Temperature Gauge

[shaf]

Dear All

Please can you help.

I have 1971 280 SL which i actually bought from one of the members. Great car 3 years given me no problems. Now my temperature gauge is not working and did not realise at the time so my water pump leaked and car stopped now after replacing it my car is building pressure and releasing it out from overflow in the expansion tank.

Q1 Can this be head gasket or air lock?

Q2 Where is the temperature swiitch on my car checked the switch on the thermostat played around with it but nothing happens in the gauge no movement.

Q 3 All the rest of the instruments are working inside exept for temperature gauge. Can my gauge be faulty?

Pls appreciate any help.

[mdsalemi]

Shaf,

The temperature "gauge" isn't a gauge at all; it is a thermometer.

What I mean by that is a "gauge" typically has some kind of remote sensor, and then an electrical connection to the gauge itself which will display the temperature.

Not so in our case; you actually have a thermometer bulb stuck inside the engine block or head somewhere (filled with thermofluid); a capillary tube that takes the fluid to the gauge on the dash.  The fluid expands and contracts with temperature; thus what we have is a true thermometer, not a gauge in the classic sense. No electricity is required for its operation.  Just heat!

If yours is not working, there is a 99% chance that your capillary tube is broken.

You'll have to go to one of the restoration places, eBay, or similar to see if you can locate a used one.  Alternatively, and much less costly, would be a digital temperature sensor that you fabricate yourself.  Our cars will easily have their head destroyed by an overheating condition, so you don't want to be w/o some means of telling the temperature.

[ja17]

Sounds like you could have a more serious issue at this point.  First of all re-torque the cylinder head and replace the thermostat. Refill the coolant after and start the engine after a working temp gauge is installed. Several start ups and coolant adds may be needed to bleed the air from the system. Watch the gauge and add coolant as the engine purges air. When the top of the radiator gets hot, coolant circulation has been achieved and you are safe for a test drive.

If the engine was badly overheated it can blow the temperature gauge.

Good luck, Keep us up to date.

[glenn]

Shaf,  Have a temp sensor/gauge available.  Long way to Dubai. ..

[glenn]

Shaf,  Have a temp sensor/gauge available.  Long way to Dubai

[shaf]

Hi Guys

Thanks for your help.
 
Do i need to remove my instrument dial to replace the capillary tube?

My dial for temperature is completely dead and does not move at all.

Kind Regards

Shaf 

[w113dude]

The temperature/sensor unit looks like this all one piece, (see photo) you have to take the gauge out, first unscrew your temperature sensor from the engine compartment next push the center gauge out enough to see a 10mm nut that you need to unscrew that is your oil pressure gauge hose. You also need disconnect a few wires, then you can pull your center gauge out. In the back of the gauge you can unscrew a few small screws and replace your new temp, gauge. installing is the reverse.  

Good Luck.

[ctaylor738]

Suggest you try draining the radiator, then refilling through the heater inlet hose, by disconnecting the hose from the heater core.  Remove the cap on the coolant tank while filling.  This will fill the system from the bottom up and eliminate any air pockets. 

[shaf]

Thanks Guys

Appreciating your help. will keep u posted.


KR

[ejboyd5]

Best suggestion is to refill the system to eliminate any air pockets - air is a poor conductor of heat, hence the true coolant temperature will not register.

Sometimes the indicator on the thermometer (needle on the gauge for those who are not purists) gets stuck.  Before disassembling the instrument panel I would suggest removing the bulb (sensor) from the engine and immersing it in a container of boiling water.  This might well free a sticky situation and will certainly confirm a malfunction if such exists.

With regard to the overflow, are you replacing fluid each time some leaks out.  Perhaps the coolant is just trying to seek its own normal level and you are trying to put too much fluid in the system?

[shaf]

Glen

Pls can you give me the price for temperature switch/gauge.

Also my vehicle comes with the short version of the water pump, this was hard for me to get here so I found the long version water pump and my people here replaced the seal spring by taking it out the new one and modifiying to my water pump. There is no leak around that area and the fan is spinning. Can this be the reason why i am getting back pressure in my expansion tank.

I will have to order brand new from UK when I go back home and replace it with mercedes genuine one later.