OBC 19.7.00 - Watcha' go? doityourself

[MrMaico]

My car is a 2003 (August 2003 build) and if we believe the indie shop that once serviced my car two owners ago, my thermostat has 85,000 miles on it and was changed around 2008. I did put in a new aluminum bodied one 10 months ago but it stuck shut, throwing a code and overheating my car, so I put the old one back on.

This morning I drove the ZHP to work (instead of the beater car) and conveniently got stuck in street traffic. Air temps 45-48F. OBC coolant temps cycled same as yesterday... rose to high 70's while driving, 80's at stoplights. When I got stuck in slow traffic, it cycled as follows
88 to 90 to 88 to 90 to 88 to 91 to 88 to 92 to 88 to 91 to 88 to 92.
On the freeway it went back down to the high 70's, and when coasting down a long off-ramp with zero throttle went as low as 73C. When parking got back into the high 80's.

Maybe my thermostat is stuck open. I have a new Wahler thermostat leftover from the warranty replacement of the aluminum one. Maybe I should put that in.

When my coolant temp cycles between 88C and 92C does anyone know if that is the thermostat opening and closing or the fan turning on and off? Are these thermostats set to open at 90C? 95C?

Just a guess on my part but I would think it is the fan kicking in at 92. Since mine seems to run at 205F I would think we have a 95C stat. I heard my fan kick in while I was idling the other day but my temp was at 210F iirc. Not sure why yours is kicking it at 92. Faulty temp sensor?

[Oli77]

It would be nice to know at what temp our T-stat opens up.

So we have the following.

Oli77: 96
Dane: 97 (Won't give us the real number! )
Telijah: 88
edlvrt: 96
MrMaico: 97
Spencers: 90
Livesnearcoscto: 90 (Sounds about right?).
derbo: 95

More data would be great.

[MrMaico]

I got to wondering today about the stat and why and how it is electrically controlled. According to Bentley.....

The electrically heated thermostat allows the engine to be operated at higher temps at idle and part throttle. Having the ability to control the engine coolant temperature electronically results in improved emissions and fuel economy.

I had wondered if the drop in temp when I run through the gears harder than normal was just to make it easier on the engine during "spirited" driving.....cooler oil temps, less chance of detonation/pinging etc. Maybe that might actually be the case?

Comments anyone?

[LivesNearCostco]

The Rock Auto parts catalog says OEM opening temp for our thermostats is 97C (206F). It's lower for my old Saturn (188/195F) and my minivan (170/180F). A 2010 Saturn Aura is spec'd at 180F. A 2011 Mustang V8 (or Focus 2.0L) is at 190F. 2011 BMW 328i (and the 1M turbo 6) also uses 97C. The 1998 BMW M3 calls for a 176F (80C) or 190F thermostat.

So newer BMWs like to run it hot and I'm guessing the others don't have a heater circuit so the computer can open it early. If we assume the DME can open a closed thermostat using the heater circuit but cannot close an open thermostat, then probably BMW spec'd a thermostat that opens at a higher temp than normal (maybe normal is 90C?) to give the DME more control.

If my thermostat is stuck open, will it hurt anything other than my gas mileage? Does running the engine at the proper temp more of the time mean better fuel economy and lower smog emissions without any tradeoffs? Or does higher coolant temp also mean less power?

[Oli77]

Last winter I drove around with a T-stat stuck open and my gas mileage dropped significantly. I did not feel a loss of power (but mine is smaller than yours )

That "heating the thermostat" business seems counter intuitive. But perhaps it allows for a smoother temperature control depending on how hard you pull on it and on exterior temp as well.

[shanneba]

My last trip where I recorded data showed an engine coolant temp max of 192F ~ 89C. (March 15th 2012)

Here is some BMW info on the thermostat MAP:

http://wds.spaghetticoder.org/en/zin...1214_M0KFK.htm

Here is some data recorded with AutoEnginuity software from my 2003 330Ci that shows the operation of the MAP thermostat.
Blue is the oil temp
green is the coolant temp in the engine
orange is the coolant temp at the radiator outlet
red is the engine rpms

You can see when the load/rpms increase, the thermostat opens to cool the engine. The coolant temp at the radiator outlet increases with the higher flow.
I see this start normally around 3000 rpms under load.

I have the stewart water pump, original thermostat, original pulleys and I run Red Line Water Wetter.
I see about a 5-8 F degree drop in my coolant temps when running the water wetter. Not much.

[GT172I]

96 max, mostly around 94 with 80*F ambient

[MrMaico]

My last trip where I recorded data showed an engine coolant temp max of 192F ~ 89C. (March 15th 2012)

Here is some BMW info on the thermostat MAP:

http://wds.spaghetticoder.org/en/zin...1214_M0KFK.htm

Here is some data recorded with AutoEnginuity software from my 2003 330Ci that shows the operation of the MAP thermostat.
Blue is the oil temp
green is the coolant temp in the engine
orange is the coolant temp at the radiator outlet
red is the engine rpms

You can see when the load/rpms increase, the thermostat opens to cool the engine. The coolant temp at the radiator outlet increases with the higher flow.
I see this start normally around 3000 rpms under load.

I have the stewart water pump, original thermostat, original pulleys and I run Red Line Water Wetter.
I see about a 5-8 F degree drop in my coolant temps when running the water wetter. Not much.

Great info! Thanks! So this confirms what I was thinking, running the engine harder opens the stat fully via the heater circuit.

I had been thinking of trying some water wetter, I think I'll have to get some. I'd much rather see 192 than the 205 I normally run. Maybe should have went with a Stewart when I did my cooling system overhaul.

Interesting to find out the temp range before the gauge actually moves....167 to 235F or 75 to 113C.

Thanks again.....Barry

[Oli77]

Man, this is not your run-of-the-mill thermostat!

That would explain why when you pull on it, temperature drops a bit and seems to have nothing to do with air flow. Instead, it is the internal thermostat control that allows for dynamic control of engine temperature at different RMPs! Not a simple closed-open T-stat, more like 2 t-stat 2 different set points and a heating element on top of it! I'm amazed. Thanks for the info Shanneba.

Back to our regular schedule programing...

Oli77: 96
Dane: 97 (Won't give us the real number! )
Telijah: 88
edlvrt: 96
MrMaico: 97
Spencers: 90
Livesnearcoscto: 90 (Sounds about right?).
derbo: 95
GT172I: 96
shanneba: 89

[telijah]

I'll check mine again this afternoon, as I am now thinking I am closer to the lower 90s. I'll update later. I'll post both was OBC shows and what OBD shows, which hopefully reads from the same place.

Apparently, according to the last recorded run, even at 116 (km/h!), mine was running at 84 degrees...