Instrument Cluster Removal

[beachbear]

Starting with a decision to repair the tachometer (rev counter), my project has expanded to include cleaning the glass of the instrument cluster and speedometer; converting the clock to quartz; upgrading dash lights to LED (where possible); replacing the dash speaker (missing) and replacing the dash bows (bolts were torn away by some mechanic during a previous repair and the bows set back in place with rubber caulk). Oh, and one of the heater control levers were broken, so that is replaced too.

I wasn't eager to remove the instrument cluster. Previous posts about the oil and temp gauges seemed to glow red with warning. Yesterday I attempted to remove the temp sensor at the elbow which also holds the thermo-time switch. Using a 3/8" 14mm brake line crowfoot on a ratchet I succeeded in loosening it, but received the sickening feel of ether leaking over my fingers as I finished unscrewing it from the socket. The capillary tube broke at the sensor. Currently, the best price I found for a replacement sensor-tube-gauge is $300 (high was $380). I haven't returned to the scene to remove the oil line from the engine yet.

I have two (three) questions for the group. Can anyone offer helpful pointers besides remembering to reinstall the oil line (still very valuable!) that I should know about regarding the oil pressure hose? The temperature sensor seemed to require a brake line wrench and good deal of torque to loosen it. Is proper torque all I need when reinstalling the sensor? Does anyone have a torque specification?

[Benz Dr.]

You should be able to get the temp gauge rebuilt. I use anti seize around the end that threads into the housing on the side of the head. Any time you are working around coolant and different types of metal ( steel and aluminium ) it's a very good idea to use this product.

[Tyler S]

You can also remove the oil line from the back of the gauge cluster using a 10mm wrench through the Tachometer opening. I have found it easier then trying to snake the hard pipe through the firewall and dash opening.

[beachbear]

An update as I put the dash back together:

I had broken the original Temperature Sensor capillary tube at the sensor. The sensor I purchased as a replacement came from Authentic Classics. The gauge was in celsius. I converted the gauge to Fahrenheit using my original gauge face. Before I pressed the needle, I used a cup boiling water and an infrared temp gun to calibrate the gauge.

With all parts back in my hands (rebuilt rev counter, new temp gauge, LED upgrade, salvaged heater control lever, new dash speaker, wooden bow, and converted clock), I began reassembling the dash instruments, starting with the instrument cluster. I threaded the new temp sensor through the firewall, coiled the excess 12" of tube, and attached the gauge to the rest of the cluster. I fastened the cluster to the dash, reattached the oil line (thank you very much Tyler S.!), and started to install the sensor into the engine.

It didn't fit. The outside diameter of the new sensor bulb was .5" in diameter at the top of the seat. Too large to insert. The original piece was .47" in diameter. All work stopped. With my goal to get the 280 back on the road this weekend fading away, I closed the hood.

 few minutes later I realized I could salvage the project without returning the sensor. I used a multitool with a diamond cutter (a Dremel would have worked better, but I don't own one), to grind .015" away from the outside radius at the top of the bulb. The sensor is installed the oil line is connected. The car runs. There are no leaks. The temperature sensor reads correctly and I'm back on track!

Lesson learned: There are Celsius and Fahrenheit gauges out there. There are at least two different sensor bulb seats that fit a 280sl.

[Tyler S]

Glad you got it all back together 

A quick tip for anyone who needs to remove a needle to replace a gauge face. Carefully move the needle up and over its stop/rest pin and let it swing to its natural resting place. Mark the location and then remove the needle.
Do your work and then reinstall the needle in the same marked location. Move the needle back up and over the stop pin. This will retain the calibration.

[ja17]

I like to remove the temperature gauge from the cluster and not even tamper with removing the sender bulb, when working on the dash instruments.  I just leave the gauge loose and attached in the dash.