Mishimoto E46 Non-M Aluminum Radiator R&D, Part 1: Stock Radiator Evaluation

Interested in purchasing our E46 aluminum radiator? Check out our product page linked below!

Mishimoto BMW E46 Non-M Performance Aluminum Radiator!

This project is another one on our list that we decided to tackle after receiving numerous requests from the enthusiasts’ boards, most notably the fellas over at e46fanatics.com. After developing and testing a very efficient radiator for M3 models of this generation, the non-M world identified a critical need for a more reliable radiator solution. As with most BMW vehicles, plastic components within the cooling system necessitate frequent replacement and have a knack for failing at the worst possible moments (like in the staging lanes of the first autocross of the season).

Along with recommendations from the forums, we also see the E46 non-M as a fantastic budget entry into performance driving, with its rear-wheel drive, sharp looks, and a reliable straight-six engine. All are characteristics of a vehicle that is ideal for soaking up mileage during the weekly commute as well as ripping around the twisties on the weekend.

Test Subject

Finding a test vehicle was pretty simple. A member of our team uses the 325ci shown below as a daily commuter.

E46 325ci test vehicle

A peek under the hood reveals a clean and entirely stock engine bay. This would be helpful because we know what components we will need to incorporate into the design of our radiator. It will also help provide clearance information in regard to how much we can increase the size of our radiator.

E46 325ci test vehicle engine bay

E46 325ci test vehicle engine bay

E46 325ci test vehicle engine bay

Removing the Stock Radiator

Once the coolant was drained we set to work and had the stock radiator removed rather quickly. The process is fairly similar compared to the M3, but the electric fan installed on our manual test vehicle made removal a bit quicker.

Stock radiator removed

Stock radiator removed

Once out, we took a good look at all the features of the radiator to determine our course of action for developing a radiator of our own.

Stock radiator removed

Along with the radiator, we removed the stock overflow tank and both the upper and lower radiator hoses. We will be evaluating the radiator expansion tank with an interest in developing an aluminum counterpart. The overflow tank on these vehicles is a common failure point, so we would like to develop a solution for that. As with the E46 M, we are planning to put together a silicone hose kit to replace the stock rubber units. If you need to replace your hoses, it makes sense to upgrade the material for greater longevity.

Take a closer look at the end tanks and hose connections featured on the stock radiator.

Stock radiator hose connections

One of the more interesting features of this radiator is the cooler port for the automatic transmission, which is located on the lower driver’s side of the radiator. Much like the E90 radiator, this port supplies coolant to the liquid-to-liquid heat exchanger that cools the E46 auto transmission. On a manual model, the plug in the base of this connection blocks flow to the bottom rows of the radiator.

Stock radiator transmission cooler connection

In the automatic version, coolant flows to the base of the radiator and through a separate heat exchanger, which allows for the transfer of heat from the transmission fluid to the engine coolant. A thermostat regulates coolant temperatures for optimal efficiency. This stock system is both complex and interesting.

After numerous discussions and debates, we will be offering a radiator that functions with both manual and automatic models. Our engineers are up to the task of designing this unit, and we see a need for this radiator for auto models as well.

To connect the transmission cooler and overflow tank, a mounting plate is used to route fluid and additionally to provide a mounting point for the fan shroud.

Manual transmission radiator mounting plate

Automatic transmission radiator mounting plate

As you can see, the manual and automatic mounting plates differ. The bottom image shows the two additional ports that move fluid to the external transmission cooler. A thermostat is also incorporated into the larger overflow port. As we mentioned earlier, this is a complex system and is not something we typically see.

Collecting Stock Radiator Dimensions

After deciding on the direction of our project, our engineering team began to collect dimensional data from the stock radiator. This meant mounting the radiator to our coordinate measuring machine (CMM) table and mapping the location of critical dimensions.

Stock radiator on CMM table

Stock radiator on CMM table

Stock radiator on CMM table

Once we have all the information needed from the stock radiator, we will begin to design our aluminum unit. Check back with us next time for a look at the 3D renderings of our plans for this radiator!

Thanks for reading.

–John

Interested in purchasing our E46 aluminum radiator? Check out our product page linked below!

Mishimoto BMW E46 Non-M Performance Aluminum Radiator!