Engine oil flush at 156k (unknown history)?

Ed H

Original poster
Member
Oct 18, 2012
167
I am the proud owner of a new-to-me 2002 TB with 156k on the ticker. I plan to replace ALL fluids immediately. Question is - do I use an engine flush product (Gumout, Amsoil, etc) before changing the oil, or let her go at this point? I have no maintanence history on the vehicle.

Also, I am throwing the CPAS code. I cleaned the screens (disgusting), but still receive the code intermitently (it is ON more than it's OFF). That being said, I am 99% set on the flush unless it is NOT recommended for a TB with this many miles. :confused:

I just need a DO IT, or SKIP IT (engine flush) from a few of you I6 pros. I would DO IT on all previous vehicles I've owned, but am not familiar with the potential weaknesses of the I6 - if there are any. :cool:
 

Mypetropig

Member
Dec 29, 2011
226
When you removed the CPAS and cleaned it did you clean the connector for it as well as disconnect the negative battery cable for 20-30 minutes? As for the engine oil flush I have used B-12 Chemtool, which is available at most auto part stores, with good results.
 

tblazerdude

Member
Dec 4, 2011
321
Ed, Im not sure how to answer this. Generally, I would say no, do not use a "motor flush." I would however, get some high milage dino oil and a can of seafoam, change the oil and add the entire can of seafoam. Drive about 200-400 miles. The change the oil again with a good synthetic. A lot of times an engine that has been neglected won't respond well to a flush. It could free up too much gunk and clog things, meaning loss of oil pressure or a dry pump, which could result in complete engine failure. Also, maybe it is just time to replace the CPAS. The seafoam product is less invasive than your common motor flushes. Just my $.02. Let us know what you decide and post the results. Also, something not mentioned frequently, is the replacement of both Oxygen Sensors at 100k. Use only OEM acdelco sensors if you decide to do this.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
And the transfer case fluid change interval is a surprisingly low 50K. If you don't know if it's ever been done, especially measure the amount and color that comes out, and that may have a clue if you're going to have transfer case problems. Did you check 4WD functionality before you bought it?

On the oil issue, I have no personal experience with debating doing it.
 

Mypetropig

Member
Dec 29, 2011
226
"I would say no, do not use a "motor flush." I would however, get some high milage dino oil and a can of seafoam, change the oil and add the entire can of seafoam. Drive about 200-400 miles. The change the oil again with a good synthetic."



This would be the same as a DIY engine flush in my opinion but with B-12 Chemtool you only leave it in for about 20 minutes.
 

Ed H

Original poster
Member
Oct 18, 2012
167
Thanks for the tips.

I did not clean the CPAS connections, but did disconnect the battery. I will give that a shot.

Yes, I did check the 4x4 before purchase. It is functioning perfectly. Otherwise I probably would have walked.

I'll check the O2s also. I am headed to dealer today for transfer case fluid. I'll see what they want to rob me for 2 new O2s.

Still on the fence with the engine flush... I have Mobil 1 High Mileage ready to go in. I may pass on the flush...
 

Voymom

Member
Feb 3, 2012
2,523
As far as the engine flush goes, I have had great success at using dino oil and seafoam. It sounds as if someone may have put engine restore(see pic below) in the truck which I know all too well, will cause issues with the CPAS. I would just change the CPAS out with a new one, their about $65 at Autozone and it is obviously a plug and play part. I have had the CPAS code once before, I did a flush and cleaned the CPAS, and although it got rid of my code, I had stalling and idle issues which are usually clear signs of a failing or failed CPAS. It would just make more sense in my eyes to replace it.

Transfer cases and rear differential fluid changes are probably a must if you don't have any maintenance history. I would also do spark plugs if you haven't already or at least check their condition. Aside from fluids, I would check all the suspension components as well, shocks, struts if their original they may need to be replaced too. You don't have to get everything done all at once, just throwing out other things that you may want to consider with a used TB. How is the t-stat running? Is the needle dead center at 210? If it is a tick below, you may want to consider changing that out too, it will save you money in gas in the long run as you can run pretty rich, and if it is bad, I would make sure there isn't a clogged cat, god only knows how long someone will drive these vehicles with a bad thermostat....Mine was horribly bad when I bought it, but lucked out and didn't have a clogged cat thank god.

Good luck!!

View attachment 23762
 

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Ed H

Original poster
Member
Oct 18, 2012
167
Funny you mention the thermostat. Yes, it is running 1 tick below 210. I thought (since I am new to TB) that the thermo was ~190 degrees and this is normal. No?

Mileage is pretty poor. I am getting 13.8 mpg around town with a very light foot (2 fill-ups dead nuts at 13.8 mpg).

Plugs were changed first. AC Delco 41-103s. It was nice to see the previous owner already installed the 103s, but I changed them anyways. The throttle body was simply disgusting. I cleaned that too.

I shocks / struts are originals and need to be replaced. See below.. :redface: I took these shots when installing the Brake Motives (very nice).

View attachment 23772

View attachment 23773

Time to start researching shots / struts. I am sure there are plenty of posts on that topic. :biggrin:

If an Autozone / Advance Auto CPAS is acceptable, I can also do that in short order. I thought AC Delco would be preferred / highly recommended. Forgot to ask how much they want for one at the dealer. The O2s were $108 each. Maybe next weeked...
 

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Mypetropig

Member
Dec 29, 2011
226
Our t-stats are 195 degree, some manufacturers produce a 192 but stay with the 195. If no one has mentioned it to you yet check out RockAuto Auto Parts for most of your parts. They carry AC Delco and and alot of other brands. I think I got my O2 sensor for around $58 fronm them. The most important one is located in the manifold and remember to stay with Delco on this as alot of other users have had issues with other brands. If you want to purchase your CPAS online gmpartsdirect.com is the place for that although there shipping is a bit steap.
12615873 is the current p/n for that.
 

Voymom

Member
Feb 3, 2012
2,523
I would also consider doing Bilstein HD's for your shocks and struts...I haven't done mine yet as I'm going to lift it so just waiting for the lift kit, and then I will switch mine out to Bilstein HD's.

The CPAS is $65 at O reilly's not sure about Autozone. I would also consider changing your thermostat as well. Here is a picture of my bad t-stat a month after I bought my truck, and only god knows how long it was driven like that, but I managed to not have the clogged cat converter.

View attachment 23774

This was taken after it warmed up in the drive way, plus a 10 minute drive and I let it run for an additional 25 minutes, it was clearly dead lol. If you change the t-stat I would also go with changing the temp sensor as well, might as well get it over with lol
 

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Sparky

Member
Dec 4, 2011
12,927
Bilstein HD is my recommendation for shocks :yes:
Don't forget new front upper mounts. You'll need them.

Be careful with the flush stuff because I think voymom had issues with something like that. If you do flush, do it before replacing the CPAS just so you don't inadvertently gum up or do something weird to the shiny new one :wink:
 

Voymom

Member
Feb 3, 2012
2,523
Sparky said:
Bilstein HD is my recommendation for shocks :yes:
Don't forget new front upper mounts. You'll need them.

Be careful with the flush stuff because I think voymom had issues with something like that. If you do flush, do it before replacing the CPAS just so you don't inadvertently gum up or do something weird to the shiny new one :wink:

Actually it was my husbands fault lol and he will never live it down either :raspberry:. I would just do the dino oil and seafoam honestly. After my experience I am very cautious at what I ALLOW my husband to put into it. I would rather not use anything other than seafoam, but I can't always babysit the old man :wink:
 

Ed H

Original poster
Member
Oct 18, 2012
167
I recovered a little over 1.5 qts from the transfer case this afternoon. I had mixed opinions on that. I checked the level with a zip tie before I drained it, and it did not seem very low at all. Maybe 1/4" below the fill hole. It appeared the transfer case had not been touched in a while. The 6-point fill / drain plugs threw me for a loop...

View attachment 23851[SVIEW][/SVIEW]


The fluid was pretty dark. Not sure if anyone can tell if this is 157k miles worth of sludge, but it's nice to know this is done.

View attachment 23852

View attachment 23853

So much preventative maintenance to catch-up on, and so little time.. :crazy:
 

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Mypetropig

Member
Dec 29, 2011
226
So much preventative maintenance to catch-up on, and so little time.. :crazy:[/QUOTE]


I know what you mean. I need to change my diff fluid, thermostat, coolant temp sensor, trans fluid (flush/fill), rotate tires and noticed earlier this week that I need motor mounts.:ugh: It seems to be that if I have the money to get the parts I cant find the time to put them on, or I have time and no spare cash. Oh well all in due time I suppose.
 

tblazerdude

Member
Dec 4, 2011
321
Sparky said:
Bilstein HD is my recommendation for shocks :yes:
Don't forget new front upper mounts. You'll need them.

Be careful with the flush stuff because I think voymom had issues with something like that. If you do flush, do it before replacing the CPAS just so you don't inadvertently gum up or do something weird to the shiny new one :wink:

You may or may not need the mounts. Inspect them. As strange as it is, I am recommending you get autozone/advanceauto upper shock mounts. I saw no difference between them and the OEM ones, and they are much, much cheaper. Local GM dealer wanted $50 per side, autozone wanted $40 for the pair.
 

CaptainXL

Member
Dec 4, 2011
2,445
Ed H said:
I am the proud owner of a new-to-me 2002 TB with 156k on the ticker Question is - do I use an engine flush product (Gumout, Amsoil, etc) I have no maintanence history on the vehicle.
:cool:

Flushing is personal preference but I think it helps. Every single vehicle I've purchased used gets flushes about every other oil change. Ive done about 4 flushes over the last two years with this truck with no deleterious effects. I have used pretty much every Off the shelf flush productlike K&W and Gunk.

Lately I have been using kerosene. Drain two quarts of oil and then put two of kero back in and idle for about 15 minutes. Flushes mainly aid in draining the oil. But I have seen good results curing stuck lifters. In fact the truck I have now used to smoke a little when starting in the winter. So a month after I got it I ran a couple quarts of K&W engine flush through it and did a full synthetic oil change with the Walmart supertech 5W-30. Never been burning any oil since. The reason I did this initial flush right after I bought the truck is because I knew it would solve stuff like this.

If you look at the MSDS for various flush products you will notice most if not all use a combination of kerosene and jet fuel. Not wanting to pay a premium for off the shelf products I just fill quart bottles with kerosene I buy at the local pump. Much cheaper IMHO.
 

vipergg

Member
Dec 7, 2011
191
Ed H said:
I am the proud owner of a new-to-me 2002 TB with 156k on the ticker. I plan to replace ALL fluids immediately. Question is - do I use an engine flush product (Gumout, Amsoil, etc) before changing the oil, or let her go at this point? I have no maintanence history on the vehicle.

Also, I am throwing the CPAS code. I cleaned the screens (disgusting), but still receive the code intermitently (it is ON more than it's OFF). That being said, I am 99% set on the flush unless it is NOT recommended for a TB with this many miles. :confused:

I just need a DO IT, or SKIP IT (engine flush) from a few of you I6 pros. I would DO IT on all previous vehicles I've owned, but am not familiar with the potential weaknesses of the I6 - if there are any. :cool:

If you feel the need to flush I would either use a high detergency oil like Pennzoil platinum for a few changes or use a milder cleaning agent like "AUTO RX" which some people swear by .
 

Sparky

Member
Dec 4, 2011
12,927
tblazerdude said:
You may or may not need the mounts. Inspect them. As strange as it is, I am recommending you get autozone/advanceauto upper shock mounts. I saw no difference between them and the OEM ones, and they are much, much cheaper. Local GM dealer wanted $50 per side, autozone wanted $40 for the pair.

Being a 2002 I'm pretty sure his will be worn out.

I can beat your price though, I got my Moog upper mounts from Amazon on some stupid sale at like 5 bucks each :biggrin:
 

Ed H

Original poster
Member
Oct 18, 2012
167
Alright, I decided not to use an engine flush at this time. I am hoping the extra detergents in Mobil 1 High Mileage will give the motor a nice gentle clean. We'll see.

What concerned me was this under the filler cap... :redface:

View attachment 24011

I was sick to my stomach as I under-screwed the drain plug. Thankfully the oil was not milky. Nothing out of the ordinary except the smell of fuel, but I will blame that on the bad CPAS, and my recent issues with the toasted TB, running in limp mode, etc.

Managed to change the lube in both differentials today too. Another unpleasant surprise here,

View attachment 24012

The fluid was a little low, but nothing of concern. I cleaned the heck out of the housing, etc and will watch for the leak point. The lube was definitely ready for a change.

On to the rear. Everything was going sooo smoothly until I managed to spill about 1/2 quart of Royal Purple on my garage floor. I tried to use a funnel and hose instead of my siphon pump. That did not work as well as planned... :hissyfit: By the way, Dawn dishwashing detergent cuts through differential lube pretty well. The garage hardly stinks anymore.. :rotfl:

I was surprised NOT to find a drain plug on my rear differential (2002 LTZ). I thought the 2002 had a drain plug. Don't mind the remnants of the spill in these images. Is it common for the rear driveshaft to be this clean, or was it possibly replaced? (157k miles)?

View attachment 24013
View attachment 24014

Only the tranny fluid remains. I noticed a leak up there to. It appears to be coming from the pan gasket. I cleaned the heck out of it, and will check for fresh fluid in a week or so... Gotta love used trucks. :biggrin:

Edit: I also installed a new CPAS. There was frigging oil in the connector - A lot of it! New CPAS in, connections cleaned, and the check engine light disappeared in about 10 seconds! I swear I can feel the difference already.
 

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tblazerdude

Member
Dec 4, 2011
321
If you do not have a drain plug and its an 02 then the axle has been replaced. All 02's and most 03's have drain plugs on the rear diff.
 

meerschm

Member
Aug 26, 2012
1,079
Ed H said:
Alright, I decided not to use an engine flush at this time. I am hoping the extra detergents in Mobil 1 High Mileage will give the motor a nice gentle clean. We'll see.

What concerned me was this under the filler cap... :redface:

View attachment 10659

I was sick to my stomach as I under-screwed the drain plug. Thankfully the oil was not milky. Nothing out of the ordinary except the smell of fuel, but I will blame that on the bad CPAS, and my recent issues with the toasted TB, running in limp mode, etc.

Managed to change the lube in both differentials today too. Another unpleasant surprise here,

View attachment 10660

The fluid was a little low, but nothing of concern. I cleaned the heck out of the housing, etc and will watch for the leak point. The lube was definitely ready for a change.

On to the rear. Everything was going sooo smoothly until I managed to spill about 1/2 quart of Royal Purple on my garage floor. I tried to use a funnel and hose instead of my siphon pump. That did not work as well as planned... :hissyfit: By the way, Dawn dishwashing detergent cuts through differential lube pretty well. The garage hardly stinks anymore.. :rotfl:

I was surprised NOT to find a drain plug on my rear differential (2002 LTZ). I thought the 2002 had a drain plug. Don't mind the remnants of the spill in these images. Is it common for the rear driveshaft to be this clean, or was it possibly replaced? (157k miles)?

View attachment 10661
View attachment 10662

Only the tranny fluid remains. I noticed a leak up there to. It appears to be coming from the pan gasket. I cleaned the heck out of it, and will check for fresh fluid in a week or so... Gotta love used trucks. :biggrin:

Edit: I also installed a new CPAS. There was frigging oil in the connector - A lot of it! New CPAS in, connections cleaned, and the check engine light disappeared in about 10 seconds! I swear I can feel the difference already.

View attachment 24018

this is in my 2003. from the matching rust elsewhere, yours may have been replaced, or is aluminum? have you tried to see if a magnet sticks? I read somewhere some had aluminum driveshafts.
 

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NewfieEnvoy

Member
Jan 25, 2012
525
Ya I just read a thread the other day that said the first batch of '02's had aluminium rear drive shafts. From your picture that definitively looks like its alu.
 

mubai

Member
Jan 5, 2012
321
Is it common for the rear driveshaft to be this clean, or was it possibly replaced?

Front drive shaft will be rusted.
Rear drive shaft is aluminum. I have 190K+ on my truck (envoy 2002) and it looks brand new.
 

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