E46 wagon cooling system replacement

Did my E46 wagon cooling system replacement last weekend, these are my DIY notes on what turned out to be not a fun job:

I bought a nice E46 wagon last month. It's a puff, with 57K miles, leather interior, pretty much like new. Bought all the parts (from RMEuropean, they do a great job and I got free next day shipping), had everything ready for Saturday morning (I've gone this before on my Z3 Coupe, so I know the routine).

I jack up the car, remove the cover on the bottom, drain the coolant and then get down to remove the nut on the fan clutch (it's an auto trans). On my old Z3, which was original, that nut came off with my 32mm wrench and counter wrench to hold the pulley with one knock from a steel hammer. I put the wrenches on and hit it a few times. Nothing. So I smack it some more, Nothing. I'm using a 2.5 pound steel hammer, so I'm thinking this should be off by now. Yes, I'm trying to remove it clock-wise, so that's not the problem.

Spent afternoon pounding, the wrench was getting deformed and I could see the pulley mounting nuts where getting some serious wear on the heads. At one point, after accidently hitting my other arm with the hammer. I stopped and put ice on it for 20 miutes, that turned out to be the smartest thing I did that day. I'm thinking maybe this ladder sitting in my garage can help? I propped up the ladder in front of the car and with the counter wrench handle resting on a 2x4 I had carefully cut and placed in the engine compartment. I climb up, lean over the engine compartment and put my foot and full weight on the wrench. Surely, my weight (180 pounds) will loosen this nut? But no, it didn't budge one bit. In retrospect, this whole climb on the ladder and jump into the engine compartment was a lame idea and precarious at best. Luckily, I didn't destroy anything on the car or injury myself further. It's about 95 degrees in my garage and I'm getting pretty pissed off by this time. Finally, I admitted defeat and I called a friend and asked him what I should do. "You need an air chisel, what are you thinking? I'll bring mine over tomorrow". So, the next day, he comes with his air hammer, which just looks like steel shaft (he couldn't find the chisel bit) and his compressor. As my friend was just about to put the hammer on the nut he said with minimal confidence "I don't think this will damage the engine. You are replacing all this other stuff, aren't you?" I was, so no problem there. I figured the engine would be ok. 10 seconds with the air hammer and the bold spun off. The water pump pulley was cracked clear through and the mount bolts were all bent and partially stripped.

My theory is that some misguided mechanic replaced the thermostat and thought it would be an awesome idea to tighen up that fan clutch nut with an air chisel (there was a funny mark on the old nut that suggested that). Here's what I say, if the factory can install this part without an air chisel, so should anyone else. Don't use Loctite either, it's not needed here. Just hand tighten with your 32mm and counter wrench good and tight and you'll be set.

After this fiasco, the rest of the job seemed like nothing at all. I replaced the old water pump with the Stewart Components version. It's a great pump, well worth the money. I did buy a new aluminum water pump pulley, so that was good and all the typical parts that need to change at this time.


Things that I would recommend replacing in addition to water pump, radiator, belts, hoses, thermostat & housing, expansion tank and coolant:

Transmission cooling thermostat (my expansion tank came out easily, even so this thermostat underneath must a one use item as it literatly fell apart with almost no pressure on it as the expansion tank was removed.

Convert to hydraulic belt tensioner (probably not a big deal, but I figured might as well since I have it all apart)

Replace idler pully

Replace lower radiator temp sensor (there is no way the old O-ring will keep a seal, you need to replace the switch or the o-ring if you can find it)

The way the automatic transmssion cooler connects to the radiator assembly is in opinion, flimsy and not the greatest design I've seen. It simply plugs in and has one metal hose clip in the center and is all that separates your engine from dumping out all its coolant. If you run an autmatic transmission, I would recommendthat you replace the two O-rings any time you need to pull the cooler off the radiator.

Also, just an FYI wagon owners- the 325iT Wagon uses a heavy-duty core radiator that's thicker than the sedans and other 3 series cars.

Everything is back together and running fine. Thanks to the previous posters that describe the change in detail and offered photos.