Crappy Silencers & Backfiring

[richardcox_lotus]

As Promised, here's a fun(?) new thread about a backfiring Sprint. Last year, my trusty (10+ yr old) silencer finally bit the dust & as part of it's service, a new Stainless item was placed on instead.

Since then, the car has slowly deteriorated in the Backfiring department, as well as generally getting noisier. I don't live too far from Gatwick Airport & they pilots are starting to complain when they're on their final approach.

So.......the issue is I'm not sure whether there is a leak in the system, or whether the Silencer box has blown out it's content. Any advice on how to check for leaks (tell-tale signs ?). I'm not happy being under the car with the engine running, due to general exhaust fumes.

Thanks in advance.

[Elanintheforest]

The silencer box has probably blown out its content, but that shouldn't make it backfire, just a little more loud. I would guess that there are a combination of issues,,,you have a leak and you're running rich. You're letting unburnt fuel into the exhaust system, and with a bit of air sucked in it's frightening the neighbours...and probably you!

It depends what you mean by backfire...if it's popping on overrun that may be just the silencer wadding having gone, and maybe a small leak. If it's a 12 bore going off then I would look to the carbs as being the main culprit.

It may be worth checking out the manifold gaskets and timing as well.
Mark

[mikealdren]

Richard,
You should be ok looking underneath to find the leak, do it outdoors on a windy day and you will probably be able to hear a significant leak.

My +2 used to backfire when it had a split in the manifold; new manifold, no backfire. The exhaust backpressure is obviously important for the +2.

Mike

[garyeanderson]

If you cover the exit of the exhaust pipe with your hand at idle, you should be able to here the leak . If the motor dies shortly there after, there isn't any leak.
Gary

[Emma-Knight]

Has the new one (silencer) been fittet with exaust sealant like fire gum?
If not, fuel remains will find enough oxigen via leaky joints do detonate, as they are still hot enough. When having sealed the silencer joint in exchange process, the more forward joints might have broken open in the undoing procedure. (especially at the two in one Y piece)

Anna

[nebogipfel]

Also check for vacuum leaks.

I had a leak on one of my headlamp vacuum pipes and the car became very anti-social.

[elansprint71]

Also check for vacuum leaks.

I had a leak on one of my headlamp vacuum pipes and the car became very anti-social.

That is a very good point! Not heard of that one before.