Seized in post Cat exhaust lambda sensor

[colb]

Having killed the sensor drifting the corroded exhaust downpipe studs out to replace with a set of stainless bolts and nuts efforts to get the sensor out using a selection of cut away lambda sockets which only slipped off the flats and rounded them off has been a right pain.
Just bought a set of Extractor Sockets that have spiral flutes inside that bite into the flats the more force you apply to undo the sensor. I already had a smaller set but the sensors flats are 22mm my set only went up to 19mm. Got mine from Amazon but they are available on ebay at a cheaper price. Will have to cut off the top of the duff sensor to get the Extractor socket on its flats but as its dead thats not going to be a problem.
Should be able to get a breaker bar on it to exert a good amount of force on it to get it turning. Space is tight but hopeful I can get enough swing to start it moving. Will apply some heat from my Map Gas Blowlamp as well which should assist. Will report back on how these extractors perform.

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[t-tony]

Going on previous experiences if you're applying heat you will need it absolutely red hot and keep heating it until the last thread. I used to use the split type of socket but I put a heavy duty jubilee clip around the "split" part of the socket next to the pipe so it couldn't spread.

Tony.

 

[colb]

Tried the jubilee clip trick but didn't make any difference it still slipped even with the pipe red hot got high hopes the extractor will defeat it

 

[t-tony]

Yep didn't work every time Col. I always found that if you cracked it loose it would screw straight out or fight you all the way. No in-between. Good luck with it mate.

Tony.

 

[Peter1450]

Morning Colb Seeing as you’ve already defeated the front studs would it not be easier to drop the rest of the system for better access?

 

[colb]

Considered dropping the system as a last resort and was getting very near to doing that but the use of the reciprocating saw on the top flange proved successful in getting a slot cut in to release the tension that was holding the stud in at the splined end.
With a fair bit of heat from the Map Gas Blowlamp on the now slotted end it came out with two taps from the air hammer.
Looking at the pictures A and C are easy to get a full size angle grinder on with a thin metal cutting disc to put a slot across the flange.
B and D are the limited access ones and even with the exhaust dropped there is not enough room to get the angle grinder in to put the slots in the Dremmel with a small cutting disc in was not man enough to cut the slots and access was still tight. Resorted to the saw blade and that managed it ok then heat and the air hammer got the stud(s) out.
Best have a pair of gaskets on hand and would suggest getting them from BMW as the ebay ones I got were not a good fit, the holes did not line up with the flange holes very well and required trimming the holes using a small grindstone in my cordless drill to get a good fit. Worth noting that bolt B is reverse fitted, thats done to get it through the flanges as the exhaust sensor close by prevents the bolt from being inserted from the top like the others. Using a combination of sockets, ratchet ring spanner and open end spanner afforded access to the bolt heads and nuts to get them done up.
Dropping the system to get at the seized exhaust sensor won't give me anymore access to it quite hopeful that some new extractor sockets I have bought will provide enough bite on the rounded off flats to break it free, will have to cut the top of the sensor off to get the socket onto it but as the sensor is dead and scrap thats not a problem, should be able to get the saw blade onto it.

 

[Peter1450]

Your flanges look to be better than the remains of ours. What Z is this on Colb? Wife’s 3.0 has a 3 hole bracket that bolts between the two flanges, yours appears to be just two?
Also has a double clamp just aft of the flanges that’s not supported by anything which seems odd as in most real oem diagram’s there always seems to be something that bolts to the chassis for extra support, the auto which we have seems to differ from the manual?
Will try and get a pic later if it stops raining!

 

[colb]

Mine is a 2003 2.5 Z4
Looking at oem depending on what year your 3.0l Z3 is it had different style exhausts for Manual and Automatics, one with a double pipe from the flanges to a single Cat for the Manual cars or a twin pipe to separate Cats for the Automatics. Make sure you search OEM site using your Vin number to see which system it left the factory with. Not withstanding the exhaust may have been changed in its life using the alternative fitting?
I looked at a Real Oem here using a 2001 car https://www.realoem.com/bmw/enUS/partgrp?id=CN53-USA-06-2001-Z3-BMW-Z3_30i&mg=18
The diagrams show the support brackets used in both systems, its not unusual to find the one near the gearbox is missing, usually fallen off during the cars life and not replaced, have found this on the smaller engined cars.
If your flanges are not recoverable then an exhaust builder not the usual exhaust garages like Quick Fit etc may be able to put new flanges on your exhaust either the downpipe side or the exhaust system side. At the end of the day might be time to have a custom built stainless system put on it especially if its a long term keeper.

 

[Peter1450]

Cheers Colb That’s the system on my wife’s 3.0, ordered 12 from the diagram but it’s not like the picture. Mine is just an upper and lower clamp that clamps both pipes together but no provision for any type of bracket for extra support.
Stainless aftermarket exhaust would be my last resort, had one on her previous 2.8 didn’t like the way it resonated.

 

[t-tony]

Bracket that the support attaches to is likely on the gearbox section of RealOEM

Tony.

 

[colb]

Would have thought item 12 would be bolted to the car at the opposite end to the pipe clamp end, it has to be supported otherwise it wouldn't be doing anything. Just noticed @ t-tony suggested looking at the gearbox diagram, support may be shown on there that item 12 is bolted to for support, maybe missing off yours?

 

[t-tony]

It should be bolted to the gearbox so that when the engine/gearbox moves under acceleration the exhaust moves too as one.
Numbers 6 or 7 in the second drawing.

Tony.

 

[colb]

Can't find the fixing for that bracket, not shown on the gearbox diagrams in oem diagrams or anywhere else didn't find any pictures doing a Google search either, at a loss to know where to look other than on another car. Next time I get the chance to look at the underside of a 3.0l will take a look and a photo. Preety sure its going to be a bracket bolted to the underside of the gearbox that item 12 gets bolted to.

 

[colb]

Just seen @t-tony responded pointing to diagram 2, I assumed as he bought item 12 from the other diagram for Auto Box which dosn't show the gearbox end of the support.

 

[colb]

Another afternoon spent on getting the duff post cat sensor out, had a go at sawing the top of the sensor off with my reciprocating saw, that managed to put a slot a quarter of the way through it then no more despite changing saw blades twice, no room for an angle grinder to get at it so had a think and decided to use the air hammer with a flat chisel in it. Put the chisel in the slot the saw left and pulled the trigger. After a few blows it gave up and parted itself from the hex fitting at the base. Now it was preety rounded off from all the previous attempts to get it out so hammered the new 22mm Extractor socket onto what was left of the Hex and got a long breaker bar on it, just enough room to get the breaker bar in. A good pull on the breaker bar and low and behold I hear a crack reposition the breaker bar and give it another pull and yes the hex is unscrewing. Quick douse of penitrating spray and continue unscrewing it, well impressed with the bite these extractor sockets exert on a rounded off hex. At last its out, ran a thread chaser down the hole to ensure the threads were clean then screwed the replacement sensor in by hand followed by using a good fitting 7/16 open end spanner between the two exhaust pipes to complete the install and finally tigten it home. Ran the sensor wire up to the top of the engine and connected it to its plug under the beauty cover.
Cleared up the array of tools I had amassed and started the car, quick check underneath for any leaks then broke the Launch Scanner out to monitor the sensors. Clean bill of health all sensors performing as they should what a relief.
Pictures show air hammer chisel and its victim, dead Sensor remains and new Sensor installed.
I would advise owners to bolster their toolbox's with a set of those Extractor Sockets for times like this they are far better than the standard cut-away Lambda Sensor sockets which slip and round off the Hex, the only downside being you have to cut the old sensor down to get them on, not seen any deep extractor sockets on offer so far. Be warned hacksaws powered or not struggle to cut through these sensors, air hammer and chisel is the way to go.

 

[Peter1450]

So this is my exhaust clamp set up , not great pics but there’s a triple holed bracket that clamps the flanges to one another, then just behind the upper and lower clamps on the exhaust. As Tony eludes to there is a holed flange you can make out on the gearbox in the pic adjacent to the clamps but there’s never been anything there since we’ve had the car!

 

[colb]

Looks secure enough nice bolts on the flange joints