2.0 170 CR exhaust sounds like a saxo for 1 minute! then fine again.. why?

[Meemo]

So my car of recent has started doing a strange thing.
2010 2.0TDi 170 CR (104k on the clock)

After a good long drive (50 ish miles) on 4 occasions now the exhaust has suddenly become so loud I hear it over my music.

So I turn the music down and it is as if I have had a DPF and EGR delete and no exhaust, the turbo becomes very loud spooling, exhaust very deep sounding and loud, at this point every guy on the road gives me a thumbs up...

when i am stationary during one of these moments the engine is now revving steady at 1000rpm rather than the normal 800rpm

It has happened 4 times now and then dissipates to normal after a minute.
Managed to have it happen pulling up at the Krispy Kreme meet last night in Kingston, and being told "wow heard you coming, your car sounds SICK"... well actually, I think it may be sick at this point lol
and a helpful, "nah it is broken, it sounds better therefore is fixed!!" thanks but not helpful

• I have no back boxes and custom pipework to the standard midbox,
• DPF EGR CATS etc are all still there, I havent deleted these currently.
• standard map
• No loss of power during episode
• My car always smells super sickly sweet from the exhuast emisions (only this year that started and since using super diesel), I am told this is a classic diesel cat smell so may have nothing to do with it
• I can feel some vibration/feedback through the peddles when pulling off from standstill when it happens (Clutch?)

Car drives a dream and is serviced twice a year with genuine parts (this is my baby afterall). Runs on Super Diesel 80% of the time.

My only random brain fart on this so far is that during a DPF regen, the exhaust superheats, is it possible this heat is causing a break in the seal since having my custom exhaust done, and then when cooling the seals meeting up fine again?

Or EGR cause any weird symptoms like this?

Anyone else got a brain fart on this one?


I have also posted this in the diesel section

 

[Matt Benns]

Hi Manda

Without hearing a clip of it it's hard to tell but I would say that you are right with the thought about the regen, although wrong about the thought that it has broken a seal or caused any damage.

During the regen the exhaust note can change. If it all goes away again and returns to normal, which I'm assuming it does as you said it happened 4 times, then I wouldn't worry about it.

Before my a4 I had a seat leon pd170 and had a straight through exhaust prior to having the dpf deleted and maped, during the regens I encountered the same thing most days on my way to work.

Are you planning on having the dpf deleted or leaving it as is?

 

[Meemo]

Thanks that's put me at ease a little. Yeah plan was always get a delete as i can afford in stages, had back section first. But no rush as i enjoy the jobs i can do myself much more.
Although still need to figure out the coolant loss ( half in a year so very very slow.), no milky oil as i checked today, power seems fine, but sweet smell as soon as the car turns over, will have my mot tester pop the sensor in the top of the coolant to check for carbons though as that will Confirm of it isn't head gasket.

 

[matt.russell]

Not head gasket, its doing a dpf regen, mine does it all the time. SOUNDS amazing .. and should judder on idle too..

 

[Meemo]

Posted in reply to diesel section response, but just in case this is helpful to anyone.



Thanks! I have come to the same conclusion at this point, glad you say that as I feel relieved now Still want deletes though, just not quite so soon!
You have back box's too?

Unfortunately am still losing coolant (very slowly) and it is burning off when the car is on, literally the most sickly sweet smell.

I have seen a small puddle on occasion under my drivers headlight which I only noticed few months back (had this car since 2013 and never seen it before), and this is when I hadnt run the air con a few months so sure it isnt condensation. #

Hopeing it is coolant leaking slowly on to something hot (part of the exhaust maybe) and burning it off. Going to take it to a friends friend at an MOT station on saturday to pop the emissions tester in the top of the coolant bottle to be certain, idea is if it detect carbons (unburnt fuel) then head gasket, if not it is a leak somewhere else and I need to keep an eye on the level till I take the bumper off to look properly.

 

[matt.russell]

No I haven't got back boxes but I bet money on it being a regen.. But when was your last cam belt change ??? Might be the water pump leaking

 

[Meemo]

No I haven't got back boxes but I bet money on it being a regen.. But when was your last cam belt change ??? Might be the water pump leaking

No back boxes either how they should sound out of the factory if Sline specced, not loud but nice! (until a regen when it sound sick as fu**)

Cambelt was 25k ago November 2013 when I bought the car, only noticed the little puddle few months back and same with the sweet smell, 4 months now maybe. Good shout on the water pump, I will have a look when I get the bumper off and under her.

 

[Matt Benns]

Have you blanked off your EGR by any chance? I was loosing coolant on my old car (seat Leon fr tdi) which had dpf and egr delete, and i needed to fit an egr cooler delete which cured the problem

 

[Meemo]

Have you blanked off your EGR by any chance? I was loosing coolant on my old car (seat Leon fr tdi) which had dpf and egr delete, and i needed to fit an egr cooler delete which cured the problem

EGR and DPF still in place, however I am informed the EGR on ours do not have cooling, although this was from 2 lads wondering why I was under my bonnet at a car show on sunday (I was checking the oil cap to see if there was any milyness underneath), I breifly said I need to check if the EGR has cooling and if it is leaking as it smells immedaitely from the exhaust and as it doesnt seem to be HGF.. they said they dont have them on mine, however some guys sometimes pretend to know things they dont know to me though about cars, I have heard some corkers! so not taking this as gospel.