13 replies to this topic

[Clubber Lang]

What size and thread is the hole for the temperature sender in the head? cheers Steve

[markl1963]

5/8" UNF.

 

Cheers

[dklawson]

As above, 5/8 UNF (5/8-18).

 

Most mechanical temperature gauges will thread right in.  HOWEVER, on some head castings the hole is too shallow for the mechanical gauge expansion bulb.  In those instances you need adapter TE5 from Mini Spares.  The adapter prevents the expansion bulb from bottoming out in the head casting.

 

If you are looking for a thread adapter to connect an aftermarket electrical temperature gauge, those are hard to find.  You can make one of those adapters yourself by taking an old Mini temperature sending unit, drilling it out, and tapping it for the thread size you need for the aftermarket gauge's sending unit. 

[Goacher65]

Bit of a resurrection. Any ideas what size the hole will need to be drilled if drilling out an SPi head to fit a temp sender in the original place? Obv there will be the tapping drill size, but what about to allow the coolant to reach the sender? Does it matter how big it is?

[dklawson]

Good question.  To get the answer right you really will need to measure an early cylinder head.

 

The temperature sender does not seal on the threads.  The hole in the cylinder head has a conical seat at the bottom of the threads and then the through-hole into the water jacket.  The conical seat on the sending unit seats and seals on the conical seat in the head.  The through-hole only needs to be large enough to let the tip of the sender go through.

 

The hard part will be for this modification to work like it does on early cylinder heads you need to drill to the right depth with a drill that has the correct point to leave the correct angular seat.

 

The tap drill is easy to work out.  For about 75% thread height/engagement (which is pretty much the standard fit) take the major diameter of the thread and subtract the pitch.  In this case, the sender is 5/8" x 18 threads/inch.  Therefore, your tap drill would be .625 - 1/18 = 0.569"  That's an odd size so you would go to the next closest (smaller) size which would be 0.563" (9/16").

 

If you can only produce the tapped through hole without the conical seat, buy the temperature gauge adapter (part TE5) from Mini Spares.  It will have the correct through hole and the conical seat.  All you will need to do is drill and tap the head for 5/8 UNF and apply some thread sealant when you screw the adapter into the head.

[Goacher65]

Fantastic! I think that covers just about everything. I shall have a measure up and work out what the best solution is going to be!

[gazza82]

Won't it be easier to put sender in replacement thermostat housing?

[dklawson]

Won't it be easier to put sender in replacement thermostat housing?

 

Yes if the t-stat housing is tapped.

[gazza82]

Or buy one that is ...

[gazza82]

Or buy one that is ... oops ... finger trouble!

Edited by gazza82, 08 April 2014 - 07:41 PM.

[Goacher65]

I have the DSN classics thermostat housing/engine stead so no option there I'm afraid! And couldn't quite bring myself to drill it if there was!

 

Also, is the TE5 adaptor also usable with an electric temperature sender, as MS seems to recommend it for capillary type with no mention of electrical....

Edited by Goacher65, 10 April 2014 - 11:36 AM.

[dklawson]

The TE5 will work for either electric or mechanical.  They mention it as being for the mechanical gauge because that is its primary use.  On many castings the long expansion bulb of the mechanical gauge bottoms out against the inside of the water jacket in the head before the conical sealing surfaces touch each other.  The TE5 moves the expansion bulb a bit further out so the conical surfaces will seal.  The electrical sender has the same conical sealing surface so the TE5 just moves the electrical sender out a bit. 

[minicooperr]

Won't it be easier to put sender in replacement thermostat housing?

Bit of a resurrection but I am trying to figure out if this is possible as not keen on drilling the head currently?

[nicklouse]

 

Won't it be easier to put sender in replacement thermostat housing?

Bit of a resurrection but I am trying to figure out if this is possible as not keen on drilling the head currently?

 

More words needed. What are you wanting to fit and where to?

 

some temp senders were fitted to the stat housing. Some were fitted to the sandwich plate.

 

they did not have outputs as they worked the gauges differently or just used different gauges.

 

drilling the head is one of the easier options.