35d worsening gas mileage - solved- thermostat/fan/EGR cooler - DIY with pics

[ZetaTre]

Originally Posted by bawareca

All gasoline BMWs after 1999 or so have electronically controlled thermostat. But what you wrote doesn't add up. When you LEFT OFF the gas the temp is raising 20C From where the heat will come if the engine is not loaded? And even more so not loaded diesel in a cold weather.

I was simply using the example of my Z4 which has a 2.5l gasoline engine and an electronic controlled thermostat as an observation of how quickly the temperature can change in the engine when the thermostat is open very quickly (and conversely shuts quickly when the ECU stops manipulating it)... I really didn't want to sidetrack the discussion, just drawing a parallel to what appears to be a odd behavior that London Lad reported.

If it's not the thermostat, then what's not working right?

[bawareca]

To warm engine or water 20C you need to take energy from somewhere. In the case of idling diesel this energy is just not there. A 6 cylinder engine full of 3 gallons coolant has a huge thermal inertia and this kind of fast warm-ups and cool downs are not plausible. My opinion is that "London Lad" is getting a false reading due to the tool that he is using or due to electronic problem in his car.

[London Lad]

OK well I have checked the reading against the dash hidden obd and another obd hand-held and the results are the same. Its as if the increased RPM forces the stat open and allows a large inrush of cold water. Running at 70 mph at light load, drop 2 gears and floor it, temp drops 15C in 5 to 8 seconds. Lift off and drop back to normal 'drive auto' and the lost temp rebuilds in about 20 seconds. All other temp readings during warm up etc look normal. No OBD fault codes are being logged.

[ZetaTre]

Originally Posted by London Lad

OK well I have checked the reading against the dash hidden obd and another obd hand-held and the results are the same. Its as if the increased RPM forces the stat open and allows a large inrush of cold water. Running at 70 mph at light load, drop 2 gears and floor it, temp drops 15C in 5 to 8 seconds. Lift off and drop back to normal 'drive auto' and the lost temp rebuilds in about 20 seconds. All other temp readings during warm up etc look normal. No OBD fault codes are being logged.

[scorpioy]

I got my thermostat replaced. On its first or second day, the temp stays around 89-90 degree most of time. Then the following days, it varies from 65-80 on highway, 84-94 on local. Outside temp is about -10 degree these days.

Is this normal? Do you guys have a steady 88 degree most of time?
I purchased thermostat from ebay with under $40. My local dealer asks more than $150.
Where do you guys buy it from?
I doubt the one I bought does not have a good quality...

Thanks.

[josiahg52]

Originally Posted by scorpioy

I got my thermostat replaced. On its first or second day, the temp stays around 89-90 degree most of time. Then the following days, it varies from 65-80 on highway, 84-94 on local. Outside temp is about -10 degree these days.

Is this normal? Do you guys have a steady 88 degree most of time?
I purchased thermostat from ebay with under $40. My local dealer asks more than $150.
Where do you guys buy it from?
I doubt the one I bought does not have a good quality...

Thanks.

I can only tell you that even in temperatures as low as -19C, coolant temperature was 83-84C on the highway once the engine was fully warmed up. On shorter trips and in -15C, coolant temperature was 81-82C but would dip down to 79 or 78C if load came off. Temperature drops pretty quickly at idle. I haven't had any experience in warmer ambient temperatures to know what coolant temperature runs in those conditions.

[seattle]

$150? Wow.
My local dealer quoted $90. Assuming OEM (is OEM even a good thing anymore?).

ZetaTre/lcapital,
Is the temperature on yours still happily 89-91 since t-stat replacement?

[ZetaTre]

Originally Posted by seattle

$150? Wow.
My local dealer quoted $90. Assuming OEM (is OEM even a good thing anymore?).

ZetaTre/lcapital,
Is the temperature on yours still happily 89-91 since t-stat replacement?

Mi wife drives the X5 so I don't monitor it on a daily basis, but whenever I drive it, the temperature is constant in the operating range. I'll ask her if she lets me drive it for a couple of days and I do some logging, including see if it holds temp when you floor it.

HOWEVER my dad is back at having longer warmups after about 70K km (45K miles). He had the dealer in Italy warranty the old one and now has to replace it again. We live up in the Alps and he said that no matter what was the outside temperature the car would get and stay in the operating range, but not recently and again while cruising at 70 mph on a flat he still sees the temp dropping below 80/75.

We'll see when he replaces it again if things get restored, but if that's the case, these thermostats are pretty much cacca

And by the way people, the MSRP of the thermostat is $79.05 so don't get stiffed by your dealer... Granted they shouldn't be jacking up price 2 fold, but for the love of God, think with your head not your wallet... Seriously...

[scorpioy]

So I think I'm screwed up by this counterfeit t-stat. I need buy a new one again.
Do you guys go to dealers or is there a good aftermarket ones I can buy from some website?

Thanks

[lanbrown]

There are dealers that offer discounted prices online. You are better off using a BMW thermostat as BMW parts come with a 2-year warranty.