Downpipe install 335xi - subframe method

[mattsfeir]

I see there's a DIY here for RWD downpipe install, but here's one for the AWD xi.

Thanks to Matt @ Camber Toe for detailing this method.

Switched back to stock downpipes and exhaust for an upcoming emissions test, here are some pics and instructions to help those thinking of doing this themselves. Going from stock downpipes to aftermarket will be the same process.


Took me about 4.5 hours and that included switching the full exhaust, much faster doing it the 2nd time.


Starting out. This was done solo with jackstands and hand tools. Jacked up the front first, then the rear, then put a few 2x4's on the jack and jacked up the front even higher so I'd have more space underneath while laying on the creeper.



Drop the plastic pan under the transmission, metal pan under engine, plus (not pictured) the plastic front belly pan and small plastic pans behind the front wheels so you can get at all 6 subframe bolts.



Front O2 sensors labeled F and R for Front turbo and Rear turbo so they don't get switched.



Rear O2 sensors labeled F2 and R2 so they don't get switched.



Disconnect the midpipes from the downpipes. Note how close the subframe is to the downpipes. I did this first so I'd have more room to reach the rear O2 sensors. Go ahead and remove all 4 O2 sensors and then loosen the v band clamps holding the downpipes to the turbos. I left the clamps hanging on the turbos with the bolts removed. Now the downpipes are loose, but won't come out as the subframe and front halfshaft are in the way.



Jacks used to drop the subframe. Black jack with 2x4's is supporting the engine while the red jack is used to lower the subframe. There are 3 subframe bolts per side, 18mm head in the pic also, the rear bolt is the short one.



Passenger side motor mount, blue arrow is a motor mount bolt, already removed, and the red arrow is a subframe bolt.
First remove passenger side motor mount bolts, then support passenger side subframe with jack and remove passenger side subframe bolts and lower subframe with jack. Then do the same to the driver side.



Driver's side motor mount, the blue arrows are the bolts for the motor mount, take these out to disconnect the motor from the subframe. The red arrow is one of the subframe bolts.



Here are 2 of the motor mount bolts. They are a reverse torx style and the socket I used was labeled E12. The first time I did this, I used a regular 6pt socket, then got a torx and reverse torx set after.



Once the subframe is dropped, it will hang by the suspension and only the jack supporting the engine is needed. Now you can see all the extra clearance between the downpipes and the subframe. One downpipe has already been removed. The red arrow shows one of the rear subframe bolt holes.



Downpipes are out.



Coated AR downpipes after 1 year on a daily driver in Denver. They look great other than scratches from install/uninstall.

[Sticky]

Great, great thread! Well done and thanks for adding info for the Xi's.

#335xi

[Lowbeam]

Anyone in denver metro area able to help with a downpipe install? Will be compensated!

[boosted-M]

Great write up!

[deadmn1337]

Great Diy! Just did this install this weekend.

[Sticky]

Anyone in denver metro area able to help with a downpipe install? Will be compensated!

Just go to AR Design... @ar design

[ar design]

[TLO03]

coating has held up well...

[Lowbeam]

Just figured I'd learn how to do it and possibly save some cash while I'm at it.

[Sticky]

Just figured I'd learn how to do it and possibly save some cash while I'm at it.

Understood but best to get it done right the first the time. Either way, however you want to approach it is up to you.

[Marz]

downpipes on jackstands. calls for a round of applause .

I dunno about trying the downpipe install. I've seen pro mechanics take anywhere from 3-5 hours to install. They can be tricky to say the least. good luck.

great job OP

[deadmn1337]

The actual install isn't hard it just take a good amount of time to align them properly. With the subframe dropped there is plenty of room to work with.

[Lowbeam]

If anyone is interested please Inbox me.

[ajsalida]

The actual install isn't hard it just take a good amount of time to align them properly. With the subframe dropped there is plenty of room to work with.

The harbor freight engine support/hoist makes it a bit easier, you don't have to have another jack under the engine. Only like 60 bucks. This is the one that goes across the fenders on top. I used an old e36 tow hook/loop in the engine to hook it up to. First time I did the Xi DP's dropped subframe with a jack under the engine, second time I just used the jack to move it slightly up and let the hoist take the load, then removed the jack. Lot more room to move under there.

[Itsbrokeagain]

Lol i remember when I wrote that up. Very long time ago


Ah how time flies. Ive spent anywhere from 2 hours to 6 on xi downpipes. Some companies fit very well, some not so much. You would think 2.5" dps would fit easier but nothing can fix improper welding/wrong bung location.

I used to loathe doing XI pipes. Until I did an E60 535, I will now gladly do 335s all day long LOL

[BMWhips]

Awesome info! this will help me save time! thank you!

[N54oreign]

Great info!

[Itsbrokeagain]

I can't believe people are still following this lol

[TEC]

It was a good write up.
Good stuff will stand the test of time.

[Sticky]

I can't believe people are still following this lol

Why?

[Boosted_hoodlum]

So I did this Saturday and today I have a coolant leak any idea what hose I could of damaged by lowering the subframe? Thanks

[Sticky]

So I did this Saturday and today I have a coolant leak any idea what hose I could of damaged by lowering the subframe? Thanks

@alex@ABRhouston @Itsbrokeagain

[Itsbrokeagain]

So I did this Saturday and today I have a coolant leak any idea what hose I could of damaged by lowering the subframe? Thanks

can be one of several. the majority of the hoses are down in that area, you probably kinked or pulled one a little tight with the subframe down.

or your waterpump just decided to crack its plastic cover like most of them do