Brake Pedal

[PRZNBUS]

Today I fired up the '86 MC9 to move it to the spot where I'll level it and raise the roof. After sitting since about October, I slid in the two charged batteries, aired up the bus with my shop compressor then hit the key and it fired up in less than a revolution. I took it for a short ride and everything worked great except......the brake pedal has to be pulled back up. The bus stops good, brakes don't get hot but the pedal sticks in the down position.

I have a trucker friend who said Freightliners do this same thing. He said WD40 the pedal hinge. I haven't done this yet but was wondering if smarter people than me know of anything else it might be?

Bruce

[digesterman]

Yep, he's right

[Jim Eh.]

Probably something with a little more silicone in it to make the lubrication last a little longer. Some good penetrating/lubricating spray. WD40 has too much alcohol and just evaporates rather than appyling a lasting lubrication.

[Oonrahnjay]

Probably something with a little more silicone in it to make the lubrication last a little longer. Some good penetrating/lubricating spray. WD40 has too much alcohol and just evaporates rather than appyling a lasting lubrication. 

       Right.  WD-40 is a pretty good penetrating fluid (note I didn't say oil) and it's an excellent water dispersant, but it's not a good lubricating oil and it's not a long-lasting one.  For what it's made for and what it's designed for, it's great -- but not as a metal-to-metal lubricant.

[Raymond smith]

On the Sterling i use to drive, dirt and stones would get under the pedal and hold it on just enough to keep the brake lights on. Just another thought. Raymond

[digesterman]

You want to be careful about putting something that will attract dust etc and hold it there, grease etc. Clean it good with WD40 and if you use the bus regularly you won't have that sticky pedal problem again.

[buswarrior]

Look underneath the floor, is there a linkage to the brake valve mounted against the back bulkhead, or is the valve directly under the pedal?

The linkage needs lube, if you have one.

happy coaching!
buswarrior

[DoubleEagle]

If you are lucky, penetrating fluid will do the trick (I use PB Blaster, it stinks, but it seems to be effective most of the time). If you are not so lucky because salty slush got down there repeatedly (like on some of my trucks) there will be bone deep corrosion that will be hard to free up unless you can disassemble the offending joint and hone it out. You might have replace the foot pedal or even the air control valve to get good action, otherwise, tie a rope to the pedal so you can pull it back up easily.

[luvrbus]

The inside of the foot valve will corrode over time I break the supply line and pour Marvel Mystery into the supply line hook it back up and pump the pedal to move the oil through the valve most of the time it will work and stop sticking.The newer vehicles with modern air dryers do such a good job but are terrible about drying the air to much and causing valve problems       

[DoubleEagle]

The inside of the foot valve will corrode over time I break the supply line and pour Marvel Mystery into the supply line hook it back up and pump the pedal to move the oil through the valve most of the time it will work and stop sticking.The newer vehicles with modern air dryers do such a good job but are terrible about drying the air to much and causing valve problems       

Not a bad idea, Marvel Mystery Oil lasts a long time on metal surfaces, but would it harm plastic air lines? PB Blaster is big on advertising that their product will dissolve plastic cups.

[Oonrahnjay]

Not a bad idea, Marvel Mystery Oil lasts a long time on metal surfaces, but would it harm plastic air lines? PB Blaster is big on advertising that their product will dissolve plastic cups. 

    Yeah, the data sheet for MMO lists "petroleum distillates - light: Stoddard solvent" as 25-30% of the content (heavier petroleum mineral oil is the majority of the oil).  Stoddard solvent is also called "white petroleum spirit" and is the main constituent in "Varsol" and similar parts cleaners.  MMO was originally developed to be a carburettor cleaner.  I'm guessing that it's a pretty mild solvent but adding it to air lines and valves with plastic seals, etc., means that it just sits on them for the long term.  I've got no experience with it on plastic parts but I'm leery.

[DoubleEagle]

    Yeah, the data sheet for MMO lists "petroleum distillates - light: Stoddard solvent" as 25-30% of the content (heavier petroleum mineral oil is the majority of the oil).  Stoddard solvent is also called "white petroleum spirit" and is the main constituent in "Varsol" and similar parts cleaners.  MMO was originally developed to be a carburettor cleaner.  I'm guessing that it's a pretty mild solvent but adding it to air lines and valves with plastic seals, etc., means that it just sits on them for the long term.  I've got no experience with it on plastic parts but I'm leery.

You have solved the mystery of Marvel Mystery Oil! Some people have said that it is close to transmission fluid, but maybe not after all. It might be prudent to keep it from plastic just in case it softens it.

[luvrbus]

You ever read what is in Bendix oil for compressors,I haven't seen in years but it was nasty.I never had a problem Marvel in 30 years, on 1986 MCI there are not any plastics or poly   

[DoubleEagle]

You ever read what is in Bendix oil for compressors   

No, but is it Marvel Mystery Oil? I know Bendix had a spin on filter that took out oil contamination in the air lines, so what ever it is they did not want to let it loose into the lines.

[luvrbus]

I don't care one way or the other only thing I am saying I never had a problem YMMD but were are the plastics in a brake system you have a few nylon seals but I don't know of any plastic parts in any Bendix valves and chemicals don't bother the poly used today for air