Water temperature sensor

[Not Happy Jan]

On the weekend I tried to fit a smiths water temperature gauge but there is not a point on the head for the sender unit to screw into ?
Are there different types of heads?
Can I mount the sender unit else where. I can always always take out the idiot light sensor but i would like to leave it in 
Thanks Nick

[Glenn 'Stinky' Stankevicius]

You can put a t-piece in where the idiot light is (ugly), you can get top Thermostat housings with a boss cast in that can be tapped for a sender, I think I have seen lower thermostat housings too.
It would be good to keep the idiot light if your not a "constant guage checker" like me.

[Harv]

Nick,

FX-FC lower thermostat housings had a 3/8” plug for the heater return hose (thermostat housing part number 7401195). This could be used for the temperature gauge provided you don't have a heater. FB-EJ lower thermostat housings (thermostat housing number 7414666) don't have the plug, but have plenty of meat to be drilled and tapped.

FX-FC cylinder heads had only a single "idiot light" hole. The later FB-EJ heads had a second hole for the heater hose - this could be used for the temperature gauge provided you don't have a heater.

It is not great practice to install a tee-piece to fit a temperature sender (such as by connecting both the temperature sender and heater hose, or temperature sender and idiot light). Doing so means that the temperature sender switch is placed a lot further away from the cylinder head, and may have no or little water flowing past it. This means the switch is not really sensing the temperature very well… you could overheat the engine well before the gauge shows any trouble.

If your cylinder head has only one hole, then the lower thermostat housing is the best place to connect the sender to.

Cheers,
Harv.

[Dave Lakin (Davo Lako)]

Nick ... obviously your engine has only the one housing ... unlike my FJ and FE ... can't recall if you have a heater , but if you do , I have a thermostat housing which fits into the heater hose ... thats how the guage was fitted to a previous engine ... and I won't be using it ... (and it's Chromed) ...

BTW ...  Saw you barrelling down Lake Road this morn with Snow White , so I assume (hope) you got your brakes sorted on Sunday ... LOL

Dave .

[Not Happy Jan]

Thanks Harv  and Stinky
I'll check it out on the weekend !
Is that a square headed plug Harv on the thermostat housing ?

I changed the clutch master cylinder on the weekend not the brakes as I ran out of time
Doesn't crunch changing down anymore 
Nick

[Oggz]

The water pump on my old sedan had plug in it, when I put a temp gauge in, I moved the idiot light to the water pump and put the new sender into the head. I figured at least the gauge worth ready was accurate.

Jemahl

[Harv]

G'day Nick,

The thermostat housing hole looks like this:



(with thanks to Ken... this one came from his collection when I was fitting a heater to the FB).

The red circle should have a square-head 3/8" pipe plug in it (part number 103867).

Cheers,
Harv.

[Not Happy Jan]

thanks again.
Is there a special tool to remove that bolt???
Hey Jamahl
How is the wagon going!

[Harv]

The plug should come out with the right size spanner, though a big wide shifter can give better grip on the square head and stop you mauling the plug if it is corroded in. Plenty of WD40 and a few taps on the end with a hammer (maybe not a BFH  ) might help the plug let loose. Failing that, take the housing off and use a torch to heat it up and let it cool a few times - the contraction and expansion can help it loosen.

Cheers,
Harv

[Dave Lakin (Davo Lako)]

Nick,

FX-FC lower thermostat housings had a 3/8” plug for the heater return hose (thermostat housing part number 7401195). This could be used for the temperature gauge provided you don't have a heater. FB-EJ lower thermostat housings (thermostat housing number 7414666) don't have the plug, but have plenty of meat to be drilled and tapped.

FX-FC cylinder heads had only a single "idiot light" hole. The later FB-EJ heads had a second hole for the heater hose - this could be used for the temperature gauge provided you don't have a heater.

It is not great practice to install a tee-piece to fit a temperature sender (such as by connecting both the temperature sender and heater hose, or temperature sender and idiot light). Doing so means that the temperature sender switch is placed a lot further away from the cylinder head, and may have no or little water flowing past it. This means the switch is not really sensing the temperature very well… you could overheat the engine well before the gauge shows any trouble.

If your cylinder head has only one hole, then the lower thermostat housing is the best place to connect the sender to.

Cheers,
Harv.

I take it then Harv , that my FJ and my FE have FB-EJ heads as they both have 2 housings on the tops of the heads

Cheers , Davo .

[Dave Lakin (Davo Lako)]

... make that 2 holes ... one for the idiot light housing , and in my case , one with a square 3/8 plug (the FE) and one in which the temp gauge sensor is attached (the FE) ....

[Harv]

G'day Davo,

Yes, to the best of my knowledge the two-hole heads are the later FB-EJ. I could be wrong though - the info I pulled together was for heaters, and drew information from a wide variety of sources. I have not done an in-depth review of cylinder heads.

Cheers,
Harv 

[Not Happy Jan]

Snapped a spanner trying to get that plug out 
I might have to take the whole thermostat housing off and undo it on the bench!
Nick

[waynos]

they are normally rusted in from water and heat and contraction obviously.
whatever you do dont use an easy out .....
been there done that and i cracked the housing..
heat is your friend if it wont budge

[Not Happy Jan]

Hi
I took the thermostat housing off and put it in the oven which made it much easier to remove the pug.
Then I fitted the sensor unit from the water temp gauge but the water was leaking from the unit when I tightened it all up???

 
Am I missing something , as there should be something to secure the base of the sensor unit in the thermostat housing but the plug hole just goes directly into the chamber where the thermostat lives.
Apart from the leak it all looks pretty good


 Well it does if you stand on you head..... Or turn your computer upside down

Nick

[Harv]

Nick,

It looks like the temperature sender unit has two parts:
a) a thermocouple, or sensor which has a long cable hanging off it, and
b) a nipple that screws into the thermostat housing.

I'm guessing that the unit is leaking between the sensor and nipple (i.e. water dripping along the cable). This part of the fitting is normally sealed in two ways:
a) by fitting a plastic gland in the nipple and having it tighten around the sensor cable,
b) by having a "seat" on the sensor that seals up against the nipple.

Hard to tell, but your fittings look like the latter. This means the sensor has to be hard up against the nipple (imagine this by pulling on the cable until the sensor bottoms out on the nipple). Is there a screw thread in the end of the nipple that would allow you to "pull the cable out"?

Cheers,
Harv.

[Not Happy Jan]

Thanks Harv... You are a champion!
You are right in that the seat of the sensor sits up flat against the nipple there is only a thread on the nipple to screw into the thermostat housing. There is no thread on the sensor or on the inner surface of the nipple. Once screwed in you can move the cable with the sensor in and out

Thanks
Nick

[Trevor_B]

Nick, usually you install the sensor end into an adaptor that in turn screws into the head/housing. The adaptor has a 1/2" male water pipe thread (I think) where as the sensor end is 3/8" pipe thread i.e. 1/2" male - 3/8 female.

The collar on the temperature sensor part is compressed by the 3/8 male screwed section onto a mating bottom surface in the 3/8 female part of the adaptor hence creating the required seal. The adaoptor 1/2" male thread seals, of course, when screwed into the head (as it is tapered).

So, if you have a 3/8" pipe thread in the therostat housing then you can not use your temp guage sensor there. Only options are to either drill & tap out to larger 1/2" thread, relocate your sensor to the head and use adaptor or change the style of guage to electric where you can you a 3/8 adaptor with a 1/8"NPT temp sensor.

If you want to see a picture of the 3/8-1/2" adaptor I could take a photo of one.

Cheers,
Trevor_B

[Not Happy Jan]

Thanks Trev
A photo would be very handy!
I might see if I can get it tapped out as the temp gauge is deg F.and all the new ones are deg C i think
Nick

[Trevor_B]

Hi Nick,
Couple of pictures below to try to help:



Fitting on left is 3/8" adaptor and electric temp sensor, middle is mechanical sensor with 1/2" adaptor and on right is  mechanical sensor with 3/8" adaptor.



Same again just pulled apart



This photo is to show the sealing surfaces - this is what you need to seal to stop the leak you have 

So, potentially you can ignore the electric one given your statement re deg F requirement.

The middle fitting is what I was attempting to describe - a 1/2" male to 3/8" female adaptor. Couple of things - the thread type maybe 1/2"BSP or 1/2" NPT - I am not sure which as I think they are very very similar in profile at that size (maybe the same at 3/8" as well). Most similar threads on the motor are NPT, perhaps someone can clarify this point?

The right one was an adaptor I didn't know I had and may well solve your problem..... it's a 3/8" female to 3/8" male adaptor with the correct mating seal as shown on the picture above. Not sure where I got it, could have come with a gauge kit or even as simple as from Bunnings. Perhaps you could even check with your local Autobarn if they have one (if you have a good one locally they can stock these types of things, the new franchises are usually not as well stocked). If all else fails then perhaps I could be convinced into selling you the one I have but I am feeling a bit reluctant to sell & post stuff at the moment - I sold Weddo a set of NOS GMH Cam Bearing for a Grey last week and Australia Post have lost them  It's more about the fact that they lost a difficult part to get than the value of them, it just holds Weddo up from his motor rebuild.

Final point, if you definitely want to go deg F but happy to use electric sensor/gauge you can easily get them in the USA, just check Ebay or the Autometer site: http://www.autometer.com/default.aspx

Just as an FYI, below is how I have just prepared my new motor for it's Temp Sensor - same location as you have but using elec sensor. The white stuff is a Lockite non drying thread sealant, very good for sealing tricky fittings (bit expensive at $35 a tube). Below in the water pump heater outlet is a 3/8" pipe fitting outlet to suit a 5/8" heater hose which is the same size as most Nasco style heaters (later model cars generally use 3/4" hose).



Cheers,
Trevor_B