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E36 M3 (1992-1999) {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999


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Old Thu, May-24-2012, 04:04:52 PM   #21
salty
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Default Re: Aluminum vs Plastic Thermostat Housing

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Originally Posted by white-hot View Post
Yeah, not sure if it would be worth it to mill one out of billet. I paid about $35 for the genuine BMW part couple weeks ago, and since it will last me (actually the next owner of the car) another 10+ years I can't see there being any point in going beyond that. Kinda the same way I feel about radiators, since the first one made it 14 years and 92k miles I don't really think I need to drop serious coin on an alloy unit. Oh wait, because racecar right?
I bought a Mishimoto and it is still in the box. Went with what I thought was OE Behr. As it turns out, the one from the dealer is superior to aftermarket Behr.
Behr expansion tanks are Chinese and inferior to original.
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Old Thu, May-24-2012, 05:12:15 PM   #22
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Default Re: Aluminum vs Plastic Thermostat Housing

In my former 928 life, the original factory Behr radiator had plastic side tanks. Mine popped at about 110k miles, unfortunately about 100 miles from home with wifey on a fun mountain drive. Wasn't so fun after all, but luckily it blew at a really nice roadside stand that had frozen apple juice - awesome. I replaced it with a very expensive aftermarket aluminum radiator because it was a lot less than the veryvery expensive factory Behr.

If the factory radiator with plastic side tanks makes it 100k miles and in the BMW world is cheaper than the aftermarket solutions, no brainer.
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Old Thu, May-24-2012, 06:46:08 PM   #23
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Default Re: Aluminum vs Plastic Thermostat Housing

My original OEM radiator had 120K miles and it still looked good when I replaced it with Behr last weekend as part of preventive maintenance of the cooling system. If this one lasts 80K, I will be happy because it is less than half price of OEM unit. I do my cooling system maintenance in 80 - 100K intervals anyways.

As for the thermostat housing, it is cheap and easy to change, and if the composite plastic lasts 50K without leaks, that is fine. Btw, when I first went aluminum, my original plastic housing had 85K miles on it and it still looked pretty good. I thought I was upgrading, but I learned otherwise.
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Old Thu, May-24-2012, 07:10:41 PM   #24
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Default Re: Aluminum vs Plastic Thermostat Housing

I think we are missing something in this discussion. Back in the day, the OEM composite housings were known to fail catastrophically with a fairly broad range of life times. The aluminum housings have not done that. I realize the quality differences lately may make them more susceptible to weeping and leaking, but I have not heard of one cracking to the point that coolant got blown all over the engine bay. On M50/M52 that results in a rapid burst of steam and a slow roll to the side of the road. On the S50/S52 it would probably result in a serious overheating while on your way to the side of the road. The S50/52 is much more sensitive to overheating than the M engines. Sometimes a more graceful failure is worth something.
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Old Thu, May-24-2012, 07:15:40 PM   #25
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Default Re: Aluminum vs Plastic Thermostat Housing

the AL housing quality has been down the last couple of yrs.

I went with OEM when i did my refresh 1.5 yrs ago
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Old Fri, May-25-2012, 12:09:16 AM   #26
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Default Re: Aluminum vs Plastic Thermostat Housing

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I have aluminum p/n 11531722531 (at least according to the invoice) in my car since PO's radiator neck exploded about 2 years ago. Independent shop put this housing on along with a new radiator, new thermostat, new expansion tank, belt, and water pump, and the housing has not yet leaked. The radiator drain plug and aux fan switch have both leaked (I have now replaced them) but the housing has been OK.

Question - why can't a durable, metal, non-leaking housing just be re-used with a new gasket? If you have a known good piece, as long as you're replacing coolant parts as a preventative plan (and not in response to a 285F+ coolant explosion, etc.) is there reason to suspect that a nonmoving metal part containing no plastic will fail? That is an honest question. I could see replacing the housing periodically if it were some form of composite/plastic since we know what happens to radiator necks and expansion tanks, but if the engine is made of metal and I'm not replacing the head every 70K miles, why replace this piece?

Question 2 - how many housing cracks are caused by people who don't bother to use a torque wrench to tighten them down (again - honest question - not trying to insinuate anything). I'm pretty careful about torquing things but I know people who just shrug and don't bother.
See my post about the profile gasket (page 1, post #10). The M42 engine has a stock aluminum housing and a paper profile gasket to accommodate the expansion cycles metal naturally goes through. The composite housings use that rubber gasket which remains static, which is fine too since the composite housing doesn't experience thermal expansion and contraction as does an aluminum housing. The aftermarket aluminum housings are essentially using the wrong gasket material; and that only explains SOME of the problems related to this application. There's also the issue of poor casting that leads to leaks and failures.
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Old Fri, May-25-2012, 12:12:24 AM   #27
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Default Re: Aluminum vs Plastic Thermostat Housing

If that is the case you should not replace it, why mess with perfection. Only replace the gaskets when servicing the coolant system and that's it.
And yes then torque wrench is a must in this type of DIY service.
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Old Fri, May-25-2012, 12:22:13 AM   #28
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Default Re: Aluminum vs Plastic Thermostat Housing

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If that is the case you should not replace it, why mess with perfection. Only replace the gaskets when servicing the coolant system and that's it.
And yes then torque wrench is a must in this type of DIY service.
Agreed. My argument for the last ten years has always been to simply treat the housing as a regular replacement item. Replace it every 75K miles with an OEM BMW housing and this part will never give you trouble. Not sure why the longevity of a silly thermostat housing has grown to become such a hallmark issue of the E36. It's a pretty trivial and inexpensive part. We should all be more concerned about preventing body rust with as old as these cars are now.
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Old Fri, May-25-2012, 12:33:21 AM   #29
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Default Re: Aluminum vs Plastic Thermostat Housing

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Agreed. My argument for the last ten years has always been to simply treat the housing as a regular replacement item. Replace it every 75K miles with an OEM BMW housing and this part will never give you trouble. Not sure why the longevity of a silly thermostat housing has grown to become such a hallmark issue of the E36. It's a pretty trivial and inexpensive part. We should all be more concerned about preventing body rust with as old as these cars are now.
You explained it simple and clear on this thread reply #27 and #29, that is what all owners should take into consideration.

I noticed years ago and probably you all did how lots of E36 (M3) owners were raving about AL T housing and how cool this mod was and they'll never go back to stock "cheap plastic", that is how it was perceived by most which meant more business for aftermarket makers of these AL housings.

Now I am kind of surprised and happy as well to hear completely different opinion on this thread, which is the right way to go.
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Old Fri, May-25-2012, 12:59:44 AM   #30
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Default Re: Aluminum vs Plastic Thermostat Housing

I buddy of mine, who I have known for over 15 years, is the senior BMW mechanic at the local dealer. He has been working on BMW's for over 25 year, been to Germany a dozen times for various training and certification, so he knows these cars. I asked him about this very issue (plastic vs aluminum) 6 years ago when I purchased my vert. He said that the VAST majority of failures in the plastic was due to over torquing older parts, plain and simple.

If you took a fresh one and preceded to over torqued the crap out of it, it is unlikely to crack as badly, if at all, as the same quality unit with thousands of heat cycles. You do a refresh after say 6 years that plastic housing has become far more brittle and more susceptible to deformation and cracks. As Brandon has said many times, just replace it just like you would the T-stat or the water pump.

As for buying an aluminum unit these days, seems pretty hit or miss on quality, which is sad. The PO of the coupe purchased one a couple years ago and when I redid the cooling system apon purchase it appeared in excellent condition, with no flashing on the inside nor improperly machined surfaces. Maybe he got lucky. In any case, I can see no reason that it can not be reused for the rest of the life of the car. I always use a thin ribbon of RTV around the outside of the profile gasket on all of these just as a preventative measure, but I seriously doubt it would have leaked without it.

All that having been said, if and when I buy another one I would get OE plastic and not worry about it again for 60-70-80k+ miles. I agree with Brandon that this has been kinda over done. It is really a no brainer.
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Discussing Aluminum vs Plastic Thermostat Housing in the E36 M3 (1992-1999) Forum - {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999 at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)