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Discussion Starter #1 (Edited)
The 4BD1T water sensor threads aren't 3/8". They are a metric thread 16x1.5mm which is close (1.5 vs 1.33mm thread pitch) and shared by most japanese cars. I'm guessing your Toyota senders are the same metric thread and will just wind in.

Your plan all looks very doable with minimal surprises.
 

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The 4BD1T water sensor threads aren't 1/8". They are a metric thread which is close and shared by most japanese cars. I'm guessing your Toyota senders are the same metric thread and will just wind in.

Your plan all looks very doable with minimal surprises.
Yes you are correct, I will need to go in and edit that. Thw coolant temp sensor on my truck is the same thread the 4BD has. I do not know the exact size though. Good catch, thanks.

I think its totally doable as well. Im looking forward to see how it works out.
 

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Nice planning and overview of your swap, it should turn out well.

On my 4BD2, I found my engine sensors were BSPT - British Standard Pipe Tapered thread. To fill the extra coolant sensor holes and to move the oil pressure sender I needed BSPT fittings. My LandCruiser temp sender screwed right in, the oil sender worked, but I think it may have been a metric pipe thread.

Doug
 

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Nice planning and overview of your swap, it should turn out well.

On my 4BD2, I found my engine sensors were BSPT - British Standard Pipe Tapered thread. To fill the extra coolant sensor holes and to move the oil pressure sender I needed BSPT fittings. My LandCruiser temp sender screwed right in, the oil sender worked, but I think it may have been a metric pipe thread.

Doug
As far as I know Toyota uses BSPT on its oil sensors too. At least my Supra (7M,1JZ and 2JZ did) as well as a couple 2H diesels. The are very close if they are NPT. I will not get to this bridge till I am doing the actual swap its self but thank you for clarifying it.
 

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Nice planning and overview of your swap, it should turn out well.

On my 4BD2, I found my engine sensors were BSPT - British Standard Pipe Tapered thread. To fill the extra coolant sensor holes and to move the oil pressure sender I needed BSPT fittings. My LandCruiser temp sender screwed right in, the oil sender worked, but I think it may have been a metric pipe thread.

Doug
Metric pipe threads are BSP. It is just that they change the name from British Standard Pipe to DN (from the French for Diameter Nominal, or some such). So same thread diameter, pitch and angle as BSP. As we know pipe threads are made to suit the outside diameter of pipe, but pipe sizes are based upon the nominal bore, not the OD.

Japanese, JIS, also base their pipe threads on BSP. Don't take this statement to mean that their instrument sensors use pipe threads, they may use some other metric diameter and screw pitch that suits them.
 

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Discussion Starter #6
Guys.

Let me repeat. The 4BD1T thermostat housing threads are not BSP, NPT or any other pipe thread. It is metric 16x1.5mm.
I have in my hands right now the thermo-fan switch I have just unscrewed from my 4BD1T and a 3/8" BSPT male pipe fitting.

They measure up close, in fact 15.8mm OD for both.
The thermo-fan switch is 1.5mm thread pitch and winds in fully and freely by hand until the sealing o-ring contacts.
The 3/8" BSP pipe fitting is 19tpi (1.33mm thread pitch) and will only thread in 1 turn by hand before the mismatch in thread pitch starts to bind.

This 16x1.5mm metric thread is common to most japanese and many non-japanese vehicles for water temperature senders and switches, the thermo-fan switch I am currently using was originally honda fitment.
On my engine the three ports above the thermostat and 2 ports below all share this thread.

There are many threads on here claiming 3/8" BSP which I will go through and correct.
 

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Guys.

Let me repeat. The 4BD1T thermostat housing threads are not BSP, NPT or any other pipe thread. It is metric 16x1.5mm.
I have in my hands right now the thermo-fan switch I have just unscrewed from my 4BD1T and a 3/8" BSPT male pipe fitting.

They measure up close, in fact 15.8mm OD for both.
The thermo-fan switch is 1.5mm thread pitch and winds in fully and freely by hand until the sealing o-ring contacts.
The 3/8" BSP pipe fitting is 19tpi (1.33mm thread pitch) and will only thread in 1 turn by hand before the mismatch in thread pitch starts to bind.

This 16x1.5mm metric thread is common to most japanese and many non-japanese vehicles for water temperature senders and switches, the thermo-fan switch I am currently using was originally honda fitment.
On my engine the three ports above the thermostat and 2 ports below all share this thread.

There are many threads on here claiming 3/8" BSP which I will go through and correct.
I'm not disputing the thread on the water temp sensor or the oil pressure port, I'm sorry my 1am typing mistake has caused a issue. I went over my post this morning and changed it here and on Mud.
 

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Dougal,

I'm sure you are correct on the thermostat plugs being the metric size you described. I could not find any to fit, so I bought them from Isuzu who told me they were BSPT. My Toyota Temp sensor fit perfect in the housing.

My Toyota oil sender did not want to thread into the Isuzu block port, so I found a BSPT to metric adapter and it went together well?? Who knows, maybe my threads were buggered.

Thanks for the correct info

Doug
 

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Discussion Starter #9
I am open to the idea of there being different thermostat housings with different threads. But I'd prefer people didn't just buy BSP fitting and wind them in without checking.
 

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heads up to all. The upper thermostat housing is a discontinued item and no one seems to have them in stock nor have them used. JB Weld is your friend....I still dont know if mine will hold up.
 

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All the Isuzu, Toyota, and Suzuki threaded fittings for things like sensors that I have encountered were BSPT.
 

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Discussion Starter #12
All the Isuzu, Toyota, and Suzuki threaded fittings for things like sensors that I have encountered were BSPT.
Any tapered threads will be BSPT. But if you strike a straight sensor thread with an o-ring face-seal, then it's likely M16x1.5 instead.

These sensors on Jarek's OM617 build are the same metric thread and fitting as my 4BD1T. They aren't tapered and screw right down into the housing and seal against the face. It's interesting that his UK original engine and German replacement also ran the same fittings.
 

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Metric pipe threads are BSP. It is just that they change the name from British Standard Pipe to DN (from the French for Diameter Nominal, or some such). So same thread diameter, pitch and angle as BSP. As we know pipe threads are made to suit the outside diameter of pipe, but pipe sizes are based upon the nominal bore, not the OD.

Japanese, JIS, also base their pipe threads on BSP. Don't take this statement to mean that their instrument sensors use pipe threads, they may use some other metric diameter and screw pitch that suits them.
I need to correct the 1st line. 'DN' is the symbol used for ISO metric pipe sizes, but the symbols used for ISO metric pipe thread sizes are 'G' for parallel threads or 'R' for taper threads - originating from Germany, G for gas pipe, R for rohr (meaning pipe).

However, the important part about ISO metric pipe threads being the same (diameter and pitch) as BSP threads is correct, with 'G' = BSPP and 'R' = BSPT
 

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Discussion Starter #14
I need to correct the 1st line. 'DN' is the symbol used for ISO metric pipe sizes, but the symbols used for ISO metric pipe thread sizes are 'G' for parallel threads or 'R' for taper threads - originating from Germany, G for gas pipe, R for rohr (meaning pipe).

However, the important part about ISO metric pipe threads being the same (diameter and pitch) as BSP threads is correct, with 'G' = BSPP and 'R' = BSPT
I am also seeing G or BSPP (parrallel) referred to as BSPF a lot.

If you want to really confuse the sales staff in a tool shop, ask for a taper (primary or intermediate) tap for a straight BSP thread.
 

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I am also seeing G or BSPP (parrallel) referred to as BSPF a lot.

If you want to really confuse the sales staff in a tool shop, ask for a taper (primary or intermediate) tap for a straight BSP thread.
I suspect you will get the same response you would get asking a journeyman machinist to machine something to a 1/3 of an inch (you should probably be ready to duck :lol: ).
 

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I am also seeing G or BSPP (parrallel) referred to as BSPF a lot.

If you want to really confuse the sales staff in a tool shop, ask for a taper (primary or intermediate) tap for a straight BSP thread.
I don't know when or why it came about that a F or M suffix was used to denote female (internal) or male (external) threads. I get particularly annoyed when they do it for NPT, because NPTF has always denoted the "dryseal" interference form of the NPT thread (best pipe thread for sealing against high pressure hydraulics).

Sorry about off topic post.
 

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Speaking of cutting threads, I have re-tapped most of the aforementioned threads to NPT.

Terry
 
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