Temp sensor connection to head

[bulfin]

Hi all,

After a fruitless search of the database, I guess I'll have to show some ignorance - not the first, nor the last time!

1969 Elan S4 (Federal)

Putting my engine back in after some work, I notice that when I put the temp sensor in and tighten the nut, the sensor can still go into the head farther, leaving a lot of space aroung the tube so it appears water can leak out. I don't remember it being this way when I took it off nor when I had the head off some years ago.

Here is a picture.

It seems like there should be a seal between the sensor and the nut. So what am I missing?
Thanks for any help.

Bob

[types26/36]

No adapter so so post not needed......deleated

[AHM]

Check the thread on the sensor. Another common size is 5/8 UNF which is 18tpi v the 3/8bsp 19 tpi in the head - it will go in a short way before locking-up.

If the threads on both parts are good and the same it should go in relatively easily. If your fitting is 3/8 bsp you don't need the adapter.

[bulfin]

It has never had an adapter, at least in the 10+ years I have owned it. Threads fit fine - just nothing to keep the sensor from going further in.

Bob

[AHM]

Well it needs a shoulder to abut....

Which hole are you putting it in?

[AHM]

Brian,
You have deleted your post.....

All the ones on an elan I have ever seen look like the one you posted. So useful to people searching later

[rgh0]

Having trouble following this thread however for what its worth

The sensor shown in the first post is not the Lotus original which used an adapter and an internally threaded compression nut. This one was used on other cars such as MG's and Triumphs. Do you have a 0 to 100 psi oil gauge in the dual gauge ? The original Lotus one only went to 60 PSI and many people swap them for the 100 psi one if they fit a high pressure pump but the temperature sensor fitting is different so needs a different adapter

You will need an adaptor for this non original sensor - perhaps you had one but lost it when pulling the engine down? As far as I am aware a suitable adapter from the Lotus head to this style externally threaded nut is not commercially available and you need to have one made.

There is no shoulder in the head for the temperature bulb to sit on when fixed in place by the compression nut so you do need an adapter to provide that seating shoulder and it must have had one to not have leaked in the past unless some bodge was done to fill up the space with a sealant of some sort ????

cheers
Rohan

[bulfin]

Thanks everyone for the helpful replies.

Rohan, as always, is correct - it is not an Elan guage since it has 100psi. I did not realize this.

Also, I was wrong about the adapter. I took a picture before the rebuild and looked at it before I posted; when I looked at it again, I see there is a sleeve in the head. Since I never took the sleeve off, I guess I just ignored its presence. So I apologize for my statement that there was no adapter. Interestingly enough, I looked through my workshop manual, parts manual and the Buckland book and never saw anything about an adapter.

I hope my builder took the sleeve off and sent it back since I have no memory of removing it and it was not im parts bag. Senility is tough.

Thanks again for the help.

Bob

[rgh0]

Hi Bob
Yes Lotus is surprisingly non specific about the presence of this adapter. I don't know why Lotus used a different design to the other more common users of this gauge setup. Maybe Colin got a special deal on stock Lucas could not sell elsewhere.

cheers
Rohan