Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[chrisdb]

My girlfriend's mum has a battered Dawoo and every year for the last 4 years it has field every MOT because of the cat (not the fury kind ).

I looked into it a bit more and the last three years the mechanic has put in a new cat each time. I pointed out they they should not really go wrong at all, let-alone have a new one every year!! She says that this current mechanic offered to try and find the underlying fault but she could not afford it. She opted for a new cat again, but this new one has obviously been damaged too by now I guess.

She does not get any smoke. She does only short trips. Any ideas what might be wrong?

Cheers
Chris

[Lizzie_Zoom]

My girlfriend's mum has a battered Dawoo and every year for the last 4 years it has field every MOT because of the cat (not the fury kind ).

I looked into it a bit more and the last three years the mechanic has put in a new cat each time. I pointed out they they should not really go wrong at all, let-alone have a new one every year!! She says that this current mechanic offered to try and find the underlying fault but she could not afford it. She opted for a new cat again, but this new one has obviously been damaged too by now I guess.

She does not get any smoke. She does only short trips. Any ideas what might be wrong?

Cheers
Chris

Short journeys are a killer for most cars and especially their exhaust system / cat.  Probably too much unburnt fuel is going down into the system and doing damage to the cat.

A cat is meant to be heated sufficiently, as is the engine, for efficient operation, and as you probably know all the time the car is in "choke" mode as it used to be called, with the engine cold, the engine runs inefficiently and unburnt fuel is at its worse levels and doing the damage!

Indeed it was always stated with cars of the past that when an engine is cold, for every gallon of fuel used a gallon of sulphuric acid, parafin, water, and other harmful substances are produced, along with unburnt fuel 'slipping' through!

The aim should always be avoid short journeys, or at least leave the engine running for at least 15 minutes to recharge the battery as well
  
Now if these 'facts' are wrong for 2008 cars please let me know as I am sure you will!

[LaserLance]

Best thing to do is give a good run up mway or a dual carraigeway at least once a week , charges battery up and gives it a clean out as well

[chrisdb]

Thanks! I did not realise that short journeys could do so much damage. As she is quite old and does not like driving much this might just be someting she'll have to put up with :-/

Cheers

[Kevin Wood]

I reckon it's got a problem if it's getting through cats that fast. Does it get up to temperature quickly and hold it roughly mid-gauge?

Kevin

[Bandit127]

Take it out for a spin for her and let it rev a bit. Unless the engine is throwing unburned fuel down the exhausts it just needs the deposits burning off. The function of the cat will be fully restored.

If the engine IS throwing unburned fuel down the exhaust, ODBII should show it (engine fault light lit and an error code stored).

If you can't drive it, make the mechanic do it before he codemns the cat again.  

A cyninc might say that he saw her coming and is making the most of it. A pragmatist that he should know better. And a realist that cats just don't go every year so what is his evidence.

[STMO123]

I agree with all that has been said. My meriva takes ages to warm up, it's a trait of the engine apparently. I only need to make short trips, school, shops etc., so twice a week I take it for a good run to blow the cobwebs out.

[chrisdb]

Thank folks, that's a great help. I'll suggest this to her next week.

[Lizzie_Zoom]

My girlfriend's mum has a battered Dawoo and every year for the last 4 years it has field every MOT because of the cat (not the fury kind ).

I looked into it a bit more and the last three years the mechanic has put in a new cat each time. I pointed out they they should not really go wrong at all, let-alone have a new one every year!! She says that this current mechanic offered to try and find the underlying fault but she could not afford it. She opted for a new cat again, but this new one has obviously been damaged too by now I guess.

She does not get any smoke. She does only short trips. Any ideas what might be wrong?

Cheers
Chris

Short journeys are a killer for most cars and especially their exhaust system / cat.  Probably too much unburnt fuel is going down into the system and doing damage to the cat.

A cat is meant to be heated sufficiently, as is the engine, for efficient operation, and as you probably know all the time the car is in "choke" mode as it used to be called, with the engine cold, the engine runs inefficiently and unburnt fuel is at its worse levels and doing the damage!

Indeed it was always stated with cars of the past that when an engine is cold, for every gallon of fuel used a gallon of sulphuric acid, parafin, water, and other harmful substances are produced, along with unburnt fuel 'slipping' through!

The aim should always be avoid short journeys, or at least leave the engine running for at least 15 minutes to recharge the battery as well
  
Now if these 'facts' are wrong for 2008 cars please let me know as I am sure you will!

In addition to what I previously stated and others members have correctly sais, with such constant short journeys the oil changes must be carried out at very shortened intervals, say every 3,000 miles.

This is due to the volume of nastie substances that are produced whilst the engine is cold that leach down into the sump.  The quality of your oil is quickly degraded, with nasties such as suplhuric acid!

[chrisdb]

Thanks Lizzie, I think I'll give it a good service too while I'm at it. I suspect it will be quite a while before she does another 3k miles