DBKissel Posted September 14, 2019 Share Posted September 14, 2019 Can anyone suggest what they know to be a good sealant for a transmission drain plug? This is a 1925 Kissel Speedster with W140 synthetic gear lube (about to be put in). I have used teflon tape with high quality plumbers pipe dope in the past, but always seem to have a drip. I'm thinking black auto RTV sealant or non hardening form-a-gasket. Just a simple pipe plug a shown. Thoughts? Link to comment Share on other sites More sharing options...
whtbaron Posted September 14, 2019 Share Posted September 14, 2019 Be careful with the thicker silicone based concoctions... not so much with primitive transmissions, but more-so with motors. Chunks of silicone can be squeezed inside and roam around causing problems. I'm surprised the teflon/dope solution didn't work for you. Have you tried cleaning up the threads? Also inspect around the hole closely. If someone has been wrapping too much material in there, if may be causing cracking around the drain hole. Normally for nasty ones I use one coat of dope... a couple wraps of teflon... then apply more dope and "usually" that fixes it. If you can get access to some small taps/dies for NPT maybe try lightly cleaning the threads. With newer automotive oil pan drain plugs, you can also get oversized plugs but I doubt you would get one in that style of plug/thread. Might be worth checking out if the problem persists, but again, be careful because going too big can split a casting or pan. Link to comment Share on other sites More sharing options...
JFranklin Posted September 14, 2019 Share Posted September 14, 2019 (edited) I use LockTite blue, easy on and off with no danger or mess. Edited September 14, 2019 by JFranklin (see edit history) Link to comment Share on other sites More sharing options...
PFitz Posted September 14, 2019 Share Posted September 14, 2019 (edited) I use Plumber's Teflon paste from my local hardware store. Does a very good job of sealing even worn drain plugs against hot engine oil leaking. Very forgiving of sticking to oily threads. Also holds up to gasoline for sealing threaded fuel line fittings. And, no worries of bits of tape ever getting into places where it shouldn't. Paul Edited September 14, 2019 by PFitz (see edit history) 1 Link to comment Share on other sites More sharing options...
joe_padavano Posted September 14, 2019 Share Posted September 14, 2019 31 minutes ago, PFitz said: I use Plumber's Teflon paste from my local hardware store. Does a very good job of sealing even worn drain plugs against hot engine oil leaking. Very forgiving of sticking to oily threads. Also holds up to gasoline for sealing threaded fuel line fittings. And, no worries of bits of tape ever getting into places where it shouldn't. Paul ^^^THIS. It's an NPT thread. Why would you use anything else? Link to comment Share on other sites More sharing options...
Locomobile Posted September 14, 2019 Share Posted September 14, 2019 Teflon tape does not work too well. This is what I use for all my steam fittings, and more steamfolk are switching over to it. Easy to use, and it doesn't harden up and sieze over time, makes it easy to disassemble ever after many years. https://www.amazon.com/General-Purpose-Thread-Sealant-8oz/dp/B01LZTXVR8/ref=sr_1_6?keywords=Jomar+sealant&qid=1568483859&sr=8-6 2 Link to comment Share on other sites More sharing options...
Guest Posted September 14, 2019 Share Posted September 14, 2019 57 minutes ago, joe_padavano said: ^^^THIS. It's an NPT thread. Why would you use anything else? Designed to not leak if tightened properly. If it leaks.weeps you need a new plug. The one on my Pontiac (500,000 miles) is still the original and does not leak, but it must be tight. I would never ever use teflon tape or paste on an engine. Link to comment Share on other sites More sharing options...
JACK M Posted September 15, 2019 Share Posted September 15, 2019 The key might be in where the plug lives. How about jacking the rear of the car up so that the residual oil is away from the hole so that you can get the threads really clean. I don't mean with just a rag. Link to comment Share on other sites More sharing options...
mike6024 Posted September 15, 2019 Share Posted September 15, 2019 It is tapered thread, pinches, wedges itself in there when tightened. i smear some grease on it, so it can be removed next time and doesn't get stuck. Link to comment Share on other sites More sharing options...
Dave Mellor NJ Posted September 15, 2019 Share Posted September 15, 2019 Plain plumber's dope is made for use with water. You have to make sure the dope is good for petroleum. read the label Link to comment Share on other sites More sharing options...
Bloo Posted September 15, 2019 Share Posted September 15, 2019 Teflon tape has no place in a car engine. Teflon paste generally works fine, but it acts as a lubricant, the taper should seal the threads. It is slippery so don't overtighten and break something if you use it. Anaerobic thread sealer might be worth trying if teflon paste is not working. . Link to comment Share on other sites More sharing options...
PFitz Posted September 15, 2019 Share Posted September 15, 2019 (edited) In a perfect world, tapered thread drain plugs should seal without a sealer. The problem with that is antiques are not perfect - most are far from it. Even in the plumbing & heating business it's recommended to use a sealer on tapered thread. Plugs that have been removed and installed countless times over 80-90 years don't just wear the plug threads they also wear the threads in the hole that is being plugged. I've had many come through my shop that did not seal hot motor oil no matter how tight you get them. And the originals are not like the modern plumbing supply equivalent, so using a sealer allows saving the original for a show car and not having it weep oil. Paul Edited September 15, 2019 by PFitz (see edit history) 1 Link to comment Share on other sites More sharing options...
Mikefit Posted September 15, 2019 Share Posted September 15, 2019 My money is on a cracked case the more you tighten the plug or wrap tape on it the more you force the crack open even a small amount. Link to comment Share on other sites More sharing options...
R Walling Posted September 15, 2019 Share Posted September 15, 2019 If the threads are NPT, put a wad of grease on a tap and turn it in until there is pressure felt, then give it a turn (dressing up the threads) and back it out. The grease will hold onto the chips. Use a new plug with Permatex. All done! Link to comment Share on other sites More sharing options...
Locomobile Posted September 15, 2019 Share Posted September 15, 2019 On an antique that is being preserved it is best to use a sealer. An NPT tapered thread connection, every time the fitting is reefed together, the female threads enlarge a small bit, depending on the material like Brass or Bronze, they can open significantly. We see this all the time with antique steam car fittings cast bronze and iron where they have been connected, disconnected and over tightened several times over the years, they get to a point where the only way to seal them is with a sealer like I listed or they must be repaired, i.e. bored, silver-soldered sleeved and retapped or go up a pipe size. -Ron 1 Link to comment Share on other sites More sharing options...
edinmass Posted September 15, 2019 Share Posted September 15, 2019 NEVER - EVER - USE TEFLON TAPE ON A CAR - EVER. 2 Link to comment Share on other sites More sharing options...
Frank DuVal Posted September 15, 2019 Share Posted September 15, 2019 Gasoila, made for petroleum products. https://www.fedprobrands.com/ Link to comment Share on other sites More sharing options...
DBKissel Posted September 16, 2019 Author Share Posted September 16, 2019 Thanks to all with your suggestions- It looks like Gasoila and maybe Rectorseal T+2 would be the best choices. Glad I asked. [Both are availalble on Amazon too!] Link to comment Share on other sites More sharing options...
trini Posted September 16, 2019 Share Posted September 16, 2019 Roger Walling has a good idea. Also run the plug with a pipe die and use Gasoila.. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now