Expansion tank

patdown · 10-07-2012, 03:56 AM

I replaced my original ET at 72K miles with PN 17117573781 and I have around 105K now. I believe the -781 ET was touted as an improved ET because of all the problems the old one was having.

Since this -781 ET has been out several years now, has anyone experienced any of the problems the old one had? Should we do a preventative replacement of the -781? If so, recommended time/miles?

Thanks.

mkodama · 10-07-2012, 04:15 AM

What was the pn of the old expansion tank?

I have a failed expansion tank in front of me with pn 7 787 039 which is the original unit from another member's 2004 325i SULEV

patdown · 10-07-2012, 04:27 AM

That -039 sounds familiar. I don't have the old one and RealOEM only has the -781 listed.

tomoyer · 10-07-2012, 06:49 AM

The "old" number for the BMW Expansion Tank was 17 11 7 573 781 and the "new" BMW Expansion Tank Number is 17 13 7 787 039, the Expansion Tanks are inter-changeable. The new one is still prone to leaking with age at the seam where the tank and tank top are "glued" together. There is also a JL (made in Germany) Expansion Tank (#51930) available for half the price of the BMW one (looks exactly the same, fits perfectly and all it is missing is the BMW tag). When replacing the Expansion Tank, I would highly recommend also replacing the Expansion Tank Mounting Bracket at the same time. Here use the correct Genuine BMW Mounting Bracket (they are different for manual and automatic transmissions).

patdown · 10-07-2012, 07:41 AM

The new part number is the -781 and the old is -039. The -781 is the only ET listed in RealOEM. When you go to Tischer (getbmwparts.com) with the -039 you will see that it is superceded by the -781.

tehcbass · 10-07-2012, 10:10 AM

how did you post this at 5 in the morning....?

patdown · 10-08-2012, 05:39 AM

Quote:

Originally Posted by tehcbass

how did you post this at 5 in the morning....?

What's does the time have to do with any post?

Zell · 10-08-2012, 08:11 AM

I want to know who has been brave enough to cut open a new expansion tank to see how they improved it.

flashmeow · 10-08-2012, 08:16 AM

Quote:

Originally Posted by Zell

I want to know who has been brave enough to cut open a new expansion tank to see how they improved it.

Someone on here has already done that

Sent from my PC36100 using Bimmer App

10-07-2012, 03:56 AM	#1
patdown Registered User Join Date: Dec 2008 Location: Canyon Lake, Texas Posts: 62 My Ride: 2005 BMW 330Ci View My Garage	Expansion tank I replaced my original ET at 72K miles with PN 17117573781 and I have around 105K now. I believe the -781 ET was touted as an improved ET because of all the problems the old one was having. Since this -781 ET has been out several years now, has anyone experienced any of the problems the old one had? Should we do a preventative replacement of the -781? If so, recommended time/miles? Thanks. __________________ Pat 2005 330Ci ZHP 6MT AA Tune, domestically engineered CAI w/aFe Pro S, UUC TSE3, Cooling Sys ovhl with Stewart WP, BMW M3 Front Strut Brace, Koni FSD struts/shocks with original springs, Cryo-Stop Rotors, Akebono Euro Ceramic pads, SS Brake/Clutch lines, CDV Delete, Mason Engineering clutch pedal, Umnitza Predator Orion AE's, smoked corners and sides, VMR V710 18" Staggered w/Hankook Ventus V12 235's/FR and 265's/RR

10-07-2012, 04:27 AM	#3
patdown Registered User Join Date: Dec 2008 Location: Canyon Lake, Texas Posts: 62 My Ride: 2005 BMW 330Ci View My Garage	That -039 sounds familiar. I don't have the old one and RealOEM only has the -781 listed. __________________ Pat 2005 330Ci ZHP 6MT AA Tune, domestically engineered CAI w/aFe Pro S, UUC TSE3, Cooling Sys ovhl with Stewart WP, BMW M3 Front Strut Brace, Koni FSD struts/shocks with original springs, Cryo-Stop Rotors, Akebono Euro Ceramic pads, SS Brake/Clutch lines, CDV Delete, Mason Engineering clutch pedal, Umnitza Predator Orion AE's, smoked corners and sides, VMR V710 18" Staggered w/Hankook Ventus V12 235's/FR and 265's/RR

10-07-2012, 10:10 AM	#6
tehcbass Registered User Join Date: Sep 2012 Location: Miami Posts: 85 My Ride: bmw e46 323i View My Garage	how did you post this at 5 in the morning....? __________________ Long Nights and Sandy Beaches

10-08-2012, 08:11 AM	#8
Zell Wears carbon fiber boxers Join Date: Jun 2009 Location: In a van down by the river Posts: 3,698 My Ride: 330Ci ZHP 6sp View My Garage	I want to know who has been brave enough to cut open a new expansion tank to see how they improved it. __________________ E46Fanatic's resident mathemagician

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10-07-2012, 04:15 AM	#2
mkodama Registered User Join Date: Oct 2006 Posts: 30,933 View My Garage	What was the pn of the old expansion tank? I have a failed expansion tank in front of me with pn 7 787 039 which is the original unit from another member's 2004 325i SULEV

10-07-2012, 06:49 AM	#4
tomoyer Registered User Join Date: Aug 2011 Location: Reading, Pennsylvania Posts: 549 My Ride: 03 325xi, 03 330xi View My Garage	The "old" number for the BMW Expansion Tank was 17 11 7 573 781 and the "new" BMW Expansion Tank Number is 17 13 7 787 039, the Expansion Tanks are inter-changeable. The new one is still prone to leaking with age at the seam where the tank and tank top are "glued" together. There is also a JL (made in Germany) Expansion Tank (#51930) available for half the price of the BMW one (looks exactly the same, fits perfectly and all it is missing is the BMW tag). When replacing the Expansion Tank, I would highly recommend also replacing the Expansion Tank Mounting Bracket at the same time. Here use the correct Genuine BMW Mounting Bracket (they are different for manual and automatic transmissions).

10-07-2012, 07:41 AM	#5
patdown Registered User Join Date: Dec 2008 Location: Canyon Lake, Texas Posts: 62 My Ride: 2005 BMW 330Ci View My Garage	The new part number is the -781 and the old is -039. The -781 is the only ET listed in RealOEM. When you go to Tischer (getbmwparts.com) with the -039 you will see that it is superceded by the -781. __________________ Pat 2005 330Ci ZHP 6MT AA Tune, domestically engineered CAI w/aFe Pro S, UUC TSE3, Cooling Sys ovhl with Stewart WP, BMW M3 Front Strut Brace, Koni FSD struts/shocks with original springs, Cryo-Stop Rotors, Akebono Euro Ceramic pads, SS Brake/Clutch lines, CDV Delete, Mason Engineering clutch pedal, Umnitza Predator Orion AE's, smoked corners and sides, VMR V710 18" Staggered w/Hankook Ventus V12 235's/FR and 265's/RR