Would low coolant temperature bring about catalytic converter failure
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  1. #1
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    Default Would low coolant temperature bring about catalytic converter failure

    All,

    The 306 2.0 litre cabrio is on a second catalytic converter in the spaceof 2 months. It is going in to be looked at tommorrow. However I have noticed something peculiar. I have noticed that the car has been running at low engine temp since day one. As it has been getting cold I have noticed that the coolant temp does not go above 75 degrees celcius. This morning it did not go beyond 75 degrees for the entire 40 minute trip.

    I even went to the shops before, a 5 minute trip each way and it still was unable to go beyond 75 degrees. On real hot days in stationary traffic it would get to 90 or so, but has not been able to recently.

    I know that until the car reaches optimum engine temperature, it runs rich. However, would this be enough to kill a catalytic converter? Or would more be required?

    Your collective aussiefrog input would be appreciated.

    Cheers

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  2. #2
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    Don't you have a thermostat ?
    Chadi

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  3. #3
    UFO
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    If the thermostat is stuck open or seals are stuffed, then the car never reaches optimum operating temp and therefore the cold start injector/s may be running all the time which of course runs the engine rich, which means perhaps some unburnt fuel down the exhaust contaminating the catalytic convertor.

    I reckon if you replace the thermo you will find the car will come up to temp, operate better, be more fuel efficient etc.

    As a subsidary question, does your heater work well on a really cold day.
    Craig K
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  4. #4
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    An update,

    The thermostat was replaced as it seems it was stuck open. Will report back on how it went. I am waiting for a good set of cold mornings to confirm the effect that changing the thermostat had.

    Cheers
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  5. #5
    COL
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    Default Changing Thermostat

    Quote Originally Posted by bad_karma View Post
    An update,

    The thermostat was replaced as it seems it was stuck open. Will report back on how it went. I am waiting for a good set of cold mornings to confirm the effect that changing the thermostat had.

    Cheers
    You should be able to see right away by faster warm up time and the heater working more efficiently
    Regards Col

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  6. #6
    1000+ Posts BIGRR's Avatar
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    Default Crook cats

    Quote Originally Posted by bad_karma View Post
    All,

    The 306 2.0 litre cabrio is on a second catalytic converter in the space of 2 months. It is going in to be looked at tomorrow. However I have noticed something peculiar. I have noticed that the car has been running at low engine temp since day one. As it has been getting cold I have noticed that the coolant temp does not go above 75 degrees celcius. This morning it did not go beyond 75 degrees for the entire 40 minute trip.

    I even went to the shops before, a 5 minute trip each way and it still was unable to go beyond 75 degrees. On real hot days in stationary traffic it would get to 90 or so, but has not been able to recently.

    I know that until the car reaches optimum engine temperature, it runs rich. However, would this be enough to kill a catalytic converter? Or would more be required?

    Your collective aussiefrog input would be appreciated.

    Cheers
    How did you know that the cat required replacing?
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  7. #7
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    Quote Originally Posted by BIGRR View Post
    How did you know that the cat required replacing?
    The mechanic made a mention of it and then I took it to my local exhaust bloke who is a trusty chap. One listen of it and he came up with the same conclusion too.
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  8. #8
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    Quote Originally Posted by UFO View Post
    If the thermostat is stuck open or seals are stuffed, then the car never reaches optimum operating temp and therefore the cold start injector/s may be running all the time which of course runs the engine rich, which means perhaps some unburnt fuel down the exhaust contaminating the catalytic convertor.

    I reckon if you replace the thermo you will find the car will come up to temp, operate better, be more fuel efficient etc.

    As a subsidary question, does your heater work well on a really cold day.
    Well it seems to be runing better this morning. The coolant temperature reaached about 80 degrees in about 5 - 6 minutes or so in 6 degree ambient temp of driving (this is with the air conditioning on full heat too). It remained at 80 all the way to work and went a bit above it at the lights, but never really dipped down below 80.

    Oh yeah, the heater seems to work fine. Did a good job this cool morning too!
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  9. #9
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    On another note i saw the car manage about a bit over 500 klms on a full tank mixed cycle driving. I am guessing that a 2 litre 16v 306 averages 10 l/100 klm so this seems to be close to the mark.

    I am hoping that it is safe to get a new cat fitted and it does not die again. Fingers crossed!
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  10. #10
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    Default head gasket

    I know the car is going fine atm but have any of your previous symptons resulted in oil/combustion gas getting into the exhaust? They will rot out a cc in no time. Something to ponder.



    David

  11. #11
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    Quote Originally Posted by David M View Post
    I know the car is going fine atm but have any of your previous symptons resulted in oil/combustion gas getting into the exhaust? They will rot out a cc in no time. Something to ponder.



    David
    Hopefully not david. I have kept a watchful eye on the coolant level and colour and it does not seem to have changed. I'll check the oil tomorrow to see if there is a colour change to something milky.

    Man I hate these problems, so hard to nail down as to what they can be. Really hopeful that it was just the thermostat.

    Regards
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  12. #12
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    Default cat

    Doing LOTS of short quick trips can shorten their life too...big time :{
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  13. #13
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    I went to start the car 2 days ago and it started very roughly, almost stalling. For about a minute or two. Will check for any error codes. I am guessing there could be a coil pack on the way out. That too over time could have been contributing to the cat failure.

    Will keep you guys informed.
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  14. #14
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    Default Fuel economy still poor.

    Quote Originally Posted by bad_karma View Post
    On another note i saw the car manage about a bit over 500 klms on a full tank mixed cycle driving. I am guessing that a 2 litre 16v 306 averages 10 l/100 klm so this seems to be close to the mark.

    I am hoping that it is safe to get a new cat fitted and it does not die again. Fingers crossed!
    My 16V 1.8L 306 routinely does more than 750km on 55 - 58l. I do use premium fuel, daily drive to work is around 30k each way, city and hightway.

    Usually works out around 7.5 to 8 litres per 100km.

    10 L/100km is very high from my experience. My car has done 150,000km, never replaced the catalytic converter and runs on original Michilins.
    racing 405
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