Master cylinder dry

[etchamp]

We hit a homerun on the parking brakes so lets try this again.

After the parking brake repair I noticed the brakes were a little soft, I found the master cylinder behind the drivers wheel and the bail closest to the front of the RV is bone dry. I filled it up and pumped the brakes till I was blue in the face and it lost no fluid and no signs of a leak. Granted, the cylinder may need to be bled to get it to start pumping fluid.

Looking at the unit, it appears the the master cylinder is mounted reverse from a normal Chevy passenger vehicle so here is my question... On a regular truck, the bail closest to the booster goes to the front brakes so it gets signal first. Can the same be said on this application?

The reason im asking is two fold...it will help narrow down a possible leak if i know which way to go first and secondly, I noticed the drivers side front tire had something wet on the back side after a long drive several months back. I looked it over and it had no smell so I wrote it off as I hit something while driving. Since that time, Its been dry and no visible sign of a leak. I even crawled under it and bled the brakes on the front and it was nothing but fluid, no air.

~no brake lights on dash
~no obvious signs of leak
~stops straight
~does not pull to one side.

[legomybago]

The larger reservoir on the MC will be for the front brake system. Sounds like you have a rear wheel cylinder leaking if drum brake equipped. You need to trace power with a 12v test light, take a look at your brake light bulbs and etc...

[bluebird]

MT master cylinder, has to have a leak somewhere. Check all the brake lines, and look at the master cylinder it self. How bad are the brake pads? If they are all worn down, that could be some of the problem.

[Rickf1985]

If you have four wheel discs both reservoirs will be same size. I remember mine being opposite of normal also if I remember correctly. The easiest way to tell is to bleed the one right there at the left front tire where you are at and see which reservoir goes down. It sounds like you have a bad caliper, it may only leak under certain heat conditions.  If you bleed the left front and the dry side goes down then I would replace both front calipers, this is your life you are talking about here and the front brakes are 75% of your stopping power. You do NOT want to lose them.

[tiinytina]

You may also have boiled your fluid off last run and gotten way lucky that it had stopping power once cooled down etc.   The Hyrdoboost unit for these P30's is under $100.  worth replacing as also does the power steering.   

[Rickf1985]

Another clarification, sorry Tina, just making your day worse, the Hydroboost does not "do the power steering". It is controlled by the pressure from the power steering pump. If the power steering pump goes out then you will lose a major amount of your braking power but even if the master cylinder runs dry it will not affect the steering. The two sections are separate.

[etchamp]

It does have discs on all wheels.

[solracem]

A new MC should cost you about $30. If you're down there, you might as well replace it and then make sure to trace and replace your connections coming from the bail that is emptying (if it's still emptying). It pretty easy to do if you have a buddy bleed the brakes while you inspect the fluid level or visa versa. This way you can narrow it down to front or back brakes.

[Rickf1985]

I would narrow it down to front/rear first. You need to find out what else you need before throwing parts at it.

[etchamp]

Rick, thats why I was asking if anyone knew which bail was for the front. Wifes not at home and im a one man gang. Ive pumped and pumped and its not losing any fluid. and I cannot be in and under at the same time.

[etchamp]

Ok, Ill take a stab at that tomorrow when I get home. What brand of manuals do you have, they sound like something I need to buy.

Thanks so much for the help!

[bluebird]

They are GM service manuals I picked up on ebay. They are for P32/42 forward control motor home  and truck chassis. I got my 95 manuals there also. I'll see if the fellow I got them from has any and put the link on here. He sells them pretty reasonable. The ones I have for the 98 is the second edition, so they are the latest for the 98 chassis.


Here is the last set he has for a 96, they should be very close to what you have but they may be for obd ll as GM changed from obd l  sometime in 96.
http://www.ebay.com/itm/1996-Chevy-GMC-P32-42-Chassis-Motor-Home-Service-Shop-Workshop-Repair-Manual-GM-/401090366401?hash=item5d62d94bc1:m:mjbb7vzuc5HMjchJn3Esmog&vxp=mtr


They may even have both systems in them I don't know. I do know my buddy has a 96 Storm but it is built with a obd l ecm with obd ll wiring. So it is a morfidite.


I did go back and look for a 95 set, couldn't find any in book form. Be very careful buying anything on cd. They are not what they appear to be.   

[etchamp]

10th digit is a S.. 1995.

[Oz]

Off topic. Wiring and troubleshooting your lights should have been posted as a new topic.  Please read the message posting rules.  Someone else could benefit greatly from this information but would never find it because it's buried in a topic that is completely unrelated: dry master cylinder.


In the future, omit "HELP" from topic titles.  That's what were here for and again, it's specifically stated in the message posting rules.

[etchamp]

Sorry Oz...It started out as the MC being dry and made its way to the lights.

I see that there are some posts missing, were they deleted for a reason?

[Oz]

Yes.  The lights question.  Since it was off topic, they should be deleted.  Again, read the posting rules.