Master Cylinder Cap

[BugEyeBear]

Where can I get a new Master Cylinder Cap?

Mine appears to be leaking/weeping...

(Might just be slightly overfilled... But it still shouldn't be letting fluid out. To be honest I'm more worried about what it might be letting IN!)

Also noticed that the vent line isn't connected to the cap....
(I've capped off the vent line to prevent any more CRAP from getting in there, but I'd rather get a new cap with proper vent line/hose & do a reconnect.)

Would Memphis Equip sell just the cap?

OR do I have to buy a new M/C in order to get a cap?

OR has anyone used something else as a substitute cap?
(perhaps a rubber freeze plug with a vent hole added... or a cap from another vehicle...)

-Bear-

 

[gimpyrobb]

Probably the copper gasket has gone missing. Different sizes of caps out there, be carefull.

 

[clinto]

I have a few w/ paper gaskets as well.

My M38A1 had a plastic cap and the new master cylinder I bought had a plastic cap as well.

 

[frodobaggins]

Probably the copper gasket has gone missing. Different sizes of caps out there, be carefull.

Truck I sold to Maverick1701 had a rubber gasket.

 

[Barrman]

Take your cap to a local auto parts store and see if they have a copper ring that will fit past the threads up to the shoulder. That should stop the leak.

Then, check the brass elbow on top for cracks. Replace if you find any. Install the cap, tighten down snug, not gorilla tight, install the vent line and go on down the road. I have found open end 3/4" and open end 3/8" wrench with a flash light in my mouth while laying on the drivers seat and standing on the running board the best way to do this.

Or, install an axle vent/check valve in the mc cap, leave the vent line plugged and go on down the road.

Or, find an appropriate plastic container that can screw to the cab wall somewhere, run a line from it down to the mc, connect them and basically don't open the mc up again unless there is a problem. Here is an example:

http://www.roscommonequipmentcenter.com/news_notes/nn17.pdf

There are several companies that offer such kits. Mike at ODIRon has his remote mc on the engine side of the firewall as another example.

 

[BugEyeBear]

Thanks guys!

I'll check the M/C to see if the gasket is missing.

& I had already planned on eventually installing a remote reservoir.
I WAS gonna come up with my own components, BUT it is good to know that kits are already available!!

Let's face it, the original design leaves a lot to be desired. Poor location to encourage frequent & easy checks of the fluid level. I'll bet the motor pool guys HATED checking the M/C fluid level....

-Bear-

 

[BugEyeBear]

I just had a thought...

I'm assumiing that the repair shop topped off the M/C fluid level.

& since the cap on this truck is NOT connected to the vent line (it is missing the hose portion) could it be that the wetness I'm seeing on the top of the M/C is simply excess that is coming out of the vent?

Seems reasonable....

What is the normal level? (I assume it shouldn't be completely to the TOP of the M/C...)

Either way, I need to remove the cap & see what is going on (whether or not the cap seal is there) & fix it.

Q: Once the vent line has been disconnected (like mine already is...) I'm assuming thet the cap just unscrews by hand. correct? Should be just finger tight? (I know, probably obvious, but I was looking at it with very little light as the sun was going down & it was starting to rain cats & dogs! Decided it wasn't time to play with it. Thought it would be better to wait for more light & less rain.....)

OF COURSE the cap is located directly below a cab floor cross-member. There is a hole in the cross member so that you can see the fluid level. But I have to wonder why they didn't position the M/C hole a little further forward? Or the cross-member a little further to the back? What were they thinking??

-Bear-

 

[doghead]

Fluid level should be about 1/4" below the top of the reservoir.

I always use a flashlight to check mine.

The cap needs a gasket to seal.

The cap needs to be tightened with a wrench. The vent line should be connected or a vent cap installed.

 

[BugEyeBear]

Fluid level should be about 1/4" below the top of the reservoir.

I always use a flashlight to check mine.

The cap needs a gasket to seal.

The cap needs to be tightened with a wrench. The vent line should be connected or a vent cap installed.

THANKS!

That ALL matches what I'd assumed!


Does anyone know the approx dims of the M/C Cap Seal?
I'm away from the truck right now (needed to work at SOME POINT this week...) but I'm going back to get the truck & drive it home to GA this weekend.

1st thing on the list for Sat a.m. is to chek the cap seal, but IF it is actually missing I'd prefer to have sourced/acquired one prior to doing the drive.

IF I have an approx dimension to reference I might be able to pick up a few gaskets (indicated size +1 or 2 extra of varying sizes, just in case) in advance & avoid the "stores all closed" or "not in stock" scenarios...

 

[Barrman]

There are at least 2 different sized master caps that I know of. That is why I suggested you take what you have to an auto parts store. We have a 50% chance of telling you the correct size without know which one you have. Taking the cap in is 100%.

 

[BugEyeBear]

There are at least 2 different sized master caps that I know of. That is why I suggested you take what you have to an auto parts store. We have a 50% chance of telling you the correct size without know which one you have. Taking the cap in is 100%.

Yeah, I know that would be the best procedure to get the right size....

But with my time constraints I was thinking I'd buy 1 of each (& maybe a few other sizes as well) and cover all of the bases.

My experience is that IF you ABSOLUTELY NEED a particular part on a Saturday morning it WILL end up being an order part that you can't get until Monday or Tuesday.
I'm just trying to beat "Sgt Murphy" and get them in advance! (easier to order today & pick-up on Friday...)

-Bear-