Coolant temp sender

[radioactiveman]

Hello again

I have a related-but-different follow-up to my post about oil pressure sensing.

I have a coolant temperature sensor that is NPT thread. To make this fit the 5/8UNF threaded hole in my block I have purchased a reducer.

My questions are:

The NPT sensor doesn't go all the way into my reducer, is this because the thread is tapered (and expected)?
Should I use something like Loctite to seal the thread, as the internet tells me that NPTF is self-sealing, but NPT is not
When putting the reducer into the block, should I use a washer? (and perhaps some Loctite too for good measure?).

Thank you!

[Bill_qaz]

When you say block do you mean the cylinder head near the thermostat housing?
Is it electric sensor or capillary type.
,

[radioactiveman]

When you say block do you mean the cylinder head near the thermostat housing?
Is it electric sensor or capillary type.
,

Sorry, yes. I should probably have said engine rather than block; it’s the hole in the head. There’s actually a temp sender there at the moment fitted by a previous owner, but it doesn’t play nice with my dial.

Both senders are electric.

[Bill_qaz]

You can get loctite thread seal.

[olonas]

I fitted a Smiths electric coolant temp. gauge, purchased from ESM. That did include the correctly threaded sender, about £8 if purchased separately.
Their listing states negative earth only. My car is still positive earth and I did contact them re this. Lo and behold, it does work with the rear connections' polarity correct,as they advised.
It requires a stabilised 10v for which I fitted a Smiths voltage stabliser earthed to the car, 12v to "B" and "I" supplying the 10v. My car doesn't have one at the back of the speedometer.
The sender has a parallel thread and I just used some thread tape to seal.

[oliver90owner]

The sender has a parallel thread and I just used some thread tape to seal.

If a parallel thread, it should be sealed with an appropriate washer.

[olonas]

https://www.morrisminorspares.com/elect ... cc-p829965

And where, pray, is a sealing washer going to seal? Yes, the original parallel thread plug has a copper washer but there isn't a suitable landing on the sender. Therefore I stick by my original, PTFE tape or a thread sealant.
How would you seal two lengths of parallel threaded end pipes using a straight parallel thread close nipple? Not a copper washer.

[philthehill]

The switch in the link above seals by the convex taper on the inner end of the switch mating with the concave taper in the head.
Therefore no washer, PTFE tape or sealant is required but I would be persuaded to smear a little Loctite Loc & Seal on the taper face of the switch.

[radioactiveman]

Thanks to everyone for their responses

As I was using a reducer without the concave bit I went with a smear of Loctite and a fiber washer which seems to have done the trick in so much as I couldn't see any leakage.

My temp gauge reads somewhere around 80, which seems a little low? but perhaps that is just because the sensor is a bit set back from where it was designed.

[geoberni]

My temp gauge reads somewhere around 80, which seems a little low? but perhaps that is just because the sensor is a bit set back from where it was designed.

Depends on several factors.
What Thermostat is fitted?
Were the sensor and the gauge a suitably 'matched' pair as their manufacturer intended?
Or did they come from different manufacturers at different times?
Or even the same manufacturer but decades apart?

Older model gauges, if old enough can be adjusted.

[radioactiveman]

My temp gauge reads somewhere around 80, which seems a little low? but perhaps that is just because the sensor is a bit set back from where it was designed.

Depends on several factors.
What Thermostat is fitted?
Were the sensor and the gauge a suitably 'matched' pair as their manufacturer intended?
Or did they come from different manufacturers at different times?
Or even the same manufacturer but decades apart?

Older model gauges, if old enough can be adjusted.

I don't know which thermostat is fitted as I've not had to go inside the housing yet. The gauge and temp sensor are matched and new but cheap which I suspect is the issue.

[geoberni]

I don't know which thermostat is fitted as I've not had to go inside the housing yet. The gauge and temp sensor are matched and new but cheap which I suspect is the issue.

I took a chance with mine; I brought a new 'Smiths' Sender and paired it up to a classic Smiths Gauge, with just C-N-H markings (Autojumble purchase, £4). I adjusted it so that at 'Normal' Temp, it sits just slightly to the right of the N.
I have an infrared Temp Gun, so I could confirm the surface temp near the Thermostat housing when adjusting it.

I wanted one that didn't have 'C' markings.

20181209_134136.jpg (532.96 KiB) Viewed 1471 times

[radioactiveman]

I don't know which thermostat is fitted as I've not had to go inside the housing yet. The gauge and temp sensor are matched and new but cheap which I suspect is the issue.

I took a chance with mine; I brought a new 'Smiths' Sender and paired it up to a classic Smiths Gauge, with just C-N-H markings (Autojumble purchase, £4). I adjusted it so that at 'Normal' Temp, it sits just slightly to the right of the N.
I have an infrared Temp Gun, so I could confirm the surface temp near the Thermostat housing when adjusting it.

I wanted one that didn't have 'C' markings.

20181209_134136.jpg

They look very nice!