Tips on removing exhaust manifold

[bnam]

I'll be removing the Ansa 4-2-1 manifold on my 74Tii over the next week to install a WB02 sensor. What should I watch for? I'm thinking pre-soak/clean the studs. Are the nuts one time use or can I reuse? It has a later gasket with integrated heat shield with about 7K miles on it (since the rebuild). Can I reuse? What about at the flange between the manifold and center section? What type of gasket goes there?

Byas

[RayC911]

I was just about to post an article on WB02 sensor install too.

[Kpeters]

I'm interested as I have to get into the exhaust manifold too and it looks waaaay rusty.

[roadhog0]

Exhaust studs will typically come out with the bolt. If they come out reinstall with some RTV. You can drop the header out the bottom our out the top, your choice. You will need a new gasket, the gasket is for a 320i if I remeber correctly.

[cvstan]

As someone has mentioned, it is likely that some of the studs will come out of the head rather than have the nuts come off the stud. Some manifolds require that all the nuts be loosened a little at a time while pulling the manifold away from the head rather than removing each nut separately because the tubing blocks the nuts from coming off. Nuts should not be reused. I would not reuse any exhaust gasket. The 318i one-piece gasket is the thing to use since it shields the plugs, wires etc. Can't say much about the manifold to headpipe gasket (triangular?) since my car doesn't have one (custom exhaust). Good luck.

[MrSharky]

Mine was a pain in the arse to take out - I would plan on having replacement studs and nuts handy - from what i know the nuts are supposed to be copper, and should never be reused - you might be able to reuse the studs, though. There is an article on stud installation here - came in handy for me.

http://www.bmw2002faq.com/content/view/19/32/

I forget the size (10 mm?) but you want to a deep socket for some of them - it's tricky to get it over the nut, as I recall. A few of mine were so rusted together (nut to stud) that I ended up cutting it off with a dremel.

Totally do-able, though - hope yours comes out easier than mine!

Matt

[Nathan]

Be careful replacing the studs. The lower studs bottom out and the upper are open into the head (on my E12 tii head). If you screw them in to far there will not be enough thread for the nut once the manifold is replaced. A 320i gasket with integrated heat shield is the way to go. I found it very difficult to back out the 5 heat shield bolts in the manifold and ended up retapping a couple - not worth it. Use the 320 gasket.

Good luck.

[bnam]

The integrated gasket is what I have and it seems in pretty good condition -- was rebuilt 5-7K ago. That's why I had wondered about reusing it.

Do all studs come out? I had ordered 4 new ones and am wondering if I should add 4 more to that order.

I'll need to get a thread chaser.

What I've read is to clean the threads with chaser and brake cleaner. Loctite the upper studs hand tight. Seal with RTV from behind?

I'm assuming it will need hi-temp copper based rtv?

Byas

[cvstan]

I would not put anything in the head that you don't want falling out into the oil. By Murphy's Law it will get sucked into the oil pump pressure relief valve or a main bearing oil hole. So locktite is OK, RTV on the inside end of the studs is asking for trouble. Things should be assembled so that someone else can take it apart in a straightforward way. BTW, newer style heads have all the stud holes blind so oil can't leak out past the stud threads.

[bnam]

Finally I had all the parts needed so removed the exhaust this morning.

The studs that were on there were not the OEM ones and were shorter. But more importantly, they had been installed reversed -- longer end in. As a result, the exhaust was not fully sealed as the nuts hit the unthreaded area before being fully tight.

Here's a comparison with the black BMW studs. The shorter end goes into the block.

The new studs were a tight fit even after cleaning out the holes. I put RTV on the threads of the upper studs.

I took out the exhaust to install this threaded bit to mount a WB02 sensor.

Will finish up tomorrow. The parts diag shows no washers for the exhaust manifold hex nuts. Is that correct?

Byas

[cvstan]

Good thing you caught this. A less observant person might have just left the old studs in there! Not sure about RTV on the upper studs, but they do tend to leak oil unless you have one of the later heads that is cast with blind holes everywhere. As far as I know, there are no washers under the copper nuts. You just need to use new copper-plated nuts. Any kind of lock washer will fail since the heat removes the temper in the washer and they just flatten out and don't lock anything (ask me how I know!). You may know this already, but the one-piece gasket with heat shield from the 318i will work in place of the 4 separate 2002 gaskets and keeps heat off the plug wires etc.

Check the nut tightness once in a while. If they loosen up, the gasket will erode away and you'll have to take it all apart again to fix it.

[jgerock]

Now would be a good time to inspect your distributor housing to see if that is also leaking oil. Makes it much easier to work on while the exhaust is off.

[jimk]

If you are using the nuts with integral washer faces then no other washer required. Those nuts without the integral washers do need a separate washer. Roundies came with washers.

New nuts are not required if usable (not buggered) and if antiseize compound like Felpro C5-A is used. It leaves a copper base when the carrier is driven off with the heat. I've never had seizing with it in 30 years of use on all my exhaust systems.

[bnam]

I used the OEM nuts from Mobile Tradition from the parts book (which shows no washers for my model).

All installed. Was actually able to get a torque wrench on all of them. Though, now that I think of it -- I did not lube before torquing so readings are probably off.

Everything went back on together nicely. Had problems with the WB02 install though. I ended up taking the sensor wire thru the hole in the pedal box cover as I could find no other hole to push it thru. Even tried the hold for the release cable. May just have to drill one.

I initially calibrated the WB02 per instructions on my regular car -- just needs 12V.

When installed it on the '74 and plugged in to cigarette lighter, I kept getting an error E9 (low voltage - check corrosion in socket -- according to the LM02 manual error appendix). So drove to parts store and installed a power outlet. Now no error message, but sensor heats up only to about 65-72% and it just bounces (regardless of throttle/rpm between 7.4 and 22 AFR. Not sure what's going on.

Byas

[BDB]

bnam,

thanks for taking pics, this definitely helps alot as i will be doing the same in the coming weeks.