Missing Caliper Part

[Mrtin]

I've begun leaking brake fluid at a mean rate on my 1992 2WD. The lines and master cylinder look fine. right caliper looks like I think it should but the left appears to be missing a pretty serious part. both pistons extend when pedal is depressed and I can't actually see or feel any fluid anywhere. Can anyone tell me what piece is missing and if that would be sufficient to cause a leak? link contains picture of each. Thank you
http://s568.photobucket.com/albums/ss121/slukma/?action=view&current=left.jpg

Also the truck does not pull to either side when braking and topping of the reservoir eliminates any brake softness but fluid is very low not long after.

 

[7.5L_STX]

i dont see anything missing.

 

[HareRazor]

Looks like there might be a pretty big chunk taken out of the piston on the first picture.

 

[AllanD]

One picture is a factory brake caliper with a phenolic piston
The other has a replacement piston made of steel.

AD

 

[martin]

If you are having to add fluid you have a leak somewhere. check carefully under the truck, it's going somewhere.

 

[Mrtin]

Thanks

Thanks everyone. AD, that explains a lot. I guess I'll get back to looking for that leak.