Hello ladies and gents -

Went out to replace the RPM sensor on my '90 245 with 223k miles last evening. Disconnect from the harness, remove the 10mm bolt, give it a wiggle - no dice. Wiggle with light tug on cable - still good and tight. Frustration starts to set in.

Cro-magnon brain starts to take over - pull harder on cable while wiggling - at least now have cable removed, but sensor still firmly planted on bellhousing. Try screwdriver to lever it out - still no luck. Grab chanel-lock pliers and liquid wrench and heat gun - one last try - but to no avail.

What am I not thinking of? Should I resort to explosives?

Cheers - Zach

PB Blaster over and over for as many days as you can stand it. I'm doing a "proceedure" myself right now, and I'm going on a week of spraying and waiting, praying and waiting, spraying and waiting.

I tend to like to try to actually "tighten" or at least try the bolt in the wrong direction so as to break the rust or oxidation bond and to save the flat surface of the nut/bolt for the actual removal direction.

Next, I've also had real good luck when using an box end, tapping on the nut/bolt at the same time (intermittently spraying PB Blaster or Liquid Wrench) and sometimes, wha la! Keep all wrenches at a strict 90 degree angle so as to reduce the chance of rounding the flat surfaces. Real important!

Good luck to you!

Sincerely,

JBeechcraft

Well - I've made some progress - I've gotten the unit to rotate in the hole, snapped off part of the tab on the sensor that the bolt goes through - but haven't yet full withdrawn the sensor. I hit it with more liquid wrench and the channel-locks this eve... slow but steady.

Try using PBlaster penetrant to loosen the sensor. This seems to be the best. Give it time to work. The mount for the sensor is aluminum and can be broken. To replace it requires removing the transmission and you don't want that!!!

Whoa Now. Take a deep breath, step back and think about it. If you break the mounting you'll be kicking yourself this time tomorrow. Give the penetrating oil time to work and try gently twisting the sensor to break the bond. It will come out.
Good luck
steve

Zach slowly steps away from the car - hands in plain sight.

I'll take another gentle shot at it this evening.