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B-Co Kid

Alternate Temp sending unit location

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Greetings, 

In need of some wisdom.  What is the thread size for the threaded port on the top side of the thermostat housing (previously occupied by the emission vacuum tree)??

Previously did the electric fan conversion using a Hayden fan controller, now the fan doesn't come on when expected and the radiator is in need of replacement.  With the radiator being replaced, I am planning to use a different fan controller with a temp sending unit placed in the thermostat housing; research suggests this is the best location.  Currently, I have a sending unit that is situated between the fins of the radiator.  Any help is greatly appreciated.

B-Co Kid

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Yo B,

Consider using a Kragen or Dorman or equivalent new t stat housing that  has a temp sender port on the top of it.

following by Seattle FSB:for a gauge, but equivalent;

"Water temperature sensor: How to tap and install 

--------------------------------------------------------------------------

Disclaimer: This will be overly detailed so as to try to give people more data with less questions as opposed to the opposite. The job is not hard, regardless of the detail.

Every aftermarket temperature gauge on the market requires a temperature sender to get it's readings. They work by using a variable resistor inside the sender that changes resistance based on water temperature. By sending voltage through the sender and comparing the returned voltage to the sent voltage can determine the actual water temp as the water temp varying the resistance results in a different output voltage. This is precisely how the gauge or control unit works to display the proper temperature (it has been calibrated to the response of the sensor already).

There are multiple places to mount the temperature sender such as the throttle body coolant lines, upper radiator hose, engine block, or thermostat housing. The goal is to obtain a location where one can have accurate readings but more importantly readings which are capable of a high rate of change. Ideally the best place would be in the water pump housing or in a block coolant passage right after the thermostat. Unfortunately due to physical design issues of the thermosensor and clearances, the water pump and/or block are a bad idea.

Almost all of the sensors out there are 1/8 NPT size threaded probes with the electrical harnesson the external portion.


Pros/Cons of locations:

1. Throttle Body coolant lines.

Pros: Easy to do. You can use a freely available tee-line with a 1/8 NPT tap in the tee to install the sensor. Reasonably accurate block coolant temperatures regardless of the thermostat state.

Cons: Slow rate of change. Less room for installation when the TB coolant lines are commonly bypassed. No advantage over the other locations except for ease of installation. Due to the flow of coolant through the block, this is really only showing you temperatures indicative of coolant passing through about half the block, post-radiator cooled. Grounding issues.

2. Upper radiator hose.

Pros: High rate of change when the thermostat is open. Harder to find a tee-line adapter for the size of the radiator hose compared to the throttle body.

Cons: Somewhat useless when the thermostat is closed as the readings are more stagnant. This can be an issue when one has a stuck thermostat. In addition we are really interested in the sum of block AND post-radiator temperatures which this location isn't best for. Grounding issues.

3. Thermostat housing.

Pros: High rate of change when thermostat is open. Medium rate of change when thermostat is closed. Since the upper radiator hose is the one delivering coolant to the radiator, as regulated by the thermostat, changes in block coolant temps. are fairly immediate. No grounding issues.

Cons: Requires removal, drilling, and tapping. Stuck thermostat is still an issue, but less so due to the proximity of the sensor to the thermostat itself - basically you'll know when things are wrong before you warp the block.

Since the goal is to do things the right way and monitor coolant temps with the most accuracy and highest rate of change one should mount the thermo-sensor in the thermostat housing. It's a good position as it lets you gauge the rate of change in coolant temps _exiting_ the block, but pre-radiator. If you are seeing a fast rise from 185 to 220F, you should know fairly quickly that there is a problem and to reduce the load on the engine or go full heater/fans and shut it down.

---

Now I know the concept of "drilling and tapping" is scary to some, but it's really not that hard at all. When it comes down to it you're basically just drilling a hole and threading it so you can screw something into it; in our case, the thermo-sensor.

All of the tools required are available at any place selling halfway decent tools. I got mine at Sears as Home Depot and Lowe's have fairly bad selection when it comes to individual taps.


You will need:

1. 1/8-27 NPT pipe tap.
2. 11/32" drill bit.
3. Tap wrench.
4. Some kind of cutting lubricant (or kerosene).
5. Teflon tape.
6. Liquid gasket (I used some Hondabond I had sitting around).

All together it's about 15$.
 

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The T-stat housing already has a threaded port there; I just need the thread size of the port

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Yo B,

Consider using a Kragen or Dorman or equivalent new t stat housing that  has a temp 9sender port on the top of it.

following by Seattle FSB:for a gauge, but equivalent;

"Water temperature sensor: How to tap and install 

--------------------------------------------------------------------------

Disclaimer: This will be overly detailed so as to try to give people more data with less questions as opposed to the opposite. The job is not hard, regardless of the detail.

Every aftermarket temperature gauge on the market requires a temperature sender to get it's readings. They work by using a variable resistor inside the sender that changes resistance based on water temperature. By sending voltage through the sender and comparing the returned voltage to the sent voltage can determine the actual water temp as the water temp varying the resistance results in a different output voltage. This is precisely how the gauge or control unit works to display the proper temperature (it has been calibrated to the response of the sensor already).

There are multiple places to mount the temperature sender such as the throttle body coolant lines, upper radiator hose, engine block, or thermostat housing. The goal is to obtain a location where one can have accurate readings but more importantly readings which are capable of a high rate of change. Ideally the best place would be in the water pump housing or in a block coolant passage right after the thermostat. Unfortunately due to physical design issues of the thermosensor and clearances, the water pump and/or block are a bad idea.

Almost all of the sensors out there are 1/8 NPT size threaded probes with the electrical harnesson the external portion.


Pros/Cons of locations:

1. Throttle Body coolant lines.

Pros: Easy to do. You can use a freely available tee-line with a 1/8 NPT tap in the tee to install the sensor. Reasonably accurate block coolant temperatures regardless of the thermostat state.

Cons: Slow rate of change. Less room for installation when the TB coolant lines are commonly bypassed. No advantage over the other locations except for ease of installation. Due to the flow of coolant through the block, this is really only showing you temperatures indicative of coolant passing through about half the block, post-radiator cooled. Grounding issues.

2. Upper radiator hose.

Pros: High rate of change when the thermostat is open. Harder to find a tee-line adapter for the size of the radiator hose compared to the throttle body.

Cons: Somewhat useless when the thermostat is closed as the readings are more stagnant. This can be an issue when one has a stuck thermostat. In addition we are really interested in the sum of block AND post-radiator temperatures which this location isn't best for. Grounding issues.

3. Thermostat housing.

Pros: High rate of change when thermostat is open. Medium rate of change when thermostat is closed. Since the upper radiator hose is the one delivering coolant to the radiator, as regulated by the thermostat, changes in block coolant temps. are fairly immediate. No grounding issues.

Cons: Requires removal, drilling, and tapping. Stuck thermostat is still an issue, but less so due to the proximity of the sensor to the thermostat itself - basically you'll know when things are wrong before you warp the block.

Since the goal is to do things the right way and monitor coolant temps with the most accuracy and highest rate of change one should mount the thermo-sensor in the thermostat housing. It's a good position as it lets you gauge the rate of change in coolant temps _exiting_ the block, but pre-radiator. If you are seeing a fast rise from 185 to 220F, you should know fairly quickly that there is a problem and to reduce the load on the engine or go full heater/fans and shut it down.

---

Now I know the concept of "drilling and tapping" is scary to some, but it's really not that hard at all. When it comes down to it you're basically just drilling a hole and threading it so you can screw something into it; in our case, the thermo-sensor.

All of the tools required are available at any place selling halfway decent tools. I got mine at Sears as Home Depot and Lowe's have fairly bad selection when it comes to individual taps.


You will need:

1. 1/8-27 NPT pipe tap.
2. 11/32" drill bit.
3. Tap wrench.
4. Some kind of cutting lubricant (or kerosene).
5. Teflon tape.
6. Liquid gasket (I used some Hondabond I had sitting around).

All together it's about 15$.
 

 

■●■●■ My notes show it's  3/8" NPT

I can't  add a reply so I added this here

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Yo B,

3/8" NPT

do you have a pic of the emission vacuum tree location?

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