willysmjeeps.com

Wes,

When you bleed each line, you should catch that other leg of the Y on my earlier description.

As for the brake switch, I did not know it was that critical, but I will do it to my jeep. I am sure any little bit can help.

Thanks.

P.S.
We still have not discussed Boyle's Law of partial pressures relating to the changes in brake fluid compressability when the temperature changes and when moisture, or air are present.

I am kidding around just in case anyone mis-interprets my sense of humor.

The problem with leaving that other brake line hooked up is not putting air in. It is that line may have air in it that gets sucked back into the master cylinder when you rerlease the pedal. If one is going to bench bleed the master cylinder in the jeep it needs to be done the same way it is done on the bench.

There's enough room in the void at the opening of the switch to trap air. It is this same void where fluid never travels more than an 1/8" or so that the free moisture droplets left there by the DOT 5 tend to corrode the inlet of the switch.

Every thing discussed in this thread is of a relative nature vs any absolutes found in the test tube. When we say spongey we mean more spongey then the other fluid. When we say hard to bleed we mean harder than the other. When we say we didn't find it hard we are not comparing it to the other we are comparing it to our personal hardness gage.

I based my opinions of the relative qualities of these three fluids on the last 40 years of bleeding and servicing both in daily use automobiles where their relative performance qualities are very easy to observe. The only quality the DOT 5 exhibits that low useage rate vehicle owners subscribe to is its ability to survive longer in storage than the others. The down side of this is when that storage is not in a climate controlled facility moistur in the for of condensation will develope in the system and since the DOT does not absorb that moisture it is left at the low points in the system to start the corrosion process. The only way to remove this moisture before it can cause corrosion is to flush the system every 2 to 3 years. That puts DOT 5 back at the same longevity level as DOT 3 & 4.

Don't be fooled by claims that folks make about 5 or 6 years of troublefree service. It is the 10 to 20 year period where the corrosion progresses to the level of being an issue. The early signs of trouble are the failing brake light switches. The DOT 3 & 4 fluids absorb this moisture and have additives to ensure the moisture doen't degrade their capabilities in their useful life of 2 to 3 years. We change these regulary and systems very rarely suffer any corroison issues. Changing DOT 5 regularly will keep the corrosion issue minimal. So in all reality the only DOT 5 has done for you is cost you twice as much as DOT 3.

Then the less mechanically inclined troop will always preach well just about every old jeep that ever makes it to the restoration shop has bad brakes and corroded parts. Well he is partially correct. The larger percentage of jeeps that make it to the restoration shop when they are 50 plus years old have not had any TLC for the last 20 years. No regular fluid changes and usually no regular use. This is the result of long abuse and lack of care not poor fluid quality. Anyone who took delivery on these jeeps in the 70's and 80's direct from the military surplus sytem found similar age problems with the DOT 5 installed.

In the final analysis DOT 5 offers no measurable performance increase over DOT 3 & 4 that can be applied to the M38/M38A1 in a useful way. How we justify using it at twice the cost of DOT 3 I cannot understand. I feel it is just like Marvel Mystery Oil. Everyone uses it without any scientific proof it does anything for their vehicle. It is the old Alixar that peddlers sold. It is one's mind that is set at ease by it's use. And with the individual mind as the governor body here we cannot compete with it's internal personal needs.