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Driving home car is working normally, driving at a constant speed then out of the blue heard a small thud then a rumble, after that the car had a problem where the acceleration was weak.

Approaching a large hill the car looses momentum a struggles to keep momentum.

Car sounds noticeably louder and deeper while running, and while accelerating it rumbles?

I've had a look around the car and underneath to see if I can spot anything a miss. The only thing I can see is below on the exhaust.

Any ideas or suggestions greatly appreciated.

Passenger Side:

VW Passat 2.8 underbody exhaust VW Passat 2.8 underbody exhaust

Drivers Side:

VW Passat 2.8 underbody exhaust

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  • The symptoms seem to tally with a puncture/leak in the exhaust but the picture is not conclusive. Could you take a picture from the other side and post it up?
    – Zaid
    Commented Jul 14, 2015 at 8:25
  • Is the damage you are showing pre- or post-catalytic converter?
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jul 14, 2015 at 11:28
  • @Zaid More pictures uploaded, if you want anything specific I'll be happy to get them.
    – AntiHaus
    Commented Jul 14, 2015 at 15:38
  • @Paulster2 Post, but right after I believe. I think the picture from the drivers side shows the location better.
    – AntiHaus
    Commented Jul 14, 2015 at 15:39

1 Answer 1

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From your description, it sounds like your catalytic convertor is shot. If the honeycomb within the converter shatters, it creates a hug obstruction within the converter. The back pressure this creates will not allow your engine to rev to its potential. This really shows up when trying to accelerate. Depending on where the hole in the exhaust is, you may be able to see up into the cat and be able to check its condition.

EDIT: You can test your cat by lightly tapping on it with a rubber mallet. If you hear things shifting, the internals are shot. Don't be beating on it, though, as this will cause it to self destruct! Just hit it hard enough to listen. It should be self evident very quickly as to its status.

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  • I'm going to take it round to a friends tonight who has some raisers to try tap it. If worse comes to worse and my catalytic convertor has gone am I good just to straight pipe it from the motor. Taking the cat out? While I think of it... the Passat has two catalytic convertors, if only one has gone would I be ok to run one with the cat and the other without, will the difference in pressure annoy the engine?
    – AntiHaus
    Commented Jul 14, 2015 at 17:27
  • @AntiHaus - You could run it with out cats, but you are still going to have to pay to have the straight pipe put in (I guess you could do it yourself for cheap). I don't know what year your Passat is, but if OBD-II, you'll have a code pop on the dash when you do take them off. You don't want to run a cat on one side and without on the other. That would be just about as bad for the engine as running it plugged. If you have a laser thermometer, you could also test them before and after. It should be ~200degF hotter after. If hotter in front, the cat is bad. I'm talking just before/after.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jul 14, 2015 at 20:23
  • Thanks FYI it's B5 2000, I know it's got an O2 sensor before the muffler so I was fully expecting the codes to pop up if removed for emissions workshop. I would goto a shop and have it professionally looked at but I have no cash this month, did timing belt, brakes and tires... my friend with a lift is a welder so hopefully we can work something out. Even if it's temp till payday.
    – AntiHaus
    Commented Jul 14, 2015 at 21:15

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