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Disco/Defender downpipe change


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In answer to my own question of, is a defender 300TDi downpipe (ESR2297) a direct replacement for a discovery 300TDi cat downpipe (ESR3495)? I can now confirm that it is, as I have today fitted one to my truck.

I thought I would try to do a small write up of this relatively simple task:-

Very few tools are required to change the down pipe just a couple of 17mm spanners, a 13mm spanner and a 15mm socket and ratchet and a couple of long extension bars.

Some WD40 or Plus gas to soak the nuts and bolts to help them undo is also probably a good idea.


Step 1:- Working under the truck using the 13mm spanner loosen the two nuts on the downpipe to centre section clamp.


Step 2:- Again from under the truck using the 15mm socket, extensions and ratchet undo the 3 nuts holding the downpipe to the manifold. The photo only shows one of the nuts and is taken from above.


Step 3:- Working under the truck undo the top bolt (using the 17mm spanners) that goes through the chassis and retains the crossmember. This bolt also holds a bracket for an exhaust hanger. I found it was not necessary to completely remove the bolt as the bracket is slotted and when rotated through 90 degrees will slide off the bolt. (Sorry no pics as the heavens opened.)

Step 4:- Finally remove the nuts from the centre section clamp freeing the downpipe. As the downpipe comes away from the manifold carefully retrieve the thin metal gasket that goes between it and the manifold and save it for later. The next bit is a little tricky as it involves pushing the complete down pipe forward carefully until the backend clears the crossmember at which point you need to feed the backend under the cross member as you pull the downpipe towards the back of the truck until it clears the axle.

The old and the new.



Step 1:- Refitting is pretty much the reverse of the removal procedure. I found that by laying the vertical section of the downpipe over at 90 degrees to its normal position allowed it to slide up over the axle easier and then having pushed over the top of the crossmember it was possible to twist it up in to its normal position. As the down pipe is pushed up onto the manifold studs remember to replace the thin metal gasket between the 2 components. Install the nuts on each stud and then tighten to the correct torque figure.

Step 2:- next line up the centre section to downpipe clamp and tighten the 2 nuts up evenly to the correct torque figure.

That’s the downpipe refitted, all that is left is to tighten up the crossmember bolt. It should be noted that due to the fact that the defender downpipe doesn’t have a flexi section it doesn’t have a hanger bracket on it, meaning the hanger bracket originally fitted to the chassis does not need to be refitted. I guess if you are fitting a downpipe with a flexi section in it you would need to re-install the bracket and hanger rubber on the chassis.



I cannot comment as to whether or not removing the cat has made any difference to the performance as I have yet to drive it as I haven’t fixed a slight brake issue yet.

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