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DIY Complete Cooling System Overhaul (Pump, Hoses, & Tank)

105K views 88 replies 57 participants last post by  Cowspoo 
#1 ·
I finally reached the mileage where I needed to do this. I took a lot of pictures since it seems like people are always doing this one and are always having questions. Anyways, I hope it helps some of you all out. Let me know if anythings wrong with the writeup, it's quite long so there's lots of room for errors.

There are directions to replace all of the following:
Water Pump
Upper Radiator Hose
Lower Radiator Hose
Expansion Tank and Cap
Temperature Sensor
Thermostat
Coolant

http://www.bmw330ci.net/maintenance/completecoolant.php

Enjoy! - Paul
 
#66 ·
Thanks for the great write-up! I did this project today and everything went very well. Since i was at 129000 miles i would say it was way over do for this car, it still had the original expansion tank, and who knows what else was original. It even had regular antifreeze in it. I feel so much better now that this is done.
 
#67 ·
This is a great write up. Im bumping this old thread coz I replaced the upper hose after it exploded. There was a big rip right across the upper hose. Good thing it happened near my house and I made it safely to my garage. I got the part from the dealer since I didnt want to tow the car anymore. I looked at the part and figured it was an easy job till I tried. getting the hose off the radiator side of the hose was a PITA and i didnt want to damage the radiator fitting. Finally I got it off. Not a bigger pain, getting the hose on. How do I slide the hose into the radiator? There is just no leverage to squeeze it in. Any advise?
 
#69 ·
Thanks for the reply sixracer. I just cant help but noticing that handsome 6 series in your sig. It's one of my favorite classic cars. I collect classics and im having an eye for that one. Nice!

Well, my friend mechanic who does my car in my garage called in sick today and cant make it over the weekend. This means I'll have to give the darn hose a shot.
 
#70 ·
Paul,
Excellent writeup, worked perfectly on my 325i, took a little over 5 hours. Only trouble I had was my own fault, as I didn't get a new temperature sensor. When I put everything back together, that was my only leak. Got lucky though, partially drained the system, cleaned the sensor and reset it, no leaks.

Dave
 
#71 ·
Wow!. I am new to this group and what a write-up with pics. Awesome!!

I wish I had this when I sprung a leak on my cooling system. Had to change out the expansion tank and the upper radiator hose. Could not pull the lower one off and since it was not leaking left it alone. Did not change out the waterpump etc as did not have this write-up. Will get to that later. Thanks for the link to the OEM parts. I paid nearly 3/4 of the price of the Tischer kit and just got the hoses and the expansion tank.

One method that I found helpful and one which I used - found it on the net - to pull the expansion tank out was...prop a hammer/or some other solid piece of metal (like a metal rod, pipe etc) onto a jack. Use a small piece of wood on the jack side and push the other end of the hammer/piece of metal on to the expansion tank. Raise the jack and the expansion tank will come off with relative ease.
 
#73 ·
I just changed out my expansion tank and I have a few observations, as I did it differently than instructed to here and I could not have done it any other way, I think. I took out the old expansion tank with the assembly it attaches to together. This was easy as pie. No hammering or pushing or anything. Though You do then have to unclip and disconnect the bottom hose as well ( don't know the name).

Then, I saw where the hard part was. With the old tank out, I ubclipped the bottom of the tank from the assembly and I could then slowly pry out the old assembly with a bit of force and a sturdy screwdriver. Viola. It would have been almost impossible to do this separation while the assembly was in the car.

Then I had to mate the new tank with the old assembly. Mere pushing with body weight is not enough. I was stumped into how I was going to mate them, as they were not wanting to. I reexamined the pieces to see if perhaps they didn't fit or something.

Then I got an idea that made it simple. I was able to mate the two by laying everything sideways on the ground and using my hydraulic car jack, also on its side, to slowly force the assembly into the new tank. No banging or grunting.

I did see how tough it was to mate the two and again, I can not even imagine trying this with the assembly in the car. Besides this unmating/mating issue, the next hardest thing is unclipping and clipping the lowest and 3rd hose as there is very little room, but not altogether that hard.

So if you can remove the assembly with the tank and then deal with the assembly once outside of the car, I think it will be much much easier. Also try to use some tool to squeeze the assembly together again. At first I tried placing everything in a door jamb, and that almost worked but the door jamb was a little too wide.

My assembly just unhooked from the radiator mountings and looked slightly damaged. I think whoever replaced the tank previously may have done this damage, making it easier to remove the assembly, but I am not certain.
 
#74 ·
OP - great write up. Thanks!

I did basically a complete cooling system overhaul this weekend with a good friend (@ 85k). Everything went very smoothly, though we did get coolant EVERYWHERE. Once you think you've drained it all, you disconnect another hose and realize how wrong you were! Thankfully the stuff we drained was still nice and blue. A few notes:
1. I personally LOVE the BMW design of the spring clip hose connections. Very controlled, simple and precise. It allowed me to remove and install the rear engine block hose without being able to see it.
2. I consider myself lucky that removing and installing the expansion tank was much easier than expected. It pried off the lower mount fairly easily with a flathead and the new one slid right on. Lower radiator hose too.
3. We did not have a short enough torx socket to remove the screw from the top of the bracket. Tight clearance between the screw head and my headlight assembly.
4. Removing the engine block drain plug is definitely very messy! Somehow my friend fit his breaker bar in there at an angle to get it off. We tried to put tubing in there to control the mess, but it just didn't work
5. I filled the system with just under 8Q of 50/50 after it was all said and done. The manual calls for 8.8Q (<- lol looks like BBQ). Since the car was on ramps, my guess is there was about 0.8Q sitting in the back of the block that hadn't drained.
6. I went with a remanufactured OEM pump instead of the Stewart pump. I don't subscribe to the theory that the Stewart pump is better "because the impeller is metal".
7. I don't like plastic drain plugs and bleeder screws. Though we did not strip them, I was very nervous tightening them.

Thanks to ECS Tuning for having a great selection of OEM cooling system parts. Here is what I replaced:

thermostat (started to stick open @ approx 75k)
water pump
coolant temp sensor
expansion tank with new cap, coolant level sensor (old one was metal, new one is blue plastic) and lower spring clip
BMW coolant + distilled water
accessory drive belts
hoses replaced:
1. lower radiator
2. upper radiator/expansion tank
3. rear engine block to heater core "valve"
4. intake-side of engine block to expansion tank
5. heater core to expansion tank
 
#76 ·
I was forced to undertake this complete cooling system overhaul after my expansion tank exploded last week. My parts just came in and so I started taking everything apart. That is when I discovered the situation was must worse than I had thought. When the expansion tank exploded, pieces of it must have hit the radiator fan because one of the fan blades was completely broken off and another one was cracked (by the way, fan came off easily with a cresent wrench and hammer strike technique). So I ran to the dealership today and paid $65 for a new fan. Tonight I got back to taking off parts. When I pulled the expansion tank off, I noticed a small part was broken where the expansion tank connects at the bottom. The part had a number on and I was able to determine it was the expansion tank thermostat. I don't want to wait to have one shipped so I will have to call and see if the dealership has the part. The list price is over $90 for that stupid little part. I also just discovered that the coolant level sensor was damaged in the explosion and I hadn't ordered that part either.

So my question to the forum is what other parts of the cooling system were possibly damaged in the expansion tank explosion? What else should I check out before I start putting everything back together? Thanks.
 
#83 · (Edited)
I just replaced my original thermostat, expansion tank, and water pump. The water pump (metal impellar with weld spots) and thermostat look to be in great shape. The expansion tank seemed to be in good shape too but i cracked the smaller upper radiator hose adapter when taking the upper radiator hose off =( . 99' 323i @ 189k miles. Some quick notes: Don't do this without eye protection, Lower and upper radiator hoses... wow hardest thing i've ever done on a car due to the limited space and strength required to pull off. If you don't have a hose that fits loosely over the engine drain bolt go out and buy one. I did this without a hose and it's extremely messy, but didn't cause any problems aside from floor cleanup. ONE MASSIVE IMPORTANT DIFFERENCE between this DIY instruction set and the instruction from the Bentley manual. The Bentley manual does not instruct to put the heater on/fan low for draining of coolant, only for fillup/bleeding. I did NOT put the heater on at all during draining, and yes coolant poured out of the heater core hose without causing any problems. I had the car up on ramps the whole time.
 
#84 ·
Hi! This is a great DIY, definitely. I wanted to ask for your suggestions: I never worked in a car before (only topping up oil or things like that), but I'm eager to learn these things, partly because it interests me, and partly because I got myself a 2001 330ci and would like to save some money with a DIY approach. Of course I don't plan to be able to do everything right now, but the first thing that I want to do is the cooling system overhaul, and after reading this whole guide, it doesn't LOOK so complicated.

Do you think I can honestly do it myself? There's no way to know for me until I try to do it I guess. I can follow directions pretty good.

Also, I don't have a garage myself. I live in an appartment complex, I do have my "own" driveway though; it's right on the entrance of the building, and it only fits one car, so no other cars around, but still has some space for me to work. However it's not really inside the building, meaning I can't just leave the car jacked up there overnight, so I was wondering how much time this job could take to a complete newbie like me. One of the posts said that it took 8 hours to someone, and I'm ok with that, even more, as long as I can start early in the morning and finish before the sun is gone.

Thanks!
 
#85 ·
Radiator replacement, too?

I've read that you should do all of this AND replace the radiator every 60,000 miles. It looks like the radiator would just lift out, right, if you wanted to replace it as well?

Terrific DIY; excellent photos.

I'm an e30 owner and am shopping for an e46. I figure I'll do this ASAP.

I have my eye on a 2001 330i.

Look forward to your reply. Gary
 
#86 ·
I've read that you should do all of this AND replace the radiator every 60,000 miles. It looks like the radiator would just lift out, right, if you wanted to replace it as well?

Terrific DIY; excellent photos.

I'm an e30 owner and am shopping for an e46. I figure I'll do this ASAP.

I have my eye on a 2001 330i.

Look forward to your reply. Gary
I'm at 140k miles on an '02 330i and i haven't changed the radiator. I did the hoses, pump, thermostat, sensor, and reservoir at 105k, but not the radiator.
 
#87 ·
bump

Im trying to do the overhaul on my 323i cooling system but i found sand on the water pump impeller and inside the ATF cooler. idk if there might be more inside the block but how can i pump all the grime/dirt/sand out of there?:hmm:

note: ignition coils are not in place.&
i drained the oil out of the car. therefore i cant really turn it on
 
#89 · (Edited)
I've spent over an hour trying to remove this small lower hose for the radiator mount/expansion tank.

Any ideas? The radiator is disconnected and ready to be removed.



May many ounces of patience be awarded to the unfortunate one who breaks one of these water pump bolts. Be careful.
 
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