MTFCA Forum

Hello....I put an oil sight gauge that I purchased from Snyder's on my car during the last oil change. It seemed to make checking the oil level very quick and easy because it is easy to see the oil level. Last night I started draining the oil out of the car when I realized how late it was and decided to call it quits for the night without refilling the oil. This morning I took a peek under the car and noticed the oil level in the Oil Sight Gauge had only gone down a little bit from where it was even though the oil pan was empty.
All I could think of was the engine running with no oil while I was thinking it was full of oil.
Anyone else have this problem? I am thinking about a dipstick to assure accuracy. What works best?
.
.

Sight glasses can and do cause so many problems up to and including engine damage (either from false readings to breaking off and draining the oil while running) that I would NEVER have one.

Dipsticks are great if you're not seriously showing the car

Looks like an air lock issue. You oil is perfectly clean and that only is like that until you start the motor.

I have two of those units on my cars and they work quite well. What you need to do is drill a teeny tiny hole in the top of the cap so that the oil equalizes in the tube. By teeny tiny hole I mean the type of drill bit that folks use to build model trains. You will have folks probably come on and tell you that the next rock that goes underneath your car is going to break the glass and drain all the oil and you were going to ruin your engine. What I did was take the glass out and substitute plastic tubing. I have been using them for over 20 years and I’ve had no problems.

It’s too bad they have to be modified with the tiny hole and plastic tubing but it is what it is. Mine were free in a box of spare parts so I paid nothing to begin with.

I drilled mine a bit bigger. Once the engine starts, the oil is pulled out of the sight glass anyway.

A really good sight glass would be expensive to manufacture. It would have a means of shutting off the bottom connection and it would have a bottom and top plug to facilitate cleaning the inside of the glass. It would have plugs to allow cleaning the upper and lower connections to the pan. It would have a vent of some sort that would exclude dust and water from the road and it would be arranged so as to facilitate cleaning. The whole thing would need some sort of stone guard attached to the pan. All things considered, sight glasses are probably best left to stationary applications. A dip stick that reads from the center bottom of the pan is the most accurate and safest. A dip stick also allows easily checking the oil level and condition, including checking for fuel dilution or water intrusion.

I really like the Advantage dipstick. Its easy to install and gives a good reading from topside. I installed one in one car and it worked so well the second car got one just a few months ago. With a dipstick you not only can gage the level, you can easily see & feel the oil. That may allow you to spot trouble like a blown head gasket early.

Paul

Make sure the top of the sight glass housing is vented, otherwise you'll get the air lock issue that someone else mentioned.

I made my own sight glass from a double male thread petcock (not easy to find), a right angle fitting, and a piece of clear vinyl tubing. The tubing is completely open on top for maximum venting. I only open the petcock when I want to check the oil level, otherwise it is closed.

With the two petcocks I have found sometimes one or the other gets plugged up with sludge. Then the oil won't run out until I push a small wire through it. I would suspect the passage between the crankcase and the glass might be clogged up. In that case, I would not trust the reading on the sight gauge, especially if the oil inside looks as clean as it does on yours, unless the clear oil was right after an oil change.
Norm

Michael, I like that APCO unit, but there is a small metal strap missing in your photo. That pipe will fatigue and break over time. The unit is too heavy to be without it. The metal strap attached it securely to the pan bolt. If you cannot find a pic, I’ll do some digging.

Dropacent wrote: ↑

Fri Sep 10, 2021 1:14 pm

Michael, I like that APCO unit, but there is a small metal strap missing in your photo. That pipe will fatigue and break over time. The unit is too heavy to be without it. The metal strap attached it securely to the pan bolt. If you cannot find a pic, I’ll do some digging.

Thanks for the heads up… I had no idea there was a strap. Most have probably been thrown in the trash because they look like spare bent metal for no particular purpose. I will make one from “plumbers strapping”. I’d bet no one under 60 years old knows what plumber’s strapping is……

Courtesy of Dr. Jay

Hi Brian,
I run a sight glass on my firetruck because some one stripped the top petcock hole out so I had to weld a plug in it. My sight glass has a small hole in the top to let air in and out so it reads accuratly. The issue you will find with the hole is if you tow on a open trailer the wind from high way speeds will syphon the oil out of the hole all over your trailer. Mine has a hex cap so I put a plastic cap on it to solve this. Yours will probably need a small hole in the cap also. As far as rocks hitting it and breaking the glass, I would limit my speed in reverse to under 20 mph.
Craig.

I'm a fan of the sight glass but it's good practice to check it before you start AND then check that it's empty when running.
That way, you can believe it.

WOW....thank you everyone for the feedback. I really like the idea of the RAJO oil gauge and I may look into that some time in the future. I still like the idea of this glass gauge and I want to see if I can make it work. Based on the advice all of you have given me it seems like my logical path forward would be to drill a very small hole in the top to create a true vent. I should also check the level after the car starts because the oil level should drop when you start the car...if it drops it is working and if it does not it is not working. Lastly, the top valve is still in place...so I should manually open it and see if a little oil will drip out just to make sure the gauge is telling the truth.
.
I liked the innovative oil level checkers made from the short pieces of clear hose. If it were my idea I would refine it a bit into a product, write up some installation instructions and make a bunch of them to sell. Just open the valves and you can see your oil levels without any dripping on the ground and then close the valves to prevent any from leaking while you are driving. Very simple and safe.
.
Take care.....Bryan
.

Wondering if you had too much oil to begin with?????...just a thought.

I don't mind the stopcock type oil level check on a tractor, where you can just walk up and make the check. On a T, you have to get under the car, and if the wind is blowing, you'll probably get oiled. Another disadvantage is waste, and the fact that you can't tell much about how far above the bottom cock the oil level is unless you fill it up until it runs out the top one. In cold weather, getting an accurate check can take a while. In hot weather, you can get burned handling the stopcock handles. The cocks can also stop up, which a dip stick is unlikely to do. One of the many practical improvements offered on the Model A Ford was the dipstick.

I have an early/period sight glass on mine, it has a small hole in the top....if you park unlevel with it full, she leaves some behind.
I have never had any problems. I will say, if it’s 1/4”-1/2” down, it needs close to a quart.

Make sure it has a vent hole
And it's clear when engine is running good chance it show low or empty as oil is elsewhere
Could have blockage in the tube to the pan
If that glass breaks youl wish you didn't have one
Not going tell you how I found that out

Don't the new sight glasses already have a vent hole in them? bobt

Mark’s set up is the ultimate addition / improvement to the original factory parts. I use the same but just push on
the plastic tube over the original lower style valve every time I check the oil level. Clear accurate reading.
Alan in Western Australia

I would extend the plastic tube up into the engine compartment and secure it with a downward facing half-loop at the end to keep out dirt and water. The extension could be made of steel or copper tubing which could be routed and secured easily. The plastic section could have a slotted section of metal or hard plastic tubing slipped over it to keep it straight and give some protection. I would attach the extension to a point near the sight glass and above the oil level to prevent flexing at the point where it connects to the engine pan.

I do not understand the interest in “dirt” getting into a sight glass vent hole the size of a human hair when the vast majority of Model T’s are being run with open screen covered oil filler inlets and dozens of cubic feet of air per minute through carburetors without air filters.

The oil site gauge is one of those topics that everybody has an opinion about.
Good thing you did not ask, " WHAT TYPE OF OIL SHOULD I RUN IN MY SITE GAUGE"

Holes the size of a human hair have a way of getting clogged up, especially if they are under a car and oil is present, and a plugged vent is likely the cause of the OP's issue. The correct oil for use in sight glasses is Marvel Mystery Oil. I take reasonable precautions to keep dust and grit out of my engine. That includes using a carburetor air filter and placing a filter (a metallic mesh pot scrubber, ScotchBrite brand ) over the hole in the block where the throttle rod would be if it had the earlier style linkage. The scrubber pad is wedged between # 2 and # 3 cylinder and is held in place by the main bearing bolt head. It allows air to pass, but picks up enough oil to trap most dust. Keeps bugs out, too. Beyond that, I avoid driving behind other vehicles in dusty conditions. My car has a fan, which I believe helps reduce the amnount of road dust that gets into the engine compartment, but it still gets some dust. The fan pulls clean air from ahead of the wheels through the radiator and pushes it into the engine compartment, which probably helps keep the much of the heavy dust kicked up by the front tires out.

I'll ask again. Aren't the sight glasses already vented? It seems if they were not vented none of them would work.

They are supposed to be vented, since they cannot possibley work if they aren't. The only way to know if yours is, or if the vent is clear, is to examine it.