thinking the positive field cable to the alternator.

 

[steiny93]

only use gm oil sensor and not from Amazon. I've seen a few threads with oil pressure drop till light comes on, pull over check stuff. restart and fine for a while. honestly don't know why, and not confident to say your o'ring is going to fix it.
can't hurt to do it, but it's a lot of work and I lean towards it's probably not it.
most people end up replacing everything before they are happy. o'ring, high volume pump, full vlom delete, cam and tuned out.

the alt, at least use the time to upgrade to the newer 220amp one. there's a thread about it here by iamdub that details the install. he goes a bit overboard for me. it's a direct bolt on and it's fine. but the numbers and stuff are there.

why it stopped charging and started again.. no clue.

I'm guessing that I have a pair of issues concerning the oil pressure:
1) low oil pressure of 25psi at idle
2) intermittent oil pressure drop which then comes back to normal

I'm thinking I'll do the following:
- manual gauge to verify dash is reasonable (I'll probably not see it drop low during this test as that only occurred once; so this test doesn't really mean the sensor is good, just means its working at the moment of test)
- pop out the screen to see if its plugged; clean and/or replace

Guessing the above will indicate nothing; so will need to decide what todo. My hunch is that the O-ring is bad AND the relief valve in the pump hung up which caused the instance of very low oil pressure. Perhaps the best course of action would be to replace the pump and change the O-ring from the front. I'm out $120 but I'll be freshened up in the oil delivery space. It doesn't account for a plugged pickup tube however.

For the charging issue; I'm also guessing alternator.

 

[petethepug]

Love the tracks on the full size. Did you add 2x or 3x glass for the windows on the trailer/beer cooler? It looks like a hell of a good time.

Those battery cables and low temps. There’s thread after thread about cables that look ok, but corroded internally and cause low voltage as well as the by product of false DTC.

Start with the -/+ battery cable replacement. If the low oil pressure persists, as stated, replace with only a new GM / AC Delco sender. If no go after that it’s manual oil pressure Ck time & o-ring time.

 

[j91z28d1]

^^ I was just going to say the same thing.. these trucks do electrical things that defi logic and in thread after thread it's the cables and or that ground on the front drivers side head. one guy found a ground wire that about 3in back in the harness was eat half way thru. everything looked good outside but inside isn't, that was a year of searching. I can't explain it. but post after post.


the alt is a odd one.. these are ecm controlled alternators but even if they lose all signal from the ecm they default to 13.7 ish. so to just shut off and come back.. don't know. but a low mileage 220amp take off on ebay can be had for around 150$. so it's worth while upgrade even if it doesn't fix it.

for the rest, you're probably right. Intermittent issues are always the worst.

 

[petethepug]

There’s also a phenomenon with some AGM battery where the posts are just a hair smaller than the battery cable can clamp down on. It overheats the battery, terminal and causes intermittent no starts. The temporary solution is a parts store lead battery post cap that slides over the post.

I had to cut up one of those lead caps and slide a piece of it between the post and cable connector once just to get home. The lead cap was too big for the battery cable to fit over but too loose without it.

 

[j91z28d1]

mine comes with quick connect battery terminals from the factory. you can only imagine the number of threads about hybrids and electrical stuff that ends if being loose battery cables that no one expects. I've seen threads of dealers running up huge bills, hybrid packs being replaced. all over a silly terminal that was used because if you need to park the truck for a month or longer the owners manual says to take a battery cable off so you don't run the hybrid pack dead.

I tell everyone, if you can move a terminal on these trucks with 2 hands and all your force, it's to loose. they gotta be what is almost over tight haha.