Engine Cooling System Summary


Top Fueler
May 5, 2003
I am using the stock brass/copper 3 row radiator that was in the Malibu. It was practically new, so I didn't see a need to replace it. There are other routes you can take, including a 82-92 F-body aluminum/plastic radiator. The stock radiator has the transmission cooler line provisions and had a fitting provision for the throttle body coolant bypass line (more about this below).

Radiator hoses:
I used upper and lower hoses for a 2004 Tahoe (what the donor engine came from). There may be better alternatives, because these required some cutting and trimming. The lower hose just required some minor trimming. The upper hose required cutting into two pieces, then shortened and connected using a hose coupler. See below:

Cooling Fan and Control:
I originally wanted to keep the OE mechanical fan setup, it's reliable and simple. But, after more thought and examining things, I decided an electric fan was the way to go. If I used the mechanical fan, it would have left me little to no room for air intake plumbing. Here is the mock up of the mechanical fan and shroud. Notice the fan was sticking out of the shroud. I would have needed a spacer for the fan to have the fan inside the shroud:

Also, you can see that it would have left very little to no room for the intake plumbling:

So, I removed the fan and shroud mockup:

There are several options when it comes to cooling fans. I decided to use a mid-90's Ford Taurus 2 speed electric fan setup. They are relatively easy to find and reasonably priced. They can move massive amounts of air on the high speed setting. It fits pretty well. It completely covers the core from top to bottom but leaves a couple inches exposed on each side. I used a cut-off wheel and modified my factory plastic fan shroud top plate to hold the radiator in place while test fitting everything (I later got a steel upper radiator plate from a 1985 Oldsmobile Cutlass). Notice the transmission cooler lines. I was able to use the stock Tahoe transmission cooler lines with some bending and tweaking. You will need to change the ends to mate with the radiator.

Here you can see a better shot of how much of the radiator it covers. Notice that I used the plastic tie-straps to mount the fan in place (see green circle). Yeah, not the best way to do it, but I've done this before with success. I used adhesive foam on the back of the electric fan shroud to provide "cushion" and provide a better sealing surface between the shroud and radiator. See below:

The Taurus shroud had an unusual cutout in the shroud on the top. I used a piece that I cut out from my factory fan shroud and used black 3M adhesive to seal it. See below:

I used a Hayden #3647 Fan control kit. It uses a through-the-fins temp probe. It has a potentiometer adjustable temp setting. It come with a built-in 40 Amp relay. The Taurus fan actually has two speeds (low and high) I'm using the low fan speed. It also has a wire to kick the fan on when the A/C is running. See below:

Closer look at the fan controller:

After driving the Malibu for a few thousand miles, I can say that this setup works great. It keeps the engine temp below or at 195 during hot Alabama days (100+ outside temps) while running the A/C. The low speed fan setting is working fine.

Temp Sending Unit:
I'm using an Autometer Phantom electric coolant temp gauge. Because of that, I needed to find a location to mount the sending unit. There is a location on the rear of the passenger head that has a plug installed that is a good location for the sending unit. You will need an adapter to convert it from metric to 1/8" NPT. Here is the adapter with the part number on the package and also the other fitting or "plug" removed from the cylinder head to install the adapter:

The adapter installs in the back (near firewall) of the passenger side cylinder head. This shot is from under the car.

Adapter installed. I then had to add a small extension since the sending unit would not fit in the hole of the adapter (not in picture).

Throttle Body Coolant Bypass:
The LSx engines have a throttle body coolant bypass hose connection. Some people plug this, others say don't do that. I decided to play it safe and connect mine to the radiator. There are other locations and methods to plumb this, including drilling/tapping and inserting a nipple in the water pump. You can go to LS1tech.com and see how this is done if you're interested. I decided to go a much easier route. My radiator had a fitting provision to install a nipple into the passenger side radiator tank. Here are a few shots to give you an idea of how I routed my setup:

Hose connection on passenger side of throttle body:

Another angle of throttle body connection:

Yet another shot of throttle body connection:

Then, I routed the hose to the passenger side radiator tank. There was a 1/8" NPT port that was plugged. I removed it, installed a 1/4" nipple and connected the bypass hose:

Filling the Cooling System: This is important! If you do not fill the cooling system correctly, you will have air in the cooling system that will cause the engine to overheat. Ask me how I know. ;) It is VERY important to follow these steps when filling your radiator/cooling system:

The highest point of the cooling system needs to be "opened" to bleed out all the air to allow the engine block to be completely filled. To do this, remove the coolant bypass hose from the the throttle body, see below:

Connect lower radiator hose between radiator and engine. Connect the upper radiator hose only to the engine. Hold the hose up while filling the engine block with coolant through the upper radiator hose. When coolant starts flowing out of the throttle body fitting, seal everything up. Now fill the radiator. Crank the engine, let it get up to normal temp to ensure you have coolant flow after the thermostat opens. After you see coolant flow, install the radiator cap and top off the coolant overflow.