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[2am Omega]

97 R plate Omega Elite 2.5 V6 Petrol engine ran as smooth as velvet .. now suddenly lumpy with reduced power and petrol consumption almost doubled. Paperclip test suggests no fault. HT system seems ok. Found burst hose which seems to be blowing air ..  Slightly tacky rubber hose which can be squeezed and crimped with bulldog clip to seal temporarily, then engine runs better .. so looks like this is the problem. Black hose has marking ending 0020555 > ECU>. Location is at front of engine bay, just nearside of centre, running vertically near radiator fan then curved over to feed a black spaceship-style 2 inch circular device, quite high, which attaches to a bracket attached to the frame of radiator fan. The frayed burst is about 2 inches long near top elbow curve. Can somebody please identify this hose and its function, including where the lower end connects? Is it an easy DIY job to replace hose or a garage job? Do I need a replacement manufacturer hose part or a length of standard hosing? Assistance welcome please.

[philhoward]

Sound like the SAI hose off the top of my head - does the non-spaceship end go down under the battery/headlight area?  In which case should be fine to run with it plugged, but generic hose repair tape would do better (get it from any DIY store)

[2am Omega]

Please explain what does SAI Hose mean. The black spaceship or flying saucer type device is about 2.5 inches diameter with 3 smaller concentric circular levels on its top. The burst hose attaches on the offside of this device, not the other hose attaching on the battery nearside, and it heads down then curls under towards the nearside headlight, under the battery area. Not sure which direction the airflow runs.

I have taken a photo of the engine bay showing this device and the crimped burst hose but not sure if there is a way to upload it to this website???

Thanks for your suggestion of hose repair tape. Does anybody else know the function of this hose and flying saucer device please?

Would this burst air hose explain the engine malfunction and the hugely increased fuel consumption?

[philhoward]

SAI - Secondary Air Injection.  There's a big fan blower under the headlight area which blows air through the "flying saucer" and eventually into the exhaust manifolds to get the cat converters up to temperature quicker for emmissions purposes.  These fans tend to fail and make sounds like a jet engine so get unplugged with no ill effects.  They tend to only play a part for the first 30 seconds from startup though.

To upload a photo easiest way i've found is something like photobucket.com which will allow you upload a photo to them, then they will give you an IMG link; copy and paste this link into your psot here and it should show up..

[Matchless]

Secondary air injection is part of the emissions control, air is blown into both exhaust manifolds for the first half minuite or so after a cold start.
The black spaceship is a vacuum operated valve which is controlled by the engine ecu and should only be openfo 30 secs or so. Follow the pipe towards the engine, there is a silver spaceship on a metal pipe. This is a non-return valve and prevents exhaust gasses returning up the pipe to melt the rubber pipe or plastic valve.
It sounds like your non-return valve isnt working (most dont work very well) but the bigger clue is poor running and high fuel consumption which could point to a blocked exhaust. If the rear box has collapsed inside it can cause a blockage affecting both banks. Other possibilities are the centre boxes or cats.
If you follow the metal pipes to either side of the engine you will find a pair of rubber couplings, these often melt when exhaust is blocked.

[PaulW]

Going from your symptoms, I'd hazard a guess this is caused by a blocked cat or blockage elsewhere in the exhaust system...

[2am Omega]

Looks like you are correct about the blocked exhaust connection. The poor running and high fuel consumption started immediately after MOT a few weeks ago. Enormous lengths of hair-like wadding started dangling from the tailpipe of the rear exhaust box .. and I removed them .. also corroded metal inner baffles. This went on for several weeks, like a magician's hat spewing scarves .. then it stopped, presumably all released. The poor running and fuel consumption improved a little, but not back to normal. I had the exhaust system checked and it was externally sound and apparently normal flow pressure .. Kwik-Fit said leave it. It would surprise me if it was still blocked, but how can I check? Is it really necessary to change the expensive exhaust, even though I know the back box is now "empty" ?

Then I discovered the burst SAI air hose. Could this have been caused by back pressure during the period when the exhaust wadding was obstructing the flow? Crimping the air hose leak has helped, but not totally resolved the fuel consumption. Also, if this air system only affects the first 30 seconds of running, would the burst hose really explain the poor fuel consumption?

I will check those rubber couplings either side of the engine in daylight, thank you.

[Entwood]

Looks like you are correct about the blocked exhaust connection. The poor running and high fuel consumption started immediately after MOT a few weeks ago. Enormous lengths of hair-like wadding started dangling from the tailpipe of the rear exhaust box .. and I removed them .. also corroded metal inner baffles. This went on for several weeks, like a magician's hat spewing scarves .. then it stopped, presumably all released. The poor running and fuel consumption improved a little, but not back to normal. I had the exhaust system checked and it was externally sound and apparently normal flow pressure .. Kwik-Fit said leave it. It would surprise me if it was still blocked, but how can I check? Is it really necessary to change the expensive exhaust, even though I know the back box is now "empty" ?

Then I discovered the burst SAI air hose. Could this have been caused by back pressure during the period when the exhaust wadding was obstructing the flow? Crimping the air hose leak has helped, but not totally resolved the fuel consumption. Also, if this air system only affects the first 30 seconds of running, would the burst hose really explain the poor fuel consumption?

I will check those rubber couplings either side of the engine in daylight, thank you.

I wouldn't trust those folks with my in-laws car let alone mine. The wadding issue means the back box is breaking up internally, it may well still have a restriction when at a high flow rate (high power), even if seems to be ok at low power. The SAI pipe issue is well known if the exhaust is restricted.

IMHO you have 2 jobs ... new SAI pipery and new exhaust.. at least a new back box.

The SAI pump only works for a few seconds.. but the vaccuum is in the pipe at all times .. so you have a vac leak which gives poor performance and bad economy

[philhoward]

Kwik Fit said it was fine?

"My exhaust has spat all of its innards out - does it need a new one?"

"No sir - unless its due for an MoT, then it also needs 4 shock absorbers and new brakes all round..."

Sorry - but i'd rather trust Master Fit than KwikFit.

[Welung666]

The rough running and higher consumption could be from when your back box was spewing it's innerds and backing the whole system up then you'd get a back up in the cats that could throw the lambda's out.

[2am Omega]

Certainly the exhaust back box has already broken up internally .. wadding and baffles .. hence "empty". Looks like it must be replaced, even though it seems fine externally.

Regarding the burst SAI pipe, hose repair tape was suggested earlier. Would this be adequate? Or is replacement essential? and is this an easy DIY job with a length of standard hose, or a necessary garage job with a proprietary replacement part?

Thanks to everyone for the advice.

[philhoward]

On mine )2.0) the rubber pipe is only thin, non-reinforced hose so a repair tape will suffice until you can get replacement pipework (probably better to do the lot) - there's a few breakers on here who will probably be able to help you out for not a lot of cash.

[PaulW]

Well if the hose is damaged or has gone brittle due to the blowback from the exhaust system, your best solution is ordering a new piece from VX.

Part number is 90500057
Cost is about £5 + VAT each

There should be 1 each side, the drivers side is positioned under the coolant hose, passenger side is similar location obviously.

Thing with your exhaust, it can either just be the backbox, either of the center boxes, or a combination of all 3...  You will only know what it is when you get to taking it all apart.

[2am Omega]

The SAI hose has not become brittle. On the contrary it is so soft and tacky that it can be temporarily sealed just by squeezing and crimping. I will try to upload the engine bay photo which will show this. Currently it has the addition of a bulldog clip to hold it closed.

So I should replace the SAI hoses on BOTH sides of the "flying saucer" valve. Are there any others important to be replaced at the same time?

I note the comment about "a back up in the cats that could throw the lambda's out". Could this cause permanent damage to these sensors? or will this resolve itself when the exhaust and SAI pipe vacuum are replaced?

[PaulW]

It can cause damage to the cats as they can overheat.  It's worth getting the exhaust sorted as soon as you can really, try not to drive it and if you do don't labour the engine too much.

If the hose is fine, just clip it all back into place when sorted.  No need to replace both sides if 1 side is gone, you can just do 1 side, both, or none  They are the only ones which can go to be honest.

One warning though, if its blowing on the Drivers side, get some tinfoil wrapped around the coolant hose.  It's not uncommon for the exhaust gasses to 'burn' the coolant hose causing it to burst a hole in it.  Had to replace the one on my MV6 due to this exact issue