Coolant temp sensor doesn't screw all the way in

Chickenhawk

Original poster
Member
Dec 6, 2011
779
I replaced my thermostat, rad hoses and ECT sensor last weekend. All went well until I tried removing the old ECT sensor. It snapped off at the head, leaving the body and threads inside the block. I finally got it out by drilling a hole in it and using what is laughingly referred to as an "easy out." (It is neither "easy" nor will it always get it "out.")

Checking for solution on line, I found a LOT of people break off their coolant temp sensors in the block or heads. Being a bit gun-shy so to speak, when I installed the new AC Delco temp sensor, I was VERY careful. There was a fair bit of teflon tape on the threads from the factory and it didn't screw down as far as the old one. It was getting tighter and tighter, to the point that I was worried about breaking off the new one. I finally stopped before the wavy washer made contact with the block.

I will monitor it for leaks but I don't really want to go through all the hassle again to tighten it if it doesn't need it. It is a tapered thread; there are several turns of Teflon tape on the threads and it is tightened to about the right spec (even if it didn't tighten down all the way.) I have done lots of plumbing, and I wouldn't tighten any tapered thread fitting more than I did.

Anyone else experience a new sensor that didn't go all the way in? Did you ever experience a subsequent leak?

Thanks
 

littleblazer

Member
Jul 6, 2014
9,265
If it is in fact pipe thread, it's fine. If it's a compression fit then not so much... My guess is it is npt or metric pipe thread so you should be okay...
 
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Sparky

Member
Dec 4, 2011
12,927
It is tapered threads I'm pretty sure. As long as it doesn't leak you're fine.
 
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Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
When I replaced mine, I didn't tighten it enough so it eventually backed off and leaked. I tightened it better onto the sealing washer. Is the aluminum washer there? It shouldn't be wavy.
 

AtlWrk

Member
Dec 6, 2011
674
They are definitely straight threads (M12-1.75 to be exact) and the washer should be doing the sealing, not the threads. Doesn't matter if it's copper/aluminum or flat or wavy.
 
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mrrsm

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Oct 22, 2015
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That Little Brass Remnant has GOT to be removed. There is an inexpensive alternative to the ordinary, spiral-fluted designs of the common, destructive and brutal Bolt Extractors that is really a "better fit' for removing soft brass fasteners out of even softer Aluminum components and it is available from Walmart. The only limiting factor here would involve the accessibility of inserting whichever of these devices gets in deep enough to get a snug bite into the inner brass portion and then hold it snugly as you carefully unwind what is left of it. Use no lubrication here... as the last thing needed to be done is make the steel to brass interface slip as you work.

The most important considerations are to try and get the Tool inserted as vertical and square as possible at a Right Angle to the Bolt Centerline. And as you apply the reverse torque... just avoid using too much force or herky-jerky motions that will distort what is left of the inner brass to the Aluminum Block or Head thread-lines and warp into a permanent locked situation. This device in the right hands and with a slow and thoughtful use has saved more Machinists from other agonies when things go sideways because other methods have already failed. The Best of Luck and hoping for Your Success:

https://www.walmart.com/ip/5-Piece-...Broken-Stud-Extractor-Bolt-Tool-Set/982244957

1981f051-91a6-45aa-9d39-a77b59ff936a_1.1e41aabfcbd576fd9b3ee9bb454d2dd7.jpeg


I would also suggest that just as important to the outcome is the choice you make for the Holding Tool. The cheap handles for holding the bits in securely will almost guarantee failure. I am not suggesting that you use an entire paycheck on getting the very best that will give you the 'perfect feel' for when the counter-force wins the battle and breaks the Brass Core loose... but something close to THIS one is what works best. Repairing Machines as being such a mundane task...gets extremely intimate in situations like this one... getting something that works to help a problem become 'unscrewed' while not getting your wallet 'screwed' yourself is the real trick:

61iS5zGKbBL._SL1000_.jpg
 
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Chickenhawk

Original poster
Member
Dec 6, 2011
779
Those are EXACTLY the extractors that I used. (Except I got them at NAPA.) Slow and thoughtful was the key. You are 100% correct.

As for the threads, some GM sensors are 3/8" NPT and some are M12 1.75. I have researched the one I removed and I can't find the thread but measured the outside diameter with a micrometer. First part of the thread is .445 outside diameter; last part is .465 outside diameter. When I tested it in an M12 1.75 die, it was a perfect fit, but tightened near the end, so it is definitely a tapered thread.

The new sensor had more Teflon tape from the factory than the old one. Because I properly torqued the old one, and the washer made contact with the block ... and it STILL snapped off when I tried to remove it, I have been gentle with the new one. Perhaps TOO gentle?

Seriously, any more torque and I will need to cut a slot in an 18mm deep socket. An open end wrench is starting to slip.
 
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mrrsm

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Oct 22, 2015
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If you had a full work field to deal with... drilling it out and getting a Tap & Helicoil Kit that is a perfect match for the Metric flavor of the ECTS would not be too hard to do... assuming there is enough room under the hood to work on that section of the block. I like using the ARP Thread Sealer in situations like these with nested threaded components because it can withstand temps up to 500 Degrees... pressures at over 100,000 PSI and it never dries out and will stay in place for as long as needed and not leak. It works with Oil, Gasoline and Water exposure, too:

upload_2017-5-25_1-45-6.png
 
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Chickenhawk

Original poster
Member
Dec 6, 2011
779
Didn't need to do any of that. The square easy out got it out without damaging the threads. It is putting the new one in that it seemed to tighten long before it made contact with the washer.

The Teflon tape applied by the factory is rated from -200 degrees F to +500 degrees F. I think it will be okay.

Two days of driving and no leaks so far.
 

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