As you know, I have been upgrading certain items on the Cruze to make it a little more reliable and help protect it when I take it to the track for a few track events now and then. One of the things I wanted to upgrade was the so-called oil cooler. GM labels it as an oil cooler, but I think its actual purpose is to help heat the oil faster for cold starts. That’s my unprofessional opinion, at least. I’ll explain the reason why I think that a little later.
The Cruze has an oil filter housing that bolts to the block, and attached to the filter housing is the oil cooler, which looks like an aluminum block with little fins around it. The cooler is divided down the center with the coolant flowing through one side and oil flowing through the other. On the oil side, the oil comes up directly from the oil pan, passes through the cooler and into the filter housing, then passes through the filter and into the engine. The coolant enters through a pipe attached to the front of the filter housing, then passes through and exits out of a pipe attached to the cooler.
The coolant temps are slightly lower than the oil temps, but only by about 10 or 15 degrees, according to my observations. I see coolant temps in the range of 210 – 220 °F and oil temps in the range of 220 – 230 °F. The cooler is also mounted directly under the turbo manifold, which gets extremely hot as everyone knows. I put an infrared temperature gun on the cooler after the car was hot from driving, and the surface of the cooler was 400 °F! So, what do you think? Is it actually cooling the oil?
I think it’s more for heating the oil rather than cooling it. The coolant heats up much faster than the oil, so it makes sense that during cold starts the coolant passing through the one side of the cooler will help heat the oil passing through the other side more quickly. What doesn’t make sense is how it is doing any cooling while mounted under the turbo manifold. Anyway, this is something I felt I needed to address before hitting the track.
I wanted a front-mounted oil cooler in front of the radiator. If you happened to read the post on the trans cooler upgrade, you know I have already installed another cooler for this purpose. The issue now is how to get the oil to it. If the engine had a spin-on filter that mounted straight to the block, it would be straightforward. Unfortunately, the oil filter assembly makes it a little more complicated.
I took a closer look at the stock cooler/filter assembly and noticed the cooler was bolted to the filter assembly, which meant it was removable. Instead of removing the one on the car, which would require draining fluids and removing the turbo/exhaust manifold, I purchased a new one to take apart and see how it all worked.
Once in hand, I unbolted the cooler from the filter assembly and could see it had a flat mounting surface with a gasket installed on the filter assembly portion. That was excellent news because it would allow me to have an adapter plate fabricated to replace the cooler. The plate would have fittings to attach oil lines to reach the new front-mounted cooler.
I had plans of strengthening the bottom end of the engine, so I decided to wait until then before doing anything with the cooler upgrade. Once that project started, I removed the engine and continued with the oil cooler upgrade.
I first purchased a 1/4″ thick piece of billet aluminum. Not having the correct tools to cut the aluminum, I decided to take it to a machine shop along with the cooler so they could cut the exact shape and drill all the holes in the correct places. I had them drill three holes, two for the oil lines, and one for the coolant line that passed through. Unfortunately, there wasn’t enough space to weld all three fittings, so I had to figure something else out for the coolant line.
After the machine shop finished the adapter plate, I purchased two -10AN bung fittings and had them welded to the adapter plate where the oil would go out and return. I also needed to add a pre-filter before the cooler, as it is unfiltered oil coming out of the block, and I didn’t want to chance the cooler becoming clogged with any debris should something go wrong inside the engine. I chose a System 1, 80-micron filter for that purpose and mounted it on the body/frame rail below the air intake tube. I added a 215-degree thermostat from Improved Racing and an Accusump Oil Accumulator to the system as well.
Once everything was mounted, I was able to measure and assemble the -10AN lines to connect everything. For the coolant line, I initially rerouted it using additional fittings, but after some research and consultations with a couple of engineer friends, we determined the line could be eliminated altogether.
Once everything was connected, I added oil and removed the fuel pump module fuse so I could turn over the engine to build oil pressure before it was started. The pressure built up and everything looked good, so I started it up and checked for leaks. Once it ran for a few minutes, I shut it down, let the oil drain, and topped it off to the correct level.
Oil cooler upgrade is complete!
DS
