Noobie, Thermostat question

[skeeter123]

Things which can affect gas mileage w/o throwing codes......
Check fuel pressure; fuel pump or fuel pressure regulator going bad may not throw code but will affect mpg.
Check for vacuum leaks; unmetered air getting in behind MAF sensor.
Check upstream O2 sensor; may be going bad but not enough to throw a code.
Check ETC temp sensor; may be going bad but not enough to throw a code.
In closed-loop operation, the ECM uses temp and O2 sensor (and other inputs) to determine fuel injector pulse widths (how much gas to squirt into cylinder). Bad input from sensors will scrog the calculations. Computer may compensate by putting even more fuel in.

[proton]

great, thank you, and what will you check first. Is there a bad history for a particular thing.

[JRL]

I'm trying to understand (english is not my first language) Got an 2005xc70 2 years ago and running an average to 15-16 miles/gal (us) 15-16 L/100. No check engine and no codes. Went to 2 different dealers, one change the MAS. Spark plug and air filter changed often. None found the solution and still having 400km or less on a tank. Not driving like crazy. Last time the dealer let me a 2005 s60 4x4 with the same engine than mine and got 10.5L/100 (us 22.4mi/gal) average for doing the same all around things. What should I check to see if that thermostat thing can be in cause? or any other idea since volvo professionals cant find it.

sorry for my english.

That's all they get 15-17 city, 21-24 highway

[tama70808]

todays routine maintenance required a new thermostat and something else related to it to the tune of over $500 because the mechanic said that when he got in it the temp needle shot up and so he put the diagnostics on it that indicated it was running hot - i have NEVER seen the needle move beyond 12 oclock and it always has risen to there predictable when warming up! i was flabbergasted since i never knew my car was over heating! no sign of it! is it really possible that it was? i have never had a reason to distrust this shop but i feel funny about this.

[polskamafia mjl]

lol this is why we advocate doing your own work. That way you know what is being done to your car and why.

[proton]

That's all they get 15-17 city, 21-24 highway

Thanks, but you probably cross read my posts or I was not clear (sorry). If I could have that, I would be very happy. 15mi/gall is good average I have. Yesterday, did 545 km (338mi) , highway only, cruise control set at 118km/h (73.3m/h) and my average was at 12.1L/100 (19.4 us mi/gal). Still normal you think ??? personally, I find this very high.

[tama70808]

to the polskamafia person - if i knew anything about it I would work on my own car - i used to do it when things were simpler but if the shop tells you their diagnostic computer codes are telling them something what can you do to protect yourself? these guys did not get my approval first either. what bothers me most is that i have had no trouble with this great car at 67K and maybe they got sick of just changing the oil for me. i am sad and mad because i do not know it the $600 repair was really necessary and it hurts the integrity of my car as well - why start changing things out for no reason? they said they were just trying to save me from trouble later on. What would have happened?

[polskamafia mjl]

Do you remember what they replaced that cost $500? That's a hefty price for something related to the coolant and/or thermostat. Is this a Volvo dealer or indepemdet shop or a Pep Boys type of place?

[E170_Driver]

I'm trying to understand (english is not my first language) Got an 2005xc70 2 years ago and running an average to 15-16 miles/gal (us) 15-16 L/100. No check engine and no codes. Went to 2 different dealers, one change the MAS. Spark plug and air filter changed often. None found the solution and still having 400km or less on a tank. Not driving like crazy. Last time the dealer let me a 2005 s60 4x4 with the same engine than mine and got 10.5L/100 (us 22.4mi/gal) average for doing the same all around things. What should I check to see if that thermostat thing can be in cause? or any other idea since volvo professionals cant find it.

sorry for my english.

15-16 MI/Gal is pretty bad, my 2001 V70 gets 28.5 MI/Gal on my 500 mile round trip to work every week on average (mostly country side roads at 60 MpH and Interstate at 75 MpH).

Jan

[tama70808]

Dear Polskamafia - the ticket from an independent volvo specialty shop(also services jags) says "noticed temp gauge reading hot during service - Checked engine; performed diagnostic check- retrieved code for engine coolant temp fault". So they installed a new THERMOSTAT ASSY which itself cost $159.95, labor was $238. My oil change was $37.30 parts and $63 labor which included a check of fluids and dash bulb check for intermittent messages failure(?) I do not want to start going to the dealer for service but I have never seen my temp gauge needle rise above the 12 o'clock position. I am wondering if they cranked the AC on full blast while servicing and the car was in need of an oil change, almost 5K since the last one, perhaps it showed overheating for that reason? I hope any good mechanic would figure that out before installing a new thermostat! I did not recognize the mechanic who worked on my car that day, I know a few of the faces there, maybe he is new? I may be getting better gas mileage now, which will interest some other posters on this site - I was averaging 24.8 and now am averaging 28.8
I have to say "may be" because the messages are intermittently visible, including the miles to empty tank and such. That repair will have to wait until next time. Any suggestions on what might be the culprit there? I have had some stiffness in the directional signal which is the stem from the steering wheel the message reset and view buttons are on.