Cooling system problem/Overheating - BMW Forum - BimmerWerkz.com
3-Series (E46, E90) Chat relating to the BMW 3-Series from 1999 to Current. Models include: BMW 316i, BMW 318i, BMW 318Ci, BMW 320i, BMW 323i, BMW 325i, BMW 330i, BMW 328 Ci, BMW 328i, BMW 325i/xi, BMW 330Ci, BMW 320d, BMW 330d, BMW 335d.

 
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#1 (permalink) Old 06-27-2006, 11:19 PM
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Cooling system problem/Overheating

My 2000 323i (which I bought used) overheated the other day. So, suspecting that the original plastic impeller water pump had failed, I took the pump out of the block. It turned out that the pump I removed, which seems to be a genuine BMW (replacement?) part had a metal impeller. The car definetely had a problem. It lost a significant amount of coolant sometime during the event.
A suggested in the Bentley manual, I tried my code reader to see if it would indicate a faulty thermostat but wasn't able to get the device to work...seems the diagnostis bus is "hung". I just get the error indicator on the code reader.
Before I start swapping out parts ( like a dealer/repair shop would probably do) , I thought I'd check the community to see what others think might be my problem. I'm hoping for some hints that might lessen the number of times I have to wrestle the fan clutch off and on...a hassle even with the fan pulley holder. Should I just get a new thermostat? It's only about a $55 part. How likely is it that the pump shaft seal is leaking? Should I get the radiator pressure tested? I hadn't noticed any leaking coolant prior to this incident, but about a gallon of it went somewhere.
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#2 (permalink) Old 06-28-2006, 12:31 AM
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Also, if I take the thermostat out of the vehicle, will I able able to tell if it's obviously malfunctioned? In an older American vehicle that had a failed thermostat, I was able to see that it wouldn't open due to lack of clearance.
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#3 (permalink) Old 06-28-2006, 07:32 AM
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Was there a know cause of why the car overheated? In other words, did it just start overheating at random, or were you pushing the car's limits at the time. . . or was there a known problem that caused the issue?

Have you tried to refill/bleed the system?

When these cars overheat and boil fluid out, you can't just add water and go with it. The boiling introduces a lot of air in the system and this must be bled out before continuing to operate.

If the system won't bleed completely and appears to always have air in it, then you may have a blown head gasket.

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#4 (permalink) Old 06-29-2006, 12:04 AM
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The overheating happened during an ordinary drive into town... no high speed or hot weather. I have, about a month ago, drained and replaced the coolant and took care to "burp" the system. The overflow tank volume was remaining constant and no air seemed to be coming out the bleeder if I opened it and added fluid. Tom
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#5 (permalink) Old 07-06-2006, 01:15 PM
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At this point you should change the Thermostat due to the fact you overheated, but you should be able to tell if it has failed once it is removed.

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#6 (permalink) Old 07-06-2006, 09:23 PM
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Curious to know what happened here. Were your fans switching on properly? Was your t-stat stuck closed?
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#7 (permalink) Old 07-10-2006, 11:42 PM
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I took the thermostat housing off the block and am going to replace it with a new one. The shaft that supports the valve, surrounded by the spring, had an area that was shiny... as if it was rubbing/binding during operation. I don't know if the fan was working during the overheating incident, but I'll look to see that it is when I put it all back together with the new thermo..
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#8 (permalink) Old 07-10-2006, 11:48 PM
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i think your thermostat is the problem... if that is gone, then the system pretty much just shits itsself to hell until its fixed...
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#9 (permalink) Old 07-11-2006, 09:54 PM
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Quote:
Originally Posted by TRuckee
I took the thermostat housing off the block and am going to replace it with a new one. The shaft that supports the valve, surrounded by the spring, had an area that was shiny... as if it was rubbing/binding during operation. I don't know if the fan was working during the overheating incident, but I'll look to see that it is when I put it all back together with the new thermo..
Good to know. Hope it solves it.
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#10 (permalink) Old 07-15-2006, 07:02 PM
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Exclamation

So I got my new thermostat, put things back together and was filling the system (with distilled water, in case it had a leak) when I noticed a drip. Closer inspection revealed a hairline crack in the expansion tank so, of course, I'm going to replace it. I did notice that the coolant level was quite low when I first started working on this overheating problem. I wasn't sure if the low level was due to the overheating causing the fluid to boil off, which I hadn't noticed happening, or it's having leaked out prior to the incident, which I also hadn't noticed. I guess the latter probably was the case. With hindsight I can see that I probably should have added fluid back to the system and looked for leaks before I sarted pulling the waterpump and thermostat.
I've been using the Bently manual as a guide for this car and, for the first time, have a problem with their directions. The manual says to remove the coolant level sensor from the bottom of the expansion tank by turnig it counterclockwise, but this is wrong! After I removed the s-shaped air duct that's located close below the ex-tank (a quick, no tool process), I was able to see that the sensor comes off by twisting it clockwise. I don't think it even has to be removed from the tank to remove the tank from the car. I also took the fan and shroud back off to better see what I was working on. I'm having trouble getting the tank free of the fluid connections on the bottom of the tank and wil probably just break the old tank up to enable me to have more wiggle/pry room. I've sprayed a small bit of silicone into the stuck joint and will wait a while to see if it frees up before I break up the old tank.
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#11 (permalink) Old 07-25-2006, 01:49 PM
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SO what happenend?
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#12 (permalink) Old 08-18-2006, 01:06 AM
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Talking

So, I finally got the new expansion tank and managed to get the old, cracked one off the mounting bracket by gently prying with a small bar. However while (I thought) carefully pushing the new tank down over the two coolant connections that it mounts on, I broke the thermostat for the ATF heat exchanger which is located inside the larger of the two connections. It seems that the plastic that most of the parts in this area are made of has gotten very brittle and weak... maybe this is why the overflow tank cracked in the first place. This thermostat just slips inside the connector, so I got a new one (for about $40), managed to get the broken one out with a big "pick" , and got the whole system back together. I had taken the fan and it's shroud off again to be able to better see what I was doing... I'm getting good at that part of the process, sorry to say! I've filled the system with distilled water again and every thing seems to be working fine. It seemed to take longer to purge the air from the system than it did last time I drained it and I was concerned that the dropping coolant level in the expansion tank might be a sign of water leaking somewhere into the engine due to overheating damage during the initial event. But no, the expansion tank level has remained constant for several days now and every thing else seems OK. It seems to be fixed now.
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#13 (permalink) Old 08-18-2006, 11:55 AM
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^^ You should fill the system with 50/50 mixture of BMW coolant and distilled water.

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#14 (permalink) Old 04-18-2007, 12:24 PM
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How many spring retainers hold the bottom connections on ?? I am also having trouble getting the old tank out.
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#15 (permalink) Old 04-18-2007, 09:31 PM
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Geez, I just threw the old expansion tank away about a week ago. So I can't take a look at it to confirm how many connections are on the bottom of it, but I SEEM to remember two. The automatic transmission cooling system interfaces with the engine cooling system at the bottom of the expansion tank. After removing the spring clips, I used a small carpentry-style pry bar (probably a 6" Wizard bar) to pry up the tank. I had my car up on ramps, had removed the splash panel under the engine and had taken the fan off to allow me to better see what was involved. I could probably do the tank removal now w/o taking all these parts off, but I needed to see better for my first operation. I probably also used an inspection mirror. Be careful prying these plastic parts. The same aging that caused my expansion tank to crack also caused me to break the cooling water connector that the tank sits on and I had to replace it, a $9.00 part. It ended up being quite a thrash, but I was able to accomplish the repair myself and I got a good understanding of this part of the engine cooling system. TR
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