My cooling system refresh is coming up. How deep do I go?

[NorCalZman]

I have decided to try to get the cooling system out of the way as I am just past 90k and its almost summer (in California).

My general list is below. Hope this helps anyone else looking for some part numbers. If you click on it a few times it will expand:



A few questions:
1) A manual car has how many of these little blue drain plugs (17111437361)? One for the radiator and one for below the expansion tank or....?
2) Has anyone included the coolant return hose in their overhaul (11531436410)? It goes from the bottom of the expansion tank to some plastic tube midway down the engine block. I havent seen pictures of the routing, but I am wondering how involved it is to include this in my project. It sounds like the air filter box needs to come out at least, right? Anyone who has replaced this chime in on your experience?

There are a few things on the list I wont be replacing. Auxiliary fan switch for one. I will just replace the o-ring with the alternate made of Vitron. Also wont bother with the coolant level sensor as I hear these rarely fail. I already replaced the expansion tank when I first got the car as it was seeping, so that is taken care of.

As for the pulleys/tensioners, I am debating whether I should just do the pulleys or if I should replace the tensioners as well. There doesnt seem to be a consensus that I can read on the various forums.

[TigerTater]

Just did it today. I used ECS stage 1 plus some addition goodies like new belts and the coolant return hose you speak of. It was a very easy hose to change in addition to the others. Whole thing took roughly 2.5 hours taking my time. I used this DIY ( http://www.bmw330ci.net/maintenance/completecoolant.php). I also have an auto so I had to deal with the clutch fan removal, yours will be much faster! I only had one blue drain screw, and drained the coolant using it and just disconnecting the lower radiator hose...did not want to use the engine block drain screw as I did not purchase a new crush washer for it. I did not change pulleys or tensioners. Mine are spinning easily without binding or noise, my tensioners are very tight (I found this out when I did the OFHG). Hope this helps!!

[NorCalZman]

It does, thanks. Regarding that specific coolant return hose, can you give a few details about replacing it? Is the airbox the only item you needed to remove to change it?

[ZHPRegistry.net]

I am probably going to have to face some flame throwers but I'll say the following...

E46's cooling system is unbelievably awesome problem for every parts store. I can hardly recall any other mass paranoia that concerns BMWs than the over the top overhaul of the cooling system.

It all started when BMW made the mistake of sticking a plastic impeller into the water pump. The problem with that particular type of plastic was that it really proved to not be up to the challenge of wide temperature swings and/or vibrations that the pump was exposed to. Starting from 03/2003 the composite impellers used in the BMWs have proven to be bullet proof. They look virtually new even after 100K miles.

In addition to the water pump problem, there were a series on expansion tank blow ups, and to this date there is no clear indication whether those were expansion tank problems or the older caps on top did not properly bleed excess pressure.

Somehow parts dealers have convinced the e46 owners that virtually every part (aside from the engine block) that comes in contact with the coolant needs to be replaced at 60ish K miles.

Aside from the expansion tank cap everything else on my 90K 3-er is original. I periodically check the water pump area for traces of dried coolant which is an indication of a slow progressing bearing failure. I do not intend to do any massive overhauls but replace parts as needed. I can respect the "while you're in there" mentality as long as it is used rationally.

Mind you, the so called "complete overhaul kits" sold by many friendly specialist call for such ridiculous things as replacing all water temp related sensors too... which by the way are used on many many other BMW models and have proven to last forever.

flame suit is on

[NorCalZman]

I can agree to an extent. Even if I owned the car since new, I dont think I would have done this work at 60k. My car is pushing 100k now though, 40k more than the cooling evangelicals say is good. Summer is coming up. My expansion tank was already leaking fluid and thus replaced around 87k. My water pump has shown signs of dried coolant nearby according to my indie (but they said it wasnt actually leaking when they were looking at it). I think the signs are there that various parts of my cooling system are nearing the end of life. Yes, a hoses here or there may develop a slow leak over time which would require me to go in to change it. Then go in again for the next leaky hose, or for a thermostat throwing a code, and so on and so forth. I dont want to do that. Same for the pulleys. I see enough threads of them just failing to make me want to change them at the same time. I can save a lot of money on labor if I knock this out in one weekend myself instead of breaking down and having a mechanic do it for me in the middle of no where.

At the same time, I am not buying into everything. Like the sensors. I am also not one to buy new bolts, etc unless the consensus is I must. If you look at my list, I think its a very rational, balanced 100k cooling service.

Its not just BMWs that have cooling overhaul people. My last car, a Nissan Z, had people saying to refresh the cooling system when the timing belt was changed: every 60k.

[TigerTater]

I am probably going to have to face some flame throwers but I'll say the following...

E46's cooling system is unbelievably awesome problem for every parts store. I can hardly recall any other mass paranoia that concerns BMWs than the over the top overhaul of the cooling system.

It all started when BMW made the mistake of sticking a plastic impeller into the water pump. The problem with that particular type of plastic was that it really proved to not be up to the challenge of wide temperature swings and/or vibrations that the pump was exposed to. Starting from 03/2003 the composite impellers used in the BMWs have proven to be bullet proof. They look virtually new even after 100K miles.

In addition to the water pump problem, there were a series on expansion tank blow ups, and to this date there is no clear indication whether those were expansion tank problems or the older caps on top did not properly bleed excess pressure.

Somehow parts dealers have convinced the e46 owners that virtually every part (aside from the engine block) that comes in contact with the coolant needs to be replaced at 60ish K miles.

Aside from the expansion tank cap everything else on my 90K 3-er is original. I periodically check the water pump area for traces of dried coolant which is an indication of a slow progressing bearing failure. I do not intend to do any massive overhauls but replace parts as needed. I can respect the "while you're in there" mentality as long as it is used rationally.

Mind you, the so called "complete overhaul kits" sold by many friendly specialist call for such ridiculous things as replacing all water temp related sensors too... which by the way are used on many many other BMW models and have proven to last forever.

flame suit is on

Haha. I started a similar thread on e46 fanatics it was locked within 2 days...after 150 posts. I somewhat agree but as you said had all disassembled for headers and proceeded accordingly.


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[ELCID86]

I'd do the pulleys and tensioners a while you have it apart. The bearings will go at some point.


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[Nivo]

I have 143k miles on mine now. I replaced the upper radiator hose and the expansion tank. I pressure tested my cooling system and held good. I was going to replace the water pump but it was replaced at bmw with a newer pump at 64k miles. Original radiator and thermostat still holding up.

I know I have seen lower pressure expansion tank caps but BMW runs the higher pressure to raise the coolants boiling point. They do so to run hotter coolant temps for better efficiency in the mpg department.

[Avetiso]

I have 143k miles on mine now. I replaced the upper radiator hose and the expansion tank. I pressure tested my cooling system and held good. I was going to replace the water pump but it was replaced at bmw with a newer pump at 64k miles. Original radiator and thermostat still holding up.

I know I have seen lower pressure expansion tank caps but BMW runs the higher pressure to raise the coolants boiling point. They do so to run hotter coolant temps for better efficiency in the mpg department.

Is that nivo?!

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[danewilson77]

Radiator?