Valley bathroom faucet leak at handle base

[Soca]

My ( old Valley ) bathroom sink hot and cold faucets leak at the handle base when the faucet is turned on. In one faucet I cleaned up the walls of the stem, replaced the spring and seat and put in a new cartridge. I tightened down the bonnet nut securely. It still leaks ! Any idea as to the cause of this leak ? BTW, I placed the new spring into it's stem hole and pushed the new seat cap securely down over it . Is that how it's suppose to be installed ? Thanks for any help.

 

[Terry]

https://www.homedepot.com/p/DANCO-3Z-6-Hot-Cold-Stem-for-Valley-Faucets-17312B/100542851

Does the stem look like this?

 

[Sponsor]

 

[Soca]

https://www.homedepot.com/p/DANCO-3Z-6-Hot-Cold-Stem-for-Valley-Faucets-17312B/100542851

Does the stem look like this?

Yes.

 

[Terry]

There are two places that seal. The small rubber seal with the spring, and the O-Ring around the stem.
The O-Ring prevents water from leaking out the top. The bonnet nut just holds the stem in place.

 

[Soca]

There are two places that seal. The small rubber seal with the spring, and the O-Ring around the stem.
The O-Ring prevents water from leaking out the top. The bonnet nut just holds the stem in place.

Terry : Should the rubber seal that covers the spring be pushed down into the hole as far as possible ? Also, even though the o-ring looks thin the stem opening for the cartridge is a tight fit that won't allow for a larger o-ring. As a last resort could I lay down some teflon rope where the cartridge inserts and screw the bonnet nut down over that ? Would that stop the water that's apparently getting past the o-ring ? Thanks.