New member checking in with speedo question

[david55838]

Hello everyone,

I'm new to this forum and wanted to say hello!  My name is David, and I recently found a low mileage (112k) 318is.  It's my second one - I actually started autocrossing with one years ago until I got the horsepower bug and went to an E28 M5.

I missed the lightness of the 318, so when this one became available, I grabbed it.  It's developed a wierd issue with the speedo, and I'm wondering if it's vacuum related.  When I let off the gas, the speedo swings down to 0, or close.  It seems to move together with the mpg needle.

Anyone have anything similar?
Cheers,
David

[FL318is]

SI battery?

[gearheadE30]

^^ +1

[david55838]

SI battery?

Sorry, newbie here.  What is the SI battery referring to?

Thanks!

[91318isguy]

The speedo is electrically powered (please correct me if I'm wrong). The first one I got, the speedo didn't work at all. I got a new speed sensor (in the differential case. If lying on your belly looking at the differential, its about half-way down on the right side. Two screws and reconnecting the wires to the new assembly and its installed) and it corrected the issue. It's around 60 from BMW, but you can do the work yourself so that will save you $90/hr in labor.

Welcome the the club by the way. I have no idea what the SI battery is either. So I'll look back to see if that question has been answered.

[FL318is]

There was a recent issue of Roundel that did a DIY on the battery.  Or try bimmerdiy.com

[david55838]

The speedo is electrically powered (please correct me if I'm wrong). The first one I got, the speedo didn't work at all. I got a new speed sensor (in the differential case. If lying on your belly looking at the differential, its about half-way down on the right side. Two screws and reconnecting the wires to the new assembly and its installed) and it corrected the issue. It's around 60 from BMW, but you can do the work yourself so that will save you $90/hr in labor.

Welcome the the club by the way. I have no idea what the SI battery is either. So I'll look back to see if that question has been answered.

Thanks!  I noticed that when the speedo swings down to 0 (it now happens even when I AM on the gas), the mpg needle is also at 0.  Plus, it's really intermittent...  Maybe I shouldn't complain - when it's happening, it isn't recording the mileage either!  

[Alpine003]

The speedo is electrically powered (please correct me if I'm wrong). The first one I got, the speedo didn't work at all. I got a new speed sensor (in the differential case. If lying on your belly looking at the differential, its about half-way down on the right side. Two screws and reconnecting the wires to the new assembly and its installed) and it corrected the issue. It's around 60 from BMW, but you can do the work yourself so that will save you $90/hr in labor.

It can just be a matter of corroded or broken off wire in the speed sensor at the diff, especially if it's a snow belt car. I fixed mine in 5 minutes with a couple new wire sections and soldering gun.

[david55838]

I'll get under the car and take a look.  Thanks!