Sealing crankcase for vacuum

Just a quick question: i’ve pretty much addressed all the common areas for crankcase leakage in order to run some vacuum in the crankcase. Does anyone know offhand if the inner passageway of the braided steel oil dipstic is sealed? Anyone found out that this type of dipstic is a leakpoint within the tube itself. The tube to block is sealed very well with an o ring and some rtv ultra grey. And the dipstick to tube is pretty tight and snug with an oring. I can’t really tell if the tube is actually lined or just braided, which might let some air in through the braids?

TIA.

OOPS!

Any other leak partially disables the system.

How much vac are you planning to pull.. if your using a vac pump your probably good to go

You must have some sort of flexible dipstick tube?? If so just look at it to see what it is made from. If it has a rubber liner then it should be air tight but it sounds sketchy to me for sealing. I guess it just depends on how much vacuum you are trying to pull. A dipstick will always be a problem unless you get one that is designed to seal. Older Mopar engines were not designed by the factory to be sealed up so it takes some work to find and fix all the leaks.

I am running a star pump and hope for 12-13”. I have tried to address all other areas. Changed the rear main to ptfe double lip. Also change out the jesel cover seals for ptfe double lipped seals up and bottom. Air tight oil fill cap, regulator for vacuum pump is inline by pump(which vacuum pump manufacturer said is preferable). Everything else is rtv sealed and all surfaces were inspected for flatness. The dipstick tube is the flacible type from milodon, i believe.

Run the late model style dipstick of current production motors that has a o ring at the top. Use a tube bender and shape it the way you need. Seals perfect.
Doug

Thank you, everyone, for your replies and advice.

On my race engine I used a dipstick from a Lexus SC300 and made my own tube. The Lexus dipstick wasn't very expensive at the dealer and it had a double o-ring at the top that sealed up really well. On my Duster I have a dipstick from a newer Chevy truck. It has a bright yellow handle and an o-ring seal.

Thank you Andy.... i’ll try to get a look inside the braided tube to see if it is lined. The stick is a very tight fit with an oring to the tube. I might also just pressurize a few psi to see if it holds 4-5 psi in the crankcase to test it.

That’s a great tip, Doug. Thx. Does that dipstick fit the older blocks good, or you had to modify? If it just fits perfect, i will def do that on the next build.

Well, it was very difficult to see and confirm, but i was able to get a small peek inside the tube, and it is, in fact, lined with some sort of material. Maybe teflon, maybe some sort of rubber. But, it was solid, so i think i’ll be fine from a sealing standpoint. Just fyi. I put an oring on the bottom parts that go into the block so that whennit is shoved down and bolted, it will seal in addition to the rtv i put on. The top, as I said is very tight with an oring.