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Tapping the brass block plugs for temp sensor

Old Oct 30, 2008 | 12:53 PM
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Default Tapping the brass block plugs for temp sensor

Who has tapped the threaded allen head block plugs for a temp sensor?
I need to mount a temp switch for the fan, in addition to the computer and gauge sensors in the heads.
I dont have an allen head wrench big enough to remove it, so I was just going to drill and tap it on the block.
Is it thick enough in the center to get a good 3/8" NPT tread in it?
Gary
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Old Oct 30, 2008 | 01:28 PM
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Yes you can tap it,I have done the same on Hi pressure hydraulic system's (300 psi) with no problems. I would remove it to keep the chips out of the coolant system/water pump.
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Old Oct 30, 2008 | 03:37 PM
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Take a bolt with the proper sized head and use that as an allen wrench. I welded a nut on the other end to get a socket on it, but you could just as easily put two jam nuts or vice grip on there. I wouldn't try working it on the block. You may not have enough depth for the tap.

Here is a picture of mine adapted to a Datsun sensor. I soldered the three left most pieces together so it doesn't leak and goes back in with a standard wrench. If I remember correctly, I tapped it with a 1/2 NPT, then used the 1/2 to 3/8 adapter (second from left). I think I had to do it that way because the bolt head was bigger than a 3/8 tap.

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Old Oct 30, 2008 | 05:18 PM
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An upside down bolt...........
Genius!!!!!!!!!!!!!!!!!!!
I didn't want to spend $100 on a wrench set I would only use once.
Originally Posted by Pop N Wood
Take a bolt with the proper sized head and use that as an allen wrench. I welded a nut on the other end to get a socket on it, but you could just as easily put two jam nuts or vice grip on there. I wouldn't try working it on the block. You may not have enough depth for the tap.

Here is a picture of mine adapted to a Datsun sensor. I soldered the three left most pieces together so it doesn't leak and goes back in with a standard wrench. If I remember correctly, I tapped it with a 1/2 NPT, then used the 1/2 to 3/8 adapter (second from left). I think I had to do it that way because the bolt head was bigger than a 3/8 tap.

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Old Oct 30, 2008 | 10:25 PM
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Default Tap the head

Just take the bolt out and drill and tap the head.

Easy to do. Drill bit and tap are about $25 tops.

No adapters that look weird.

My .02 cents worth.
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Old Oct 30, 2008 | 11:51 PM
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On the passenger side of the block, the even side if you please, just in front of the crank sensor is a smaller plug that also goes to a water jacket. I, well kinda forced my temp switch sender into that one. It felt pretty tight going in but with a little pipe thread compound I've had no issues with leaks, and it and the fan works great.
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Old Oct 31, 2008 | 02:07 AM
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Why go through all the trouble!! The passenger side rear already has what you need. You don't even have to rethread anything...VDO makes a metric temp sensor costs all of $10. Save yourself tons of headache
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Old Oct 31, 2008 | 02:10 AM
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do you have a link to that sensor? I found one that fits but the ohms are wrong so it pegs my gauge
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Old Oct 31, 2008 | 07:54 AM
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Front drivers side head is used for comupter temp sensor.
Rear passenger side head is used for the temp gauge sensor.
Then I still need a place for the fan on/off temp switch.

Originally Posted by fast400
Why go through all the trouble!! The passenger side rear already has what you need. You don't even have to rethread anything...VDO makes a metric temp sensor costs all of $10. Save yourself tons of headache
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Old Oct 31, 2008 | 08:44 AM
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If anybody knows of a source for fan on-off temp switches that fit in the stock heads, I would like to know about them. Painless offers a relay kit that includes a metric switch, but they don't sell just the switch. At least I couldn't find it anywhere. somthing that comes on around 200° or more to trigger the high speed fan would be perfect.

I have read a number of posts that say to lathe down and rethread a 3/8 NPT switch, but don't feel like buying a die for this one time thing.
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Old Oct 31, 2008 | 11:01 AM
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Originally Posted by garys 68
Front drivers side head is used for comupter temp sensor.
Rear passenger side head is used for the temp gauge sensor.
Then I still need a place for the fan on/off temp switch.
You can let your computer handle that with it's temperature sensor.
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Old Oct 31, 2008 | 12:12 PM
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Yeah, I realize that, but I'm not sure where the setpoints are or if it's even functional in my reprogrammed computer.
So I figured I already had the temp switch, the engine is out, and plug accessable. Better to tap it now if I need it later.

Originally Posted by 6spdgto
You can let your computer handle that with it's temperature sensor.
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Old Oct 31, 2008 | 02:50 PM
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VDO makes the switch. I got mine with my Dakota Digital gauge package.
Thunderstruck, I'll check on a part# tomorrow.
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Old Nov 2, 2008 | 01:11 PM
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Looks like the VDO sensor is for the dakota digital gauges...don't think they'll work on autometers...
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Old Nov 2, 2008 | 07:11 PM
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I'm looking for something that will put a stock type gauge in range

doesnt have to be accurate...just read normal and have room to go for if the engine is getting "hot"
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