classicxj2000

I'm putting in a new controller for my electric fans. I need some help trying to figure out where I can put a 3/8 NPT sensor on my 2000 4.0L. I looked at the inline radiator hose adapters. They say you need 4in of straight hose. There's no 4in of straight hose in the upper radiator. Maybe heater hose? It would be great to have it read radiator temperature. Any thoughts?

Thanks,
Dave

1991Jeep_Man

If you must, use a heater hose going to the heater core, out of the t-stat housing. I would think it would give good readings, since coolant is always flowing through it anyways.

classicxj2000

What's the thread size for the radiator temp sensor in the older XJ's? The one on the driver's side tank. My replacement radiator has a plug in this spot. Looks about 1in diameter or so. If I remember right this was the temp sensor for the aux fan in the older models? This would be a good spot if I can adapt it down to 3/8 with a bushing.

Dave

5-90

That's an ISO thread - M20x1.5, I think. Use a short bushing if you're going to do this - you want the sensor tip to be as much in the direct flow path as possible.

There's also the idea of soldering/brazing a bung into the radiator tank if you need to - I'd probably put it in on the "hot side" (inflow tank, where the upper hoes goes) so you'll know if the radiator needs the extra airflow - vice putting it on the cold side, which introduces a number of unpredictable variables... The same tip on getting the sensor tip as far into the direct flow path as possible applies.

classicxj2000

Thank you for the info. I like your idea of brazing a bung on the hot side tank. That would be the perfect place. I'll see if I can find someone in my area who could do that for me. Too bad radiator shops don't exist anymore(at leas not where I live).

5-90

Can you solder? If you can solder, you can braze - it's the same process, just hotter and with a different filler metal (soldering a bung on can be done as well, tho.)

Soldering uses a soft, low-melting alloy - typically tin/lead, sometimes tin/bismuth, and "hard" solders usually are silver-bearing (tin/lead/silver or tin/bismuth/silver.) Soldering filler alloy usually melts around 750-850*F, and can be done with an electric iron (for wires & small mechanical joins) or a small torch (bigger joins, plumbing, and light structural.)

Brazing typically uses a brass or bronze alloy (which is where the name comes from,) and therefore is done around 1500-1800*F. You can still do it with a propane or MAPP torch, but propane/oxy or MAPP/oxy will work better. You're working much closer to the melting point of copper or brass, so it can be difficult - if you're not experienced with brazing, you're probably better off soldering (more room to screw up.)

Neither of these is a true "fusion" process (welding is, but it's generally "like-to-like,") they're more properly "adhesive" processes. It's just that the "glue" you're using is molten metal - and this is why dissimilar metals may be joined easily by soldering or brazing. Soldering can be done relatively quickly - locate where you want the bung, drill the hole, clean the surrounding area (about 1/4" larger than the hole) down to BARE METAL, place the bung, and solder. Repaint when you're done (if you can find "radiator/thermal paint" locally, it's better to use.)

You can practise soldering withs ome scrap metal and some plumbing (acid core) solder - you put the join together, heat it, and use the heat of the parts (not the torch!) to melt the solder. It should wick in between the parts and stick them together.

You can still break a solder join using muscle power, but it should take some effort (you're not making two pieces of metal into a single piece, you're just sticking two pieces of metal together.) Make sense?

classicxj2000

I can solder. Thanks for the education on brazing. I might try it one day for something easier than this project. I don't trust myself to have it hold liquid and pressure. I found a welder locally that said he can do it for about $85 (his hourly rate).

Can anyone confirm the M20 x 1.5 threads? I can't even seem to find one of those sensors/fan switches to purchase (thinking I could get one, measure it, return it). I found an adapter to reduce that to 1/8 NPT. I can drill and tap it up to 3/8 NPT.

Dave

classicxj2000

I found the sensor on autozone website. Part number SW594. Tech specs say it's a m22x1.5 thread for anyone else who want's to know. Now I'm going to try and find an adapter to get that to NPT. Any ideas of where to look?

Dave