Author Topic: Help, impossible tacho removal (Read 11325 times)

RAY · « **on:** December 12, 2015, 18:38:10 »

just spent all day trying to remove the tacho. I need to remove the centre cluster in order to remove the temp gauge which is not working. I removed the steering wheel, the seat, dropped the wiring loom down and removed the tachometer cable in order to get as much access as possible and have spent the rest of the day on my back with my head up in the footwell tearing my hands and wrists to pieces whilst repeatedly saying dam and blast or words to that effect. The problem is that the knurled nut that holds the securing plate in place for some reason must be the rustiest nut on the car, there seems to be no way to loosen it and have, for the time being given up, having sprayed it with lubricating oil.
Remarkably, i did manage to easily remove the nut and plate securing the centre cluster but of course cannot pull it out very far because of everything still attached to it.
Has anybody actually had to resort to breaking the tacho out from the front and just buying a new one as at the moment i am seeing no other way unless someone has a tiny laser cutting pen that will cut through the bracket.

merrill · « **Reply #1 on:** December 12, 2015, 23:18:56 »

Try to remove the speedo and center cluster entirely to give you room to work
Another option is to bend the tach bracket enough to spin it

Im sure you have tried a small vise grip on the knurled nut

ja17 · « **Reply #2 on:** December 13, 2015, 01:21:50 »

Try a thin leather driving glove to give your fingers more grip on the knurled nut. Do not break the gauge (very expensive). Last resort, I have a special tool I use on the impossible ones. I can attach a pic if the glove option does not work..

Tomnistuff · « **Reply #3 on:** December 13, 2015, 03:46:04 »

I hate those tiny knurled nuts that they use. They are so small that it takes two fingers to tighten them. Access is definitely a problem. I took a plastic bottle cap, trimmed the lower edge to be as tall as the knurled thumb nut, placed the thumb nut in the center of the plastic cap, filled the space around the thumb nut with quick-set epoxy and opened up the nut hole through the plastic cap. Once I got the new larger thumb nut started on the stud, I could torque it tight with just one finger. It now is much easier to tighten them and loosen them.

Tom Kizer

RAY · « **Reply #4 on:** December 13, 2015, 09:07:25 »

Thanks guys, all great ideas, i love this forum.
Tom, your idea is great once i get it undone but i,m wondering if i could use your idea now and epoxy a cap over the knurled nut so i can get hold of it better. Is the knurled nut all part of the threaded shaft or is it a separate nut, i cant see any of the shaft protruding beyond the face of the nut.

ja17, I did try a thin glove yesterday but to no avail. I,m wondering if i use Toms idea and it still doesn't shift would i still be able to use your special tool, i'm intrigued as to what it looks like, the space is so goddam tight and its not like i have big hands either.

Merrill, It looks to me as if the access to the speedo is worse the the tacho, maybe i,m wrong, and i'm only removing the tacho in order to get access behind the centre cluster to remove the oil pressure pipe etc so i can remove the whole cluster, take out the temp gauge and send it away to get it fixed. The bracket looks to be pretty sturdy metal and i guess would be hard to bend in such a restricted area but as a last resort who knows. I did try various grips and pliers but was unable to get a good enough purchase on the nut to have any affect.

RAY · « **Reply #5 on:** December 13, 2015, 10:41:47 »

just another thought, I think i will use the time when my temp gauge is away being repaired to source some ' wing ' nuts with the right threads to replace the knurled ones on the tacho and speedo !

merrill · « **Reply #6 on:** December 13, 2015, 14:58:41 »

I remember sometimes the nut can bind

If you can get an assistant, have that person push the tach into the dash while u push the bracket the other direction and turn the nut
Yes space is limited but this may work

Be sure to push on the tach chrome and not the glass

ja17 · « **Reply #7 on:** December 13, 2015, 15:09:42 »

Rust or a bent threaded stud can make this job miserable. Here is a picture of the tool. You need to find a small one, this size or smaller and cut the handle down. Works great.

Tomnistuff · « **Reply #8 on:** December 13, 2015, 15:40:07 »

Merrill's idea is a really good one, and it usually works for me. The instrument is isolated from the dash with a rubber gasket. Unless the gasket is really age hardened, it will compress, relieving the load on the nut a little bit, making it easier to turn.
I had forgotten that one.
Tom Kizer

RAY · « **Reply #9 on:** December 13, 2015, 17:01:05 »

Thanks guys, i will try all suggestions , have seen similar tool over here, its called a steelson, but never one any where near as small as that, the harder you push the more they lock on to the nut, will make enquiries.
Unfortunately, i don't think the epoxy / plastic cap idea will work now as its been sprayed with penatraiting oil.
I will keep you updated on progress.

66andBlue · « **Reply #10 on:** December 13, 2015, 17:23:51 »

Try to lock a thin and flexible cable tie around the knob, then wrap the end once around the knob counterclockwise and pull. But not downward, to prevent bending the stud, but sideways along the central bar in the bracket.

badali · « **Reply #11 on:** December 14, 2015, 00:06:05 »

This may be a silly question, Are you turning the nut the correct direction? When reaching in backwards sometimes I turn the wrong direction the first time.

merrill · « **Reply #12 on:** December 14, 2015, 16:19:36 »

hi, after some thought, your temp gauge is not working, double check with your re builder if they are replacing the capillary tube.

if so, you can cut the capillary tube off in the engine bay, from there you should be able to push the center cluster out far enough to un screw the oil line and then the whole unit should come out with the wiring harness.

at that point you will have plenty of room to mess with that stubborn tach nut.

waltklatt · « **Reply #13 on:** December 14, 2015, 18:24:19 »

Marilyn,

If the bracket of the center cluster is off, then you can disconnect the oil line from the oil filter from the engine compartment (if you have a 250/280SL), (230SL can be disconnected from behind the booster on a bracket).
That should give you enough play to pull the center cluster out to disconnect the oil line from within tiny 10mm wrench.
Plug as you see is already exposed on the underside near the steering column.
Then the temp gauge wire is pulled out through the firewall.

Try to keep the bulb at the end of the temp line so the repair man has the correct length to copy for the new line.

Patience is the key here.

No need to damage other things.

Walter

RAY · « **Reply #14 on:** December 14, 2015, 20:45:36 »

Thanks Guys for all your input and ideas, am going to try and make time tomorrow and give it another try, the hands and arms are healing well !

Benz Dr. · « **Reply #15 on:** December 14, 2015, 21:38:44 »

It would be very hard to use some heat on that thumb nut unless you had a small plasma cutter.

Benz Dr. · « **Reply #16 on:** December 14, 2015, 21:44:31 »

Oh, one more thing. Don't try to bend the bracket that holds the tach in place. There's no place to bend it into, no room to work, and it won't get you there anyway. The key is to remove the nut of course, but that may prove a challenge. I've used small needle nosed vice grips with some success. If you break the small stud off during remval that's not a large issue as it can be replaced.

stickandrudderman · « **Reply #17 on:** December 15, 2015, 21:14:17 »

I have revealed my own technique on here in the past........

tel76 · « **Reply #18 on:** December 16, 2015, 08:44:25 »

But that technique could result in the chrome outlet locating pegs breaking off.

RAY · « **Reply #19 on:** December 16, 2015, 19:25:05 »

Its a great day in England. The nut is finally off. The down side is that it was so badly either corroded or cross threaded on there that the stud has sheared of as Benz Dr mentioned. I eventually removed the centre cluster, cut the handles off of a small die cutter holder, clamped that on the nut with the allen key bolt in the side of the holder which then gave me something big enough to get hold of, it was like it had been welded on there until it broke.
The company in Germany who i was going to send it to for repair have quoted me 14 weeks ! ! turnaround for service and repair of my gauge so i think i am going to purchase a rebuilt exchange one from buds benz $375.
Benz Dr- it looked as if the stud is all part of the back plate which is spot welded to the gauge surround, didn't want to get into dismantling the tacho realy. Was going to snap off the remains of the stud and make up a plate with a new screw stud fixed to it then bolt that to the back of the gauge, am definately going to get a wing nut for the install.

Thanks for all your continued comments and help

Benz Dr. · « **Reply #20 on:** December 16, 2015, 19:45:12 »

Glad you were able to get it apart. Many times, these jobs will become very frustrating and can even overwhelm those with years of working experience. It takes a certain amount of grit to push through these tough spots to achieve positive results.

Good work! ( You're hired! You can start on Monday........ )

merrill · « **Reply #21 on:** December 16, 2015, 20:27:50 »

you may also want to check with Palo Alto speedo. http://paspeedo.com/

they may provide you faster turn time.

66andBlue · « **Reply #22 on:** December 16, 2015, 20:56:41 »

The shaft on my speedometer had not threads left and this company put a new one in:
http://www.nhspeedometer.com/
Only 1 week turn around!
Having dealt with Palo Alto speedo (PAS) I now prefer NHS.

stickandrudderman · « **Reply #23 on:** December 16, 2015, 21:38:26 »

Search for Speedy Cables. They can overhaul your guage(s).

RAY · « **Reply #24 on:** December 23, 2015, 19:28:08 »

This may sound ridiculous but can someone point me in the right direction as to where the sensor end of the temperature gauge connects to the cylinder head ? the previous owner had cut the temp tube and just coiled it up and the manual makes no reference as to exactly where it connects. i,m assuming its somewhere around the thermostat but nothing appears to be obvious looking for a bolt that is temporarily blocking the hole.

Happy Christmas to all the members of the best forum group out there.

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Author Topic: Help, impossible tacho removal (Read 11325 times)