Need to double pump brakes to get pressure

[Odss91b]

I noticed today that in order to get braking power I had to double pump the brakes. Is this normal?

[TripleJ]

definitely not normal to have to double pump the brakes  time to get them checked out.   

to start you could check the brake fluid level, then inspect all the lines and hoses for leaks.  it might be something simple like that

[joev]

once you have done that did a visual check and you still have that problem you will need to have the drum brake checked and adjusted usally means that the brake shoes are worn out or the self adjusters are not working and need to be serviced

[tiinytina]

now on correct thread.
double pump to get pressure = air in lines or low on fluid

Low on fluid = check for leaks or you boiled the fluid and hydroboost most likely needs to be replaced (this also controls your power steering with a P30 so is important)...

you may have a brake cylinder dragging (stuck) if you detect rig pulling to one side or other....

my 87 has disk brakes all the way around no drums...

28' p30 is nearly 7 tons to stop... brakes are needless to say important... been there done that when the light came on and 18 wheeler in front of me at a stop light.. in my case the fluid had boiled....
Tina

[DaveVA78Chieftain]

What causes the "boiling"?

Heat - 1) Don't ride with left foot on brake pedal; 2) Excessive brake use on a downgrade (slow down and downshift to engine brake); 3) Dragging brake caliper (disk) or brake shoe (drum) [clean things up]; 4) Old fluid (flush system)

A 87/88 Chevy based rig will most likely have 4 wheel disk brakes with hydroboost.   Hydroboost power comes from power steering pump pressure so make sure power steering fluid is topped off and bleed.

Air in brake lines or leaking master cylinder normally cause this.


Dave

[joev]

Make sure you are using the correct brake fluid

Boiling point ranges [2] Dry boiling point Wet boiling point DOT 3 205 °C (401 °F) 140 °C (284 °F) DOT 4 230 °C (446 °F) 155 °C (311 °F) DOT 5 260 °C (500 °F) 180 °C (356 °F) DOT 5.1 260 °C (500 °F) 180 °C (356 °F)

[Rickf1985]

VERY IMPORTANT!

Do NOT mix DOT 5 with any other fluid. DOT 5 is silicone brake fluid and is used extensively in the military and also in racing. To convert to DOT 5 is a very complicated set of procedures you have to go through. I am quite familiar with this because I rebuild old military vehicles.

Rick

[Odss91b]

I used dot three is that not right ?

[joev]

dot 3 fluid will boil under hard braking and cause brake fade  when excessive braking is to be done eg. going down a mountain with a trailer or car in tow . the bigger the vechicle the higher the boiling point you need  only my experiance  check the manual for you motor home

[Rickf1985]

DOT 3 is the standard fluid you buy at the store and is what is specified for the vehicle. DOT 3 will work in all but the most extreme situations and in those situations the fluid boiling will be the last of your worries because the brake pads themselves will have given up the ghost and faded away. Once the brakes reach a certain temperature they no longer create the frictinon needed to stop and that is called brake fade. Metalic brakes will tolerate a little higher temp but in return you will get much less life out of the rotors. If you go to ceramic brakes they will hold the best under high heat conditions but then you will have the boiling problem. What this all comes down to is proper driving for the conditions. As a former truck driver I can tell you that you made dang sure you were in a low enough gear for the engine to hold you back on a steep grade because the brakes alone would not do it. Now, if the fluid is old there is a very good chance that it is loaded with moisture, brake fluid is hygroscopic. What that means is that it will absorb moisture from the atmosphere. Moisture in the fluid will make it boil at a MUCH lower temperature. If your fluid is dark colored then it is time to change it out. This is not a herd job, just tedious. Take a turkey baster (not the one from the kitchen) and suck all the fluid you can out of the master cylinder and then replace it with fresh clean fluid. Then starting at the right rear wheel bleed until you see clean fluid. This wheel will take the longest because you are bleeding the entire line all the way from the front. Be very sure that the master cylinder never runs out. Once the right rear is done move to the left rear. This will take much less bleeding. From there move to the right front and then to the left front. You are done.

[Froggy1936]

Volkswagon Brake syestems are not vented to atmosphere Basicly a sealed syestem As are most nowadays And they reccomend a fluid change ea 2 yrs Due to moisture absorption causing rust inside the syestem leading to failures .  Frank

[Stripe]

If you want to do this bleeding/refill job yourself, I HIGHLY (read better get) recommend you look into this...
http://motiveproducts.3dcartstores.com/0115-Early-American-Rectangular-Bleeder--Large_p_48.html
This is the kit you want if your style reservoir is similar to THIS one.



I own one of these power bleeders and they are GREAT!  The link I posted has the adaptor for the part style in the above photo.


You fill the tank, pressurize it with a few PSI, (It comes with a guide for the amount of pressure you want to use, I used 15 P.S.I when doing my Rover, you may need more for a bigger system) and do your bleeding. Check the pressure bleeder levels regularly.

[Odss91b]

My friend looked at the brakes for a quick couple of minutes yesterday. He thinks I need to replace the brake master cylinder. I went to autozone to see if they had it. They did for $75. Question does the 89 chieftain have disc brakes all around?

[DaveVA78Chieftain]

You have to get under the rig and look.  You can see them on the rear.  Most had 4 wheel disk but some did have front disk / rear drum.

dave

[Rickf1985]

My 89 Chieftain has disc's all around but as said it is best to check.

[tiinytina]

The day I boiled the fluid it was 100F heat in bumper to bumper traffic.  I was not riding the brakes just using them stop and go for 10 miles.  Pedal went to floor so I pumped it for all it was worth and got enough back to stop literally 2" from the back of the 18wheeler in front of me.... was not a fun day.  I geared down etc....  thankfully was not going that fast to begin with... crept off the road when there was space and a place to do so into a parking lot...   Once cooled down and in clean air brakes were fine and luckily I was only about 4 miles of no traffic road close to the campground... Once home after weekend replaced hydroboost, and while at it ran all new brake lines, new pads and one rear cylinder if I remember...  Hydroboost unit was only $45.

dont' know if the above pressurize reservoir would work give the lovely location the current reservoir is in on the P30 unless you have been able to access through the driver side floor....

Tina

[Odss91b]

The PO just told me it has disc all the way around and that he replaced the front calipers both sides as well as the soft brake lines up front.

[Stripe]

I would double check anyway, we all know about what the PO says needs to be taken with a grain of salt..    Right everyone??


http://www.classicwinnebagos.com/forum/index.php/topic,8851.0.html

[Thundercloud]

 :DI'm not sure. My 79.  is the same way . Keep in mind older vehicles may not have as good of brakes as newer ones. I always double pump the brakes when I'm coming to a stop (usually) in older vehicles that rely purely on hydraulic pressure. I know rust is a major factor in old master cylinders so maybe consider replacing that and bleeding your brakes. You could be losing a little pressure through your cap and replace all bleeder valves. Not a bad Idea and they couldn't be too much. Also sometimes the brakes will feel funny when the pads get low. That and the fluid level will actually drop. Good luck

[Rickf1985]

I haven't really been following the whole thread but if the coach has been sitting for a long time and it has disc brakes they will rust, if the rust is bad then when you use it the rust just glazes over and you have very little friction which means very little brakes. The rotors will have to be cut if they are like that.

[Neil Carrick]

Good morning.. while not a lot of experience with motor homes, a brake system is a brake system.
In drum brakes, if the linings are wearing and the auto adjusters are seized, then there is additional travel each time the linings are in motion to grip the drum, hence more fluid to displace which translates into pumping the pedal to get a solid brake application. Do you have to double pump each time the brakes are applied or just the one time which gave you cause for concern?
If you only have to double pump once with a disc brake system, I have had the experience where the friction pad has either let go its bonding to the backing plate or had the rivets rust off allowing the pad to roll forward out of the caliper area which in turn means the thickness of the pad ( now missing) has to be taken up by additional fluid inside the caliper pistons. Once again, the only way that fluid gets to where it is needed is by pumping the pedal. You would see a drop in the fluid level in the reservoir for a few reasons.

   
• there is a leak somewhere , but even pumping will not get you much better results more than a time or two as the reservoir will soon be empty and then you will be introducing air into the system, ( air is not solid and will compress under load, giving a spongy feel to the brake application once fluid is put back in)
• normal wear of the pads and or shoes which requires the pistons to be pushed out, the fluid filling the displaced space
  
  All in all, I would be sure you have someone knowledgeable look at your brakes as they are a life and death option on any vehicle, changing the fluid is a good idea as it can get quiet contaminated, but it is only one scenario that can be playing out here.
  
  Play safe !!!   
  

[Odss91b]

After looking under the Winnie today, I wasn't able to see the drivers side rear brake caliper, but every other wheel I did not see a leak anywhere. I did however see that the master cylinder looked a little wet and the power steering hose had drops forming on it. Thoughts?


Seann

[Stripe]

As to the master cylinder, the top gasket may be in need of replacing, or at best a looking at. The PS hose(s) may need servicing if they are showing signs of looking like they are wet. Another member on the forums just had his engine oil cooling lines remade after experiencing the same thing.

http://www.classicwinnebagos.com/forum/index.php/topic,9336.msg48299.html#msg48299