Water Temperature Sensor
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Thread sealer only on the last few threads. The first threads will ground the unit.
Without any type of sealer, I would bet a chili dog, fries & shake it will leak. You have two different types of metals. Two different types of expansion / contraction rates plus corrosion and metal to metal reactions
Without any type of sealer, I would bet a chili dog, fries & shake it will leak. You have two different types of metals. Two different types of expansion / contraction rates plus corrosion and metal to metal reactions
Race Director
Joined: Jul 2018
Posts: 10,591
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From: San Antonio, TX/Mahopac, NY
2026 Restomod of the Year Winner
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NPT requires thread sealer.
Le Mans Master
Joined: Oct 2010
Posts: 6,937
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
Rectorseal #5 available at any home center the stuff works on high pressure steam it will seal l anything.
Last edited by 7t9l82; Mar 20, 2021 at 06:40 PM.
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Plumber's pipe 'dope' will seal the threads to keep coolant from leaking. And any contact points between the two threads will wipe the sealant clear and allow electrical contact. Silicone sealants or teflon tape/paste may or may not prevent making 'ground'.
Team Owner
Joined: Jan 2006
Posts: 39,390
Likes: 171
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
Guess I've been outvoted 
Hasn't leaked yet but maybe I will use some plumber's dope on the new one that's on the way.
Hasn't leaked yet but maybe I will use some plumber's dope on the new one that's on the way.
Thread Starter
6th Gear
Joined: Dec 2020
Posts: 6
Likes: 0
Answers run the entire gambit! I originally installed mine with tape. Think I'll let it alone and see if it works. A real pain to get to it at this point. Thanks for your help. BTW, There is an open, threaded hole on the left rear of the block just above the oil sending fitting hole. It goes clear through the block wall. It is in the area of the flywheel. Does it need to be plugged? What is its purpose? The guy who did my engine had a plug in the oil sending fitting hole but left this hole open.
Melting Slicks
Joined: Sep 2004
Posts: 3,226
Likes: 668
From: Northeast
This is what the 78 Service Manual states " When installing new engine temperature sending unit. DO NOT use thread compound on unit threads".
Team Owner
Joined: Jan 2006
Posts: 39,390
Likes: 171
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
