Brake Problems 1983 Holiday Rambler Chevy P30 Chassis

Hotdawg22 · January 03, 2016, 07:40 PM

Hello everyone. Hope i am in the right area. I need some professional help on the problem and am sure there are others out there that have experienced this.
Now my current issue is the brakes.
This unit is a 1983 Holiday Rambler with the CHEVY P30 chassis. It has the HYDROBOOST brake system on it .
Nothing was wrong with the system when i started , i just wanted it all to be new. (lesson here... if not broke... don't fix) lol. So I replaced the entire braking system, hydrobooster, master cylinder, portioning block etc. , pads, calipers, lines power steering pump.
At first the system seemed to work for the first 5 miles but then i noticed the engine was dragging down. Note here that engine was warmed up to normal engine temp.
Then i realised it was the brakes applying themselves and the peddle was hard as a rock and all the way up so when i put my foot on the peddle is was no play in it. All six wheels heated up and started smoking so i know something is bad wrong. I had to remove the return line on the booster and let the PS fluid out before i could move the thing. So with the fluid low as it was the PS pump could not build up pressure to lock the brakes , but i was able to drive it back home. (PS was really growling on turns and braking)
This brake system is all mechanical and no auto park stuff. All hoses of any type were replaced and i just finished checking them again for kinks etc. Return lines are clear and new and no kinks.
All SIX wheels were engaged and hot as fire when i stopped. The tag axel operates off an independent hydraulic over vacuum booster system that just applies to the tag axel itself. That vacuum booster is activated when the brake pedel is pushed causing brake fluid from the main master cylinder to engage the tag axel master cylinder and that will engage the tag axel brakes.
Anyway, maybe someone out there has had the same issue and can help me locate the trouble maker. lol
Thanks for any help.

circleD · January 03, 2016, 08:36 PM

The tag axle booster is under the PS frame near the walk in door. It has its own fluid reservoir and it is a vacuum system. There is a 3/4 inch vacuum line coming off the rear of the motor that does the vacuum part. The brake line going to the rear system is to "trip a switch" so they engage with the other system.
The lock up issue is probably a combination of things. I've learned that the brake fluid needs to be flushed really good and make sure to bleed the power steering pump also.
You changed the working parts but what about the flexible brake lines? They do close up on the interior making their own one way valve. Is the block installed in the correct way?

Hotdawg22 · January 03, 2016, 09:05 PM

circleD, you really know these rigs and i am impressed. It took me forever to just put it all together and i still don't understand it all. Getting there tho.
I had that tag axel unit completely rebuilt by a firm in Houston and thay did a great job. Parts for that unit are not available any more.
I have replaced the flex hoses but i would have to rule them out because of all the wheels locking up. If one or two wheels locked up...it would most likely be the flex lines.
This is most definitely a case where the brakes are being applied internally and since i replaced the booster again and fixed the high pressure relief valve in the pump, it almost has to be pressure restriction related.
I am leaning heavily towards a restricted return line, even tho it is brand new the symptom's of a plugged return line are there. I will once again replace it with a new one. The proportioning valve is new and if it malfunctions, it only affects the front brakes OR the back ...but not all the brakes at the same time.
Here is what i have done since i first learned of the problem:
1) Replaced the new booster with another new booster.
2) Checked the rod between the MC and booster. It is fixed in length and is from the old system and there is no binding or excess there. The rod length and the distance between the ms and booster are exact. so no extra play or push there.
3) Took the high pressure valve out of new PS and found it to be defective in that it was not installed properly and the set screw was almost conpletely out of its seat. I was actually getting about 600 PSI.
4) Took high pressure valve and spacers out of old pump and put them in the new pump and with the spacer it is supposed to produce 1100 PSI, according to the spec sheet.
5) bled entire brake system and pedal then jumped from almost on the floor to about 3/4 way up. That is where it should be.
6) Was confident i had it fixed and then went for another test drive and within three miles (everything was then warmed up) brakes locked up and i never touched the brake pedal just as before. Stopped and cut engine off and pumped brakes and was able to go about 1/2 mile at a time and they would lock up again without me ever touching the pedal. Took some time to get back home.LOL
Don't know where to go to from here.
Tracing it all backwards there is just nothing else left: new booster, new MC, new PS pump, lines and pads and everything else in line. I have asked some local mechanics about it and they just kinda of shrug and say they don't know.

Froggy1936 · January 03, 2016, 09:09 PM

Most likely from what you are describeing, There is no play in the push rod from the pedal to the actuator or the push rod from the actuator to the master cly If it non adjustable the gasket thickness will change it ! Frank

Hotdawg22 · January 03, 2016, 09:54 PM

Gasket? This is throwing some new light on the subject. lol So, are you saying that there is (should be) a gasket between the booster and the master cylinder? Wouldn't it have to be very thick to make a difference?
I don't remember it having one when i took it all apart. But...i kinda slept a day or 2 after that,
Maybe you can expand a little on your thoughts.
Thanks, HD

circleD · January 03, 2016, 09:59 PM

Frank knows about this and so does a few others on here. I'm with you on what the issue is. Wait until tomorrow and others will chime in. Be patient.

MotorPro · January 04, 2016, 06:45 AM

There was no gasket on mine.

Rickf1985 · January 04, 2016, 09:38 AM

There may or may not be a gasket. The pushrod between the hydroboost and the master cylinder is adjustable and needs a fraction of an inch of play when not applied. What is happening s your brakes are not fully releasing. You will have to determine this by measurement with a caliper, it is not something you will be able to see or feel. Unfortunately a lot of people are led to believe that all parts are just bolt on and go but they are not. If it has moving parts then nine times out of ten there are adjustments that have to be checked before bolting on. If you unbolt the master cylinder and it pushes out a hair on its own that can be a clue that the rod is too long. You can shorten it until it no longer does that and then give it another half turn for good measure. Using a caliper is best but that is acceptable as long as you can feel the resistance when you put them together. You do NOT want to feel that rod push in when you assemble the two parts.

Hotdawg22 · January 04, 2016, 10:07 AM

Thanks for the input and you are right about that little rod, it has to be near exact. Also, even if there should be a gasket between the two units, i do not feel it would make any difference cause gaskets are normally less than 10 thousands thick.??
Unfortunately in my case, the rod between the booster and MC is not adjustable. It is the same one that came from the old system and when i put it together there was no resistance. I had an old ford one time with vacuum booster and i adjusted that little rod a little and bolted it back together and the brakes were locked up immediately.
I am leaning towards the return lines being the problem, especially the one from the booster, which is about 7 inches long. I feel, even tho it is new, that it some how is not letting the fluid back into the pump? After it warms up today i will take it all apart one more time and try some things. This system has 2 return lines: 1 from the booster and 1 from the gearbox. Each has a separate port on the pump and i have switched the hoses from one port to the other with no change.
I will also change out the high pressure relief valve in the pump and see if that is the problem. I have failed to find a mechanic here that will even tackle the problem, let alone speculate what it wrong. I may re-install the old MC as well.
Problem with changing it all at one time is i will never know what the problem really was. But at this point i can't be picky. Just get it fixed. LOL

Rickf1985 · January 04, 2016, 04:31 PM

Just get a piece of clear vinyl hose the right size (it is cheap) and put that on the return and see if it is flowing and see if it still locks up. The vinyl hose will last a day or so but I would only use it for the duration of the test. You can also leave the end off of the pump and run it into a can and see if you are getting decent flow. You say this was a new hydoboost? Was it NEW or Rebuilt? It could be that which is the problem. Have you checked the rod between the brake pedal and the hydroboost for free play? No free play there could also give a constant on situation.

M & J · January 04, 2016, 07:43 PM

I want to know where you found a prop valve for an 83? I couldn't find one for an 87 P30 and thought they were unobtainuim.
Did you buy a new or reman hydro boost unit?

Froggy1936 · January 04, 2016, 08:21 PM

http://www.brakeandfrontend.com/operation-diagnosis-and-repair-of-hydro-boost-power-assist-systems/ Hereis a place with a lot of info and trouble shooting Seems your problem is quite common Frank As far as proportioning valves go anyone with the same fitting size will work !

TripleJ · January 04, 2016, 08:46 PM

Youre probably tired of hearing this, but your description is exactly the symptom of too long a master cyl pushrod.

There needs to be an amount of gap (.020" maybe more) at the master cylinder pushrod before the booster applies the brakes, or when temperature changes under the 'hood', the brakes will never fully release... eventually dragging/overheating/locking up.

One way to check is to look in the fluid in the bottom of the master cylinder, you will see a small hole. That is the compensating port. The front of the piston should be at the rear of the hole. Slowly push the pedal while you look at the hole. If the pedal has to be pushed a ways before any fluid squirts up from the hole, the rod is too short. If fluid never squirts, the rod is too long, and the brakes will drag.

If its just a small amount, you might be able to shim the MC out from the booster to test for length.

Hotdawg22 · January 05, 2016, 01:09 PM

I bought the proportioning valve on Ebay and it was new. I bought the first rebuilt booster on Ebay and the next one i bought at O'reill's.
They atre all rebuilt these days and done by the same company, Cardone. Can not buy a brand new one anymore.
On the matter of the pushrod i guess i am operating under the assumption that it worked on the original setup so why doesn't it work on the replacement. After all it is NOT adjustable and if too long i have to grind some off.
However, i am now going to focus on that rod and armed with all the good advice i got here i should be able to pin it down and make it work. I will start with the visual inspection and work my way out from there.

Hotdawg22 · January 05, 2016, 09:16 PM

OK. Today i took out the fender well and was able to access the booster and MC area. The test that was suggested by looking down in the MC to see where the piston was can't be done on this rig cause of the way the mc is sitting. I can barley take the top off and pour fluid into it.
So i loosened the bolts that hold the MC to the booster and fashioned 2 washers that i could just drop down over the mounting bolts and then tightened those bolts up again. The idea here is to test if spacers would fix the problem by increasing the distance between the booster and MC. Tomorrow i will do a test drive and see if that fixed the brake lockup problem.
Now here is the kicker... as i was working on that problem i noticed antifreeze dripping from the front of the engine. Looks like the BRAND NEW ALUMINUM HIGH VOLUME WATERPUMP with less than 50 miles on it ,is bad. So lesson here is buy all your stuff from a local parts company where you can take it back if it fails. All my items were bought on ebay and there is no extended warranty on any of it. Lesson learned.
Now i have to completely dissamble the front of the engine to change out the water pump. UNLESS someone knows a better way?? Help would be greatly appreciated.

CJ7365 · January 05, 2016, 10:45 PM

Does your engine sit back far enough where you could change out the water pump from the dog house? you would still have to take your fan shroud/fan off. I would at least give this a shot, instead of removing radiator etc...

Hotdawg22 · January 06, 2016, 07:53 AM

Changing it from the doghouse is next to impossible and i was hoping someone had a miracle alternative. lol
Anyway, i will just whip out my trusty sawsall and cut that radiator bracket and then weld it back in place afterwards. I will have to disconnect all the hoses, coolers a/c stuff etc. No sense in putting it off, i will just dig in and get it done.
Thanks again.

Hotdawg22 · January 06, 2016, 01:37 PM

OK. Just took the MH on a trial run to see if the 1/64th shim between the MC and booster had solved the problem.
Unfortunately it did not solve the problem. It is driveable and will stop on demand . However, after i parked it back in the barn i tested the rotors for heat and they were all way too hot, so hot i could not touch them. It is about 40 degrees here so the rotors should have been cool to the touch. This tells me the brakes are still dragging but not locking up as before. Also, as i was driving it i could tell that the engine was lugging down so i knew right away it was still not fixed.
When i put my foot on the pedal it goes about half way down before it starts applying the brakes whereas before there was only about 1 inch travel before it would get the brakes. So putting that shim in there made a tremendous difference. Any shim thicker than that and i more than likely would not have any brakes at all.
Back to the tear down. I am just going to rip it all out and start over with new stuff, AGAIN.
Thanks to all.

jeno · January 06, 2016, 02:06 PM

I just wonder if the calipers are sticking?

Rickf1985 · January 06, 2016, 05:44 PM

Have you opened a bleeder to see if there is residual pressure in the brakes? You need to diagnose it more before throwing a bunch of parts at it again. Take it for a ride and have a bleeder screw wrench ready. When you stop go to one of the calipers and crack the bleeder and see if fluid shoot out. If it does then the problem is in the booster or master, if it does not then the problem probably is in the calipers. Did you lube the slides? Is the tag also dragging? The rotors will get very hot instantly when you stop and will stay hot for quite a while after you are sitting. If you have a long straight level road then get on it and then just coast to a stop, do not touch the brakes at all. downshift as you slow down to help slow down but don't touch the brakes. Then feel the calipers. Also when you are stopped put it in gear without hitting the gas and see if it starts to move without effort. If so the brakes are not dragging. Remember, disc brake pads are always in contact with the caliper, just barely but they are touching. This style with the spring slide holding the caliper tends to cause them to drag a little more so they are always going to be hot to a point. Remember also that 120-130 degrees it about max before you can't hold your hand on it. That is not hot for a brake rotor.

TripleJ · January 06, 2016, 06:37 PM

Rick and jeno have said it already, but we're all just trying to help so here it is again.

If you have driven any length of time, and slowed the vehicle to a stop from 30/40/50 mph, the rotors WILL be too hot to touch. Especially the friction surface/shiny surface that you can see through the holes in the rim. When you can start feeling the heat on the hub of the axle, or the middle portion of the rim, THAT is when youre looking at too much heat.

Also as Rick said, disc brakes DO "drag" slightly, or ride at the surface of the rotors. There will be heat, even without applying brakes. This is by design.

Another thing is now that you have 'let the smoke out' of the brakes a few times, chances are the rotors are glazed, brake pads are roached, possibly there is damage to the calipers/boots/seals from heat. Rotors can be de-glazed as long as they're not warped, pads probably need replacing, calipers need inspection.

Also I don't know the specific method, but regular brake fluid can be overheated. I would maybe move some more fluid through the system.

As for brake pedal height, I agree that roughly 3/4 way to the top SOUNDS about right, but the old school design of this chassis definitely wont feel like a modern car or light truck. Somewhere between 3/4 and 1/2 way down is realistic to me as long as it was properly bled and as long as the wheels will lock up before the pedal hits the floor.

Anyway, as you said before... if it aint broke... etc. But I understand. Theres a fine line between preventative maintenance and IT WORKS FINE, LEAVE IT ALONE!!

Good luck! Keep us informed on your progress

Rickf1985 · January 06, 2016, 07:06 PM

I just went back over your second post and it sounds exactly like a plugged return port on the master cylinder. Here is the problem with that theory, you have TWO return ports, one for the front circuit and one for the rear circuit. The odds of both getting a piece of crap in them at the same time are astronomical. The only other thing that would block BOTH ports is if the piston is not returning all the way to the home position. You have spaced the master from the booster and it made a substantial difference in pedal height so I know you have clearance. At this point I would point my finger at the master cylinder and say it is bad. Something got behind the piston and is holding it from returning. You could disassemble it but I strongly advise you not too, send it back for a replacement.

circleD · January 06, 2016, 07:39 PM

I have to push my pedal all the way down then let it up then another half way down to get a good stop.
I know I know its air in the lines and other minor issues. W%
Don't let it bother you friend. We ALL have had these issues and get through it. Even the 1980 corvettes don't handle like today's corvettes. You know what I'm saying

Rickf1985 · January 06, 2016, 08:00 PM

D, If you have drum brakes adjust them and if you have discs check the front wheel bearings. You will find your travel problems in one of those things. Could actually be a rear wheel bearing considering the full floating rear but if it was it would have spun and seized buy now.

Rickf1985 · January 06, 2016, 08:01 PM

D, If you have drum brakes adjust them and if you have discs check the front wheel bearings. You will find your travel problems in one of those things. Could actually be a rear wheel bearing considering the full floating rear but if it was it would have spun and seized buy now.