Oil Temp Dipstick, DIY homemade, simple & cheap Jun 21, 2011 23:46:41 GMT -5
Post by dogbunny on Jun 21, 2011 23:46:41 GMT -5
My homemade oil temperature dipstick.
Back: donor dipstick. Cut the blade handle off, and cut the stem off (green arrows). Save the cut-off stem, you will need this later.
Front Left: thermometer, McMaster-Carr part # 3965K11, specify the 50 to 300 degree F. temperature range, $23.55 plus about $5 shipping. www.mcmaster.com/#catalog/117/577/=cuoefb This is the "clip-on dial thermometer" with 1-3/4" dial and 8" stem length. I ordered this at night, and it came two days later (fast!). Most of the other McMaster-Carr thermometers have 3" dials. This was the best fit in a small-dial thermometer. The 8" stem length is a couple of inches too short, but we'll deal with that later.
Note the adjustment nut on the back of the thermometer (blue arrow). Turning this nut rotates the dial needle, in other words, this is how you calibrate the gauge.
Front Middle: 1/8" NPT nipple and fitting. Ignore these parts (red X's). These fittings were part of a much more complicated design that didn't work.
Front Right: Modified donor dipstick. I made the top surface concave (red arrow) to be a better fit with the back of the thermometer, which is convex. The hole I drilled through it is way too big -- that was part of the complicated design that didn't work. The hole you will drill should be about twice the diameter of the thermometer stem. The hole gap will be filled with JB Weld.
The finished product. Slide the thermometer through the hole you made, and bond with JB Weld. It's that simple. Note the nice bead of gray JB Weld (green arrow). Ignore the 1/8" NPT fitting (blue arrow); that was part of my unnecessarily complicated original design that I couldn't undo.
Now you are done, except for one thing -- the dipstick is too short. Take the original left-over piece of stem that you cut off of the donor dipstick, and cut it to size to make up the difference in length. Weld this make-up piece to the end of the thermometer, and you are done.
BTW, before you JB Weld everything, take a scratch awl, and deeply etch the shiny tin back of the thermometer so that the JB Weld will have something to grab on to.
I put 100 miles on this dipstick while it was still too short -- before I welded the make-up piece on -- and it worked just fine as a temp gauge. It doesn't matter that the short stick doesn't contact the oil in the sump when the engine is cold. When the engine is running, oil is being splashed all over the stick, and it works just fine. The temperature readings I got were consistent with everything I have read about XS650 engines.
I put another 100 miles on the dipstick after welding the extension on, and it still worked just fine. I also ran a couple of calibration tests. Before the JB Weld, I calibrated the gauge (using the nut on the back) to 100 degrees (which was the ambient temp here in Texas at the time), comparing it to several weather thermometers. After welding the tip on, I re-checked it, and it was still good. I then checked it again in a pot of boiling water, comparing it to a cook's candy thermometer at 200 degrees. The thermometer-dipstick is accurate.
Two final notes: As they pass through the engine, the dipsticks on XS650s are positioned extremely close to one of the tranny gears. The stem of the new thermometer is about twice the diameter of the original stock dipstick. This is just enough to cause rubbing on your new oil temp dipstick, which results in a small groove (red arrow). I took extreme care to make sure my stem was perfectly straight, and the small amount of tranny gear rubbing is negligible in my case, and I am not sweating it. However, it is something to be aware of and to watch out for.
Finally, when you do your welding, attach the ground electrode of your welder to the little extension that you are welding on, NOT to the thermometer. The bi-metal thermometer probe does not like having welding current go through it, which is why mine looks somewhat fried in the last picture.
Oh yeah, almost forgot -- before you do the JB Weld, screw the dipstick in, and make a note of the orientation of the gauge. You don't want your gauge to be upside down relative to your seated position.