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Old 09-13-2012, 05:52 PM
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bluebee bluebee is offline
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Location: San Jose, California
Join Date: Mar 2008
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Mein Auto: 02 BMW 525i M54 auto 130K
So these tips and tricks don't get lost, here's one posted today:

Originally Posted by Adamcan2 View Post
Two weeks ago I did a cooling overhaul for my 530i with 123,000 miles on it. I bought a bundle from that included:

Nissens Radiator
Expansion Tank
Graf Water Pump w/Metal Impeller
Wahler Thermostat and Housing
Upper and Lower Rad Hoses
Cooling Temp Sensor
a small washer in its own bag

This bundle cost around $430. I spent an evening pricing things out from different suppliers, figuring out what the cost individually would be, etc. It looked like I could have saved about $10 if I sourced all the parts separately, but I was happy to the extra $5 for the convenience of having everything put together and shipped at the same time. In addition, most of the best individual prices that I found were on eBay which is always a bit of a crapshoot.

The day of my fix, I also decided that I should change the Serpentine Belt. This part costs $30 online, but since it was day-of I went to the stealer and paid $61.86. Oh well, better than worrying about it.

I primarily used cn90's excellent DIY for the fix, which can be found here:"]. Besian also has good information about the fan shroud removal at I have heard that Pelican Parts has a good DIY as well but I did not use it. Because there are such great resources out there for this fix, I will not go into it step by step, but will put down a few details that I ran into. I also did the double Vanos during this fix, but I will put my specific experiences on that in a different post.

I recommend getting the serpentine belt and A/C belt if you are going to do this fix. If you plan ahead (unlike I did) you can have both for around $40, and again, peace of mind is why we do these fixes. You will be removing both of these during the course of the work, so it is no extra effort to replace with new.

Another item is the catch pan for coolant. I wasn't sure what size I needed. I ended up using a Rubbermade 3 gallon rectangular container. I only ended up draining about 1.5 gallons of coolant, but to be fair a good amount ended up on the garage floor. I also cleaned this puppy thoroughly after use. Since I had an issue with my fix I had to open everything up again, and having a clean container meant that I could re-use the new coolant when I had to drain it for the second time.

You will need a 32mm wrench for this fix as well. I bought one at a local bike shop for $12. This is also the wrench you will need if you want to fix the headset on your bike. Hooray, double use! I think I saw some posts that said they got away with using a wrench, and while I am sure this is possible, my life was made much easier with the 32mm. Also, if you have a choice of lengths when purchasing this wrench, get the longest one you can find. Mine was a bit short which makes it awkward to smack with a hammer, but even so it is not too bad.

Moving on to the fix, the first item that I was not clear on was how the radiator plug works. It is on the bottom of the radiator on the drivers side, and I guess it is usually blue (mine was). I turned it 90 degrees, as specified, and nothing happened. What you have to do then is pull straight down on it. It will pop out with moderate force, and you will get coolant all over your shirt. Or at least that is what happened with me. If I knew better, I would have positioned myself more out of the way and yanked more firmly. Then I would have only gotten it on my hand. You will get it on your hand.

The second item that gave me a bit of trouble was the hoses themselves. They are held on with a metal clip that is easy to pry up, but even after doing that the hoses can be difficult to dislodge. I wasn't sure if I needed to do something else or not. I did not. Just pull up the clip (half of them will fly off the hoses, but this is no big deal) and start to work that bad boy off. The first hose you take off, the one that connects to the auxiliary water pump, will spray quite a bit of coolant out even after draining the radiator, so be prepared. It comes out with a small amount of pressure so factor that in with your catch pan positioning.

Once you follow the directions and get the fan shroud loose, you get to the dreaded fan removal. I have removed this thing several times now, and it has been different every time. I assume it is because the fan is "clutched", so depending on the clutch position the fan may spin easily or it may not spin much at all. At any rate, the method described is exactly right--put the wrench on and hit is with the hammer. It is reverse threaded so you want to go righty-loosy. A snap of the wrist is better than a wind up power shot. You don't need power, you need pop. Two out of the three times that I removed the fan I popped it and then spun the fan to remove it, but the other time I couldn't spin the fan and had to use the wrench the whole way. It sucked, but it worked. I also had some trouble lining up the threads when I went to put the fan back on. Just keep at it, and know that this part is (normally) the biggest PITA in the whole project.

When I got to the Serpentine belt I was having some trouble removing it. The DIY says to use an allen wrench in the middle of the tensioner pulley to release the tension. I did not have a wrench that would fit. What I did find was a 16mm (I think) bolt head cast into the tensioner arm. I was able to use this to release the tension. It seemed easier to me than working with the rather small hole in the middle of the tensioner pully. The only other detail here is that when you release the tension the instructions are to put a drill bit into the holes that line up above the tensioner pulley to keep the belt slack. This works well, but you definitely want to put in the largest drill bit that will fit in the hole. I started out with a drill bit one or two sizes smaller than the hole, and that half millimeter made it so I couldn't release the belt.

Another issue that I ran into was the coolant temperature sensor that goes on the lower radiator hose. It didn't feel tight when I put it in, and I had this washer in a bag all by itself for which I did not have a purpose. Since the washer fit into the socket for the sensor, I put it in and replaced the sensor. I must have pushed too hard because I broke the housing of the sensor. It didn't leak any more, but I was throwing the code for that sensor--sorry I can't remember what the code was. I ended up buying another sensor and installing it without the washer, and no more code.

My last issue outside of the DIYs was that once I buttoned it all up, I was getting coolant leaking from behind the serpentine belt. I couldn't tell if it was the thermostat or the water pump. I posted a question about it on this forum and got many helpful suggestions, but the reality was that I made a mistake. I have a $20 torque wrench that is a POS. It is one of the beam-style ones. When I was replacing the Vanos during this fix, I broke a post from torquing it too hard, because to my eye the torque wrench had not reached the recommended N/m. Because of this I was way too careful when I installed the thermostat, and didn't bolt it back in strongly enough. When I finally inspected the thermostat I could turn the bolts with my fingers! I torqued this back down and everything was fine.

Based on my experience I strongly suggest getting a digital torque wrench. Sure, it costs $100 or more, but if you are a DIY person, tools don't cost you money, they save you money. Add that onto the fact that you will use this tool with nearly every fix you do, and the $100 seems pretty worth it.

To finish, a quick question: what is that little washer for? While it fits in the temp sensor socket, the bottom of the sensor is pointed rather than flat, so it doesn't seem like it is made for that application. With the new sensor that I put in without the washer I am getting random droplets of coolant leaking out. Not much leakage--maybe 2-3 drops on a 10 mile journey--but it seems the seal is not as good as it should be. Is that actually what the washer is for? Was I just being too much of a boy when I shoved the first sensor in and broke it?

Thanks to everyone for their posts and DIYs. This was a fun fix and I am feeling much better about my cooling system. I am running consistently 93 degrees C on the high cluster and I can just tell my car is much happier.


Update: Drat. My cooling system sprung a leak yesterday!

Originally Posted by bluebee View Post
Well, it's 'my' turn again!

I noticed a puddle on my driveway today ...

So I started looking for the telltale white spots:

And, watching for a while, I found the culprit!

Note: I last replaced my Behr expansion tank in 2010 as noted by the markings on the side.
Please read the suggested threads and add value, either by pictures or by descriptions, so the next person stands on your shoulders.
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