My ‘97 Defender 90 didn’t come with any coolant level warning, and it seems the only way is the DIY... so, I assembled the parts and made this setup over the weekend. Now, if my coolant runs low, I get a warning light on the dash. Here is a write up and some pix of what I did...
Parts & tools you'll need (you don't have to get the exact parts, but these are what I used):
Parts & tools you'll need (you don't have to get the exact parts, but these are what I used):
- a float switch. I decided to spend a little more for one from liquidlevel.com (a company in CT). Their floats have published specs...and that's goodness in my book. part#LS-11-051/2. You can also find cheaper ones (w/ mixed reviews) on amazon.
- Legines Brass Pipe Fitting, Bulkhead Anchor Coupling, Bulkhead Tank Fitting, Frame Nipple, 1/8" NPT Female, 1-1/2" Length (Pack of 2) from amazon.
- LED bulb size74 part#74-NW from superbrightled
- 1'x1'x 1/16" silicone sheet to make my own gasket to seal the bulkhead fitting, also from amazon.
- metric washer (home depot)
- Step drill bit to drill the reservoir, round file/sandpaper, and some high temp thread seal (ARP or Permantex 59124) to seal the various threads
- Find your coolant reservoir/overflow tank. In the Defenders, this is a brass unit, and drill a hole big enough to fit the bulkhead fitting (measure twice, drill once). Also, drill it far enough you can still open/close the filler cap after sensor is installed. File/smooth out any sharp edges - you don't want this to cut into the silicone gasket later.
- Fit the float switch into the bulkhead (apply thread sealant) - noted this pic is different than the final assembly I had. After taking this pic, I found float was sitting too high in the tank.
- Make a gasket for the bulkhead for inside the tank, and another gasket for outside the tank (square orange with round cutout in above pic).
- Check the float to make sure it has continuity when float is down (low coolant). If not, remove circ clip, flip the float to make it so.
- Thread the float wires through the tank - through the fill hole then out the drilled hole. Then, drop the float into the tank and check fitment and as important, float depth/height. Ideally, you want the float to almost touch bottom of the tank. You can make float sit lower in tank by adding the extra bulkhead nut to the bulkhead fitting, then silicone gasket, and also how much you turn the float into bulkhead fitting (step 2).
- Once the height is good, you can put the other gasket on the outside, put a washer, lock washer then the nut. I put thread sealant between gasket and also at the nut. Tighten things down.
- (Optional) using some shrink tube/rubber grommet to keep the float wires from rubbing against the threads of bulkhead fitting. Test again for continuity by filling up the tank. If all OK, put the tank back in the truck and connect up all hoses.
- Run one of the float wires to ground, the other inside the cab where you can wire up the light and 12v source.
- For the in-dash warning light - i used the unused coolant warning lamp in the panel (below turn signal). You'll find the socket and just add the LED bulb. Run power from 12v power source when key is in the on-position.
- Once wired up, test it to make sure light is on when no coolant. Then fill reservoir and the warning light should go out. If you set the float low enough in the tank... filling the overflow reservoir a little more than 1/2 way should not trigger false warnings - even when going around turns, up/down hills, etc. Then run the truck, get up to temp and check for leaks. If you did a good job, things should stay bone dry.