Garagistic M6X Swap Guide- Cooling

For this swap, I decided to use as stock of a setup as I possibly can.  This includes using the E34 540i radiator & hoses. TOOLS REQUIRED

Table 12

Socket Wrenches Misc.
13mm Socket Flat Head Screwdriver 
Philips Head Screwdriver 
Drill for coolant reservoir
Wire Snips 
Grinder & cut off wheels 
16 gauge steel 
Mig Welder TIME & MONEY

- 5.2 Hr and $20 INSTRUCTIONS


As the cheapest alternative, I suggest you use the donor E34 540i or E32 740i Manual radiator, which was the harder task and involved modifying the frame rails. I was so determined to execute a stock 540i setup that I was willing to modify the frame rails to use the stock radiator that BMW designed the system to use.


Mounting the E34 540i radiator was not difficult, but getting to that point is! On the E30, you must cut the frame rails as shown in the following Figure 84 and Figure 85. The final fitment as a whole is shown in Figure 86.

As shown in Figure 86, the radiator’s final fitment is exemplified. I did not use the black shroud. It made the radiator too wide for the engine, so it was not used. Instead, a SPAL puller fan was used. Continue reading for information on the SPAL slim puller fan.

While the frame rails needed to be modified quite extensively and backfilled in with steel, in my mind it was worth it. Again, if I were to do it over again, I would use a Moshimoto radiator and do no modifications to the frame rail, but since I needed to do a slight widening due to the compressor installation, I figured I’d just go all the way with it.

For the bottom of the radiator, ensure that you made rubber mounts for the radiator to sit upon. This will involve welding of homemade brackets for the radiator to sit on. Drill a hole in the brackets for a rubber mount. It is recommended to use the stock rubber mounts. But be sure to design a system that keeps the radiator from moving in all 3 axes: X, Y, and Z. The top of the radiator will be held by the stock E30 radiator brace and modified as shown in Figure 87.

Again, from the donor car, here are the hoses I used:

  • Upper radiator hose: E34 540i unmodified
  • Lower radiator hose: E34 540i unmodified

Use the coolant reservoir from your donor car if you can. If not, you can easily pull one from a junkyard. They are one of the most popular coolant reservoirs in the 90’s for BMW’s. You cannot keep your E30 ’88-91 reservoir as its mounting location is where the brake booster is now located.

I utilized the stock E34 540i coolant system and that includes the coolant reservoir part 14 as shown in Figure 88. All lines to the coolant reservoir came from the E34 as well.

The E34 coolant reservoir utilizes 2 holes on either side for mounting against the firewall of the E30. These shall be modified and used for installation. This modification involves the following steps:

1. Position the reservoir where it belongs in the engine bay

2. Weld threaded studs to the firewall so that it goes through the holes.

3. Re-fit reservoir so that it now goes through the studs. Remove

4. Use thread locker to thread a nut on the stud.

a. This will be used to position the reservoir to the perfect depth depending on your application

5. Re-install the reservoir to ensure that the nuts are at the correct depth.

6. Use another nut on the threaded stud to “clamp” the reservoir in place.

The wiring for the coolant tank level sender must be relocated from the driver side wiring bundle to the firewall. See Figure 99 for details as to how you must modify the wiring of the coolant Tank level Sender. The wiring goes directly from the E30 body to the sender connector. There is no C101 connection here. In most cases, the wires are BR/RD & BR that need to be extended and relocated

Now that you have the reservoir installed, you WILL have clearance issues with your hood. You have 2 options for the hood modification: Cut the hood bracing so that it will fit or bang the hood bracing in.

I decided to cut the hood this time around. See below in Figure 90 for the hood modification. Notice the 3 way Wiper Tee that was moved to the side to make way for the cap of the reservoir.

The major challenge was the firewall modification to accompany the coolant block outlet in the back of the engine. The firewall was modified in Figure 93 to accompany the outlets.

If you decide to use the 540i engine shroud, it must also be shortened by at least 2” to accompany the location of the coolant reservoir. The first picture of Figure 91 has a red dotted line which is to be cut. See below in Figure 91.

 In Figure 93, you can see the Inlet/Outlet for the Heater Core as well as the introduction of the reservoir, which mounts to the firewall. The hose which also connects to the reservoir is the lower heater core hose.

Note A: I had some trouble with leaks after I installed the engine. Due to that, I highly recommend the following: Before installing the hoses onto the aluminum nipples, put a thin coat of silicone sealant around the circumference of these 2 nipples, then install the hoses and use a the appropriate hose clamps. You cannot get to these hoses after the engine is installed. It is a very difficult and trying exercise. Also, when you install the hose clamps, ensure that you have the screw facing upward in the event that you need to tighten or adjust the clamps while the motor is installed. Again, it is possible, but very difficult and frustrating to get to.  

There were notable changes to the heater core so that the hoses would match up adequately to the heater core inlet/outlet. In Figure 94, you will see the modification to the heater core inlet/outlet.

After reviewing the changes to the heater core, I do not recommend making this change. I think that it can be done without having to angle the heater core lines. The picture shows one of them “Pinched”, but it has not affected the functionality of my heating system thus far and is therefore not an issue in my swap.

A note about which line goes to which hose: My swap, as shown in Figure 93 shows the reservoir hose going to the lower heater core hose, which has worked in my swap and I recommend.

I had a stock E30 2 stage electric fan. It cools the engine “ok”, but I could definitely do better. I was thinking of getting an E32 fan due to the larger fan blade diameter, but in the end decided to go with a SPAL fan. These fans suck a lot of amperage. (16-20amps), but it’s worth it for the cooling that it does. You can have many setups, but I will highlight 2 options.

1. The fan can run off of a low temp switch from the E34 540i radiator. The switch will be low temp switch and close at 82C. I got it from

2. You can always forget the radiator switch and run a switch yourself to the fan. This is what I did and only use in during traffic conditions at hot temps. For this, I would use a relay. This way I can turn the fan on and off whenever I please. I have low amp line and the high amp line fused for safety.

The following section is not a guaranteed way to cool the engine better. It is something that was tried and worked temporarily until the fan was replaced.

What if the E30 fan itself isn’t enough? Well, it should be, even if you don’t have a clutch fan. Maybe your fan isn’t installed close enough to the radiator itself to make a substantial difference. In this case, you need to make a shroud over the circumference of the fan. It will not prohibit air getting to the radiator, it will channel the air that is being blown by the fan to the radiator to ensure that all the air goes THROUGH the radiator. This makes the fan work a little harder (suck slightly more amperage), but it makes a huge difference in the operating temperature of your engine, especially in traffic.

I had a space between my cooling fan and the radiator. This was bad because when I turned the fan on, most of the air blew outwards instead of going through the radiator. This was ineffective approach and I thought how to get most if not all the air blown by the fan to actually go through the radiator. Well, a shroud makes this possible. You can make it out of sheetmetal, plastic sheet, or any other pliable waterproof material. Here are a couple of before and after pictures.

Here is my setup initially with the E30 fan and without a shroud. Because the radiator itself has inherent air resistance, air flows to the area of least resistance, which is to the sides where air can leak out…

Now the plastic makes the fan air go through the radiator with nowhere else to go. I know it’s a cheapo way to go and the material I used was inferior, but the principle is there and the fan cooled the engine better.

Fill the coolant slowly while the engine is running and the pump is circulating the coolant. Keep the heat on, which opens the heater core valve. If you can pre-fill the heater core, it is recommended.

The M60 is a self-bleeding system and does not have a bleeder screw. If you are having trouble bleeding the system, you must drive the car, exercise the heat and eventually you’ll get that big “BURP”, which tells you that the last of the air has escaped the system.

Going the extra mile! TOOLS REQUIRED

Table 13

Socket Wrenches Misc.
13mm Socket Flat Head Screwdriver 
Welder for Bracketry TIME & MONEY

- 3 hours & $600 INSTRUCTIONS

Many people have gone with a Moshimoto radiator. These are all aluminum and offer very good cooling. You can also avoid modifying the frame rails for this swap. If I were to do this again, I would likely have gotten a Moshimoto radiator. It is plenty thick, but not too thick where it would interfere with the belt drive of the M60. While quite expensive, it is worth it. has a wide variety of radiators to choose from. Some people who have done M60 swaps in E30s have used the Moshimoto. MMRAD-E36-92 as in Figure 98. This radiator is less than 2” wide at its max and can provide more than adequate cooling.

The Moshimoto E36 Radiator is geared as a direct upgrade for the E36, but it is easy to adapt for the E30.

It is recommended to weld brackets upon which the radiator sits. shows the teal arrows. Weld 2 tabs for the radiator to sit and add rubber bushings to prevent metal-to-metal vibration.

The wiring for the coolant tank level sender must be relocated from the driver side wiring bundle to the firewall. See Figure 99 for details as to how you must modify the wiring of the coolant Tank level Sender. The wiring goes directly from the E30 body to the sender connector. There is no C101 connection here. In most cases, the wires are BR/RD & BR that need to be extended and relocated.

Recently, I decided to beef up my cooling system by purchasing a SPAL fan from The P/N that I purchased was 30102048, priced at $178. Make sure it mounts as CLOSE to the radiator as possible. The fan is pictured below.

For the coolant sensor installed on the engine, use the M20/M10/M42 sensor. You can either remove it from your M20/M10/M42 engine or buy a new one. For compatibility of the temp sensor, the M20/M10/M42 temperature sender should be used. It’s also cheaper b/c you should already have one from your M20/M10/M42

For the relay wiring for the electric fan, please refer to the Figure 101.

This is how to hook up your electric fan using an external relay. You can tap into your +12V battery supply through the remote +12V battery station located on the passenger side firewall. Ground can be anywhere on the chassis.

As far as you can push back the M60 engine in the E30 bay, you still cannot fit a clutch fan. You can work to obtain a very rare and expensive E30 324td fan, which is a low profile version of a clutch fan, but it not guaranteed based on your engine position that there is room to fit without hitting the radiator.

Instead, I decided to spring some money for an additional SPAL fan that is routed through a separate switch. See information on the switch wiring via relay as shown above. The P/N of the SPAL fan was 30100400 from It is a Low Profile Puller Fan and was installed using the supplied hardware. Please see Figure 102 and Figure 103 for details on the installation.

I purchased the following hardware from SPAL to install this fan and installed it to the radiator support as shown in Figure 102. This eases the installation a lot and ensured that the fan was sturdy since you can see in Figure 103 that there is very close proximity between the fan and the pulley.  

Again, to hook up your electric fan using an external relay, refer to Figure 101. You can tap into your +12V battery supply through the remote +12V battery station located on the passenger side firewall. Ground can be anywhere on the chassis.