I just replaced my old Wahler with another and drained about a gallon out of the radiator, otherwise coolant leaks all over the belts. This will be the third Wahler I've put in, the first one threw the P0128 code and the second leaked where yours did. 2 failures since 2012, IDK how old the first one I replaced was, but in late 2015 I replaced the original expansion tank from 10/2002.

 

Behr. Better design to Wahler. Have Behrs on my xi and my E53.

 

Behr for sure 4 years on it and working fine

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I was wrong behr are crap .2 behr thermostat broke inside the engine with less than 20k miles on both . now im using wahler thermostat.

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Get a thermostat that's keeping your engine temp in the lower 90C.

Behr, Wahler, both can run on the hot side (upper 90s and into the lower 100s), which isn't going to help increase the longevity of the plastic cooling system components, and probably isn't good for the head and the head gasket in a long run.

I replaced three thermostats in 2017 (OE from a dealer, or OEM units from good vendors) until I got one that kept the temp between 91 and 95C.

 

BMW-North may know of a source for E46 thermostats spec’ed in different temperature ranges. Pretty sure he posted about it in the last year or so.

 

Thank you for sharing the post.

 

Sounds like there's a few fans of the Behr, so maybe I just got unlucky-ish with this one. Thanks for the replies.

I'm having trouble digging up anything that goes into detail about what could be "bad" about the thermostat heater not working? Is the car more likely to overheat - perhaps only under very 'spirited' driving? If so, then maybe I don't need to worry. I don't track the car, but I do take it on long [500mi one-way] roadtrips which are mostly crusing at 70-80. I took it on a 1200mi trip a couple weeks ago - no problems. (I may have just jinxed myself as I'm about to do the same trip again)

 

The thermostat heater element is used quite frequently even in everyday driving.
This way the engine management commands the thermostat to open and lowers the engine temp whenever you step on the gas pedal a little less gently, or when you rev the engine above certain RPM limit, when driving above certain speed, etc.

I don't think it is a good idea to keep this thermostat. At the very least you should change the buffer range of the instrument cluster temp gauge if you haven't done that already. The factory interval is just too wide, so if you only rely on the needle to monitor engine temp, you wouldn't know it's running hot before it exceeds 115C.

 

I replaced three thermostats in 2017 (OE from a dealer, or OEM units from good vendors) until I got one that kept the temp between 91 and 95C.

My Wahlers ran at 93°C even in 90+°F weather at freeway speeds.

 

G'day,

See if you can find bmw - north's posts on cooling system stuff, very informative.
One recently was a kind of quiz which give a good insight also.

I recently did a ton of reading re t-stats similarly to you. Had one not open, i wasnt driving at the time, luckly engine was stopped in time and towed. The heater was also toast on this & threw same code as you.

I went with the Behr, few reasons - the Borg ones all tended to leak from the same place & aussie online bmw crowd Clickable Automotive have Behr at only $75 which is a good price for us here.

Checked Behr in boiling water before a installed, plus heater element with 12v, all good.
Car runs about 94-95C.
Chucked a Saleri WP in too while i was at it.

I think my 325i has a Behr in it too, been fine for 5 years, runs same temp as i monitor alot via OBD to catch a soft failing t - stat.

I did read that its an or ring or something that leaks on the Borg t-stats, & maybe down to it pinching,spinning etc during bad assembly manufacturing practices which may have crept in on a particular batch maybe. I often read the posts & wondered if it was as simple as replacing an o-ring, maybe using viton instead of NBR etc.

 

G'day,
....
Checked Behr in boiling water before a installed, plus heater element with 12v, all good.
Car runs about 94-95C.

The fact that you took the time to put a new t-stat in a pot of boiling water is either awesome or OCD, I'm not sure which, but I like it anyway.

 

I replaced my thermostat once in February 2010, so nine years and 120k miles ago but it is still working great. I just looked up my receipt and I paid $68 for a "Genuine BMW" branded thermostat from BavAuto.com. Looks like FCP still sells the BMW branded one but they are asking $102 these days.

 

The wisdom (at least here on e46fanatics) seems to be that the "Genuine" one is the Wahler, without the BMW logo. $49 today.

I suspect that there's probably more than a couple folks on here who think that 120k on a thermostat is asking for trouble.

Your data point is noted. Thanks!

 

You will prob wet yourself skydaver when u find out I rigged up a thermocouple & connected it to my hand held digital temp meter

The type we use in foundries to dip in liquid metal, I use it for checking the pool temp & my home brew these days mostly

- - - -

Jokes a side, I had to be sure it was working, inc heater element 100% , because after its install n system bleed, my then subsequent analysis of whether head gasket was comprised by overheat