On a 91 850i with 75,000 miles should the o2 sensors be replaced? I know they have not been replaced yet but I have not had any problems with the car. Maybe preventative maintenance?

I'd replace them. In fact, I'd replace pretty much everything tune-up wise: IM gaskets, PCV valve (whatever they're called on the V12), sparks, upper front bushings, entire lower arms+bushings, caps/rotors, hoses, fuel filter, etc...

Being a '91 and having 75k, all of these things will need attention sooner than later. Your car will love you for it! :D

I have already replaced air filters, fuel filter, added ss brake lines, fuel hoses, flushed the transmission, spark plugs, and a few other things. What is a PCV valve and are the intake manifold gaskets really important?

The IM gaskets are important. The 8 is very sensitive to vacuum leaks. I had planned upon replacing mine further down the road but after a couple of months of owning my 8, the car shut down and went into Trans-Fail-Safe mode (I limped home in the highest gear alloted by the OBC ---> 2nd gear). The V12 crankcase is supposed to have a slight vaccum so it has a VCV, which is essentially a PCV but since the V12 has a little vacuum action going, the valve is called a Volume Control Valve instead of Pressure Control Valve (PCV). The PCV is made out of cheap plastic. It is prone to wear and ideally should be replaced when replacing the IM gaskets since it is accessible once the IM is removed from the car. Plus it's inexpensive :D

The VCV is actually mounted right behind the DK Motors on the Intake Runners themselves.

should I use gault to get these parts?

BTW, new O2 sensors along with the stuff above that I replaced instantly boosted performance and gave me 2-3 more MPG City. Makes sense, but the difference was very noticeable.

I'd also replace the engine mounts, too. And the V12 likes clean DK Motors (easily accessible like the VCV).

Ahh yes, like TxGR8White mentioned, the V12 has it right behind the DKs.

Gault is king for OEM parts. I use Autohauz.az for everything else.

PS. I didn't mean to make a list of stuff to do. But bro, your car will run as smooth as glass if you give her maximum love! Cheers :beermugdr

who can clean the dk motors

Sick Puppy Motorwerks has been known to clean a DK or two....

I won't be able to get to it until I get my car back from getting a new headliner but when I do can I just pm you and send them to you or how does that work

TxGR8White (http://forums.bimmerforums.com/forum/member.php?u=154902) everytime im reading your posts the excited dog gets my attention, and i have to tell myself if not your picture...lol

are there 4 intake manifold gaskets that should be replaced?

Yes 2x part No. 10+11 http://bmwfans.info/original/E31/Cou/850Ci-M70/ECE/L/A/1992/06/mg-11/ill-11_0949/

But you can use "Hylomar" too, if they are not broken!

Yes 2x part No. 10+11 http://bmwfans.info/original/E31/Cou/850Ci-M70/ECE/L/A/1992/06/mg-11/ill-11_0949/

But you can use "Hylomar" too, if they are not broken!


Oh NO!!! The HYLOMAR debacle is back....


:)

Yes 2x part No. 10+11 http://bmwfans.info/original/E31/Cou/850Ci-M70/ECE/L/A/1992/06/mg-11/ill-11_0949/

But you can use "Hylomar" too, if they are not broken!

what really shortens the life of the gasket is a missing rubber mounting.
it is supposed to take stress from the intake, but is missing many times.
have a look at yours and do yourself a favor and replace them if they are gone.
it's #18 in that pic
http://static.bmwfans.info/images/epc/NDUzX3A=.png (http://bmwfans.info/original/E31/Cou/850Ci-M70/ECE/L/A/1992/06/mg-11/ill-11_0949/)

The price of owning a 8 is not cheap. But i just love this car too much.

Oh NO!!! The HYLOMAR debacle is back....


:)What would you recommend for reusing on these expensive gaskets if they appear good? Thanks!

I personally have used, and will continue to use a product called REINZOSIL. It is a High Temp Silicone sealer made by Victor Reinz Company of Germany that Mercedes, Audi, VW,and Porsche use on their engines.
You need to make sure that the gaskets are indeed in good enough shape to reuse.
The tube is about $8 and there is enough to do 3-4 engines worth.

I Appreciate it, Throughout the whole Hyl--ar incident, I didn't know if it was good or bad, Too funny to pay attention to the real details, Thanks!

I personally have used, and will continue to use a product called REINZOSIL. It is a High Temp Silicone sealer made by Victor Reinz Company of Germany that Mercedes, Audi, VW,and Porsche use on their engines.
You need to make sure that the gaskets are indeed in good enough shape to reuse.
The tube is about $8 and there is enough to do 3-4 engines worth.


Can you pick this up at a local dealer, auto parts store, or does it need to be special ordered from someplace?

I got mine locally at a place called Foreign Car Parts. I would imagine any parts place that carries things for non-US automobiles should have access to it.