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Discussion Starter · #1 ·
So for the last 10+ years I have been pumping out the hpop reservoiron my 01 7.3 during oil changes . I was reading on the forums here that after pumping there is still dirty oil left in the rails . This may be proven out by the fact that after I do the first pump out ,refill it, run it for a minute or so then pump it out again ,the oil is dirty . So usually I repeat this minimum of 2 or 3 times till I get clean oil ( or cleaner oil) even after 4 times it is still a bit dirty . So here are my questions for you experts :

1. Where does the oil in the hpop reservoir get replenished from ? Does the oil in the rails return to the reservoir or to the crankcase?

2. I seem to remember that once during an oil change that the hpop res. drained by itself ... I could be dreaming here since I am old and forgetful. Is this possible?

3. My sequence has been drain crankcase , change oil and filter ,then pump the hpop res. and change it several times . I don't mind wasting the oil ...I want maximum life out of my injectors . Is there a better way ?

Thank you very much for any tips .
 

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The oil returns to the crankcase, and the HPOP is supplied by the low pressure oil pump.

There was a member who figured out how fast the HPOP oil gets changed while the engine was running and it is amazing at how fast it gets replaced.

There was also a member who sent off two samples of oil from his truck to get analyzed. One from the crankcase and one from the HPOP, they came back exactly the same.

When it comes down to it if you get that warm fuzzy feeling changing the HPOP oil then continue to do it but there is no need to.
 

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Discussion Starter · #3 ·
Thank you Bugman , So if I just do the oil change then the hpop reservoir should be clean or as clean as the dip stick oil after running the engine how long? My experience is that after changing crankcase oil running the engine for 2 or 3 minutes and checking the hpop res. the oil is still black .
 

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The problem is that unless you do a complete engine rebuild you will have left over oil in all the oil passages, this includes the oil that goes to the HPOP from the LPOP.

What does your oil in the HPOP look like after you have ran it for a week compared to the oil in your crankcase? Also dirty looking oil does not mean that it is bad. Oils are designed to get dirty but as long as the additives in that oil is still doing their job there is no need to change it. That is where on a lot of newer engines they are going 10,000 miles between oil changes.

On my 96 and on the last sample that I sent in to get analyzed it came back that I could go to 7,000-8,000 mile changes. The additives were still working and the oil viscosity hadn't changed enough to worry about when I changed it at 5,000 miles.
 

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Discussion Starter · #5 ·
Thank you bugman , OK I'm listening better .. Are these additives already in your oil, and if so what brand do you use ,or if you are adding them, what are they ?
 

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Regardless of the YouTube advice by Captain Flip- Flops changing the oil in your HPOP reservoir is not necessary, anyone can pick a neglected "Fleet" example and find a nasty one, doesn't mean it's typical. Changing the HPOP oil is however a good opportunity to pour in unfiltered oil to go straight to the injectors. If everyone had tested new oil right out of the barrel new as often as I have they would not do that.
 
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Thank you bugman , OK I'm listening better .. Are these additives already in your oil, and if so what brand do you use ,or if you are adding them, what are they ?
Everything is in the oil right off of the shelf.

If you have any questions on your oil get it analyzed. Contact a company that does it and get a sample kit and follow their instructions. I along with quite a few here use Blackstone Labs. The sample kit if free and the turn around for your results are quite quick if you have them sent to your email.

 

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Discussion Starter · #8 ·
Regardless of the YouTube advice by Captain Flip- Flops changing the oil in your HPOP reservoir is not necessary, anyone can pick a neglected "Fleet" example and find a nasty one, doesn't mean it's typical. Changing the HPOP oil is however a good opportunity to pour in unfiltered oil to go straight to the injectors. If everyone had tested new oil right out of the barrel new as often as I have they would not do that.
Thanks for your input
 

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Regardless of the YouTube advice by Captain Flip- Flops changing the oil in your HPOP reservoir is not necessary, anyone can pick a neglected "Fleet" example and find a nasty one, doesn't mean it's typical. Changing the HPOP oil is however a good opportunity to pour in unfiltered oil to go straight to the injectors. If everyone had tested new oil right out of the barrel new as often as I have they would not do that.
Yeah I'm surprised he hasn't said that the key to keeping your fuel system alive is to drop your tank and change your diesel every 5k miles 🤣👍🏻
 
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There was a member who figured out how fast the HPOP oil gets changed while the engine was running and it is amazing at how fast it gets replaced.
I don't remember who that was, but the oil in the HPOP system turns over at a rate of about 7 times the fuel consumption. So if you burn a gallon of diesel, about 7 gallons of oil will have run through the HPOP system (and back into the crankcase.)
 

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Discussion Starter · #11 ·
I don't remember who that was, but the oil in the HPOP system turns over at a rate of about 7 times the fuel consumption. So if you burn a gallon of diesel, about 7 gallons of oil will have run through the HPOP system (and back into the crankcase.)

Thank you Sir !
 

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But the oil in the HPOP reservoir should not be dirtier than the oil in the crankcase or on the dipstick if you drip a bit of both onto a white paper towel.
 

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When you change the oil in the engine, you carry out most of the settled particulates from the bottom of the pan. The oil in the HPOP system never gets that bottom flush out. I believe that is the difference.
 
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Discussion Starter · #15 ·
When you change the oil in the engine, you carry out most of the settled particulates from the bottom of the pan. The oil in the HPOP system never gets that bottom flush out. I believe that is the difference.
Yes I believe you are correct . I did my oil change yesterday , I pumped out the hpop res. then added just about half a cup of clean oil and pumped that out too ... It was only slightly tainted . Then refilled . Despite what others have said that it is a waste of time and insignificant ,I don't buy it. Makes sense to get as much old oil out as possible ,even though we know we can't get it all out . So yesterday I unplugged and let it drain . I decided to take care of another chore while it drained and estimate that in the 4 hours it took to get back to the oil change better than a cup dripped out of the pan. Thank you and everyone for your feedback .
 

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Might as well pull the injectors out so you can clean them, and the heads so you clean clean the hpo galleys.

Sent from my SM-G988U using Tapatalk
 
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Might as well pull the injectors out so you can clean them, and the heads so you clean clean the hpo galleys.

Sent from my SM-G988U using Tapatalk
There are two reasons the TDS is the best forum on the internet.

One is the expert advice.
Two is the friendly and supportive camaraderie between its membership.

So next time you want to leave a smartass comment, please try and remember what forum you are on.

Changing the HPOP reservoir oil is an additional 5-minute procedure and has been discussed ad nauseam with no definitive right or wrong answer.
 
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You would think that if changing the HPOP oil reservoir you would think that Navistar the builder and designer of the engine would of put a easy to access drain and fill plug onto it.
 
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Everyone has their own sense of order even when it's net zero. The overwhelming statistics of successful long engine runs with no HPOP oil change or flush is not enough for some, that's OK, it makes some feel better and satisfies a pedantic need. I don't think it hurts anything in itself, but certainly opens the opportunity door to introduce contaminants directly into the HPOP in the process.
I will just go by what works and put my money and time into the traditional maintenance items, must be working, my current truck has 260K on it, the Service trucks at the company I worked for, before starting my own, had 6 service trucks all with more than 300k, none ever had a separate HPOP oil change, and no one I know has bothered to do it.
 

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Discussion Starter · #20 ·
Yes I'm sure you are probably right that in the long run it might not make a hill of beans difference doing this ... but like you said it is only a 5 minute procedure and yes it does make me feel better to get that extra dirty oil out . It's like when I sweep swab the deck for my wife , or do anything for that matter, I try to do the best job possible . Thanks for your friendly response. .
 
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