Temp sending unit in the radiator hose??

my slanted six on my 61 Dodge has a tiny sending unit for the temp gauge. I have a "mechanical" temp gauge and matching oil PSI that I removed from another project before I sold it. they are practically new, only used when I started up my new motor.

the aftermarket temp gauge sender is way bigger than the hole in the head (the cars head, not mine) so I was thinking I could put a tube in the radiator hose and weld in a threaded piece and put the sender in there.

anybody see any problems with this???

 

I would wonder if it would read the correct temp until the thermostat opened? Most bypass a little water before they open, but is it enough to get a good reading, and/or does that matter. Once it is open it would be reading the correct water temp for sure.

Just remembered that some early 289/302 engines have a sensor in the thermostat housing, which would put it past the stat. I don't think it is a gauge sensor however.

 

They make a brass threaded plug that adapts the unit to the smaller hole in the head. On a different note,, I also made a radiator cap with a manual temp gauge in it.

 

this hole is tiny. the probe from the temp gauge might fit in there, but that's about it.

 

I had one on my 318 Dodge PU that was inserted into the upper hose. It was mechanical, not electrical. Worked great!!!

The Mopar stock water sending unit IS small.

 

I drilled a hole and tapped it out on my slant in the HA/GR. This was in the thermostat housing. The only bad thing is that you can not run a thermostat with the sending unit in the housing. I installed a washer in there to slow the water down.
Some of the later model heads had a bigger hole and the adapter will fit in them. The early models did have a very small hole in them. This is what I have on the HA/GR.
Robert.

 

measuring the temp in the heater hose will be fine until the thermostat sticks shut....

If you're not running a heater, use that hole. If you are, maybe you could put a T on the heater hose fitting.

or drill/tap the temp sender hole bigger, looks like it might take a 3/8" or maybe even 1/2" pipe thread?

 

You can, it will just read the temp of the water it sits in (the hose), so until it warms up and the 'stat opens, it will read cooler than the motor is actually running.

 

I ran a temp guage in the upper hose for many years. It took a while to show anything until the stat opened, but after that it worked well. For the first few stat cycles you could tell when the stat opened and when it closed by the guage reading. Gene

 

I also have done about what you are thinking of. Worked for me.

 

FWIW I know BeCool makes a sending unit that attaches to the radiator hose. I've spoken to the owner a couple times, if he says its OK I'd be inclinded to believe him.

 

Why does this remind me of a rectal thermometer...?

 

Autometer makes this type of deal.....If you have some tubing and other stock, you could make your own should work fine. I have a 225 and that hole is 1/8 pipe thread. I don't see a problem hoggin' that hole out to whatever, if I had to.

 

for those who don't have a slant 6 in laying around in their yard...poor, deprived souls they are

 

These work good if you don't mind the non traditional look. Come in several ID hose sizes so measure before buying. comes drilled for 1/8" pipe but plenty of meat to make the hole bigger. About $10.00 at a local speed shop.



Please excuse the non hamb friendly rice burner installation.

 

claymore , can i assume that little screw right next to the sender is for a ground wire? i hadn't given that any thought until looked at your last picture....with the sender being isolated by the rubber hoses it would need one

 

Looks like it's easy enough to drill and tap the hole to the required size.Of course a you may not want to spend 25 bucks on a drill and tap you use one time.

 

Some fan senders are put in the radiator hose. As has been mentioned it won't register until the T stat opens. So if you loose a stat you won't know you overheated until something bad happens.

You can put a close nipple and a bell reducer (enlarger?) in the head then screw your sender into that. I have done it that way before. You will probably need to bleed it intially. But it works like a champ. Or you can probably drill and tap the sender hole.

 

This is exactly what I run to turn on my electric fan. It seems to work just fine.

 

Use the sender that came with the gauge. Chrysler did change sending unit values. I put a 63 383 in a 57 Plymouth. I connected the stock 57 gauge to the 63 sender already in the engine and it worked. I spent an assload of money trying to fix a hot running engine. When nothing helped I put the 57 sender in the 63 engine and bingo...normal operating temps. There never was a running hot problem. Just a mis-matched gauge and sender problem. It was an expensive lesson. Don't assume anything.

I'd drill and tap the small hole to take the larger gauge sender adapter. You want the sender to be in the engine. Don't fret the shavings in the cooling system. Like Squirrel said, with the sender in a hose a stuck thermostat will never show up on the gauge to prevent damaging the engine. Your first indication will be the boil over. Gauges are to monitor the condition of the engine. The senders need to be in the engine. IMHO

 

SAABs at your local Pick A Part have a tube in the upper rad hose, with a sender that also controls the fan? IIRC they are tapped and removeable.
The oldest ones are brass and don't corrode as much.
The oldest ones also have a thermostat with a hard wax plug that melts when overheated to prevent engine damage, what a concept.

 

x 2

.

 

Look at that thing. And I cut one out of solid bar stock. Oh well.

 

Is there room to make the hole in the head larger? Cast iron drills pretty easy. You can always run a reducer if you wanted to go back to the original sender. Just a thought. Depends on how original you need it to stay

 

thanks for all the ideas. seems like it would work great until the thermostat gets stuck... maybe I'll drill and tap. prolly get most or all the shavings out with a magnet.

because you are one sick fella.. that's why.

do you know how to tell the difference between a rectal thermometer and an oral thermometer???




the taste.

 

Sure is a place to ground the sender good catch.


For those that hate the billet look you could always paint it flat black and slide it around so the sensor is on the bottom side where it is harder to see.