I want to get the 85 degree thermostat... is this the pathway?

**cyclops2** · 03-14-2018, 02:30 PM

UPDATE: Option 2 will not work. Option 1 will work and is a simple bolt on, no mods or special requirements. More info lower in thread.

Just been researching the mod of lowering operating temps with the 85 degree thermostat. I have the pre-facelift 5/96 build M62 with radiator hoses that clamp on (not click on style like M62TU models).

I understand there are a couple approaches. One is an integrated stat and housing for a about $120 and another is the housing and stat separate for about $30.

Can someone confirm these options? and specifically part numbers as follows:

Option 1: single unit - 11531742964 $116 here: http://www.bmwpartsupply.com/oempart...531742964.html

Option 2: 2 piece - 11531720173 (housing from M60) for $7.47 and 11531729720 (85 degree stat from M60) for $20.89 both at rockauto. NOTE> I bought these but they do not fit a M62 water pump.

ATTENTION: There is a 88C and 95C version available for M62TU with click on style radiator hoses. Check ECStuning.com

Thanks

**nmlss2006** · 03-14-2018, 03:26 PM

I will ask the same stupid question I used in another thread: why?

**cyclops2** · 03-14-2018, 04:27 PM

Originally Posted by nmlss2006

I will ask the same stupid question I used in another thread: why?

Well I am no expert on this, but here are my thoughts. First this mod has been around for many years. In the reading that I have done, I have heard nothing but positive praise for the mod.

The basics are that the OEM design is a 105 degree C thermostat with run temperatures of 103 to 110. That is extremely hot when compared to other vehicles. Why? it is surmised that BMW designed it to operate at a high temperature for fuel economy and primarily emissions. That higher temperature is not for performance.

I have read that this engine's optimum temperature is around 95; this may be common among most engines because that is a common operating temperature. People that have made the mod to a lower temperature thermostat have commented that the car feels a little livelier and this could be.

The big thing though is that it is widely believed that the lower operating temperatures will prolong the life of the plastics which fail so "prematurely"; particularly the cooling system. I recall one guy commenting how his cooling system was 7 years without any problem.

Anyway, it seems like worth doing. I hope others that have made this mod will comment. Perhaps someone can verify the parts I noted in the first post are correct for the pre-facelift models.

I have seen a different part number for a single piece unit for the newer M62TU with the "snap on" cooling hose. I think both designs are offered by ECS Tuning.

**nmlss2006** · 03-14-2018, 06:33 PM

I know the operating temperature is high, yes. And yes, fuel economy and emissions may well be factors, but to infer from that that a LOWER operating temperature would give measurably better performance is quite a leap. I could even make a fairly good case for the opposite.

As to the durability of the plastic, I am still trying to wrap my head around the complaints. Yes, plastics fail - after a good number of years however, typically ten or more.

All things considered, I would not call that premature.

Thus my question: I will grant that BMW's priorities in engineering at times do not mesh with long term users'. But it would take significantly more than a few posts on a forum to persuade me to override their thinking unless I had hard data.

It's sort of like the people who replace the engine driven fan with an electric fan for GREATER RELIABILITY. To quote a movie, I don't believe that word means what they think it means.

**lewvirg** · 03-14-2018, 09:35 PM

The 90degree thermostat I bought from this seller - at the very bottom of the listing goes into a detailed description of what lowering the operating temp versus the 105degree BMW temp accomplishes. If you go and research what is stated, you'll find all sides of the argument about this and not even running a thermostat. When I was younger, guys used to just yank them out and not just for track running, of course that was with points and distributor. People have been arguing about lowering temps and performance and longevity of parts since probably the 40's or 50's. Even if in the end it accomplishes nothing - it feels better to see the temp at 96 degrees.

https://www.ebay.com/itm/BMW-OEM-90C....c100005.m1851

**BMWE36Greek** · 03-14-2018, 11:42 PM

The owner of Mesa Performance in Costa Mesa, CA has been selling BMW parts since the early 80's. He's one of the more knowledgeable guys on German cars that I've ever met. A lot of BMW mechanics buy parts from him for side jobs. If you time a visit to the store when the BMW mechanics are there from Sterling BMW in Newport Beach or Chrevier BMW in Santa Ana ... you get to here some great info and honest opinions from factory trained mechanics that they probably not say while on there jobs at the dealerships.

When I recently got my E38 740iL ... they recommended I change out the thermostat to a Mahle 85 degrees Celsius.
IMAG1407.jpg

**cyclops2** · 03-14-2018, 11:55 PM

Originally Posted by BMWE36Greek

The owner of Mesa Performance in Costa Mesa, CA has been selling BMW parts since the early 80's. He's one of the more knowledgeable guys on German cars that I've ever met. A lot of BMW mechanics buy parts from him for side jobs. If you time a visit to the store when the BMW mechanics are there from Sterling BMW in Newport Beach or Chrevier BMW in Santa Ana ... you get to here some great info and honest opinions from factory trained mechanics that they probably not say while on there jobs at the dealerships.

When I recently got my E38 740iL ... they recommended I change out the thermostat to a Mahle 85 degrees Celsius.
IMAG1407.jpg

Excellent. That is the part number I noted in the first post, so looks like I am on the right track. Thanks. Did you install it yet? Did you replace the housing? what year is your 740iL?

**oldroller** · 03-15-2018, 06:13 PM

I have to add a note here...it's not all about temperature. The increase in pressure is also a major factor. The difference in pressure
from 110c to 93c is dramatic. The plastic cooling components/gaskets/hoses have to resist this added load to function, and long term.

Changed to 88c on my 01 at 155k, now 170k. Did I see an improvement in performance/economy? No. But I didn't worry about blowing
a hose at 80 on the interstate, 'buffered' gauge stays right in the middle, no spark knock, and opening the hood after a run didn't reveal
swollen hoses and snapping metal and a blast of heat from the powerplant.

A often overlooked benefit is a cooler running alternator, transmission and less long term degradation of gaskets and seals. A no brainer in my book,
but to each his own.

**cyclops2** · 03-15-2018, 06:18 PM

Originally Posted by oldroller

I have to add a note here...it's not all about temperature. The increase in pressure is also a major factor. The difference in pressure
from 110c to 93c is dramatic. The plastic cooling components/gaskets/hoses have to resist this added load to function, and long term.

Changed to 88c on my 01 at 155k, now 170k. Did I see an improvement in performance/economy? No. But I didn't worry about blowing
a hose at 80 on the interstate, 'buffered' gauge stays right in the middle, no spark knock, and opening the hood after a run didn't reveal
swollen hoses and snapping metal and a blast of heat from the powerplant.

A often overlooked benefit is a cooler running alternator, transmission and less long term degradation of gaskets and seals. A no brainer in my book,
but to each his own.

Excellent post. perfect timing for me to move to 85 degree since I have just replaced practically everything..lol

I'll get the parts on order.

Speaking about pressure, I was going to start another post on Evans Coolant.

**BMWE36Greek** · 03-16-2018, 01:03 AM

Originally Posted by cyclops2

Excellent. That is the part number I noted in the first post, so looks like I am on the right track. Thanks. Did you install it yet? Did you replace the housing? what year is your 740iL?

I installed it right away. I already had an aluminum housing. My car is a 1995 / M60.

**cyclops2** · 03-16-2018, 03:36 AM

Originally Posted by BMWE36Greek

I installed it right away. I already had an aluminum housing. My car is a 1995 / M60.

OK, I am going to order the thermostat and the housing (since mine is a '97) from Rockauto for $30 tonight.

I will no longer be using the stat heater wiring, but I have read about using a resistor. seems this is controversial with some people saying "no need" and some saying "it is needed". anyone have thoughts on this?

Thanks again BMWE36Greek.

UPDATE: comment: this is where I went wrong. BMWE36Greek has a '95/M60 which he states, but I didn't catch, or realize I needed to catch. the M60 has a different WP which uses an individual thermostat and housing. The parts I ordered would work on an M60 in fact, the housing wouldn't be needed since it has one in the first place. So on a M60 it is only necessary to order the lower temp thermostat. For the M62 and M62TU the single piece stat/housing assembly needs to be purchased. More info follows in this thread.

**oldroller** · 03-16-2018, 05:50 AM

I secured the harness, no resistor, no CEL light. But this is on '01.
I have read of others getting a CEL. I suggest trying it without, go from there.

**cyclops2** · 03-16-2018, 08:59 AM

Originally Posted by oldroller

I secured the harness, no resistor, no CEL light. But this is on '01.
I have read of others getting a CEL. I suggest trying it without, go from there.

Excellent, thanks. Will do.

**DorinDav** · 03-17-2018, 02:23 AM

Lower operating temp & electric fan are tried and true

Cheers

- - - Updated - - -

There is a 1.2 bar expansion tank cap on the market

Expensive though at $35

**PiotrC70** · 03-17-2018, 01:18 PM

I've been running this on my '01 for about 2 years and maybe 5-7k miles worth and zero issues. I did notice that the car felt more nimble as driving it throughout the day eventually made it feel like a pig from being heat soaked and that is no longer the case after the upgrade. Relatively cold temps of say 30-40F do nothing in terms of affecting coolant temps and I've verified this with OBC data. I'll also add that my MAP plug is also tucked back, no resistor and no CEL. There's a saying "heat kills electronics" Doesn't matter if we're talking about a circuit board, relays, or a rack mount server. Keeping electronics cool will definitely prolong the life of everything.

**nmlss2006** · 03-17-2018, 09:37 PM

Cars running better without a MAP, cars suffering from heat soak (!!) and concerns about hoses blowing because of the increased pressure of running 107C as if they hadn't been designed to do so (how many recalls for E38s were there because of blown hoses? Right.). Colder temperatures affecting the temperature of the coolant? That's what the thermostat is there for...! Electronics suffering because of temperatures while the car is running...

To each their own but let's please remain in the neighbourhood of things happening according to physics. Yes, a cooler thermostat will keep the stress on the hoses lower. Except that's not actually an issue.

I guess the answer was what I expected, this gets filed right along the IMPROVEMENT of switching to an electric fan. Onwards.

**PiotrC70** · 03-18-2018, 01:17 PM

nmlss2006, you make it seem like everything that was designed for the e38 is perfect and is gospel so you shouldn't touch it except to replace like for like. This is the same e38 that has a shitty glovebox latch that breaks. Hell, I had a door stop on my drivers side break... wanna know how many glove box latches and door stops I've broken on all the Japanese cars I've ever owned? ZERO. My late model '01 doesn't have a radiator drain plug, something that was available in earlier years... so I don't hold much faith in German engineering as being superior and one shouldn't mod to make things better. As you stated... to each their own.

**armiller1** · 03-18-2018, 07:11 PM

The M62tu coolant system is much more reliable on the L322 Range Rover than the e38s. Whether it was due to subtle design changes or a lower running temp I can’t say yet. What I do know is very few other brands have as many coolant system issues as our cars. That was the impetus for companies to develop aftermarket improvements. Instead of making these changes themselves, car manufacturers just move on the the next generation of the line. They have the luxury of not having to fix all the bugs. So others step in and see an opportunity to make some money. I think it’s just an natural progression. It all makes sense to me. There are some brilliant minds that find their outlet in all different types of engineering. They don’t all have to work for NASA.

Sent from my iPhone using Tapatalk

**oldroller** · 03-18-2018, 08:02 PM

An informative discussion, and as may have said, 'to each his own'. Physics is forever, BUT innovative materials and procedures always march on.
I once owned a ChrisCraft duck stern runabout with cranky points and condenser ignition system...a high energy electronic ignition turned it from a PTA
into a weekend joy to take for a spin....

The point being, our cars were designed 18 years ago or more. Science of materials and operational procedures have changed, as we get better at understanding
the criteria. Once told we had 'lifetime trans fluid', now we know better. Lighting, exhaust, suspension, etc are all changeable according to the owner's desires.

And it does all come down to physics... heat/pressure characteristics affect our engines and components over the long term. Should we not attempt to alleviate some load if at all possible,
provided we don't compromise the longevity of the powerplant? Of course we should, if it is what you wish to do.
It's all good, be it airplanes boats cars houses, etc. The crux of the biscuit is the happiness of the beholder/owner.

Having been in the automotive industry for 40+ years, I know without a doubt that heat is the enemy of longevity. Reduce it where you can,
be attentive, do research, and learn from your efforts that do not produce the results you expected.

Nothing is unchangeable.

**racer2086** · 03-19-2018, 11:34 PM

This has been a topic that has been debated on here many times. Bottom line, there is no research study conducted to see the actual results, but common sense does say that the 108*C-110*C running temp of the engine is high and will require higher pressure to avoid boiling. That higher pressure, in my opinion, is the primary reason for gasket or component failure in the cooling system.

Now, that being said, there is zero information or evidence that says running an engine cold (like with 85*C stat) is healthy for it either. In fact run it too cold and it's not good (increased wear).

So I bought the "modified" stat from logic7amps linked above. Actually, I just sent them a new stat I bought from FCP and paid the fee to have it modified. The 90*C stat they sells runs at about 99*C in cooler temps. Here in FL, I see 104*C max plodding around town with A/C blasting. So it seems somewhere in the 98-104 realm is where this goes. That to me is still better than 108-110. 104 to 110 is an 11*F difference (219 vs 230). That is a great improvement to me.

Best part is, I can still plug the heater in, so the car has the control it was designed to have -- at lights idling with A/C blasting, the heater will kick in and drop that sucker down to low 90*s. When the outside temp is super high or I'm flogging it on the highway, it'll kick the heater in and drop the engine temp. So in reality, it can lower the temperature a good amount in addition to its baseline temperature being lower.

I do wish it maxed out lower at about 100*C, but it's better than nothing, and I didn't want to drop as low as the 85*C one with the housing modifications and thermostat codes that go with it. So far, 7-8k on the modified thermostats in my M62 and M62TU in the 540 and so far so good. No cooling system issues to speak of (*knock on wood)

IN FACT, I just changed my oil this weekend, and before closing the hood, went to check the coolant level. THE CAP WASN'T EVEN SCREWED ON. It was just sitting on there. I've been driving it like that for months, and never a boil over, coolant warning, or an increase in temperature. Crazy.

**DorinDav** · 03-20-2018, 01:42 AM

I don't mind if you run your E38 bone stock
Good on you---->nmlss

**lewvirg** · 03-20-2018, 09:12 PM

Racer - that is the same type I have been running in both of mine. One for 4 years and the other a year and a half - no hesitation, knocking or loss of performance.

**Timm** · 03-21-2018, 06:40 AM

There's no problem running an 85C thermostat - the E31 840ci has an 85C thermostat as standard when using the M62B44 engine in some country variants:

http://www.realoem.com/bmw/enUS/show...diagId=11_4950

.....and has a 95C thermostat everywhere else

**DorinDav** · 03-21-2018, 10:10 AM

I run mechanical 85° tstat in South Florida with electric fan. Slight loss of fuel efficiency but very happy running in 90s instead of 110-113.

Also: the constant up and down from 113 to 99 to 113 with electronic stat is a thing of the past

**racer2086** · 03-21-2018, 03:42 PM

Originally Posted by lewvirg

Racer - that is the same type I have been running in both of mine. One for 4 years and the other a year and a half - no hesitation, knocking or loss of performance.

Great isn't it? Everything looks and hooks up stock, but it runs cooler and can cool itself more on command. Can't complain.

Originally Posted by Timm

There's no problem running an 85C thermostat - the E31 840ci has an 85C thermostat as standard when using the M62B44 engine in some country variants:

http://www.realoem.com/bmw/enUS/show...diagId=11_4950

.....and has a 95C thermostat everywhere else

Do you think they mapped the A/F and/or other stuff differently for the lower stat, though? I don't know anything about the DME programming, but I would imagine that things would be mapped differently for a hotter vs cooler stat?