I took this picture last night when a question was asked about the proper oil level in a sight gauge. I pointed out how low the oil was.
Today I filled up with new oil and left the upper petcock open to let the excess drip.
When I came back later the level in the gauge was low and the container I left to catch the drips was overflowing. Oil was dripping from the gauge.
It's time to go back to the factory setup.
Murphy's Law - Fresh oil leaks more then dirty old oil from a site gauge. :-)
I have seen times when the sight gauge was full of oil but none was in the crankcase.
I remember on a group tour going to the National Tour in Auburn Ca. one of our member's '15 touring slowed down to where it would hardly go 25 MPH.
It had developed an oil leak in the hogs head gasket and it lost so much oil the engine was seizing up but the sight gauge still showed full.
They also get broken from tree branches & junk on the ground. Git rid of it.
Get your wife a rubber kneeling pad so she doesn't snag her stockings when she checks the oil with the original style petcock.
I don't see how that would work any
way without an air bleed at the top which would then cause a leak. Is that why the top un-screws? To let the air out perhaps the first time you use it?
You are correct, the sight gauge will not work without some kind of vent on the top. Some rely on leaky seals and some drill little holes in the top.
More info at:
I probably originally was no different than any other T newbie...read, read, and read some more and although odd...the fill to the top petcock. drain to the lower petcock and pour 1/2 back in seemed to be the conventional wisdom.
I later found that filling to the top before going out didn't cause any issues and really didn't spot any more than the previous Longer safety factor, yea team! for some reason my cars do like to spot, but never use that much oil. My top off is less than a quart combined for a season. Yes, I do poke petcocks.
Then after what was 30 years of the other way and several cars with no issues the Hack came with a funny looking thing in the bottom petcock. Ah, maybe I play, maybe I try, but turned out too lazy to care It hasn't broken or gotten snagged, I did check and it has like a 3/64 hole in the top that I figured should be poked from time to time but never poked it...I still fill to top petcock, even on the Hack before going out and don't even try to look at what the level shows! Maybe this summer I might make that an observation goal...to see how well it even works
Sight gauges are excellent. You can see exactly how much oil there is. There is no way of knowing this with the factory cocks alone.
It does need a tiny vent in the top. Mine has a gap in the top O ring.
You need to check it before you start to see the oil level
occasionally while the engine is running - when the glass should be empty. If it isn't, there's a blockage somewhere.
you can clean the glass with the engine running; just unscrew the top, lift out the tube, wipe it and replace.
I prefer to take the glass out of the sight gauges and install clear plastic tubing from the hardware store. A simple 25 cent fix with not much chance of breaking from road debris, and I do drill a tiny vent hole on top. This APCO oil gauge is what I use on my '19 Touring and the white ball is really easy to see even in low light...
The accessory RAJO oil gauge works very well,and is being reproduced.
The sight gauge I have on my roadster has a petcock before it that can be closed after I've checked the level. To check, just open the petcock and wait for it to find its level. No chance of leakage should it get damaged.
OK. makes sense now (about the air bleed). Never thought about the fact that the level drops past the lower opening while it's running meaning you'd have to manually bleed it basically every time you ran the engine. About as much work as the petcock check set-up is.
Sight glasses on boilers have shut offs at top and bottom. It is standard procedure to open and close the shut offs periodically to see what the level in the glass does due to pressure from only one end. If the water level changes, you know the lines are not blocked and it is reading proper water level with both shut offs open. I could easily see how an oil sight glass could show oil in the glass but the crankcase be empty, if the top vent were to somehow get clogged.
Some people rant that sight gauges are a risky bet, as they may fall off or get broken and you lose your oil.
Here's how I mount my sight gauge so it's up close to the pan and not on a 3" long pipe.
You don't need liquid flow for a pressure or liquid level gauge, so I always run a sheetmetal screw into the fitting next to the source, and make it just tight enough to flow a few drops a minute. I then cut the head off if needed.
Then you can break the line, lose the sight glass or whatever, and liquid loss will be insignificant.
I bought this one from Lang many years ago, and the vent is built in to the cap.
Rocks can break the glass. That was the only draw back.
Here's some links to a number of different Oil Site gauges I have posted previously under the Accessory Of The Day threads.
Here are some remote oil gauges
did you ever think of making a transparent communication with plastic tubing between the top and the bottom valve ? The valves could stay open temporarily or all the time .Even with the valves replaced by 2 connectors and transparent plastic tubing between the 2 that would work perfectly and give a permanent indication .
It's not very hard to get down on one knee and turn the petcock. I just fill it till it runs out the bottom and then add enough to run out the top or one quart, whichever happens first. When I check it I open the bottom one and if oil runs out, it has enough. Simple. If it is slightly above the upper petcock it won't hurt anything. before each tour I check it and if it doesn't run out the bottom I add. On long tours I check it every day before I start. I installed a sight gauge many years ago and it broke, so that was enough for me. I now use the original system on all 3 of my cars.
Here's three different petcock tools that come in handy when getting down to check the petcocks. I personally like the one with the poker on the end to clear the debris from the petcock to get and accurate check of oil flow.