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[ajr3773]

Hi there, needing some help identifying a pipe on a 3.0ltr MV6 and could somebody also tell me what it does?

As you lift the bonnet and look into the engine just below the left hand bank of cylinders 5 3 1 there is quite a thick metal water pipe and directly below that there is a thinner metal pipe that comes right round the front of the engine but is pieced together as it comes round the corner of the engine and gets thicker behind the two plastic pipes off the plenum and up to a valve near the top of the radiator.

As the pipe comes around the front of the engine there is about a 3 inch piece of black flexible pipe that pieces the two metal pipes together on the left hand corner of the engine, so my question to all you specialists out there is that this black flexible pipe has blown a hole in it on mine causing what can only be described as leaking exhaust gases. the entire pipe gets exceptionally hot meaning that i require some sort of specialist heat resistant replacement but i have no idea what the pipe is or what its function is or what i need to ask for as a replacement as i know that flexible rubber hose aint gonna do the job.

[Andy B]

Sounds like it's something to do with the secondary air injection.
A picture paints a 1000 words. 

[geoffr70]

Sounds like the 2ndary air injection. I think it injects air to the exhaust manifolds under cold start conditions to increase efficiency of cats by heating them up more quickly? Or so I've heard.

The same thing happened to me. I thought it was the manifold gasket and changed it - doh! When the pipe burnt through again i replaced it with copper.

The cause of this might be the internals of the exhaust collapsing causing back pressure and the exhaust gases coming up through the SAI pipes which they're not meant to do. I think there is also meant to be non return valves in the SAI pipe but not sure where or how many, so these could have failed aswell.

The SAI can be removed, but you would have to eal the holes in the exhaust manifolds.

I think I've got all that right!  :-?

[ajr3773]

Thanks gents for the advice.
As it appears to be a secondary air injection pipe am i right in thinking that this will get very hot and if so what type of hose do i require to replace the 2" rubber connection that has split on mine?

[geoffr70]

It's only meant to get as hot as the ambient air temp in engine bay. I used a new piece of hose on mine but that burnt through half an hour after re-assembling it all after a manifold gasket change -  I wasn't impressed.

Yours will burn through again most likely. As said i replaced mine with copper and compression fittings - not ideal, but I know my exhaust is ok, so I'm assuming the non return valve must be shot. I just haven't got round to removing the whole thing yet.

[Osprey]

There is a non-return valve in the fat metal part that stops hot exhaust gases flowing back up to the black flexible pipe.  As geoffr70 says, it sounds like this valve has failed.  Once replaced, the flexible hose won’t get too hot and the standard Vx materials will be fine. 

This parts list and parts diagram might help. 

[I_want_an_Omega]

Great diagram ........... 

It sounds like the one-way valve has failed - but its probably easier to remove the whole system. Basically just rip out the mechanicals and make sure that you:

1) Remove the fuse feeding the system
2) Keep the solenoid in place - that way the ECU wont throw up a fault light. Just cable tie it up somewhere nearby.
3) Blank off the pipes. The easiest way is to keep the rubber couplers in place and use a bit of 15mm copper pipe with an end stop soldered in place. Held on with a jubilee clip. Push it into the rubber as far as possible.

Job done. 

[ajr3773]

Thanks for the help guys but ive read somewhere that this can happen due to a blocked CAT causing back pressure back into the system. Is this correct and if it was caused by a blocked CAT how would i be able to check, would the CAT need replacing and would this throw up a EML??

The reason i ask is because ive had a misfire on the car for 4 days which is now cured having replaced the DIS, leads and plugs but im just wondering if the CAT has been blocked as a result of the misfire.


Also in i remove the non return valve do i need to blank off 2 hoses just ive no idea where the other hose is ?

Does anyone have a part number for the non return valve and any idea on cost to replace this?

And finally if i remove the non return valve which fuse do i need to remove and from where and will car run okay?

Many thanks in advance.

[rickmv6]

on my old elite one of my cats had blocked which caused back pressure that melted the rubber pipe. i changed the rubber pipe for a new one which lasted 2 mins. only way i found out it was cat was to disconnect middle boxes from where they connnect to cat   you could feel a big difference in the air flow coming out which tells u which one had gone  might not be same but thats what i did.

[I_want_an_Omega]

Thanks for the help guys but ive read somewhere that this can happen due to a blocked CAT causing back pressure back into the system. Is this correct and if it was caused by a blocked CAT how would i be able to check, would the CAT need replacing and would this throw up a EML??

The reason i ask is because ive had a misfire on the car for 4 days which is now cured having replaced the DIS, leads and plugs but im just wondering if the CAT has been blocked as a result of the misfire.


Also in i remove the non return valve do i need to blank off 2 hoses just ive no idea where the other hose is ?Does anyone have a part number for the non return valve and any idea on cost to replace this?

And finally if i remove the non return valve which fuse do i need to remove and from where and will car run okay?

Many thanks in advance.

There are the 2 rubber couplers that connect into the exhaust manifolds - I did the same treatment for both of these with the 15mm pipes blanked off. The inlet pipework can just be cut off - if the fuse for the pump is pulled then there will be no air pumped.

[ajr3773]

Thanks for the help guys but ive read somewhere that this can happen due to a blocked CAT causing back pressure back into the system. Is this correct and if it was caused by a blocked CAT how would i be able to check, would the CAT need replacing and would this throw up a EML??

The reason i ask is because ive had a misfire on the car for 4 days which is now cured having replaced the DIS, leads and plugs but im just wondering if the CAT has been blocked as a result of the misfire.


Also in i remove the non return valve do i need to blank off 2 hoses just ive no idea where the other hose is ?Does anyone have a part number for the non return valve and any idea on cost to replace this?

And finally if i remove the non return valve which fuse do i need to remove and from where and will car run okay?

Many thanks in advance.

There are the 2 rubber couplers that connect into the exhaust manifolds - I did the same treatment for both of these with the 15mm pipes blanked off. The inlet pipework can just be cut off - if the fuse for the pump is pulled then there will be no air pumped.

would i be right in thinking there is one on either side of the manifolds

[I_want_an_Omega]

Thanks for the help guys but ive read somewhere that this can happen due to a blocked CAT causing back pressure back into the system. Is this correct and if it was caused by a blocked CAT how would i be able to check, would the CAT need replacing and would this throw up a EML??

The reason i ask is because ive had a misfire on the car for 4 days which is now cured having replaced the DIS, leads and plugs but im just wondering if the CAT has been blocked as a result of the misfire.


Also in i remove the non return valve do i need to blank off 2 hoses just ive no idea where the other hose is ?Does anyone have a part number for the non return valve and any idea on cost to replace this?

And finally if i remove the non return valve which fuse do i need to remove and from where and will car run okay?

Many thanks in advance.

There are the 2 rubber couplers that connect into the exhaust manifolds - I did the same treatment for both of these with the 15mm pipes blanked off. The inlet pipework can just be cut off - if the fuse for the pump is pulled then there will be no air pumped.

would i be right in thinking there is one on either side of the manifolds

Yes, just look down and you will see them - they are on the same level as each other. They are held on with hose clips. The system needs to be removed to do a cambelt change on pre-DRW cars - so plenty of info available.