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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 07-30-2009, 11:37 AM   #1
MB2000BMW323i
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Exclamation Replacing Radiator Expansion Tank, need help, 2000 323i

HI,
I read through the other post on the replacing of my tank expansion, but never found an answer for my biggest problem.
1st, I got the tank out ok, and have the new one, but when I put the old tank on the ground and was looking at it, I noticed a small piece fell out, or off of it, its round and the same size as a quarter, it has 3 notches on it, and its black, made out of a hard plastic type material, it broke into 4 pieces so can't be used again, but I can't seem to find where this went originally, and if I need to find a replacement, I can't find where it came from, like if it was from inside the old tank, and maybe the new one has it inside where I can't see.
Any advice on this?
2nd problem,
When I look from the top in to where the expansion tank goes, there is a spring sticking up. Does this need to be put back on in a certain way? Or do you think this broken piece has something to do with the spring. I did see someone had asked about the spring in another post, but didn't see an answer. I would appreciate any help.
My car is a 2000 323i and it has 164,000 miles, and this is the 1st thing I have had to replace due to wearing out, (big crack in side, ive done basic maintenance) Runs awesome though, and want to get it back on the road.
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Old 07-30-2009, 12:40 PM   #2
wolfman
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From memory of my own replacement, you could have broken the thermostat for the Transmission Fluid cooling block (on the bottom of the rad - correct me if your car's not an Auto 'box). I did the same thing and had to go out and get a replacement. It seemed to break quite easily and that's probably what the spring is.

Some pictures would probably help, but I'm guessing that's what your problem is.
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Old 06-10-2010, 04:21 AM   #3
kiwi330i
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Yep definately the auto tranny cooler thermostat. MB2000BMW323i - did you have any luck replacing it ? If so, did you have to replace the mounting plate that the thermostat attached to ? Would love to know how hard/easy this was..... mine just broke, so am trying to figure out how the mounting plate can be removed....
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Old 06-10-2010, 05:01 PM   #4
jjrichar
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I had this problem recently. The whole thermostat unit needs to be replaced. Unfortunately you can't replace just the cap that holds it all down. You don't have to replace the housing that it sits in. The thermostat will just pull out, and you push in the new one. You will need some sort of hook tool to pull the old one out. It takes a bit of force to remove it. Just take it slowly.

I've attached a picture that I took last time I had everything apart. Hope this helps.

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Old 06-12-2010, 02:38 AM   #5
jjrichar
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Regards another question above, the thermostat can be removed from the mounting plate with it still in the car, but if you need to remove the mounting plate, it can't be removed with the radiator in the car. There are a few screws that hold it on. The top and bottom can be removed with the radiator in the car, but there's another that attaches to the side of the mounting plate that can't be removed with taking the radiator out.

Removing the radiator is no big deal. You do however need the tools to get the fan housing and fan out. Once that's done, remove the expansion tank, disconnect all pipes to the radiator, disconnect the ATF heat exchanger (the coolant connections, not the ATF pipes), loosen the two big rubber bolts the the top of the radiator. Once that's done, grab hold of the radiator and move it up and towards the rear of the car. It will come out easily. It's then easiest to remove it out the bottom of the car rather than out the top if the car is on jack stands.

Hope this helps
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Old 06-12-2010, 03:11 AM   #6
BimmersGarage
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You're experiencing the classic plastic cap break of the automatic thermostat... See here for reference:


You're have to pull the entire OLD unit out (it's going to be a PITA with it damaged like that) but you'll have to get the whole thing out before you can replace it with a new one. You CAN NOT just ignore it, since you're risk burning up your transmission if you don't get it replaced.

And, are you sitting down...? The price of this little thermostat is more expensive than the main Thermostat unit... $80.

Good luck.
And, REMEMBER to BLEED your cooling system afterwards or your risk overheating.

Last edited by BimmersGarage; 06-12-2010 at 03:17 AM.
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Old 08-28-2010, 09:01 AM   #7
lmx107
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Thank you so much for the informative video and explanation. I totally agree with you on your analysis of why the damn expansion tank failed. I just took mine out today and found exactly what you described. This isn't the first time I've had to replace the expansion tank either. The first time was done by a mechanic and either the thermostat hadn't failed yet, or he just didn't noticed. Anyhow, I think this whole problem may have caused me more than just the cost of the expansion tank since the car was driven without knowledge that the coolant had leaked (out of the hairline fracture you mentioned). I have a suspicion that there's damage to the engine but don't know. The car cranks but won't turn over and I can't tell if that could be related to the coolant loss or not since am not a mechanic. I fear that there's damage to the head that everyone talks about when your car overheats.

It's a long story about how the car got to this point and I am just going 1 step at a time. Assumming after I install the tank and add coolant, and the car starts. How will I know if there's any damage to the rest of the engine? And if it doesn't start, does that mean that the engine's been damaged?

Thanks for any input on this.
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Old 12-02-2010, 04:55 PM   #8
akhterbuilders
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Wink automatic transmission thermostat installation

Hi

i have read and seen pics of this goofy design thermostat. Mine was in pieces when I took out the expansion tank(cracked). I have yet to see any thing showing or telling how this little rascal fits in the hole it came out from.The part that broke is not on the same centerline as the whole unit, it also has a little nib on one side. you can push it in the hole so that the cap(looking from top is to the right,left,front or back which is the right way. What is the orientation of the nib.(looking from the top)Maybe the cause of these things breaking is incorrect installation. HELP!!!!!!!

Last edited by akhterbuilders; 12-02-2010 at 05:00 PM. Reason: mis spelled
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Old 12-02-2010, 05:07 PM   #9
akhterbuilders
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What is the orientation for the thermostat sitting in the hole.looking from top. The little nib must have some porpose.what is the location of the nib. Thanks
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Old 01-19-2011, 09:46 AM   #10
racermech
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Quote:
Originally Posted by akhterbuilders View Post
What is the orientation for the thermostat sitting in the hole.looking from top. The little nib must have some porpose.what is the location of the nib. Thanks
Bringing up an old thread, I am replacing my tank and stat this weekend. Last night I pulled it all apart and saw my stat broken, pulled out the top and pretty sure I got the entire bottom out. But same question is there an orientation to it?
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Old 01-22-2011, 05:49 AM   #11
gsbmw
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Quote:
Originally Posted by racermech View Post
Bringing up an old thread, I am replacing my tank and stat this weekend. Last night I pulled it all apart and saw my stat broken, pulled out the top and pretty sure I got the entire bottom out. But same question is there an orientation to it?
Yes, the purpose of the nib on the thermostat is for orientation, and it also limits the distance that the thermostat will slide into its cylindrical housing in the mounting plate. There is a similarly sized slot in the inner edge of the cylindrical housing into which the nib sits. This slot is located on the FORWARD INNER SIDE (ie, top inner edge of the cylindrical housing, the "forward" side of the cylinder closest to the front bumper). Run your finger around the inside of the top edge of this cylindrical thermostat housing and you will feel it for sure. And/or look with a flashlight.

You could definitely break the top black plastic cap of the thermostat when you mount the expansion tank, if you don't seat the thermostat completely and correctly. Should be easy though once you locate the slot for the nib. As usual, use some 50/50 coolant/distilled water mix to lubricate all of the rubber O-ring fittings that are in this and other areas of the cooling system.
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Old 07-17-2016, 10:16 AM   #12
00325i
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Exp tank thermostat....

Guys, what if this expansion tank thermostat is eliminated??
Might be harmfull or no danger at all?
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Old 07-19-2016, 09:29 AM   #13
OnTheFence
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Is it easier to replace the radiator and tank all at once?
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