Philly98540, I've installed thermostat and it works well

[rf900rkw]

The one spare thermostat I have isn't marked, of course. Everything I can find gives an operating temp of either 108, or 108-110. It's possible the markings on the stat are the nominal point at which it starts opening, as the manufacturer won't know the characteristics of the engine and where it will find balance. So if the same is true on OP's 95, ie thats the marking rather than the balance point, then I could accept a 97-98 operating temp.

[AK_5eries]

Performance vs Efficiency

Why would a colder engine perform better? Is it to keep air intake temps down?

[BMW540san]

So 540san, the correct part number for non vanos M62 95C thermo is: 11531745476?

Correct. Tomkinson BMW (I highly recommend them) has it for $75. Shipping is flat $12 unless something real big and heavy. I usually try to buy something else to offset the shipping cost.

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To clear the confusion, the thermostat I pulled has 105 C markings on it just as M62TU, which means the reason for M62TU running slightly higher temp is due to different input from DME. 105 C is simply mechanical opening temp in case heater fails.

I don't understand the theory that 5-6 C difference between KTMP and thermostat rating means something is wrong. It makes the sense as KTMP reading might not be 100% accurate and there are way to many factors in play such as ambient temp, engine load, radiator fins not 100% clean, aux fan sensor not 100% accurate etc. It seems that quite a few owners see that temp difference with no cooling problems.
Why am I seeing almost identical temp and no difference in fluctuations with the 95 C thermostat? It's simple, map controlled thermostat does what it's suppose to do but not as much as it's claimed. Engine temp (head) matters but coolant temp doesn't? Sorry but I disagree, because they're related to each other and of course there will be a difference.
Also, the claim about higher engine temp and potential engine pinging. That's all fine in theory and I'm sure map controlled thermostat helps with that but it's glorified too. So BMW comes with new technology and suddenly the old technology that's been working fine for many years is obsolete.
BMW wants to be the leader in technology and one of the main reasons is the competition. Look how great all that new technology is working on E60, E92 etc. We don't have to wait 15 years, there are already number of problems that exceeds E39 problems.
Draw your own conclusion, but I switched to the thermostat that's been originaly on M62 and eliminated the potential wiring issue, I call that improvement.

[supra94tt]

I hope I'm not hijacking this thread but here is an update: I ordered the 88C thermostat from Europe(Romania), total time being shipped-6 days(it spent sitting at US customs for 3 days, lol, well it was weekend), put it in today, test drove the car, ambient temps were about 70. After a decent haul on high-way the temp was around 92-93F doing about 70mph, once in traffic it stayed that way for a while then it climbed up to 96-97F, once i started moving it goes down to 92-93F. I think I know now, why we see the temps a little bit higher with the lower temp thermostats----our cars' fan clutches were designed for higher temps to lock up the clutch, I noticed that if I shut my car off for 5-10 min. and then start it and drive, i can hear the fan clutch engaging from the heat soak and my temps go down to 92F immidietly, anyway I love my new "upgrade" . So now I'm on a search for lower temp fan clutch, lol, or go electric as I already have the Lincoln MKVIII fan .

Edit:
I just checked realoem, and they actually rate fan clutches in degrees Celsius , but they dont display it for E34 535 which I think may work in my application since the stock thermostat is rated at 80C.

[AK_5eries]

Supra, the 88C thermo is stock for which application?

[supra94tt]

Supra, the 88C thermo is stock for which application?

http://www.realoem.com/bmw/partxref....r=on&details=1
Part # 11512248542
E38 740d Sedan, M67, Europe, AUTO (GE81) : Waterpump - Thermostat
E65 740d Sedan, M67, Europe, AUTO (GM41) : Waterpump - Thermostat
E65 745d Sedan, M67N, Europe, AUTO (HM61) : Waterpump - Thermostat

[Alpina540i]

Sweet supra thanks for the update I have my 88C thermostat right on the bench but I haven't installed it yet as my car has been a the body shop.

I have polished it in the mean time....haha

Can't wait to install this.

[AK_5eries]

Thanks

[ninetyseven1]

Can you please tell me what you used for the dummy load or resistor?

[supra94tt]

Can you please tell me what you used for the dummy load or resistor?

I used nothing, why?

[ninetyseven1]

I used nothing, why?

because another member said he got the
code: 06-8B Electric thermostat control final stage after disconnecting the wire without using a resistor. ??

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BMW540San , what did u use for a resistor? to stop any CEL?

[JimLev]

Can you please tell me what you used for the dummy load or resistor?

See post #19

[supra94tt]

You should not get any CEL by disconnecting the thermostat, maybe a code in DME, but that's about it.

[Alpina540i]

I have installed my 88 C thermostat today and I have run the engine to bleed it but I haven't driven it yet will keep this thread updated on the temps I see.

I have not used a load resistor on mine and no CEL.


Oh B.T.W. Randy my original BMW thermostat I just took off says 105 C on it.

[BMW540san]

because another member said he got the
code: 06-8B Electric thermostat control final stage after disconnecting the wire without using a resistor. ??

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BMW540San , what did u use for a resistor? to stop any CEL?

Still haven't got any CEL and I don't think I will. What's even stranger, I didn't even get the any type of code. That's according to my AutoEnginuity which is fairly competent scan tool.

[philly98540]

Still haven't got any CEL and I don't think I will. What's even stranger, I didn't even get the any type of code. That's according to my AutoEnginuity which is fairly competent scan tool.

That is strange as mine threw the "stat final stage" code very quickly. I guess BMW changed the program in the computer at some point. Some get, some don't.

[supra94tt]

That is strange as mine threw the "stat final stage" code very quickly. I guess BMW changed the program in the computer at some point. Some get, some don't.

Do you have a CEL or just a code in DME, two diff. things .

[philly98540]

Do you have a CEL or just a code in DME, two diff. things .

Both CEL and code showed up. Sorry for not clarifying.

I can unplug my resistor and make the CEL light up. My car is a 6/98 build date.

[mifesto]

im confused... some claim thermostat code is stored in DME only while others say it throws a CEL. sigh.....

[AK_5eries]

Philly, are you using a 12 ohm 25 watt resistor like Jim mentioned?

[philly98540]

Philly, are you using a 12 ohm 25 watt resistor like Jim mentioned?

I used a 10 ohm 100 watt. I posted it on one of these stat threads somewhere.

The one Jim posted will work too. I went 100 watt since it runs cooler and i was unsure how hot the thing would get. I think i got it off amazon for cheap.

[Alpina540i]

I have a 10/98 Build date with no cel

[ninetyseven1]

I have a 10/98 Build date with no cel

I guess my next and only other questions would be: Is your fan on more often now? OR does the car operate the same only runs much cooler? If I recall this past summer ,my clutch fan was really robbing power one day and sounded like a school bus. I wonder if there is high speed and a low speed in the fan itself? I ask this because, I hope putting in a lower temp thermostat would not make the fan come on more often.

[Alpina540i]

The reason the fan is called to high speed for is hot engine temps thus reducing the overall engine temp will make the fan turn on much much less.

[Alpina540i]

So to update this thread I have installed my 88 c thermostat and in 80 degree Fahrenheit weather today I saw 93-94 c while crusing at continuous speed and in stop and go hardly moving conditions 101 was the max. While stopped and idling with AC on I saw a steady 99 c temp.

Much better than the 103-109 c temps I had before.

All of these temps are measured without a mechanical engine fan installed and just auxiliary fan.