PD150 Cat Advice

[iammooks]

Over the past six months, I've noticed some performance issues - engine seems throttled when I turn the engine over, but it clears itself (with a bit of smoke) with some gentle revving, as well as some power delivery issues on the road. Sometimes I'll put my foot down in second or third and it'll feel like it's pulling in sixth. I've also had MoT emissions fails that don't sort themselves out no matter the fuel additive, injector cleaner or how "spirited" my driving is.

This seems to point to problems with the cat - it's got 166k on it after all. Last I checked under the car, it was intact (no rattles), but I can't think of anything else that would cause these kinds of problems.

Number one priority is to get confirmation from other diesel drivers that this is what it is, and the second is to find a cat from a reputable brand.

It seems like a bit of a wild west out there, and I don't recognise any of the brands and the prices are wildly different.

Has anyone got any advice when it comes to diagnosing the problem, but also, if I do need a new cat, which one I should go for?


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[Nam-uk]

Remove the cat out of the exhaust pipe

 

[iammooks]

Remove the cat out of the exhaust pipe

Does it have any effect on emissions? The car fails enough as it is...


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[Nam-uk]

Does it have any effect on emissions? The car fails enough as it is...


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Mot is a smoke test that’s it on ours it’s probably the cat making it smoke more anyway as if you do short journeys it will build up if it’s off the smoke is out I wasn’t going to take it off until the mechanic suggested it and I’m glad I did, you’ve done everything Elise so has tobe that then dump a load of additive in fuel, that hydra stuff I use now is night and day difference
Took mine off in 2012 always passed, when the cat exhaust was off it was stabbed out with a long screwdriver then cleaned and at least on first look you’ve still got a cat on mot.
I’ve been using another garage since then for over 8 years and they don’t know the cat is missing.

car was all ready mapped after that 2nd gear spooled out and 3rd was miles better than 2nd, 2nd before cat out was the better gear,
Made car breath allot better

 

[bruceR]

I bought a miltek downpipe and go a welder to weld a dummy cat on it - never had an issue at MOTs


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[Nam-uk]

I bought a miltek downpipe and go a welder to weld a dummy cat on it - never had an issue at MOTs


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Catless is the future

 

[iammooks]

Where in earth are you getting your cars MoT-ed? The places here run a plated value for emissions and it's so hard to get it under these days.

Is it a six-pack and a secret handshake or something?


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[bruceR]

Diesels are are “soot/smoke” test and not emissions like petrols.
I give my TDI a good ragging an hour before the MOT and never had any issues in that department


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[Nam-uk]

Like Bruce says

 

[iammooks]

What are the symptoms of a blocked cat anyway? Moved the car last night and when I revved the engine a bit, when I lifted off, the engine started juddering like crazy. This was when the car wasn't in gear, so there was no load on the turbo. The only other place there could be a blockage would be the inlet manifold, but it's so hard to get a straight answer on google specifically for a diesel engine. I wouldn't have thought the engine would judder on lift-off if it was the intake that was the problem...

 

[Nam-uk]

I couldn’t tell you mate I’ve never had a blocked car

 

[Battoussai]

What are the symptoms of a blocked cat anyway? Moved the car last night and when I revved the engine a bit, when I lifted off, the engine started juddering like crazy. This was when the car wasn't in gear, so there was no load on the turbo. The only other place there could be a blockage would be the inlet manifold, but it's so hard to get a straight answer on google specifically for a diesel engine. I wouldn't have thought the engine would judder on lift-off if it was the intake that was the problem...

Couldn't a blocked EGR do that?

 

[iammooks]

Couldn't a blocked EGR do that?

Possibly - but I’ve cleaned my EGR a few times over the years and if it’s dirty, it’s not likely to be dirty enough to really cause a problem.

The one thing that’s a bit of an unknown is the intake manifold. If my doors hadn’t been leaky and the locks not stopped working, I’d have shoved a endoscope through the EGR to see if that’s blocked. That’ll be a job for next week maybe.

The main reason I’m thinking it’s the cat is because I’ve spent so long poking around with the inlet, EGR valve and the boost pipes that the cat is the only part I’ve not been able to rule out - that and the fact a lot of the sites I’m looking at are saying it should be replaced after ‘x’ number of years and ‘y’ miles, and it’s been at least double that number for both... That and the fact I’ve had real problems on the MoT with emissions for about five years now.


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[MoToJoJo]

Cats aren't that expensive for our cars so I say go for it. Of course an alternative is to gut what you've got but that's outside of my experience

 

[iammooks]

Cats aren't that expensive for our cars so I say go for it. Of course an alternative is to gut what you've got but that's outside of my experience

I'm thinking that's what I'm going to do - are there any reliable brands out there? I'm probably spend the next month trying to understand how many cells I'm supposed to have...

Have you taken one out before? I know my flex pipe won't be a problem, as I took that off a couple of years ago and smothered it in copper grease, but what's it like further back? I'm guessing heat cycling and direct exposure to the elements might create some sadness...


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[MoToJoJo]

Don't worry about cell count, not super important for diesels our age as it's not a strict test. I bought a BM Exhausts one which was alright, but I doubt it'll be a bad time regardless of brand.

I hate dealing with exhausts full stop but it's a pretty straightforward process really. Just prepare for a lot of swearing and questioning life choices, such is the joy of slip joints (next exhaust I get is having v bands)

 

[iammooks]

Don't worry about cell count, not super important for diesels our age as it's not a strict test. I bought a BM Exhausts one which was alright, but I doubt it'll be a bad time regardless of brand.

I hate dealing with exhausts full stop but it's a pretty straightforward process really. Just prepare for a lot of swearing and questioning life choices, such is the joy of slip joints (next exhaust I get is having v bands)

Boom...

I ordered it with the fitting kit as well - could probably do with a new gasket on the turbo side after eighteen years, and what's there now on the exhaust side, bolt-wise, is probably hanging on by a thread.

Any other tools or 'persuaders' I might need to get the old one off? I know some people have exhaust hanger tools, so if there's anything I should have ready, not to mention consumables, that'd be great to know.


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[MoToJoJo]

Iirc the kit comes with the front (subframe mounted) hanger, although if yours is in good condition then some WD40 or similar with a screwdriver will do that one, might be worth changing the bolts out as well but that's personal choice. Beyond that, not really anything. It's literally the three nuts on the turbo, the hanger, and the slip joint to the rest of the system

 

[iammooks]

Iirc the kit comes with the front (subframe mounted) hanger, although if yours is in good condition then some WD40 or similar with a screwdriver will do that one, might be worth changing the bolts out as well but that's personal choice. Beyond that, not really anything. It's literally the three nuts on the turbo, the hanger, and the slip joint to the rest of the system

Thanks! The new cat arrived today - came home to find it leaning against the front door, which given the number of thieving bastards that like to make their way down the street, was a bit of a surprise/disappointment.

I'm probably going to have to get under the car in the next few days to take a look so I know what I'm dealing with. I've not touched the exhaust before, and I don't want to get under it only to find I need to drop the subframe or some crap like that. You know I've got work to do on the subframe too, so I'd rather do it all at the same time if that's the case.

It looks like the only things I've got in the fitting kit are two new clamps for the slip joints, a gasket for the turbo and three nuts, which I'm guessing are for the turbo too, so if I have the energy to get under the car tomorrow or Wednesday, I can order anything else I'm going to need. I'm going to have to control myself not to try and do the job while I've got the car on stands - I always seem to end up doing stupid stuff like that...

 

[iammooks]

Managed to get under the car this morning and take a look. Guessing the hanger just slides out from here? The clamps don't look to be in too bad condition, so I should be able to get those off with the noisy gun. Everything got a liberal spraying with penetrating lube too.

I'm guessing the slip joint is going to be a massive PITA, but it's not like I'm not used to fighting this car on every job I do...


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