Today I took my car on it's first ever long motorway drive. 400 miles there and back. Computer reported average speed of 60mph, and 25MPG (Imperial I assume, my car is a European car).
One area of concern is that at speed, the car appears to run somewhat cool, at or even just below the first dot (i.e. the 1/3 level). I checked this with the MFD, and it reported around 68-69 degrees C. This seems low.
I'm assuming that this means my thermostat is sticking open, and allowing too much coolant to flow through the radiator? Is it worth looking at the coolant temperature sensor as well - I don't think this has ever been changed? I have no reason to think that the sensor is faulty - in town the temperature gets /near/ to the middle and sits there happily.
What are the implications of this? I understand that fuel consumption may suffer, but 25MPG isn't bad on a run, no? Then again, I think 25 Imperial = under 21 US, so perhaps my fuel consumption is a bit crappy after all? I'm using 99 octane super unleaded from Tesco, or 97 if I can't get hold of the 99.
Also, I have no check engine light - is it possible to have a faulty thermostat without a check engine light?
Wow, I know I've asked quite a lot of questions above - the bottom line is, from the data above, should I change my thermostat and / or coolant temperature sensor?
Last edited by topper; 10th March 2008 at 02:09.
Reason: Fuel octane
[quote=topper;1273032]Today I took my car on it's first ever long motorway drive. 400 miles there and back. Computer reported average speed of 60mph, and 25MPG (Imperial I assume, my car is a European car).
One area of concern is that at speed, the car appears to run somewhat cool, at or even just below the first dot (i.e. the 1/3 level). I checked this with the MFD, and it reported around 68-69 degrees C. This seems low.
I'm assuming that this means my thermostat is sticking open, and allowing too much coolant to flow through the radiator? Is it worth looking at the coolant temperature sensor as well - I don't think this has ever been changed? I have no reason to think that the sensor is faulty - in town the temperature gets /near/ to the middle and sits there happily.
What are the implications of this? I understand that fuel consumption may suffer, but 25MPG isn't bad on a run, no? Then again, I think 25 Imperial = under 21 US, so perhaps my fuel consumption is a bit crappy after all? I'm using 99 octane super unleaded from Tesco, or 97 if I can't get hold of the 99.
Also, I have no check engine light - is it possible to have a faulty thermostat without a check engine light?
Wow, I know I've asked quite a lot of questions above - the bottom line is, from the data above, should I change my thermostat and / or coolant temperature sensor? [/QUOTE
A faulty thermostat can trigger OBD II codes without a check engine light being present.
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Today I took my car on it's first ever long motorway drive. 400 miles there and back. Computer reported average speed of 60mph, and 25MPG (Imperial I assume, my car is a European car).
One area of concern is that at speed, the car appears to run somewhat cool, at or even just below the first dot (i.e. the 1/3 level). I checked this with the MFD, and it reported around 68-69 degrees C. This seems low.
I'm assuming that this means my thermostat is sticking open, and allowing too much coolant to flow through the radiator? Is it worth looking at the coolant temperature sensor as well - I don't think this has ever been changed? I have no reason to think that the sensor is faulty - in town the temperature gets /near/ to the middle and sits there happily.
What are the implications of this? I understand that fuel consumption may suffer, but 25MPG isn't bad on a run, no? Then again, I think 25 Imperial = under 21 US, so perhaps my fuel consumption is a bit crappy after all? I'm using 99 octane super unleaded from Tesco, or 97 if I can't get hold of the 99.
Also, I have no check engine light - is it possible to have a faulty thermostat without a check engine light?
Wow, I know I've asked quite a lot of questions above - the bottom line is, from the data above, should I change my thermostat and / or coolant temperature sensor?
A faulty thermostat can trigger OBD II codes without a check engine light being present.
Okay, I can plug in the Carsoft. But, can I rephrase one of my questions - if there is no OBD code being flagged, does that mean that my thermostat is definitely okay?
Okay, I can plug in the Carsoft. But, can I rephrase one of my questions - if there is no OBD code being flagged, does that mean that my thermostat is definitely okay?
No. I know my tstat is sticking open, but because temps here in south Florida tend to be warm, the harm seems to be minimal. I will eventually have it changed out. No codes showing up.
Regards,
Jerry
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'01 Black/caramel
Dinan Stage 3 suspension, SS jet coated headers, ESS SC kit, open brake ducts, Hamann front splitters, TEC cupholder, U.S.(Euro style) tilt/slide armrest, 6k HID fogs, 6k super white low beams, V1/Stealth1, dual head LI, 2.65 diff w/40% lockup/2x dynamic, compact spare, Euro trailer hitch, Mocal oil cooler, ACS type rear spoiler, Rogue custom SSK and tranny mounts, ST 355 BBK (fronts), BP sway bar brackets, Bluetooth retrofit
One area of concern is that at speed, the car appears to run somewhat cool, at or even just below the first dot (i.e. the 1/3 level). I checked this with the MFD, and it reported around 68-69 degrees C. This seems low
The 68-69 degrees C is when you go to Test 7?
You either have a bad temperature sensor, which is cheap and easy to replace or more likely a faulty thermostat that is stuck open.
I was in your position (mine read 75 degrees on a run) and had the thermostat changed and the coolant gauge is now bang at 12 o'clock and never falls below 79 degrees.
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Anders
'02 BMW M5 (Carbon black / black leather)
Stock apart from Eisenmann Sport, E60 545 short shifter mod, MKIV nav and Intravee II
ex '01 BMW 530D Touring (Sterling grey / beige leather)
ex '98 Mercedes C43 T AMG (Smaragd schwarz / black leather)
ex '99 BMW M Coupé (Cosmos black/ black-kyalami leather)
ex '93 Alfa Romeo 164 24V Super (Silver / black leather)
You either have a bad temperature sensor, which is cheap and easy to replace or more likely a faulty thermostat that is stuck open.
I was in your position (mine read 75 degrees on a run) and had the thermostat changed and the coolant gauge is now bang at 12 o'clock and never falls below 79 degrees.
Okay, so it's basically one of the two problems I thought. Have you noticed any difference in the way the car runs, fuel economy etc?
Okay, so it's basically one of the two problems I thought. Have you noticed any difference in the way the car runs, fuel economy etc?
I haven't noticed any real change in fuel economy, but it might be there. I guess it would be most noticeable on long trips when the car runs cooler, but if there is a change, it has been gradual. I get mid 20's in U.S gallons, with taller gearing which accounts for about 10%
Around town, the car runs warmer since there is a lack of sustained airflow, so fuel efficiency seems about the same.
Regards,
Jerry
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'01 Black/caramel
Dinan Stage 3 suspension, SS jet coated headers, ESS SC kit, open brake ducts, Hamann front splitters, TEC cupholder, U.S.(Euro style) tilt/slide armrest, 6k HID fogs, 6k super white low beams, V1/Stealth1, dual head LI, 2.65 diff w/40% lockup/2x dynamic, compact spare, Euro trailer hitch, Mocal oil cooler, ACS type rear spoiler, Rogue custom SSK and tranny mounts, ST 355 BBK (fronts), BP sway bar brackets, Bluetooth retrofit
No. I know my tstat is sticking open, but because temps here in south Florida tend to be warm, the harm seems to be minimal. I will eventually have it changed out. No codes showing up.
Regards,
Jerry
I just talked to my service advisior here in Tampa. I have the same issue in that the OBDII test 7 shows 73-74C on sustained highway runs, but there is no code when scanned. Dealer won't replace the T'stat unless there is a code. The car is in for a bunch of other work so I hoped to get it all done at once, but not to be. As you mentioned, here in Florida, the penalty is minor except for a slightly richer running engine and tail pipes that get dirty quicker! The fuel economy isssue is likely very minor.
fuel economy is a minor issue. the problem is that the car does not go into closed loop mode until 80C, so the car is constantly running rich, diluting the oil with fuel, and potentially washing oil off the cylinder walls, causing increased engine wear, as a worst case scenario.
The fact that a dealership will not replace a thermostat without a code is ridiculous (mine was the same, but i was able to convince them).
There seems to no longer be anyone who will actually troubleshoot a problem, if there is a fault, replace a part etc.
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Mike
91 M5 Alpine White II, Silver Gray 3/90 production
17x8/17x9 M system with PS2, 20mm touring roll bar; Ground Control Coilovers; EAT Chip, CD43; bmw/nardi blackline steering wheel, 3.8 Cam Gears
08 535i / 6 speed
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00 M5 Ti Silver; Imola/black sportiv --Sold
Engine:
Supersprint Headers, Dinan CAI kit and MAFS, Throttle Bodies, Cams, Ported heads, Exhaust, Custom dinan software, Evosport Pullies, Dinan clutch and lightened flywheel; Ignition solutions plasma coils
Suspension:
Dinan Stage 3 with front and rear Strut Tower Braces, Beastpower Sway bar brackets, Dinan Wheels with 275/285 PilotSport, X5 Thrust arm bushings, Stoptech 355mm 4 piston front, 355mm 2 piston rear brake kit, Dinan 3.45 diff
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Eurodash, updated steering wheel, Bluetooth retrofit, Sirius Retrofit, hardwired V1, Widescreen Mk4 nav, M audio retrofit, Ice Link, BSW Stage 1 speaker upgrade, bmw towbar
fuel economy is a minor issue. the problem is that the car does not go into closed loop mode until 80C, so the car is constantly running rich, diluting the oil with fuel, and potentially washing oil off the cylinder walls, causing increased engine wear, as a worst case scenario.
Interesting. Could this account for higher-than-normal oil consumption?
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