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jkaftan · 06-25-2014, 12:08 PM

Hello:

I think I need to replace my calipers. Pulls to the right when I brake and the left rotor gets super hot.

Anybody know where to find parts?

John

SebasSF · 06-25-2014, 08:09 PM

I had this happen with my 79 Excella on the way to Yosemite. After replacing calipers and pads, and still having the same problem we found out there was a small bit of debris in the line that was allowing fluid through, but not back...acting like a valve. Sounds like you may have the same problem...cheap fix.

jkaftan · 06-26-2014, 07:55 AM

Hmm that makes sense. I find when I press on the brakes I have to pump them a couple of times before the really grab. Then it pulls to the right a little. Then afterwards, while not braking, it pulls to the left and the left rotor is really hot.

The fact that I have to pump it thickens the plot and makes me think you are on to something. Perhaps I can just have the brake lines flushed.

mayco · 06-26-2014, 08:02 AM

Have you flushed your brake fluid? Its a good idea to do every few years. Have you replaced the flex lines? They are a common problem when they get old. They will expand and not push the fluid through to the caliper. Just a couple ideas. These brakes are just a bit different than anything ive ever driven.

SebasSF · 06-27-2014, 12:09 AM

Yup, a good flush was all I needed, but I ended up with all new calipers.

idroba · 06-27-2014, 12:59 AM

Replace the brake hoses (the rubber ones) when you do the calipers and fluid change. It is not uncommon for the hoses to have internal issues which act like check valves, you can put pressure on the fluid, it locks the brakes, but when the brake pedal is released the pressure is not relieved from the calipers. Remember 1983 was 31 years ago. We replace rubber tires every 6 to 10 years, rubber brake lines are replacement items too.

idroba · 06-27-2014, 01:06 AM

Oh, forgot, your '83 AS motorhome is built on a Chev P30 chassis and so that is what you ask for, brake parts for a '83 Chev P30. Pretty commonly available.

jkaftan · 06-29-2014, 09:25 AM

Ok went to work on this yesterday. I flushed the brake fluid on the driver side front. It made no difference. While I had the rig up in the air I was able to do some troubleshooting. We noticed that after we pump the brakes the wheel will not turn. So I am able to confirm that I have a problem on that side. No wonder it is getting so hot.

What we noticed is that the brake remains engaged until we turn off the motor. Then it lets go immediately. So that can't be a problem with the line or caliper etc. Kind of has to be an issue with the power assist for the power brakes.

I also noticed that when we were pumping the brakes the hoses attacked to the power assist thing (attached to the master cylinder would jump and it would make a straining sound.

It doesn't look like all of my cars in the past with the big donut looking thing against the firwall. It looked like this.

Reading online about the auto parking brake but I don't think I have that.

John

mayco · 06-29-2014, 10:47 AM

Is your rig gas or diesel? The hydroboost works off the power steering pump. I believe its belt driven on the gasser and direct drive pump on the diesel. When i had my break fluid flushed i also had the power steering fluid flushed and also replaced the master cylinder because of the nasty debri in the old brake fluid. Flex lines and new pads all the way around. Made a big difference in the braking but they STILL dont feel like any other brakes ive had on a vehicle. Nature of the beast i think. Mine is a diesel so my power steering pump is quite a bit different from the gasser. My approach has been just to eliminate the obvious sources of potential problems and start with as much fresh as i can afford. I think if i was in your position i would flush the entire brake system AND the power steering. Then the flex lines and master cylinder. Just my two cents, no mechanic here for sure.

Smartstream · 06-29-2014, 11:45 AM

Quote:

Originally Posted by jkaftan

Ok went to work on this yesterday. I flushed the brake fluid on the driver side front. It made no difference. While I had the rig up in the air I was able to do some troubleshooting. We noticed that after we pump the brakes the wheel will not turn. So I am able to confirm that I have a problem on that side. No wonder it is getting so hot.

What we noticed is that the brake remains engaged until we turn off the motor. Then it lets go immediately. So that can't be a problem with the line or caliper etc. Kind of has to be an issue with the power assist for the power brakes.

I also noticed that when we were pumping the brakes the hoses attacked to the power assist thing (attached to the master cylinder would jump and it would make a straining sound.

It doesn't look like all of my cars in the past with the big donut looking thing against the firwall. It looked like this.

Reading online about the auto parking brake but I don't think I have that.

John

That is called a hydro-boost and was used by GM for many years. It uses hydraulic pressure from the power steering pump rather than vacuum to provide power assist for the brakes. It may be the cause of your problem but I would have thought it would lock all the wheels not just one. You may have more than one problem.

jkaftan · 06-30-2014, 12:33 PM

Both of my front wheels were hot. I never checked the back ones.

I am trying to get out of town this Wednesday. I am focusing on the power assist. Otherwise why would my brake finally release when I shut the motor off? If it were debris in the line or hoses it wouldn't matter when I turned the motor off.

I did some reading about the P30 Chassis braking system and many folks are having issues with the "Auto Brake" feature. They keep blowing a fuse and losing their breaks. Need to find out of the Auto Brake was offered in '83. So far everyone who had the issue had newer models.

Smartstream · 06-30-2014, 12:40 PM

Quote:

Originally Posted by jkaftan

Both of my front wheels were hot. I never checked the back ones.

I am trying to get out of town this Wednesday. I am focusing on the power assist. Otherwise why would my brake finally release when I shut the motor off? If it were debris in the line or hoses it wouldn't matter when I turned the motor off.

I did some reading about the P30 Chassis braking system and many folks are having issues with the "Auto Brake" feature. They keep blowing a fuse and losing their breaks. Need to find out of the Auto Brake was offered in '83. So far everyone who had the issue had newer models.

The auto brake is the parking brake and yes caused lots of problems failing to release. I don't believe they were used in 83 but I may be wrong. From what you say I would replace the hydro-boost.

jkaftan · 07-01-2014, 06:48 AM

Called some brake specialists here in town and they are suggesting I replace the hoses between the Hydro-boost and the power steering pump. He used the term scalloping in the hose. He said that it is not likely the rubber lines attached to the caliper because the wheel releases when I turn off the engine. He said start with those hoses and then go for the Hydro-boost and or the power steering pump.

I noticed that I could not turn the wheel when the rig was at a stand still. I could but I had to put all I had into it. Anyway it seems to be either the power steering pump, hydro-boost or the hoses in between.

I did see a post on a P30 forum where a guy with similar symptoms had the brake light switch interfering with the brake pedal being about to return all the way. After replacing all of these parts his fix was to adjust that switch so that the pedal could fully disengage. Talk about pulling your hair out.

I am grateful that I do not appear to have the Auto Brake. I do have the big honkin lever next to my seat that seems to lock me in hard. Is that just a clamp on the drive shaft?

Oh and this is a gas motor Mayco.

John

mayco · 07-01-2014, 08:13 AM

These brakes are something else for sure. Hope those hoses do the trick for you! Pretty easy fix if thats it. Good luck. Stopping goooood................

Waipio Rim · 07-01-2014, 11:35 AM

I do have the big honkin lever next to my seat that seems to lock me in hard. Is that just a clamp on the drive shaft?

Yes. It's a cable operated brake drum at the front of the driveshaft.

Mike Leary · 07-01-2014, 12:00 PM

Keep an eye on the rear output shaft, mine leaks, though we've replaced the seal a number of times and it floods the e-brake housing, causing NO e-brake!

Smartstream · 07-01-2014, 01:38 PM

Quote:

Originally Posted by jkaftan

Called some brake specialists here in town and they are suggesting I replace the hoses between the Hydro-boost and the power steering pump. He used the term scalloping in the hose. He said that it is not likely the rubber lines attached to the caliper because the wheel releases when I turn off the engine. He said start with those hoses and then go for the Hydro-boost and or the power steering pump.

I noticed that I could not turn the wheel when the rig was at a stand still. I could but I had to put all I had into it. Anyway it seems to be either the power steering pump, hydro-boost or the hoses in between.

I did see a post on a P30 forum where a guy with similar symptoms had the brake light switch interfering with the brake pedal being about to return all the way. After replacing all of these parts his fix was to adjust that switch so that the pedal could fully disengage. Talk about pulling your hair out.

I am grateful that I do not appear to have the Auto Brake. I do have the big honkin lever next to my seat that seems to lock me in hard. Is that just a clamp on the drive shaft?

Oh and this is a gas motor Mayco.

John

I believe the hoses are way too large for this type of problem. Also shutting off the engine wouldn't open up the hose. The PS pump only provides oil under pressure, the hydro-boost has the control valves, I believe you have a tired valve. Unless the brake light switch was changed recently it is not likely the problem. If the linkage is binding due to corrosion it could be a problem. Reach down and pull the pedal up, if it moves check the linkage. If it returns to the stop on it's own go back to the hydro-boost.

This is a 31 year old truck, you cannot spin the steering wheel at idle like a new Caddy, rev the engine a little and roll forward a little and it will turn with little effort.

Waipio Rim · 07-01-2014, 08:02 PM

Shortly after we got our 310, the brakes started dragging and eventually stopped us dead in traffic. Had the master cylinder and hydroboost replaced and the brakes were good for a few years until hoses started acting up.

jkaftan · 07-02-2014, 05:12 AM

How did you determine that you needed to replace the master cylinder AND the hydroboost?

jkaftan · 07-02-2014, 05:16 AM

Yeah now you have me thinking it is the hydroboost. Mechanic said there was nothing left on the brakes. I guess I ground them down to a nub front and back. I am having him replace the front but I am leaving the back for me to do. He told me $1800 for the back. I found the parts for about $300. That is a lot of labor?

BTW I couldn't find a jack. Do I just use the levelers?