Dip ta Dip ta Dip...

[timjuhl]

OK - In helping a guy on the G503 I came across a couple of things I want to throw out for discussion.

First: The difference in CJ versus M38A1 dipsticks. The engine in my Jeep is from a 1962 CJ5 - as part of the restoration process I replaced the dipstick tube and dipstick with one from one of my parts jeeps. Here is what I've observed.

1.) The dipstick tube on the CJ is 14.75 inches long (from hole in engine block to top) and the dipstick is 25 inches long.

2.) The dipstick tube on my M38A1 is 16.75 inches long and the dipstick is 27.5 inches long. The calibrations on the end of both dipsticks are identical.

If you do the math, you will find that a CJ with oil to the full mark would actually contain more oil than a M38A1 at the full mark. Indeed, since 1/2 inch on the dipstick equals about a quart, there could be as much as a quart different between the two. Am I missing something here?

Second:
I've noticed when I check my oil there tends to be a tan foamy material on the cap and collected on the little disc that is attached to the dipstick. The oil looks and smells normal and the "foam" has a slight oil smell to it. I assume that it is primarily moisture but there seems to be a lot of it. The engine doesn't get that hot this time of year which may explain why it collects. Also, the way the vents are set up in the M38A1 there is really nowhere for it to go. Is this something I need to be concerned about???


Thanks for your help!
Tim

[wesk]

Dipstick lengths do vary and they vary between individual jeeps of the same model as well. A one quart error is not really that important. Yes in the desert it will result in higher oil temps but that's not the norm.

I have never trusted any dipstick on any engine. I have always made a point of the first oil change on everything I have owned over the years to first add the specified quantity of oil and then check the oil level on the stick with the vehicle level. I take a file and mark the stick. From that point on I service it to that same mark and I know I am dead on.

The condensation will always be there after running the engine for short periods that were not long enough to get the oil hot enough to cook the moisture off. The greater the humidity and the shorter the run the worse it will get. The only real concern with the gray matter is that whatever it lays on will corrode.

[timjuhl]

Good info, Wes. I'll take your advice on marking the dipstick after the next oil change.

My old Ford tractor produces the same kind of foam so I assumed there was nothing to be too concerned about but I thought I'd ask.

Tim

[wesk]

You'll see that foam quite often on aircraft engines as well.

The modern auto engines run coolant temps much higher than the 160-180 our old jeeps do. The new cars run 200 to 210. The newer tighter clearance engines run oil temps much higher as well.

[timjuhl]

Wes,
RE: Aircraft engines - my continental C85 definitely produces some of the gray foam. I have an air / oil separator that catches a lot of it.

RE: M38A1 - It bothers me that some of the gunk makes it's way into the crossover tube ahead of the carb. I'm tempted to close the fording valve to prevent that and maybe tee-off the hose that connects the crossover to the dipstick tube and install a vent tube similar to those used on aircraft engines. I have no intention of entering deep water so I would think that would be OK to do so although not "correct."

Tim

[wesk]

Or you could leave all the stock plumbing as is and insert an air/oil separator between the dipstick tube and the crossover pipe fording valve. Call a few aircraft salvage yards for a 300 or 400 Cessna twin air/oil separator. The two hose nipples are about the right size.