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[John_Clayton]

I've just joined this forum and found it very helpful regarding the problem I'm having - namely the n/s short hose (part no. 90500057) that joins the two air injection pipes, keeps blowing. Apparently it's caused by the cat. being blocked. However, last week it passed its MOT. The new hose just lasted long enough but blew again on the next journey. If the cat. is the cause surely the emissions would have made it fail the MOT? The readings were - Fast Idle (2829 rpm): HC = 76ppm, CO = 0.05% and Lambda = 1.020. Natural Idle (885 rpm): CO = 0.01%
I've only recently bought the car. The previous owner had just replaced the coil pack so it may have ben misfiring which I understand can damage the cat. I intend replacing the cat. myself, if necessary, but would you recommend a ceramic one at around £66 or a metal one at twice the price? What other parts should I replace at the same time? i.e. the o/s cat.? Many thanks in anticipation.
(If my vehicle details don't show up automatically it's a 1997 2.5 V6 Tourer with 110,000 miles on the clock)

[jonathanh]

Are you sure it is the cat not the exhaust?  My guess is that if it passed the emissions test the cats work but there may be blockage later on.

Someone more knowlegable than me will know the way of checking but my guess would be to drop the exhaust off and try blowing through it.  Depending on how old the exhause is, if it is on its last legs, you may as well change it now  'cost you may as well do it when you change the front pipes.

BTW aftermarket cats are not recommended here, known good cats from a scrappy may be better

[Entwood]

Exhausts are know to block when the internals fail ... there is a thread somewhere with a picture of one that exploded !! Looks like hair all over the place !!  I'd check all the boxes before buying a new cat ..

edit :

found it .. eventually ..

http://www.omegaowners.com/forum/YaBB.pl?num=1191427168

[John_Clayton]

Thanks for those suggestions and tips. On further inspection the o/s centre silencer appears to have been replaced recently whereas the n/s one looks pretty old. I'll replace that and hopefully that will fix the problem.

John

[JasonH]

Exhaust blockages on Omegas seem to be relatively common - and hard to diagnose sometimes.

[JamesV6CDX]

My car has been down on performance for a while... took the backbox off and it's totally blocked with bits....

Hopefully a new system will sort me out!

[John_Clayton]

Here's an update from the originator of this thread. It was the cat! I first replaced the centre n/s silencer, as I mentioned I would, but that made no difference. With it removed I felt for exhaust gasses coming out of the cat. but there was hardly anything there. I've now obtained a second-hand cat. from a local breaker and it appears to have cured the original fault. The car runs better and the short hose has lasted some 50 miles without blowing.

Footnote: I had to use a welding torch to heat the nuts securing the front pipe to the manifold studs in order to remove them. I mentioned while at the main dealer and a chap on the service desk agreed it made more sense when manufacturers fitted brass nuts on exhaust systems. They didn't rust like steel ones. Apparently Vauxhall claim there isn't a problem. Well, there would have been if I'd set light to something under my Omega!

[Marks DTM Calib]

Here's an update from the originator of this thread. It was the cat! I first replaced the centre n/s silencer, as I mentioned I would, but that made no difference. With it removed I felt for exhaust gasses coming out of the cat. but there was hardly anything there. I've now obtained a second-hand cat. from a local breaker and it appears to have cured the original fault. The car runs better and the short hose has lasted some 50 miles without blowing.

Footnote: I had to use a welding torch to heat the nuts securing the front pipe to the manifold studs in order to remove them. I mentioned while at the main dealer and a chap on the service desk agreed it made more sense when manufacturers fitted brass nuts on exhaust systems. They didn't rust like steel ones. Apparently Vauxhall claim there isn't a problem. Well, there would have been if I'd set light to something under my Omega!

It was a good move to use a good second hand part, the cats are very reliable and after market ones are bloody awful.

The nuts are an interesting point as they were changed for a a helicoiled version around 1998ish....

[theowletman]

John
I've recently replaced the cat on my 1995 2.0 16v. I got a cheap one from a motor factor and it has done the job, passed emissions test etc, but, it rasps badly at certain revs, sounds like an Alfa, it has spoilt the quiet cruising of the Omega, sounds like the diff or a wheel bearing is about to explode at 75mph. If you are going to keep the car buy an original.