2020 Duramax L5P Oil Cooler Upgrade

Croatan_Kid

Croatan_Kid

How's your hammer hangin'?
Joined
Nov 4, 2007
Location
New Bern
I figured I'd go ahead and start this before I forgot. I've got a bunch of pictures to resize on my phone before I can post them.

The main objective here is to replace the oil cooler in my LB7. I just happened to see some stuff about the 2020 L5P cooler bolting up to all previous generations and being literally twice the size of the LB7, LLY, LBZ, and LMM coolers. 10 plates vs 20 plates! LMLs went to a 14 plate, IIRC, and 2017 to 2019 early L5Ps used a 17 plate.

I had gotten some weird stuff in the last two or three oil samples I sent in and decided that changing the oil cooler would be the easiest place to start. I'm the type of person that always looks for an upgrade with a replacement, if possible. Stock worked well for 315,000 miles, but might as well look for something better!

So, Duramax engines have never seemed to have much concern with oil temps. They don't monitor it and haven't monitored it until a few years ago. We all know that when oil gets hot, oil pressure drops. In stock form I'm sure everything would be fine. I don't live that stock truck lifestyle :D

In my searching, I also found that replacing the cooler with this newest variant is cheaper. The cheapest complete assembly I found was 290 bucks (plus gaskets) and the cheapest cooler stack was around 200 plus you need a full gasket set to the tune of about 60 bucks and you have to disassemble it. There's also no replacement gasket between the halves for the earliest LB7 oil cooler, so you'd have to replace it anyway. It was a metal framed gasket covered in silicone. Later ones use a large o ring that sits in a machined groove.

2020 L5P Cooler: 112706188 supercedes old PN 12701592 ($205)
Adapter: 12675428 ($10)
Gasket: 12676826 ($4)

Pictures are posted in order of part number listings and you can see the part numbers on the bags they came in from GM.
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Prices rounded up to the nearest whole dollar and vary slightly from place to place. I got them from GM Parts Direct.

It does use a different oil filter than 2001-2019. It's an AC Delco PF26 filter. Cross reference that to your particular brand preference. Make sure it has an anti drain back valve and bypass valve at the proper pressure ratings. I used an Amsoil EAO11. It's a slightly smaller filter, but that doesn't necessarily mean it has less pleating inside of it. I'm sure someone will eventually make a longer filter for it if the demand is there.

Thus far, you can order the parts and know what you're getting. The next post will let you know what few extra things you'll need over a standard oil cooler replacement job.
 
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If you've made it this far, you've probably looked at an earlier oil cooler. You'll notice this new one has a 3 bolt flange from the cooler to the elbow. You'll need another bolt as the older ones only used 2. The mounting bolts for the cooler are also different lengths. There are 5 of them total. I actually found these lengths on a post while doing my initial research and can confirm they are the proper lengths.

Here are the 5 bolts that hold the cooler to the side of the engine block.

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You'll need:
2- 8mmx1.25 120mm long bolts
3- 8mmx1.25 40mm long bolts
1- 8mmx1.25 20mm long bolt

All of the 20mm are for the coolant elbow. 3 hold the elbow to the cooler and 2 bolt the elbow to the bellhousing adapter plate.

The cooler is held to the engine block with 5 bolts, as you can see. 2 120mm and 3 40mm. You can't mix those up.

I opted to get 5 20mm long bolts to replace all of the ones for the coolant elbow. Might as well while you're at it.

You'll need a few more seals, o rings, and some coolant to get this done. I opted to hit up Lincoln Diesel because they offer everything individually and it's much cheaper than buying an oil cooler gasket kit!

You need:
Water pump to coolant pipe gasket
Coolant pipe to cooler o ring
Coolant elbow to bellhousing seal
3 gallons of whatever coolant you use
3 gallons of water

Here they are in order of how they're listed from left to right.

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I went ahead and order the o ring and seal for the oil cooler to the block. Green and black in the picture above. I didn't know it came with them. Better safe than sorry, but now you do and hopefully I can save you a few bucks! It's unlike GM (or anyone, really) to throw in anything extra...

This will likely be all until I get around to changing it out. Up to this point, you'll have gathered everything you need and it's a standard oil cooler replacement job. There will still be more pictures and data once I start monitoring oil temperature. Unfortunately, I won't be doing a before and after. I'm changing the oil pan as well and the new pan has a 1/8 NPT hole for a temp sender and I only want to change the oil once!
 
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02gmc5.3 said:
Appreciate the post, I'm gonna do this on my lmm soon. With 440k miles I've been getting more pressure drop while hot here lately.
Click to expand...

LMMs ran lower oil pressure by design already. I'm sure a drop from that, while likely just fine, is still worrisome! I like oil pressure! If you haven't already, taking your cooling stack apart and cleaning it wouldn't hurt either. At 400k, I'm sure it's accumulated some filth.

Btw...Unless they've changed something, these oil pumps flow 18 GPM at 2000 rpm. That's a lot of oil circulating and taking heat with it. Might as well try to keep it as close to coolant temps as possible! The bottom end of basically every water cooled engine is oil cooled anyway, plus these have oil squirters that hit the bottom of the pistons and adds even more heat.
 
Happy to report that all the bolt lengths I previously posted worked well. It's just a standard oil cooler replacement. Definitely bolt the coolant elbow to the cooler before you bolt the cooler to the block. You can't access the lower, inside bolt on the bottom of the elbow once the cooler is bolted up.

So far, it seems to hold a little better oil pressure at hot idle and oil pressure rises quicker with throttle input. My original cooler was one of the early ones that you can't get the body gasket for...so the whole thing would have gotten replaced anyway. It all worked out.

I didn't have to do any clearancing since I don't have factory exhaust manifolds. If you have them, all you have to do is trim the heat sheild. No big deal.

Here's some pics!

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I literally just made an account on here just to tell you that this was an excellent write up. Thank you for taking the time to do itđź‘Ś
 
No problem! Where did you see it posted?

I like doing stuff like this that people talk about, but nobody ever posts pictures...or nobody is sure if it'll work.
 
I am getting ready to do this upgrade this weekend. My one question is if I could just take off the current threaded adapter on my LBZs oil cooler and put it on the new oil cooler to be able to retain my stock LBZ oil filter. I like the idea of having the larger LBZ filter and the ease of maintenance since I won't have to remember that it's a 2020 filter on my 2007. I'm not sure if this would cause any issues.
 
Just made an account here to say thank you for saving us all money! I am getting ready to do this upgrade this weekend. My one question is if I could just take off the current threaded adapter on my LBZs oil cooler and put it on the new oil cooler to be able to retain my stock LBZ oil filter. I like the idea of having the larger LBZ filter and the ease of maintenance since I won't have to remember that it's a 2020 filter on my 2007. I'm not sure if this would cause any issues.
 
No, the gaskets are a different diameter. PPE makes larger filters to fit the 2020s though. One is about 6.5" long and the other is around 8.5" long. They're also different threads. 01-19 are 13/16-16 and 2020 is M22x1.5. Even if the threads IN the oil filter mounts were the same, which they're not, the original filter gasket would be too big to seal properly.
 
Ok makes sense to me thank you for the quick reply. Looking forward to getting it started this weekend. Already had the water pump, turbo, and the turbo up pipe off so I figured I would knock this out while the fluids are drained and the parts are already out of the way.
 
If you think you have all the coolant drained...well, you're not exactly right. :D You will after you unbolt the oil cooler though!
 
I also just replaced my turbo for the second time after the first replacement 67mm shit the bed. I'm getting proficient at replacing them and that's NOT something I want to be good at!
 
I agree that turbo was a real struggle to get out, I broke 4 of the pedestal bolts. I can't wait to hear what it sounds like but I think I'm a ways off from getting the new one back in. I did the down pipe while I was in there and now im thinking about doing the up pipes.
 
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