Topic: 1939 temperature sending and steady rod removal


MICHV8    -- 04-13-2025 @ 11:40 AM
  I'd like to remove the original flathead from my 39 for some work, but the temperature sending unit in the head is not budging. Is there another option? The dash gauge looks like it would be difficult to pass through the firewall.
In addition, the steady rods have a flat circular head connector that has an odd size square recess...any ideas? Maybe grind a bolt until it fits the square recess?
Any help is much appreciated...

This message was edited by MICHV8 on 4-14-25 @ 4:30 PM


nelsb01    -- 04-13-2025 @ 4:39 PM
  The steady rods have two ends --- the square end is a bolt, but on the other end is a nut and cotter pin that you should be able to remove.


carcrazy    -- 04-13-2025 @ 10:42 PM
  To remove the temperature gauge sender for the '39 Ford which is mounted in the top of the driver's side cylinder head use either:
a special 5/8" sending unit wrench ( Snap-on) makes one
or a 5/8" hex (six sided) box wrench which has been modified with a slot cut into it so the gauge capillary tube can pass through it.

If the sender is truly stuck in the head, try soaking it with a good penetrating oil. Be patient, you don't want to round off the hex of the temperature sensor. If after a day or so of soaking the sending unit with penetrant, it still won't move, you may have to apply some heat to it - be very careful with heat as you don't want to over heat the gauge and ruin it.


MICHV8    -- 04-14-2025 @ 4:52 AM
  I had no problem getting the nut off, but the capillary tube is stuck fast. I've soaked the head overnight with a 50/50 mix of acetone and automatic transmission fluid. I will try to apply heat to the head while staying away from the tube. I took the radiator hose off and can access the capillary tube, but can't think of a way to apply upward pressure from inside the head.
Thanks for the help

This message was edited by MICHV8 on 4-14-25 @ 4:31 PM


kubes40    -- 04-14-2025 @ 5:02 AM
  The end of the rod requires a square driver. It is 5/16". Be certain the clean any junk out of the recess so the driver can be inserted all the way.
You can buy a square drive or grind back a 3/8" ratchet extension. If you grind back an extension, make it on the tight side and pound it into the recess a bit.

The bulb gets pulled through the instrument panel (aka firewall) to remove. In other words, the unit is removed through the passenger compartment.

The best wrench for turning that sending unit is termed a flare nut wrench.


Mike "Kube" Kubarth

This message was edited by kubes40 on 4-14-25 @ 5:03 AM


marko39    -- 04-14-2025 @ 5:07 AM
  for the steady rods, i use a piece of key stock and a wrench to unscrew.


MICHV8    -- 04-14-2025 @ 11:32 AM
  I heated the round steady rod nut and followed Mike's advice to keep the ground bolt slightly too large and tapped it in the recess. Both twisted free with some torque...thanks to all.


carcrazy    -- 04-14-2025 @ 8:23 PM
  To apply pressure to the bottom of the capillary bulb in the cylinder head, you can try using a brake spoon or another "L" shaped tool. The tool will provide a fulcrum for you apply an upward force on the bulb through leverage.


MICHV8    -- 04-15-2025 @ 8:27 AM
  I'll give that a shot. The angle of the head opening and the bulb doesn't allow much leverage. I've tried an open end box wrench underneath the tube, but once again, hard to get any upward leverage... Thanks for the hint


39 Ken    -- 04-16-2025 @ 5:04 AM
  Here's an idea out of left field so consider it as such...

Pull the head off and leave it there. Pull the motor and start your work on
that, all the while soaking the temp bulb with MMO and acetone
mix until it loosens.

If it never loosens up and the head doesn't need work, then remount the
head after the motor is installed.

As mentioned, an odd approach, and obviously a last resort solution to save the
temp sender.


TomO    -- 04-16-2025 @ 8:18 AM
  The temperature bulb probably has some calcium deposits keeping it from releasing. Try vinegar or CLR to free it up.

Tom


MICHV8    -- 04-17-2025 @ 6:17 AM
  Thanks folks...I'm working on it!


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