300E With a FAST speedo!

[admin]

OK, my daughter just got home and said she hit 45 on our street - the speedo is reading about TWICE the correct speed. I've heard about the opposite problem before, but never this one. Anyone have any ideas?

[Robby Ackerman]

Yes, tell her to lift her right foot. :)

My daughter has a similar same problem though her speedo reads 80 or higher.

[Dean Yelenik]

Is it off that much - i.e. double, at all speeds? When a speedo has been taken apart the needle could be put back on the wrong position - causing the speed to off by a set amount across the range. If it hasn't been taken apart I don't what could have gone wrong - but it sounds like you'll need a speedo shop to recalibrate it.

[bill streep]

Well, I should have known better - apparently I was logged on as "administrator" - nice to know after all these years of messing with this forum software I can still screw it up!

Anyway, it's my 300E - and no, it hasn't been touched. Runs about twice normal at any speed. I'm going to drive it today for a while and see if I can figure anything else out...

Thanks!

[DIAZ-CANEJA]

If your speedo is electronic, looks like a worn resistor, if the speedo is mechanic, dust between the friction disks can cause a problem like yours, or the retaining spring broken.

[jtripp]

You might need a new impulse coupling on the transmission. Maybe you can clean it and retry it before replacing it. If your speed is doubled you would be getting 2 pulses per revolution. There may be a problem in the electronics.

[bill streep]

Just got back from driving it. Started out just fine. As I left my last appointment and got on the freeway, it was definately fast. Twice as fast as it should be.

[bill streep]

Well, since I didn't get any answers, I thought I'd post the solution:

At some point in time, someone greased the back of the speedo where the cable goes in. After time, the grease ran down the cable and into the sensor, screwing up the sensor. Had it cleaned and it works fine. I understand this isn't an uncommon problem.

[Robby Ackerman]

Bill

I hope you got plenty of those three-digit photos before you degreased your speedo. :)

[pfphipps]

It has been quite a while since you posted but I bought a new 93 300E in late 1992 that developed the same problem after about a year and 10,000 miles. It did not always do it and it seemed worse when it was hot outside. Odometer was correct, only the speedometer was in error. When my wife first told me, I laughed at her but I was convinced when she took me out to show me.

New speedometer was the fix under warranty. (Actually, the dealer ordered the wrong part about three times before they finally got the right one.)