I'm thinking I may have to replace the section of my exhaust that includes the flexi and DPF.

I can source a replacement but I'm not sure how big a job it will be to fit. The back end is simple, just an exhaust clamp, but the front section looks like it might be buried deep in the engine bay. I'm expecting lots of heat-seized bolts and rusty, rounded heads...

 

There are also sensors involved, I believe- just behind the dpf itself (is this it the lambda sensor?) and a couple of tubes leading from the dpf, I think these must be for the differential pressure sensor? It doesn't looks too tricky to undo the rubber pipes connecting these. I am expecting that some sort of re-programming might be required, but I know someone who says he can do that for me.

 

I'm not sure what the box is at the very front of this section, possibly the cat? And will this present any difficulties?

It’ll not be too difficult.

 

i found there to be a fair amount of space on our 1.6 so getting to the nuts/bolts at the top of the exhaust should not be too difficult but if you struggle you could try undoing the bottom mount and that will give you some movement in the engine.

 

personally I’d get the car in the air and supported, spray any nuts/bolts you think might pose an issue with WD40 then remove the back and mid section then tackle the front section.

 

 

@Baxter - Rather than WD40, I'd suggest a proper dismantling lubricant such as PlusGas.

Thanks, I'd come across some talk of having to drop the subframe which is obviously a whole different kettle of fish.

Will have a poke around and see what the access looks like...

Are you wanting to change the full downpipe so dpf delete too? 

1 hour ago, AMD87 said:

Are you wanting to change the full downpipe so dpf delete too? 

 

Not as such- just want to get the car running again and get through the next MOT

OK I've managed to disconnect the section of exhaust completely, and detach the various sensors.

BUT how the heck do I actually get it out of the car? I can't wrestle it past the subframe and steering link rod. I suppose I could cut it in half near the flexi but that doesn't help getting the new one on!

 

Any suggestions for the least painful way forward from here?

 

Edit to add: this is probably a total bodge, but what about chopping out the flexi section and using this to join it back together?

https://www.ebay.co.uk/i/362439181727?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=362439181727&targetid=595627705353&device=c&mktype=pla&googleloc=1007386&poi=&campaignid=1880675215&mkgroupid=75768494811&rlsatarget=aud-739442097805:pla-595627705353&abcId=1140496&merchantid=109802908&gclid=CjwKCAjwkqPrBRA3EiwAKdtwk5fTuB_Hd5hGhE0PFStVd6pm394CAbWP62UL39KSGN7OgBX-Ob6FnBoCMiQQAvD_BwE

Edited 30 August, 20196 yr by Baxter

Just nipped out and had a quick look underneath ours. I can see why your having problems. Sorry to say it but due to the size of the cat you might actually have to drop the steering gear down to fit it.

What about the bodge idea... cutting out the flexi and replacing it with a clamp on one? If I can get the right length.

So long as it seals and doesn’t blow then it shouldn’t fail an mot or anything so yeah maybe lol

Oh well no going back now! 

Well you’ve got it out. So long as you can get it back in and get a good seal with the flexi your going to use I can’t see it being a problem 

Edited 31 August, 20196 yr by mikey362

One of these should do the trick for getting it back together:

http://www.everyexhaustpart.com/cart/exhaust-flexi/clamp-on-flexi/54mm-2-1-8/54mm-x-300mm-clamp-on-exhaust-flexi-2-1-8-x-12.html

 

And whilst I have the DPF off the car I might as well pressure wash the filter. Going to try welding it up and sticking it back on, but if that doesn't work I guess it's £500 for a new one!

Yeah not looking forward to that expense in the future. 

So Baxter what year and milage is the car? What a bit more specifically was the problem?

 

I've just had to do something similar. Mines 2011 and 83k miles cayc engine. The flexi was failing, the curved pipe into the dpf was corroded and holed, the pipe out of dpf was corroded and blowing where it exited dpf.

 

I cut off the flexi at top nearest to cat leaving max pipe length. Bought aftermarket flexi clamp type. Made double bend pipe to replace corroded one. Got piece 2inch stainless for dpf out. Cut the O2 boss out of old output pipe and rewelded it into the stainless pipe. The 2" pipe fits inside old pipe in the dpf and was duly welded in.

 

It seems poor do to me that the corroded pipes are of inadequate material or thickness. Poor show again.  There are going to be a bundle of cars facing a similar failure. I got quoted £1400 for replacemant dpf/cat unit not including fitting.

 

Malcolm

Mine's a 2010, just over 100k.

I think this section has failed before in the past- welds on top of welds. All in the short section of pipe between the DPF and the flexi.

I'm still waiting on the new bolt-on flexi arriving in the post. Got a mate welding up the leaky bit of pipe for me.

Really hoping that getting it all sealed up will let me clear the faults and out of limp mode.

I had a similar quote on a new DPF/downpipe/Cat. I wonder whether they would really fit it in one piece- the subframe is the in the way. Labour cost would be massive.

Still not resolved this one, it's taken weeks for the bolt on flexi to arrive. And now struggling to get a seal, I don't think it's a close enough fit.

 

One question- does anybody know just how much air resistance a DPF ought to have? If I try blowing down mine, it seems 100% blocked. This might explain the pressure I'm seeing in the exhaust which is thwarting all my efforts to get the joins sealed up. I got a fair amount of flaky soot coming out of the upstream end of the filter when I gave it a tap. It might be time to try some sort of cowboy DPF cleaning trick- oven cleaner? Fill it with petrol and set it on fire?? (I'm joking, obviously... but getting desperate!)

On 24/09/2019 at 20:31, Baxter said:

Still not resolved this one, it's taken weeks for the bolt on flexi to arrive. And now struggling to get a seal, I don't think it's a close enough fit.

 

One question- does anybody know just how much air resistance a DPF ought to have? If I try blowing down mine, it seems 100% blocked. This might explain the pressure I'm seeing in the exhaust which is thwarting all my efforts to get the joins sealed up. I got a fair amount of flaky soot coming out of the upstream end of the filter when I gave it a tap. It might be time to try some sort of cowboy DPF cleaning trick- oven cleaner? Fill it with petrol and set it on fire?? (I'm joking, obviously... but getting desperate!)

Should be pretty free flowing, doesn’t become a restriction till 175-180bhp

You need someone with VCDS to check the DPF loading, and do a regen if required.

Update: with a bit of heat and an air compressor I got a lot of the carbon out of the DPF, and got it cleared to the point where you could blow through it with ease.

Have now reinstalled it on the car.

On starting up, the various lights still came on (DPF, glowplug, EM) and the car was still in limp mode, which I expected as I haven't been able to clear the fault codes. It was behaving a heck of a lot better than it did last time I drove it.

However after just a few minutes it started getting very unhappy with me, and I barely made it home without stalling.

 

I reckon this is a symptom of massive back-pressure that the engine can't cope with. So I bet that when I remove the DPF again I will once more find it caked with soot- after just a few minutes driving.

 

What could be happening upstream to cause this? A turbo seal failure maybe? Or just a big backlog of carbon in the downpipe waiting to land in the DPF??

 

I don't mind throwing £500 at this  by getting a new 3rd party DPF, but if there's some underlying cause I really need to get to the bottom of it.

Just straight pipe it and be done 😂

Straight through pipe will throw up errors if not mapped out of ECU. Get it scanned with VCDS for DPF loading, read codes, clear log and if required do a forced re-gen. VCDS may show any underlying issues and stop un-necessary costs.

Hi Baxter,

Just went through this, see here :

 

heres some pictures of how i cleaned the dpf....

 

 

 

 

 

Thanks for the replies.

Any thoughts on the underlying cause of the sooting up? I'm guessing a turbo issue but not really sure where to start.

Get hold of VCDS vagcom OBD from Total Diagnostics.

You need to know the soot levels to start off with. When my DPF was clean, I could blow through the pipe with some pressure, a bit simlar to blowing through a clasped right hand...!

You may not have had it clean enough to start with.

VCDS will allow you to reset everything, Autoaid (and i assume others) wont let you reset the levels of soot in the DPF.

You need to know what the pressure is by reading the levels of the differential pressure sensor thats on one side of the DPF.

Thats one of the items used in the calculation of how much soot may be accumulated.

Check the pressure at the tail pipe by blocking it off with your hand at idle when reasonably cold. It should push your hand away to let the exhaust out (compare to another similar diesel, same engine size).

If the pressure is low there, yes you have something restricting it. (the engine needs air in, make sure that the air filter etc is clean, and not blocked as well. This could be the cause of your bad journey home).

A bodgey Exhaust Gas Reciruclation system can make the air filter clog up with black moist muck. Check that as well. If its discoloured to black, you have other issues.

Again, VCDS will diagnose this in detail.

Dont give up!

Regards

T