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Old 05-06-2015, 09:53 AM   #41
LeMansteve
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Updating this thread. I am on my 2nd failed Wahler t-stat. Both developed leaks where the electrical connector enters the body, both within 2,000-5,000 miles.

My Genuine BMW t-stat, which was installed at 90k miles in 2011 and never leaked, threw a code last summer around 152k miles indicating a failed heating element (I forget the Peake code number). Again, it failed internally and was not leaking.

I replaced it with a non-Genuine / Wahler part and within 5,000 miles the new t-stat started to leak. The manufacturing date code stamped onto the body was Sept 2013.

I returned it and the vendor sent me a 2nd Wahler, which held up for a little while but is now leaking again at the same place. There are no other obvious cooling leaks outside the engine.

I think I will just replace it with a Genuine BMW t-stat and see what happens. Not sure what I will do if that one leaks, too!
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Old 09-11-2015, 12:11 PM   #42
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thread kick...

Not certain when I last replaced my t-stat, but the failed Wahler just removed was dated 5/12 so either late 2012 or early 2013.

And yes, leaking from the connector, not the housing like many of you have found. I didn't take a close look at the new Wahler that went in it's place, but can check later today.
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Old 09-11-2015, 01:41 PM   #43
camrydriver111
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Quote:
Originally Posted by LeMansteve View Post
I think I will just replace it with a Genuine BMW t-stat and see what happens. Not sure what I will do if that one leaks, too!
Get your money back and buy a Behr.
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Old 11-07-2015, 09:55 PM   #44
saneesh8
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I don't have a 3 series, but a Z3 with a 2.5L engine. Bought the Wahler unit from NAPA and started leaking after some time (less than 5K on it). It also leaked at the electrical connector. After some talk (even with life time warranty promise), NAPA replaced it with a new Wahler unit. Today when i checked, now it is leaking under the unit between two bolts area. Very slow leak and most of the time, you wont even notice it on the floor. The lever drops very little.

It is not worth it. I think OEM is the risk free method. It is not worth to replace it once a year or less and refill the coolant, bleed etc. The money you save, will be spending on buying coolant and time.
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Old 01-28-2016, 06:24 PM   #45
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Originally Posted by Mau330i View Post
Today I removed the 3 months old Thermostat and reinstalled the previous one (also a Wahler) but with a new / thicker o-ring.

After analyse this part and because if this leak again it can be detected with no risk to the car I decided to change the original o-ring with an "improved" one to see if this fixes what I think is a design problem. If it doesn't I will use a new Behr thermostat.

Attached some pictures of the disassembled thermostat I just removed so you can see the o-ring I change and let me know what do you think about this.

Lets see if this works....
Just wanted to chime in: my Wahler is leaking from the OP's spot - electrical connection.

I'll try to update this with the date when i get a chance.
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Old 10-17-2016, 01:26 PM   #46
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Excellent thread and info here provided by Mau330i and others. My Genuine BMW/Wahler thermostat has developed the exact same slow leak from that sensor sealing area just underneath the electrical connector as described by many and as pictured by Mau330i.

The theory of a manufacturing issue perhaps involving incorrect dimensions or materials for sealing that area for the Wahler thermostats within a certain date range is interesting, especially since many state that they've gone tens of thousands of miles with no leak, and likely the majority are perfectly fine. But perhaps it is just as likely an ongoing issue that only a small percentage of us are affected by.

Quote:
Originally Posted by Mau330i View Post
Maybe this problem is limited to a certain manufacture date or defective production lot.

I have just checked and both thermostats were manufactured on Jul/2011

If some of you who had problems with this thermostats still have them maybe you should check the manufacture date and see if it is the same or close to 07/2011
Quote:
Originally Posted by RMAAS View Post
I just replaced my Wahler with a Behr. The Wahler was leaking from the o-ring like the one shown in Mau330i's pictures. My Wahler's production date was 06 2011.
Quote:
Originally Posted by TLM View Post
Not certain when I last replaced my t-stat, but the failed Wahler just removed was dated 5/12 so either late 2012 or early 2013.

And yes, leaking from the connector, not the housing like many of you have found. I didn't take a close look at the new Wahler that went in it's place, but can check later today.
Quote:
Originally Posted by LeMansteve View Post
Updating this thread. I am on my 2nd failed Wahler t-stat. Both developed leaks where the electrical connector enters the body, both within 2,000-5,000 miles.

I replaced it with a non-Genuine / Wahler part and within 5,000 miles the new t-stat started to leak. The manufacturing date code stamped onto the body was Sept 2013.

I returned it and the vendor sent me a 2nd Wahler, which held up for a little while but is now leaking again at the same place. There are no other obvious cooling leaks outside the engine.

I would note for those who purchased a Wahler with this issue and are saying that they now will buy or should have bought the Genuine BMW part instead, it has been detailed by others here they are the exact same part as Wahler supplies them to BMW. Comparison of good images found on sites like FCPEuro show no discernible difference between the Wahler and Genuine BMW part design. I think the Genuine BMW part has the Wahler stamp on it as well.

As Zell pointed out, the Mahle/Behr part has a distinctive difference in their design of the sensor insertion area where we are experiencing the leak from. Modifying just that part of the design could've been a proactive attempt to improve what they thought to be a flaw, or if the issue was known then it was likely a corrective action to fix it. No proof of any of that at this point.

Quote:
Originally Posted by BimmersGarage View Post
I have a Behr thermo. & it's held solid for 48k+ miles so far. I personally prefer the design of the Behr - where there's a big metal C-clip holding down the heater element vs just a tiny plastic latch.

My 330 sat for about a month in a cold Northeast US winter before I took ownership of it, and I do not know if the gradual leaking condition was present while it was being driven normally before that. At the time I purchased it the leak was already visible. It has thankfully continued at a very slow pace and forms a small stalactite of hardened coolant mix if the leak area is left for 4-6 months untouched. It requires frequent checks of the expansion tank level when cold and occasional top-ups. I cannot recall if I saw a date on mine or not and will have to update that info later. It is a Wahler/Genuine BMW part.
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Old 10-18-2016, 12:26 PM   #47
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I can see my manufacture date but unfortunately cannot read the numbers on it while the thermostat is still installed. I'll add that info at a later time after doing the cooling system refresh.
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Old 10-18-2016, 01:41 PM   #48
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Originally Posted by captechm View Post
I would note for those who purchased a Wahler with this issue and are saying that they now will buy or should have bought the Genuine BMW part instead, it has been detailed by others here they are the exact same part as Wahler supplies them to BMW. Comparison of good images found on sites like FCPEuro show no discernible difference between the Wahler and Genuine BMW part design. I think the Genuine BMW part has the Wahler stamp on it as well..
Yes, but just because two parts are produced on the same assembly line, doesn't necessarily mean the parts meet the same specs.

For any supplier - parts that meet BMW requirements are shipped as Genuine BMW parts and have the BMW logo on them.

Some parts will not meet BMW requirements. For example: order quantity (too many parts made), materials, dimensions, appearance, etc. Instead of scrapping these parts, they can be sold under the supplier's brand name. The BMW logo must be removed from these parts.

It's entirely possible Wahler had an issue with their o-ring supplier and could not sell them as Genuine BMW, so they decided to sell the suspect and/or marginal thermostats under their own name.

We really don't know.
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Old 10-25-2016, 04:39 PM   #49
captechm
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Good points on the OEM vs genuine parts.

Quote:
Originally Posted by LeMansteve View Post
It's entirely possible Wahler had an issue with their o-ring supplier and could not sell them as Genuine BMW, so they decided to sell the suspect and/or marginal thermostats under their own name.

We really don't know.

Like I said though, my Genuine/Wahler thermostat has the exact same issue as the OEM Wahler thermostats. I'd lean toward the issue being just as prevalent with the Genuine/Wahler thermostat as it is with the OEM Wahler part.

Last edited by captechm; 10-25-2016 at 04:41 PM. Reason: typo
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Old 10-25-2016, 07:53 PM   #50
e46alfonso
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I've had two genuine and one wahler stat and they all leak. They are exactly the same so don't even bother buying the oe stat for twice the money. will give behr a try next, I hate adding coolant every month.
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Old 10-26-2016, 07:22 AM   #51
klax
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I had two Wahler T stats leak at low mileages. The first one was replaced in less than a year under warranty and the replacement started leaking not long after, both leaking from the same place (not the mounting seal).

The Behr T stat replacement has been leak free ever since.
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Old 10-27-2016, 06:54 PM   #52
Megalocnus
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Originally Posted by e46alfonso View Post
I've had two genuine and one wahler stat and they all leak. They are exactly the same so don't even bother buying the oe stat for twice the money. will give behr a try next, I hate adding coolant every month.
This is very disappointing to hear. Do you remember the production dates of these?
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