ottomatik Posted April 12, 2016 Report Share Posted April 12, 2016 Long time lurker of the forums, reaching out for help with an ongoing issue with my 2001 V40 1.9T On an annual basis, my car throws a coolant system code and the ECM goes haywire with idle speeds of over 2.5K. These symptoms are cured by replacing both the ECT and thermostat. I am tired of repeatedly replacing both the ECT and thermostat with new OEM parts and have heard before that this is a common issue with this model year. Each time I replace the sensor, I find it super corroded after less than a year of use. Do you have any idea what could be causing the rapid corrosion of the sensor? Could that be leading to its failure? Sharing any insight or prior experiences would be greatly appreciated! Thanks! Link to comment Share on other sites More sharing options...
apeacock Posted April 13, 2016 Report Share Posted April 13, 2016 What kind of coolant are you using? Link to comment Share on other sites More sharing options...
MadeInJapan Posted April 18, 2016 Report Share Posted April 18, 2016 Check where it's plugged into the connector. Often these heat up and corrosion sets in...I've pulled a set completely apart and cleaned them and reconnected when or previous V40 (also a 2001) was having issues and that fixed it. I know the sensor itself corrodes but the connection does equally (at least it did no mine). Link to comment Share on other sites More sharing options...
ottomatik Posted April 19, 2016 Author Report Share Posted April 19, 2016 To the first question, I have been using a variety of coolants; simply topping off the coolant when it is low. I was considering flushing the system and starting fresh with Volvo OEM coolant. To the second point, I will take a closer look at the connection tonight. Link to comment Share on other sites More sharing options...
gdog Posted April 21, 2016 Report Share Posted April 21, 2016 Can you post a pic what you're talking about? And you're shot-gunning it by replacing both; symptoms point to the sensor and not the therm, but you should do one thing at a time to be sure. No need for OEM coolant but you are probably due for a flush; should be done every 3 years or so.. For best results use distilled H2O instead of tap too. But I've never bothered with that myself; depends on how mineral rich your local water is.. Link to comment Share on other sites More sharing options...
Midnight Caller Posted April 21, 2016 Report Share Posted April 21, 2016 Yep, always use demineralised water. Tap water could contain chlorine and that reacts with the aluminum the block is made of... Link to comment Share on other sites More sharing options...
ottomatik Posted April 21, 2016 Author Report Share Posted April 21, 2016 I will post a pic of the sensor when I remove it tonight or tomorrow. I had planned on replacing the thermo because this happened while driving and there is a good chance the car overheated (which I believe would open the thermostat). I may be way off base here; please let me know if I am. As for the use of water with the coolant, I live in WI and typically just use pure coolant because of the cold winters and don't cut it with water. Link to comment Share on other sites More sharing options...
Midnight Caller Posted April 21, 2016 Report Share Posted April 21, 2016 1:1 original coolant should last down to -35 degrees Celsius. Is it colder there ? Pure concentrated coolant is a big NO ! Link to comment Share on other sites More sharing options...
gdog Posted April 23, 2016 Report Share Posted April 23, 2016 OP: you're starting to scare me; maybe you should take it to a shop where they know what they're doing.. Link to comment Share on other sites More sharing options...
ottomatik Posted April 27, 2016 Author Report Share Posted April 27, 2016 Lots of follow-ups. First, regarding coolant, I reviewed carefully the coolant I had been using and it was not concentrated coolant and had a warning on it to not add water. That being said, a coolant flush is still a good idea and will be done. Replacing the sensor fixed the problem, at least temporarily. I have attached some pictures that show the connections (which look clean), corrosion at the sensor, and a comparison against the new sensor (keep in mind the old sensor is ~9 months old). Does anything jump out at you when you see the corrosion around the sensor? Is there something like Teflon tape I should apply to the thread of the sensor to prevent it from leaking as it appears is happening? I did replace the washer on the sensor with the new sensor so that has been addressed. Link to comment Share on other sites More sharing options...
MadeInJapan Posted May 4, 2016 Report Share Posted May 4, 2016 Unfortunately they just do that- clean very well and use some dialectical grease in the sensors- should be good! When I cleaned mine, I used MAF cleaner in my sensor plugs. Link to comment Share on other sites More sharing options...
TEEKAY Posted May 4, 2016 Report Share Posted May 4, 2016 Do not use teflon tape you might regret it Link to comment Share on other sites More sharing options...
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