Anyone Use a 90C Bremmen Thermostat in their M62TU 4.4?

[tempest411]

Hello,


I happened across a video on YT that suggested one of the reasons why M62TUs are so unreliable is due to their high operating temperature. I did a quick search as I hadn't really thought of this before and, holy cow, the thermostats on these are rated to open at 105C! That's 220F!! No wonder the guides become brittle and fall apart. How could they not??? There is a cooler thermostat available by Bremmen, rated at 90C, which is much more reasonable. The only question is, will the DME freak out about this? Will it go into closed loop operation at this temperature? Your thoughts?


Thank you!

[andrewwynn]

I've got the n55, it runs at 109c=228.2 f until you hit the gas then it drops to 95c=203 f.

90c vs. 105. Seems like a lot but pull that down to zero reference you find it's (90+273)/(105+273)=0.96 or 4% cooler.

M62tu can go 300,000 with original chain guides if you change the tensioner frequently enough. The rubber seals are screwed because EU forces BMW to use rubber that disintegrates (I guess so if you crash your car into the ocean even the internal o-rings will dissolve).

On the m54 where they tend to kill their coolant reservoir, people would use a lower temp tstat to get a lower pressure in the coolant system but PV=nRT suggests the same 4% prob too subtle to make a difference.

I looked into the lower temp tstat and opted no on the m54.

I'm pretty sure the M62 has a heater in the tstat so it opens up under load. ; Not as effective as N55 since that motor also doubles the speed of the water pump in combination. I've seen the coolant temp drop from 109c to 94c in under 20 seconds.

I don't know how you'd ever know if the benefits outweigh the risks unless you did an actual a-b comparison.

N55 running at 109 is definitely not more self destructive than m62tu.

I notice that other than freeway driving my temps average 5-8c lower and I suspect m62 similarly averages lower as long as you use the throttle occasionally.

[X5chemist]

90C if perfect for aluminum heads. I've experiment on a few domestic engines. Carb and fuel injection. The high temp is for emissions. My '21 HEMI was lowered to a 194F thermostat (203F stock). No lights and great for summer Texas heat. It passed emissions testing in my county. Even better for highway use. I didn't like it reaching 220F before air dams opened up to cool it. I removed a few air deflectors to keep it at 90C all day long. My '83 C10 with a crate ZZ4 motor also uses a 194 thermostat. Best gas mileage is obtained using a 90C thermostat. Too hot boils fuel. Too cold and optimization suffers.

My 3.0i has a new thermostat It runs right at 194F. I saw no lights and smooth running.

Install it!!

[Henn28]

A complicated topic, and one with lots and lots of different views. I agree that the M62TUB runs hot, maybe too hot for cooling system longevity and power. My understanding is that the M62TUB runs hot to reduce emissions, but the DME can manage pre-detonation in real time through the ignition/timing (reducing power) and the MAP cooling function.

The MAP cooling system on the M62TUB wasn’t ready for prime time I think. I watch it on my long drives sometimes and see it operate too late to give me the power I needed, and cycle on and off repeatedly on long flat highway drives for some reason I can’t understand. I think it is better in newer BMW motors and Bosh DMEs.

It’s interesting to me that (I believe) the S62 motor runs much cooler.

Lots of guys run cooler t-stats and other mods like electric fan setups, double or triple pass radiators, etc., but I think the thing to consider is that the cooling system is a closed loop and one change may need another to keep things in balance.

I’ve been considering a lower tstat for a while as a way to keep the DME from retarding the timing in response to knock amd gain some power back potentially. But I think it needs to be paired with a more efficient radiator since the coolant will be moving faster through the core at any given time than with the OE tstat. A double or triple pass radiator would do the trick likely, but now the water pump is working harder than intended by BMW, and the radiators that could work require other mods.

[andrewwynn]

I can def get on board with the map tstat "first generation" symptoms. N55 definitely got the system down but maybe to an extreme but days when I get 27mpg on a full tank I can appreciate why

[tempest411]

Thank your for your input. I'll order it and see how well it works.

[Themoog]

Just as a side note.. last year I had the AC compressor replaced on my M62tu V8. The one I supplied was broken so I ran the X5 for two weeks before the garage could get round to installing the new one.
During that time I noticed a marked difference on the temp gauge in that the needle was always between 1/4 and 1/2 whereas before it was always stuck at 1/2 .
The engine also ran smoother and quieter.
I too have been searching for a way to run my engine slightly cooler. I put in Redline Water Wetter the other week but I haven’t noticed any difference other than it gets up to temp faster.
I may get a lower temp thermostat but saying that, I had the car in for a check a few years ago and chatting to the technician he said that mine did not use map cooling. There is an electrical connection to the thermostat housing though so I think he got that wrong..

[andrewwynn]

On the e53 the temp indicator on the dash is not a thermostat or even close.

If it's at noon is supposedly at closed loop but bad programming will allow noon indication and open loop. (no idea how much fuel I wasted driving open loop for about 4-5 months with stuck open tstat).

If the needles didn't point up you're open loop.

It's possible for a wire to tstat to be a sensor but I think all e53 use map tstat.

[andrewwynn]

Somebody makes a modified map tstat where it has a resister to fake out the ECU and opens lower temp.


Sent from my iPhone using Tapatalk Pro

[Henn28]

If it’s got a wire to it, then it’s a MAP tstat I believe too.

I think there are cooler map tstats someone makes that still set an SES light/code due to the DME not seeing the running temp it needs. Others run them with no problems. As Andrewwynn mentions, guys also run non-map tstats with a resistor in place of the map plug to fool the DME.

I’d recommend the OP do some reading over on bimmerforums, particularly the e34 board as they’ve been having this discussion for years, and guys have gone all sorts of different routes. A couple guys even engineered a box to make the MAP function progressive (rather than the “1 or a 0” BMW made it), and programmed it to open at whatever lower temps they wanted.