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D2 - Fuel and Exhausts Everything to do with getting fuel into the engine, and fumes back out again

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  #1  
Old 13th June 2020, 03:14 PM
strummagnet strummagnet is offline
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Default Advice needed passenger side exhaust downpipe.

Hi All,

Newbie advice required. Currently removed the nearside manifold (bit of a PITA) but have left the downpipe in situ. Yes I have probably attacked this arse about face but it seemed logical to me at the time . I found that there must have been a previous removal and replacement as the gasket is split and some seal has been applied. All removed, cleaned and a new gasket ordered. That should alleviate the blow from the exhaust.

Now being the curious type I thought I would send my camera into the downpipe to have a look at the CAT internals. Now I am pretty sure it is a cat as the coding underneath says its a CAT (I googled it) but my camera just went sailing right through - Its empty!! Is that right? Funnily enough I remember a rattling coming from this side of the engine a while back, and then it disappeared....

So, I am assuming the downpipe will need to come out - will help with the F125 later.......

Question:

1: On the downpipe I find two O2 sensors (lucky me) and can locate the connector affixed to the bulkhead for the pre-cat sensor, but Im struggling to locate the rear connector. I am looking at the tight tangled mess of pipework in the way and thinking why did I start this Can anyone advise where to spot the rear sensor connector? I am thinking once found to run some string through connected to the cables, as I have no other method of re-routing upon replacement? Otherwise, is it a good idea just to unbolt the sensors from the exhaust, leave them in the car and take said exhaust away?
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  #2  
Old 13th June 2020, 03:26 PM
MikkiJayne MikkiJayne is offline
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If thats an AMX then yes there should be something in that can. I guess the rattling was the matrix disintegrating and going out of the tailpipe. Does yours have cats under the gearbox too? Someone has hacked about with mine and it just has pipes where the V8 has cats, but I can't remember whether the 2.8 is supposed to have a second set as I don't see them very often. It may have just been someone changing the flexi pipes.

The connectors for the secondary O2 sensors are underneath the trim panel behind the airbox.

Interesting that yours has a heat shield between the cat and gearbox cooling pipes. Mine doesn't have that.
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Old 13th June 2020, 05:10 PM
strummagnet strummagnet is offline
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Quote:
Originally Posted by MikkiJayne View Post
If thats an AMX then yes there should be something in that can. I guess the rattling was the matrix disintegrating and going out of the tailpipe. Does yours have cats under the gearbox too? Someone has hacked about with mine and it just has pipes where the V8 has cats, but I can't remember whether the 2.8 is supposed to have a second set as I don't see them very often. It may have just been someone changing the flexi pipes.

The connectors for the secondary O2 sensors are underneath the trim panel behind the airbox.

Interesting that yours has a heat shield between the cat and gearbox cooling pipes. Mine doesn't have that.
Yes its an AMX engine. so looks like I am going to have to look for a new downpipe. Yes there are cats under the gearbox too. Well they were, they were shot and i had them replaced for aftermarket jobs. Attached Pic. - well i think they are cats - I am still trying to catch up with all this mechanical stuff. last time I played with engines it was powerpacks on Chieftain tanks.

Behind air box, right I will go hunting tomorrow for that.

Many thanks
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Last edited by strummagnet; 13th June 2020 at 05:12 PM.
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Old 13th June 2020, 08:40 PM
MikkiJayne MikkiJayne is offline
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Mm I thought mine should have cats there too. No wonder it just barely passed the MoT emissions test Odd that it has the post-cat sensors after the pre-cats rather than the main ones though.

You may find the remains of your missing cat jammed in the front of the lower one, unless it made its escape before you had that done.
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Old 13th June 2020, 09:41 PM
strummagnet strummagnet is offline
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Originally Posted by MikkiJayne View Post
You may find the remains of your missing cat jammed in the front of the lower one, unless it made its escape before you had that done.
Yep, I thought that. Suppose a vacuum cleaner down the pipe is not a good idea? Otherwise I am dropping the whole system to have a look.

Guessing it is prudent to do the other side as well..
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Old 14th June 2020, 05:00 PM
strummagnet strummagnet is offline
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Quote:
Originally Posted by MikkiJayne View Post

The connectors for the secondary O2 sensors are underneath the trim panel behind the airbox..
Well I found them, logical place to be i guess (note the cynicism). Ok, before I go any further I managed to detach the connectors (so far so good). The route for the post cat sensor seems doable with 4ft arms and tiny hands but the pre-cat connector against the bulkhead is jammed up with more pipework than I have seen on the QE2. Now before I go 'postal' and start taking apart pipework to get this thing to route back through, am I missing something? (part of my brain I am now thinking)

The postal route would involve cutting the cables to the existing sensors, removing downpipe, source new downpipe and source new sensors. I have had a look online and prices vary for the sensors so advice welcome on this course of action as well.

As always, many thanks for your input.
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Old 14th June 2020, 08:54 PM
MikkiJayne MikkiJayne is offline
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It would be a shame to cut the wires to good sensors. You may be able to fish it out from underneath?
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Old 20th November 2020, 04:01 PM
strummagnet strummagnet is offline
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Quote:
Originally Posted by MikkiJayne View Post
It would be a shame to cut the wires to good sensors. You may be able to fish it out from underneath?
Well it has been a while and now working on putting back on this side of the car what I took off. Decided to replace the sensors as the advice is to replace at 160,000KMS. I thought it would be a good idea

Now the original part numbers on the sensors are:
NS Exhaust Lambda Sensor parts:
Pre CAT:078906265M - approx 500mm cable length
Post CAT:078906265R - approx 1600mm cable length

I cannot seem to find an exact match, maybe there is not one anymore? I have been offered BOSCH Equivalent 0258010073 to suit pre and post positions. Can you advise this is the best course of action / component?
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Old 20th November 2020, 07:05 PM
B@fink B@fink is offline
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Interesting seeing the difference between the years. The pre cat sensor is in the same place my ACK engine (bit fiddly to untangle but I managed to winkle it out) but mine is a lower (older) emission standard so I don’t have an after cat sensor. The cat looks quite different, I only have a small resonator box and flexible pipe at the manifold flange and a bigger single cat after the gear box. However for my ten penneth, the U bolts on the cat to main pipe joint are utterly useless at sealing those pipes. They’d been on mine for ages and every few months they’d leak and need new sealant and tightening back up and we’re frankly nothing but a PITA. I replaced them with a constricting band type like originally fitted (significantly more expensive than u bolts) and they make a much better seal. Worth every penny to save me having to crawl underneath with 13mm spanner’s and a tube of exhaust sealant! But looking at your pictures that could be because the down pipe has no supporting mount (like yours has after the cat) and a flexible pipe at the manifold joint so it moves more and pulls the pipe joint.
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Old 20th November 2020, 07:44 PM
MikkiJayne MikkiJayne is offline
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Quote:
Originally Posted by strummagnet View Post
I have been offered BOSCH Equivalent 0258010073 to suit pre and post positions. Can you advise this is the best course of action / component?
That appears to have a 1700mm cable, but looks like a standard 4-pin connector so it ought to work in both positions. You'll just need to tie up the extra 1200mm for the pre-cat sensors.
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