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Originally Posted by tylerwillingham  Yes i have an m42 ti. The alluminum housing was cracked. New aluminum housing is in the mail with the gasket for the housing and I have the new thermostat and o ring for that. So you're thinking that my pulled fan doesn't need to be on without the AC on (makes sense to me) and the conclusion may be drawn that when the shop that just did my inspection drew out some of my coolant they may have let air in requiring me to bleed the system? And the air lock is what could cause my overflow tank to boil over? |
Pretty much, that's the conclusion that I came to given the information you provided. Of course it's just my own personal opinion from the little experience that I've had with these cars. I've had Ti's with M42's and M44's, but to be honest I based everything off of my experiences with the M44 since I didn't own my '95 clubsport long enough to notice if the fan kicked on. Of course the fan "should" kick on if the temp sensors and relay are functioning properly, you may want to try to get that fixed later down the road for added security and peace of mind.
Most shops don't understand the importance of bleeding these systems unless they specialize in BMW's and even then, the 4cyl wasn't really popular here in the US so some BMW specialists don't make it a regular practice to bleed the system. I had a hairline crack in my radiator for the longest time on my '97 Ti. The crack was so small I couldn't see coolant leaking, but I kept losing coolant and the system eventually developed an air pocket. Luckily I noticed the temp needle when it first started to move and was able to shut the engine off before it made it past the 3/4 mark.
These engines do not like to be overheated. If it runs hot for just a few seconds, you run a significant chance of blowing a head gasket or significantly weakening it. Again, this is just my opinion, I'm not an expert by any means. But I think your situation may be similar to mine in respect to a hairline crack allowing coolant to escape and air to accumulate.
If time/money permits, I always recommend that people replace the entire cooling system whenever something like this occurs since you'll have the loop opened and require a bleeding cycle anyway for the thermostat replacement. The whole thing can be done over a weekend and it won't cost more than 300 bucks.
Good quality radiators typically sell for less than $140 bucks on ebay. I purchased a Behr on ebay for $125 and it was identical to the factory radiator. The plastic coolant fitting should be purchased from getbmwparts.com(pelicanparts was selling defective ones). I believe the M42 only requires the one on the side of the engine block and not the "Y" fitting on the back of the block like the M44(might want to check into that). The fitting cost less than 15 bucks. Water pumps cost about 60-70 bucks and it's pretty easy to get to since it's located on the upper front side of the engine right next to the thermostat. You might also want to replace the temp sensors, fan relay and/or fuse if necessary, radiator hoses, o-rings, clamps & coolant.
I know finances might not permit a complete overhaul, but the peace of mind and avoidance of having to re-bleed the system everytime you replace a part is worth it in the long run. Best wishes in whatever you decide to do, we're more than happy to offer help if you run into any snags.
BTW, the water pump usually breaks in half when you try to remove it. The best/easiest way to remove it is to remove the bolts, then grab it with a big ass pair of channel lock pliers and twist it side to side while slowly working it out of the timing cover. There's no need to hammer or pry it as doing so you'll run the risk of damaging the timing cover.