Duramax Oil Cooler Upgrade: Installing the 2020+ L5P Cooler on LBZ & LMM Engines
Why You Should Retrofit the L5P Cooler
If your LBZ or LMM oil cooler is leaking, do not waste $600 on a rebranded kit when you can build a better one from newer model such as this one here.
The Short Answer (TL;DR)
You can bolt a 2020+ L5P Duramax oil cooler (GM Part #12706188) onto an older LBZ or LMM block. This provides 20 cooling plates versus the older 14-17 plate design for superior heat dissipation. However, you must use longer M8 flange bolts, specific gaskets, and switch to the newer AC Delco PF26 oil filter due to a thread pitch change.
The DIY Process Overview
The factory oil coolers on the LBZ (2006-2007) and LMM (2007.5-2010) eventually leak at the elbow or gaskets. Instead of a direct replacement, sourcing the 2020+ L5P cooler assembly allows for significant cooling gains. This retrofit generally costs under $300 if you source the parts individually rather than buying a pre-packaged "upgrade kit" from a vendor.
The Critical Parts List:
- Oil Cooler Assembly: GM 12706188 (2020+ style)
- Elbow & Gaskets: GM 12675428 (Elbow), GM 12676826 and GM 97192667 (Gaskets)
- Hardware: You need longer bolts than stock. (2) 120mm Hex Flange bolts and (3) 40mm Hex Flange bolts.
- Modification: There is a small casting "nub" on the back of the L5P housing that must be sanded or ground off to sit flush against the older engine blocks.
Why You Should Upgrade While You're In There
To install this cooler, you are working in tight quarters near the driver-side exhaust manifold. The 2020+ cooler is larger and may contact stock manifolds. Many mechanics find it easier to remove the manifold to ensure proper fitment and clearance.
Since the manifold is coming off, this is the exact moment to replace the restrictive factory log-style manifolds with high-flow aftermarket cast manifolds. This prevents the need to grind the stock manifold for clearance and lowers Exhaust Gas Temperatures (EGTs).
Recommended Upgrade:
High-Flow Exhaust Manifolds & Up-Pipes
Replacing the constricted stock piping helps the engine breathe, lowers EGTs, and provides the necessary physical clearance for the larger L5P oil cooler stack.
Frequently Asked Questions
Will my old oil filter fit the new cooler?
No. The 2020+ L5P cooler uses a different thread pitch. You must switch to the AC Delco PF26 (or equivalent) filter. If you absolutely want to keep using the older PF2232 filter, you must source a 2017-2019 L5P cooler, but you will sacrifice cooling capacity (17 plates vs. 20 plates).
Does this work on the LMM engine with EGR?
It requires modification. The LMM engine has a specific coolant line routing for the EGR cooler that connects near the oil cooler elbow. The 2020+ cooler does not have the provision for this connection. You will need to fabricate a solution or perform an EGR delete/reroute where legal.
Do I need to lift the engine?
No. You can access the cooler through the wheel well. On 4x4 models, disconnecting the front driveshaft at the differential provides the necessary room to maneuver the old cooler out and the new, thicker cooler in.
