Hard Brakes

[cosmic]

hoping for some help here. I am currently in Darian lake Ny. as I was coming into the boarder crossing I stepped on the breaks and click. the pedal goes hard and now my breaks are hard as hell. I  have to stand on the pedal to stop.
I suspect the  the booster. I read the chassis manual and it shows a diaphragm in the booster. but on my m300 I cant find that diaphragm. do I need to change the whole booster.
I have proper vacuum. on my dash gauge. I have checked all the hoses going into the booster. I have checked my power steering pump. Good.
when im on the break pedal I feel a slight chugging of the engine.
Any help would be great. I still need to go 200 miles home. The rig runs great but stopping it is another story.

[Froggy1936]

 ??  The click could have been the safety valve closeing off 1/2 of the syestem due to a fluid leak Most likely on one of the frt wheel brake lines , Leaving only the rear brakes operating causing the haveing to stand on the pedal to stop . You shoulds also have gotten a brake warning light come on on the dash . Look for fluid wetness everywhere ? Frank

[legomybago]

You lost your power brakes for sure...I think if you lost your booster diaphragm you would have a vacuum leak ALL the time, not just when you press on the peddle...The check valve on the lower portion of your booster housing could be stuck??

Wait...do you have Hydroboost? or Hydravac brake system? Sounds like you have Hydroboost due to you not finding the vacuum diaphragm can Hm? and you mentioned the power steering pump.  i??

Im going to go and ride a roller coaster myself now......

[cosmic]

I just inspected all the lines and looked under each brake for signs of fluid. Nothing. I opened the reservoir and im not missing any fluid. The light on dash has not come on. when I start the engine with the brake pedal pushed. the pedal does not soften as the engine starts. this is why I suspect the booster for being the culprit.
I pulled the hose on the booster and I have tons of suction on the line going into the booster.

[legomybago]

can you pull the bottom check valve assembly out? make sure its allowing the vacuum to activate your power brakes? Idea?

[cosmic]

I don't have a bottom check valve. to me it looks like the booster is a sealed unit and I saw the check valves on the bottom of the other kind of boosters in the manual. unfortunately this is not the system I have.

[legomybago]

Can you have someone pump the brakes and bleed the unit? See if fluid/pressure is going out of the unit? maybe the inner power pistion is stuck in the cylinder not allowing power brake to work? idea??

[cosmic]

bleed the master cylinder?
Ok I cracked the lines on the master and bleed the master. no difference.
I then phoned napa to find out that there is no availability on the booster and master. how ever they can send it out and get it back to me in 3 to 4 weeks. lovely. just my luck.

[DaveVA78Chieftain]

Before you get inundated with questions you have a Bendix Master-Vac System with the booster mounted to the master cylinder



Indications say you no longer have any boost assist.  Link to description and checkout procedure.

Let me run down parts

Dave

[cosmic]

Thanks for jumping in Dave. test one. there is no difference at curb idle. the feel is the same either way.on the pedal. I do have plenty of vacuum when I pull the hose out of the booster.

[DaveVA78Chieftain]

Did NAPA say that neither 5473143 (booster alone) nor 509261 (booster with mastercylinder) are available?  NAPA is a CARDONE distributor.

CARDONE Rebulder  54-73143 is he universal CARDONE number for both 74 and 75

Booster Sources

Dave

[DaveVA78Chieftain]

Then based on the test (was extracted from service manual)

   
• A. With engine running at curb idle (engine at normal operating temperature) check manifold vacuum level and correct as required.
• B. Apply the brakes several times with moderate force and NOTE the general relation between pedal travel and force.
• C. With engine off, apply the brakes 6 times to remove the booster reserve. Now apply the brakes with moderate force and again NOTE the relationship between pedal travel and force.
• D. If there is a significant difference in feel between step "B" and "C" the booster is operating properly.
• E. If there is no significant difference in "Feel" either the booster is failed or no vacuum is getting to the booster.
• F. Check the vacuum hose from the engine manifold to the booster check valve. If the hose is in good condition and not plugged or closed replace the booster.

You sort of have your answer.  Sorry it is not what you want to hear.

Dave

[Rickf1985]

Really long shot here but since you are on the road and parts are not available you have nothing to lose. Pull the check valve out of the grommet in the booster and make sure vacuum is going through it. You say you heard a click and I don't think I have ever heard of a booster going bad by going "Click". IF that check valve is bad then you could get a new one or scrounge one in a junkyard, they are all about the same I believe.

Rick

[legomybago]

Bummer..
The click sound could have been the internal spring breaking inside the booster assembly

I was working on the wrong type/part....my bad. It doesn't even look like you can easily take that type of booster apart to work on it.

Hope you find a booster assembly

[cosmic]

I was looking for the booster and master cylinder. The guy said it was unavailable. tomorrow I will call back with the part numbers you have gave me Dave. And try again.  i??
Thanks. Vic

[DaveVA78Chieftain]

I simply used NAPA cross reference feature using Dodge P/N 3732195

[cosmic]

in the diagram Dave provided. what is the valve assembly that is located on the frame rail by the cross member? is this basically a splitter?

[DaveVA78Chieftain]

Combination Metering Valve / Brake Warning Switch

Dave

[cosmic]

 
So as of this morning. neither of them are available. they needs to call the Cardone plant Monday morning.
I always thought these were still available. lesson for all here. I have a spare of everything but the booster. of course....lol.

[RickBright]

 I was checking on parts for a M500 Chassis with NAPA about a week ago, went to my local NAPA with the NAPA and the Dodge part numbers they said parts not available. I called a second NAPA about 30 miles and they had the parts I wanted in the store.  The second store I just gave the year/make/model. First Napa was in a mid sized town, second was in a small rural town.

First store counter guy just clicked on the computer, second guy looked in a book. First Napa guy was about 25 years old second Napa guy was about 60.. Just my recent NAPA experience.

Rick

[Rickf1985]

I would bet the second guy looked under different years instead of what the computer said to look at. This has been brought up before, old vs. new. Old wins every time.

[cosmic]

Update.
We made it home without any issues.
now Monday i'll find those parts. Now I don't care. it can sit in my driveway until the master and booster are changed.

Thanks for all your help everyone. It sucks when your on the road and in the back of your head your wondering if you will make it home. Or how long until you make it home. lol I guess this is the nature of owning a vintage rv.
I bet the new ones break too... i??

[Elandan2]

Glad to hear you made it home OK.  I don't know if you have tried any of the small parts jobbers in your area, but I find that they are much better at finding obscure parts than the major parts stores in Canada. BTW, those new rigs look cool, but when they break down...  Friends of ours had a BRAND NEW rig on a Ford chassis.  They took a trip up to northern Ontario and the transmission went out.  They spent two weeks waiting for Ford to supply a new unit.  So although it was under warranty, it was still a major inconvenience.  Rick

[Oz]

A lot of us know the feeling... stressed-out on that drive back... hands aching and white knuckles clamped on the steering wheel, talking all the way, "Come on... you can make it."  Approaching the traffic light... "Turn green... turn green... turn green..."

I'll be you let out one long, loud sigh of relief when you finally turned-off the ignition.

All's well that ends well. 

[DaveVA78Chieftain]

Glad to hear all is well.  Now you can concentrate on getting the brakes fixed without a lot of worry.

Dave