Sealing leaky NPT fittings

[gnvair]

I have used different sealers over the years. Some work better than others. I was turned on to Leak Lock by a friend who does hvac work. It works really well and is alcohol based so it cleans up easily.

 

[jiho]

I thought the Teflon was for lubricating the threads to get them tighter, not seal them...

The tape does both. It deforms, shreds and bunches up, kind of like a rag. I like tape because it's easy to remove.

Anyway, I guess I just don't understand how wrong I am not to have leaks.

 

[Clone TIE Pilot]

I found an article at the carb shop that says to not use Teflon tape or sealant on the brake booster fitting. The reason for not using Teflon on that fitting is that it lubes the threads too well so you screw the fitting too deep into the baseplate and crack it which ruins it.

 

[565bbchevy]

Any liquid Teflon sealer should realistically work for this application so are you sure this didn't already happen?

The reason for not using Teflon on that fitting is that it lubes the threads too well so you screw the fitting too deep into the baseplate and crack it which ruins it.

 

[Clone TIE Pilot]

Any liquid Teflon sealer should realistically work for this application so are you sure this didn't already happen?

I looked with an inspection mirror for cracks and there are not any.

 

[fleming442]

I looked with an inspection mirror for cracks and there are not any.

Really? Sounds like you need to go back to square one. This thread has fallen into the "i'm-not-hearing-what-i-want-to-believe-it-is" hole. Pull it apart; start over.

 

[Clone TIE Pilot]

Really? Sounds like you need to go back to square one. This thread has fallen into the "i'm-not-hearing-what-i-want-to-believe-it-is" hole. Pull it apart; start over.

That can happen both ways. I have taken them apart a few times to try different methods. Since the threads are in soft aluminum, taking the fittings off and on will wear the soft threads out faster. Each time I take them apart makes it worse. In general, NPT fittings can only be removed a limited number of times before the threads deform too much, especially in aluminum.

For the record, I tried Teflon tape, it leaked, tried pipe dope and it leaked, tried gas line pipe dope and again leaked, tried installing the fittings dry and still leaked. I cleaned the threads between each attrmpt. Neither ports or fittings are cracked, crossthreaded, or galled. The fittings do bind before their heads bottom out like NPT fittings are supposed to. Its likely the soft threads are deforming and the Teflon might have acted as a cutting lube cutting thr NPT bores a little deeper and wider as I retighten the fittings.

There are a lot of differing opinions regarding the use of thread sealants which can lead everyone to not hearing what they want to believe syndrome, OP and responders alike. Even professional carb experts have opposing opinions on the subject of sealants. Either way, there is a reason why most modern cars do not use NPT fittings as they can be pretty problematic.

 

[pontiacgp]

I always used a brass adapter that is left in the base and installed the flared brake vacuum line fitting into the adapter. I don't trust aluminum threads....

 

[Clone TIE Pilot]

I always used a brass adapter that is left in the base and installed the flared brake vacuum line fitting into the adapter. I don't trust aluminum threads....

That is the fitting I am talking about, I guess its really an adapter. The stock one on my Qjet is steel rather than brass.

 

[Clone TIE Pilot]

The loctite did the trick.