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X3 E83 (2004 - 2010)
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  #26  
Old 11-04-2013, 06:19 AM
white_lancer white_lancer is offline
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O.......M.......G

I recognise all of those parts - the brass piece and the spring and the plastic "top" of the AT thermostat. All I can conlude is that all three of the expansion tanks that I have replaced have had the AT Thermostat broken. And the expansion tanks have all split in exactly the same place as shown in the video......

The wierd thing is both my X3 and the X5 are now driving around with the AT Thermostat in pieces and everything seems to work just fine?

I will be ordering two of the new AT Thermostats right away and will replace both. Thanks for all the help on this post!
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  #27  
Old 11-04-2013, 07:16 AM
jlex jlex is offline
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I wouldn't have thought that a broken thermo could result in increased fluid pressure that would have ruptured the tanks... but that is just what the guy in the video is suggesting. Don't know why BMW wouldn't engineer a thermo with a metal housing if that's what's afflicting our cars... I suppose it would result in a lot of lost revenue to the dealerships.
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  #28  
Old 11-04-2013, 04:56 PM
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halltristan halltristan is offline
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split expansion tank

Quote:
Originally Posted by jlex View Post
Be careful not to overfill that tank or you'll be replacing it again...
This is not true.


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  #29  
Old 11-05-2013, 07:00 AM
jlex jlex is offline
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[QUOTE=halltristan;7937357]This is not true.


Are you saying it's okay to ignore the indicator stick and overfill the expansion tank?
I'll have to disagree with you on that. Expansion tanks are designed to take on the additional volume of water when it expands once heated. If there is no place for it to expand to, you have to rely on the pressure release cap to open and relieve the excess pressure before something bursts.
Problem as I'm reading about it is our earlier model pressure caps open at 2.0 bar to relieve excess pressure from overfilling. According to what German Auto Solutions says, that's way too much pressure in light of the plastic parts in our systems that have now become weakened with age. They indicate the industry standard is 1.2 bar which, according to them, is what BMW is now using in caps on their newer models. They sell a 1.2 bar replacement cap to help insure against plastic component ruptures. Check out their web site for some pictures of broken plastic components.
I'll agree with you that overfilling won't automatically result in a broken tank. As long as your 2.0 bar cap is working to get rid of the excess fluid and 2.0 bar isn't too much for old plastic components and as long as you don't mind coolant running all over your engine until the valve closes again once normal pressure is achieved, go ahead and overfill. For me, I'll continue to pay attention to the stick indicator and fill it to only between the two points. Way too much plastic on these cooling systems without having to worry about pressure problems as well...
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  #30  
Old 11-06-2013, 04:28 AM
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halltristan halltristan is offline
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split expansion tank

[QUOTE=jlex;7938256]
Quote:
Originally Posted by halltristan View Post
This is not true.


Are you saying it's okay to ignore the indicator stick and overfill the expansion tank?
I'll have to disagree with you on that. Expansion tanks are designed to take on the additional volume of water when it expands once heated. If there is no place for it to expand to, you have to rely on the pressure release cap to open and relieve the excess pressure before something bursts.
Problem as I'm reading about it is our earlier model pressure caps open at 2.0 bar to relieve excess pressure from overfilling. According to what German Auto Solutions says, that's way too much pressure in light of the plastic parts in our systems that have now become weakened with age. They indicate the industry standard is 1.2 bar which, according to them, is what BMW is now using in caps on their newer models. They sell a 1.2 bar replacement cap to help insure against plastic component ruptures. Check out their web site for some pictures of broken plastic components.
I'll agree with you that overfilling won't automatically result in a broken tank. As long as your 2.0 bar cap is working to get rid of the excess fluid and 2.0 bar isn't too much for old plastic components and as long as you don't mind coolant running all over your engine until the valve closes again once normal pressure is achieved, go ahead and overfill. For me, I'll continue to pay attention to the stick indicator and fill it to only between the two points. Way too much plastic on these cooling systems without having to worry about pressure problems as well...
Wow. You are way too concerned about nothing. Here's the simple truth: if over filling the tank cause it to fail, almost everyone in America would have to replace their tanks each winter. The cap is designed to release any fluid it doesn't need.


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  #31  
Old 11-06-2013, 07:22 AM
jlex jlex is offline
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That's right. The cap is designed to release excess pressure. Only problem is it's designed for 2.0 bar which according to GAS is too high. (Maybe they're right and maybe they're wrong) I'm relying on their testing & product development so I'm assuming their research and development of the 1.2 bar cap is correct. The 2.0 bar standard cap (which is what I use) won't open until 29 psi which GAS says is too high. The 1.2 bar cap pops open at 17.5 psi. which they say is safer. Seems to make sense.
Who knows... maybe they're over-playing the issue so they can create & sell a product. Maybe it's really bad t-stats as stated in the video that's causing pressure buildup. Maybe it's just old plastic. Who really knows the cause? The only thing I do know is these expansion tanks pop from something. Heck, the OP had three of them go bad for him.
Since I have the 2.0 bar cap, I'm going to err on the side of being conservative and not overfill. May just get one of those 1.2 caps anyway...
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  #32  
Old 11-06-2013, 09:22 AM
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halltristan halltristan is offline
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split expansion tank

Quote:
Originally Posted by jlex View Post
That's right. The cap is designed to release excess pressure. Only problem is it's designed for 2.0 bar which according to GAS is too high. (Maybe they're right and maybe they're wrong) I'm relying on their testing & product development so I'm assuming their research and development of the 1.2 bar cap is correct. The 2.0 bar standard cap (which is what I use) won't open until 29 psi which GAS says is too high. The 1.2 bar cap pops open at 17.5 psi. which they say is safer. Seems to make sense.
Who knows... maybe they're over-playing the issue so they can create & sell a product. Maybe it's really bad t-stats as stated in the video that's causing pressure buildup. Maybe it's just old plastic. Who really knows the cause? The only thing I do know is these expansion tanks pop from something. Heck, the OP had three of them go bad for him.
Since I have the 2.0 bar cap, I'm going to err on the side of being conservative and not overfill. May just get one of those 1.2 caps anyway...
Again, you're putting way too much thought into nothing. It appears from your profile that you're fairly new to BMW. Nothing wrong with being eager, but you need to cool down a bit. You're driving one of the best cars ever built. You don't need worry so much, they did that for you.


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  #33  
Old 11-06-2013, 11:01 AM
jlex jlex is offline
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That's right, I admit I am fairly new to BMW. (My old VW and Porsche are aircooled so this isn't usually a worry for me ). None of my water-pumpers ever had expansion tank problems. Tank went on my 2005 and the original poster blew through three of them. I'm "eagar" to keep from blowing another one. What's your opinion on why the expansion tanks are failing?
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  #34  
Old 11-06-2013, 11:27 AM
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What's your opinion on why the expansion tanks are failing?
Simple: they're plastic. The repeated heating up and cooling down is what destroys them.

Most other cars also use plastic expansion tanks. And most other cars usually have to replace the tank once or twice in their lifetime. It isn't just BMW.
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  #35  
Old 11-06-2013, 12:21 PM
jlex jlex is offline
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I respect your opinion on that, but it hasn't been a problem on my 25 yr old Volvo or my 8 yr old Hyundai both of which use plastic expansion tanks. Heck, the Volvo has it's original plastic radiator!. No, from what I'm seeing, BMW has a problem here...just look at the OP's experience with this.
BTW, when do you take the bar?
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  #36  
Old 11-14-2013, 09:05 AM
DangermouseX3 DangermouseX3 is offline
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Originally Posted by swampX3 View Post
yes the cap is not a pressure regulator but just a pure relief ....so it would pop at ~ 17 psi and save the plastic parts/old pipes/old heat exchangers that warm our feet etc

the blurb covers the notion that most auto engines relieve over pressure thru the cap at 1.2 bar or ~ 17 pounds ish ......and that newer BMWs have migrated to the lower pressure 1.2 bar caps also

could be that a simple cap change would give some extra lease on life to older plastic cooling system components but I would still go the careful not to over fill and swap weak point system stuff out based on time/climate and miles

also noticed that when we ran a gauge on the x3 and some 3 series older units they averaged about 9 psi of system cooling pressure......plenty of extra left even with a relief at ~ 17 psi

the x with the stewart pump showed no difference in the 9 psi average pressure but looks like a much more robust product.....probably will outlive the car by a 10 factor
I was just thinking about this the other night, and the fact that these expansion tanks spilt. Interesting to find out that the stock cap is 29psi. Is there an overflow hose somewhere?

I guess an alternative notion is that the stock cap fails in some way and doesn't even relieve at 29?.

I may look into getting one of these 17psi caps.
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  #37  
Old 11-14-2013, 09:12 AM
swampX3 swampX3 is offline
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got one

took the plunge and got one .....very well made .....the alu cap feels like a brass one on a vintage engine....on two weeks with no issues .....put gauge on .....system runs in the 10 poundish range .......average ambient in the swamp now around 70f........but......can't beat overhauling known failure parts in the cooling system we find out about on sites as good as this though.....cooling stuff is one of the things shade tree folks can still do with ease
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  #38  
Old 11-14-2013, 09:16 AM
swampX3 swampX3 is offline
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steam

yes ....when you cook the coolant and make steam the expansion can be rapid indeed ......if the cap doesn't pop at 29 because of some problem look out plastic parts etc.....always work on hot cooling systems as if there's a 500 lb gaitor in there !
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  #39  
Old 11-14-2013, 10:35 AM
jlex jlex is offline
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I'm thinking along the same lines as you guys... the 29 psi caps may very well be too high when used in combination with lots of plastic components. I'm going to get the 17psi cap soon. Putting an additional 20lbs on the system before the cap opens may be stretching it a bit far. People overfilling the tank a bit probably helps test the limits too.
GAS says BMW has switched to the 1.2 bar cap on their later models, so what does that tell you? Another thing: I'll bet these caps get "lazy" and don't open when they're supposed to the older they get. My 8 year old cap is going to retire soon....
Oh.... no overflow hose that I'm aware of. I suppose the cap just pops and lets coolant fly everywhere until it closes...

Last edited by jlex; 11-14-2013 at 10:38 AM.
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  #40  
Old 11-14-2013, 12:37 PM
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Quote:
Originally Posted by DangermouseX3 View Post
.... Is there an overflow hose somewhere?
My modest understanding of automotive cooling system design is that you either have an overflow tank (with the traditional pressure relief cap on the rad.), or,
you have an expansion tank (with its own cap and no cap on the rad.).

It's one or the other. Not sure that you can combine features of one with the other.

Both types of design are in current use.

I would prefer the traditional type but I guess there is a good reason for having the expansion tank type.
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  #41  
Old 11-14-2013, 01:52 PM
DangermouseX3 DangermouseX3 is offline
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Looking at realOEM, I see that the expansion cap for the N20 and N55 engines in the new X3s are stamped at 1.4bar (part # 17117521071) like the vendor notes.

They are only about $15 too. I wonder if they are threaded the same as ours?
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  #42  
Old 11-14-2013, 02:40 PM
swampX3 swampX3 is offline
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good logic

a good piece of logic .....maybe call bavauto and ask if they fit the different rad tops

the alu cap from from german parts I got has a very nice cap but the guts are just plastic .....looks like they machine and anodize the cap and set in the guts ......wish it was on the outside ....it looks so good

Last edited by swampX3; 11-14-2013 at 04:00 PM.
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  #43  
Old 11-14-2013, 04:37 PM
jlex jlex is offline
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Swamp: I pulled the trigger at your lead and ordered the 1.2 bar cap. Can't be too careful with these finicky systems...replacing one tank is enough for me...
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  #44  
Old 11-16-2013, 07:59 AM
white_lancer white_lancer is offline
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I changed the AT thermostat on both the X3 and X5 today. Both the expansion tanks cracked within a few weeks of each other but I never replaced the AT thermostat when I changed the tank. Weird how both tanks cracked almost at the same time and both AT thermostats failed?

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  #45  
Old 11-16-2013, 08:22 AM
swampX3 swampX3 is offline
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nice coolant vid

showing what the expansion tank does etc

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  #46  
Old 11-16-2013, 08:32 AM
white_lancer white_lancer is offline
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cool video
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  #47  
Old 11-17-2013, 07:31 AM
jlex jlex is offline
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Isn't what they show in the video just an overflow tank to keep from losing fluid in the event the thermo on the cap opens up? I was thinking that an expansion tank is different in that it is actually part of the system & is under pressure which is why we're running into problems w/ our BMW's.... I think the tank shown in the video isn't pressurized at all.

White Lancer: good job. You could probably change out these tanks with your eyes closed now...
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  #48  
Old 11-17-2013, 08:05 AM
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Quote:
Originally Posted by jlex View Post
Isn't what they show in the video just an overflow tank to keep from losing fluid in the event the thermo on the cap opens up?
Yes, not representative of the type of cooling system in a BMW or many others.
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