Flaming Brakes

[beerob63]

Good evening all,

My name is Bryan and I just purchased my first RV; a 1990 Airstream Land Yacht 36' 50th anniversary edition. It has meticulous maintenance records, 55K+ miles (5K on recent rebuild), and I am the third owner. I drove it home this evening and when I arrived my front left brake was red hot and actually erupted in a small flame. After extinguishing the fire I concluded the caliper had ceased which caused the molten flame. I intend to change both front calipers and rotors tomorrow, however my questions is two fold:

1. Is there something could have I failed to do that may have led to the brakes not being disengaged completely? (emergency brake is not the issue).
2. The seller was the grandson of the deceased owner and knew nothing about operating the vehicle, any suggestions for this rookie besides trial and error?

[AirsDream]

Welcome to the exciting world of Airstreams!

But seriously, the best thing you could do, you have already done: join up here. Now plan to do lots of reading. Use the search function and read as much as you can as soon as you can ... and pretty soon you'll know a lot about your machine.

I'm a trailer owner, so can't comment except in generalities, but I will say that as with most vehicles, there are only a few things that can easily kill you: brakes, tires, and steering. So you need to attend to those first. Then there are lots of things that can disable and strand you: electrical failure, cooling system issues such as leaking radiator cores and cracked / burst hoses, plugged fuel lines, broken serpentine belts, etc. So those need attention next. Finally, there are all the "house" systems such as furnace, plumbing, stove, etc. that make the machine more than a mere vehicle, and you've also got to make sure they're all up to snuff. So work your way through it all little by little and with a little luck and some advice from Forum members, you'll soon be having a ball in places you never thought you'd visit! Enjoy!

[panheaddale]

There is noway you could have known the caliper was going to stick. Neither could the seller. Replacing the calipers and rotors is a great idea also make sure to put new brake pads on. You should check your frt, brake lines also and make sure they are good. GM vehicles especially are prone to the brake lines collapsing inside. They will look good but they will let brake fluid flow into the caliper but not return out of it. I would guess that was the initial problem but since it has all been so hot I would replace it all. Hope this helps.

[blkmagikca]

Having had a LY moho, I can tell you that if the rig sits in storage for any length of time the disc brake calipers will stick. Disc brakes are meant for everyday use, otherwise they can stick. After sitting for a while, brake maintenance is more critical for disc brakes than drum brakes.

[rwnash]

I'd also change the brake hoses if they are more than a few years old. I had a car that had 15 year old hoses which I did not change when doing a rebuild. It turned out that they deteriorate and can act like a check valve and not let the caliper retract. Also, brake fluid attracts moisture which can cause the pistons to lock up - a good bleeding helps flush out the system.

Good luck,

Whit Nash

[92landyacht]

Originally Posted by rwnash

I'd also change the brake hoses if they are more than a few years old. I had a car that had 15 year old hoses which I did not change when doing a rebuild. It turned out that they deteriorate and can act like a check valve and not let the caliper retract. Also, brake fluid attracts moisture which can cause the pistons to lock up - a good bleeding helps flush out the system.

Agreed with above. The most common cause for a "stuck caliper" is actually a collapsed soft rubber brake hose. When I purchased my 92 LY 36' it also locked the front caliper within one block. One turn of the bleeder reveled the true cause of the problem. Pressure could not return back from the caliper. I replaced all 5 (yes there are 5 if you have rear disc brakes) hoses for under $70.

The calipers are probably OK but replacing them isn't that expensive either. Rockauto.com was doing a closeout on the brake calipers that our LYs use and I picked up all 4 loaded with Wagner Thermo Quiet pads for under $80 delivered as spares. If you have 4 corner disc brakes then the fronts and rears are the same.

I would have the rotors turned and put on new pads. Don't scrimp on what pads you use. These babies aren't light and the brakes on the 36 footer were marginal in my opinion.

Don't forget to replace ALL the brake fluid as well. DOT 4 or 5.1 fluid is best IMHO. I would stay away from DOT 5 unless you feel like flushing every bit of your current fluid before putting the DOT 5 in. They are not compatible.

Don't forget the electric brakes on the TAG axle as well. They usually need to be serviced since they're often ignored. Good time to lubricate the bearings and replace the seals as well.

Welcome to the world of AS. There are several on here that own 90 to 92 Land Yachts so you're in good company. If it needs to be done, then someone here has done it. Just ask and don't be shy.

I have one rule that I always try to pass on... NEVER believe what a PO says they did unless you were there to verify it. All POs were trying to sell you their MH before they became POs. Trust what you know... not what you've been told.

[perryg114]

Put some DOT 5 brake fluid in the system and flush all the old stuff out. New brake hoses are not a bad idea. You can get some stainless ones made. The DOT 5 won't suck up water like the conventional stuff. The military uses it for this reason. It does not go bad and it is not corrosive. Another issue with trailer brake controllers is that most of them are an on off system. 100% on then nothing. There is a time delay when you hit the brake but for the most part is a dumb system. There are brake controllers that are proportional and they are much easier on your brake system. Cheap calipers can also get a stuck piston from sitting with conventional brake fluid in them.

Perry

[92landyacht]

The problem with DOT 5 is it doesn't absorb water and thus it will leave water trapped at the lowest point. This is usually the caliper. Because DOT 5 doesn't absorb water it keeps it separated in the system. Moisture invades brake systems even if you use silicone based brake fluids like DOT 5. DOT 5 brake fluid has a much lower boiling point then DOT 4 or 5.1 and any water trapped at the caliper will boil at a much lower temp. The last thing you want is to overheat and boil your brake fluid when doing a steep downhill grade.

The best method for maintaining your brake system is annual maintenance which should include replacing your fluid at least every 2 years. Putting DOT 5 in and forgetting it will not resolve your future brake issues.

Don't screw around with years++ old soft brake lines either. I'll bet $$$ that it is the source of your problem and not the actual caliper. The symptom is classic of a failed inner liner on a soft brake line.

[perryg114]

If you get the water out of the system none will come back in. I have a car I bought in 91 and I put the stuff in there and I have never changed it and I have never had to replace anything but pads. The car sits a long time between uses. The DOT 5 won't boil near as quick as the glycol based stuff. Car restorers use the stuff because it will keep the brake system new forever. I use to put it in my my dirt bike rear brakes because the standard fluid would boil too easy and I had no brakes. The silicone fluid cured about 90% of that. Standard brake fluid attracts water and eventually it absorbs so much that it won't stay in solution and then you have corrosion. I have even mixed the stuff with regular brake fluid with no ill effects. I don't know where you get your information but real life experience and that of the military don't agree. I use standard fluid in my daily drivers. I have heard this argument about silicone trapping water and have never heard it from someone who actually used the stuff. I have been using it for over 30 yrs in stuff.

It does not replace maintenance but it will stop the corrosion end of things. Till you take the caliper apart you don't know what happened. If you pull the piston out and there is a rusty ring where the piston sat then you can assume that caused the piston to stick.

Perry

Originally Posted by 92landyacht

The problem with DOT 5 is it doesn't absorb water and thus it will leave water trapped at the lowest point. This is usually the caliper. Because DOT 5 doesn't absorb water it keeps it separated in the system. Moisture invades brake systems even if you use silicone based brake fluids like DOT 5. DOT 5 brake fluid has a much lower boiling point then DOT 4 or 5.1 and any water trapped at the caliper will boil at a much lower temp. The last thing you want is to overheat and boil your brake fluid when doing a steep downhill grade.

The best method for maintaining your brake system is annual maintenance which should include replacing your fluid at least every 2 years. Putting DOT 5 in and forgetting it will not resolve your future brake issues.

Don't screw around with years++ old soft brake lines either. I'll bet $$$ that it is the source of your problem and not the actual caliper. The symptom is classic of a failed inner liner on a soft brake line.

[Kota]

Welcome!

If mine sits for any length of time I stop and check tire, brake, hub temps after a few miles of driving. Generally, from storage to home (3 miles) I always do a quick "post flight" check when we stop after driving any distance.

[92landyacht]

DOT 5 is for cars that never see the road and never have to brake hard. Car collectors use it because the cars don't need to brake hard and really never get driven. Trailer queens are not what a MH should be and when in use demand more from their brake systems then DOT 5 can offer. The brakes on a MH work harder then any car on the road. I wouldn't trust anything other then DOT 4 or 5.1 in mine and hope that the guy behind me thinks the same. What's the big deal about replacing your fluids every couple years. We can agree to disagree on this but I'm sticking firm on this one.

[Punch]

You seem to adopt a religious fervor in approaching issues that would benefit from a more scientific detachment.

It would be very strange if a manufacturer of brake fluid were to continue making something with such apparently inferior performance, as indicated by your posts. DOT 5 fluid has been shown to effectively eliminate corrosion in clean systems; and if your brakes get hot enough to affect DOT 5 performance, then your DOT 3 or 4 fluid would have turned to vapour by then.... at least the DOT 5 will still stop you under extremely hot conditions (read long descents in your Airstream), but with a somewhat longer pedal travel. There is no problem of DOT 5 fluid mixing with the glycol based fluids, but there is indeed a potential problem if moisture remains from a contaminated system due to previous use of DOT 3, 4 or 5.1. When filling your system with DOT 5 fluid you should flush well through the system..... but you should do that in any case, no matter what fluid you are putting in there! The only real downside to DOT 5 is that extra care needs to be taken in bleeding, and a rebleed a week or so after the initial bleed is advisable. The upside is reduction of water ingress and therefore corrosion, especially in vehicles that spend much of their time standing...... read motor homes. An extra rebleed will keep your system safe and moisture free for up to five years, much less effort than the 2 or 3 fluid replacements in the same period with glycol based fluids, and even with that, you'd still get corrosion with the glycol fluids!

The absolutely ideal time to use DOT 5 is if you completely rebuild the master and slave cylinders in your vehicle, you can then kiss your corrosion problems goodbye.

[Globie64]

I'm sorry, but "Flaming Brakes" makes me think of a punk garage band.

[ROBERT CROSS]

Water will get in the system, the reservoir is translucent for a reason.
Don't remove the cap, look thru.
If your low on fluid because of pad or shoe ware and want to add, get the smallest container that will do the job and discard any fluid left over. Remember when you retract the pistons during pad/shoe replacement the fluid will be forced back into the reservoir.

DON'T add fluid from an open container and flush the system every 2-3 years.

Fluid degradation happens slowly, you won't believe the improvement if you've never flushed.

kno-nothing Bob

[perryg114]

I have seen cheap rebuilt calipers where the inside bore was sand blasted and was rough as a cob. It should be smooth and if the bore is not smooth it will cause the pistons to stick. Hydraulic brake systems are well sealed and water won't come in if there is nothing to attract it. However, if there is conventional brake fluid in the system it will absorb any and all moisture. If you don't believe me take a piece of bare steel and put a drop of DOT5 and a drop of DOT 3 or 4 on the steel and tell me which one rusts first. Do the same thing on a piece of painted steel. The conventional fluid will eat the paint off and start rusting. The silicone won't do any harm. Silicone is used for its chemically inert properties and high temperature properties. If you are using conventional brake fluid and the vehicle sits for a long time, the small amount of brake fluid that leaks past the O-rings on the pistons will start to absorb water and corrode the bore. If you drive the vehicle every day, then the rust does not have time to form and the heat from braking helps dry things out. Driving an RV often is a good thing if you can do it. Any system that sits will degrade faster than one that is driven. The Silicone does not attack rubber like conventional fluid does.


Perry

[92landyacht]

Some things to consider if you do choose to go DOT5:

Silicone fluids are not miscible with water. It’s the classic oil and vinegar scenario. DOT 5
Silicone, being less dense, tends to float on water. Therefore, if water ever entered the system
it would collect at the lowest point, meaning the bottom of the caliper. Water in the bottom of
the caliper could be hard to get out without removing the caliper and rotating the caliper to
place the bleed nipple at the lowest point. Any trapped water will have the lowest boiling point of any brake fluid ever used. Since trapped water will form at the lowest point in the brake system it will also be at the highest temp area as well, the caliper. You wont boil the silicone, but you will boil the water.

While it’s permissible to mix DOT 3, DOT 4 and DOT 5.1 brake fluids, DOT 5 Silicone fluid
cannot be mixed with any other type. If the system is not completely purged before
conversion, the mixture may gel and result in very poor braking. Therefore conversion
usually requires disassembly and a thorough cleaning, or at least numerous bleeding sessions
over several days. Obviously then, the best time to consider conversion to DOT 5 is before

rebuilding the master cylinder, hydraulic power assist unit and caliper.

DOT 5 is not compatible with most anti locking brake system.

[Punch]

That's a good reply.

DOT 5 should indeed not be used with ABS systems. I have been unable to find original documentation of this, but brake and auto manufacturers certainly believe it so there must be firm documentary evidence.

DOT 5 is also unnecessary in a vehicle that is driven regularly.

DOT 5 is appropriate for vehicles with non-ABS systems and that spend most of their lives (months on end) standing.

To avoid all potential problems associated with DOT 5 fluid replacing a glycol-based fluid (3 or 4), it is best to use it following a complete rebuild of your braking system.

But, for a vehicle without ABS that does spend most of its life unused, DOT 3 or DOT 4 filled systems will corrode, thus rendering seals ineffective and leading to leaking and potentially failed brakes.

It's your choice.

PS. I am dealing with the consequences of DOT 4 caused seal failure on two classics I own right now.

[92landyacht]

Great!! Now on to the original issue here. If the brakes were locked, then lets determine if it's a caliper failure or a colapsed soft line. Not likely a master cylinder issues since it only affected one wheel. Go into the MH and step onto the brakes hard with the engine running and then stop the engine. Raise the suspect wheel and see if you can turn it by hand. If not then open the bleeder on the caliper and see if you get a squirt of fluid and then the wheel will turn. If so, then it's a soft brake line issue and you should go and replace all of the soft lines. Probably should anyway. If you have disc brakes on all four corners, then you have 5 lines. Two in the front, two at each rear wheel and one that connects at the center of the differential. If you have rear drums then you only have 3 lines.

Let us know how it goes and above all.... Post some pictures of you new to you AS.

[is.chowa]

Previous suggestions re the lines and replacing pads, calipers and disks are valid. Also flush every 2 years and lubricate the slides. And forget about using DOT 5.
Here are the facts re: DOTS 3,4 and 5. Rather long but worth the read

Stolen from the Airheads BMW Club newsletter - July 1995
Battle of the DOTs

DOT 3-4 Verses DOT 5. Which brake fluid should I use?
From Oak Okleshen #35 "With regards to the DOT 3-4 verses DOT 5 brake fluid controversy, here is an article sent to me by Mr. Steve Wall. It is one of the most professional treatments I have seen on the subject".

[I had to condense this article from 6 pages to 1 due to space limitations -ed]

Brake Fluid Facts
by Steve Wall

As a former materials engineering supervisor at a major automotive brake system supplier, I feel both qualified and obligated to inject some material science facts into the murky debate about DOT 5 verses DOT 3-4 brake fluids. The important technical issues governing the use of a particular specification brake fluid are as follows:

Fluid compatibility with the brake system rubber, plastic and metal components.
Water absorption and corrosion.
Fluid boiling point and other physical characteristics.
Brake system contamination and sludging.
Additionally, some technical comments will be made about the new brake fluid formulations appearing on the scene.

First of all, it's important to understand the chemical nature of brake fluid. DOT 3 brake fluids are mixtures of glycols and glycol ethers. DOT 4 contains borate esters in addition to what is contained in DOT 3. These brake fluids are somewhat similar to automotive anti-freeze (ethylene glycol) and are not, as Dr. Curve implies, a petroleum fluid. DOT 5 is silicone chemistry.

Fluid Compatibility
Brake system materials must be compatible with the system fluid. Compatibility is determined by chemistry, and no amount of advertising, wishful thinking or rationalizing can change the science of chemical compatibility. Both DOT 3-4 and DOT 5 fluids are compatible with most brake system materials except in the case some silicone rubber external components such as caliper piston boots, which are attacked by silicon fluids and greases.

Water absorption and corrosion
The big bugaboo with DOT 3-4 fluids always cited by silicone fluid advocates is water absorption. DOT 3-4 glycol based fluids, just like ethylene glycol antifreezes, are readily miscible with water. Long term brake system water content tends to reach a maximum of about 3%, which is readily handled by the corrosion inhibitors in the brake fluid formulation. Since the inhibitors are gradually depleted as they do their job, glycol brake fluid, just like anti-freeze, needs to be changed periodically. Follow BMW's recommendations. DOT 5 fluids, not being water miscible, must rely on the silicone (with some corrosion inhibitors) as a barrier film to control corrosion. Water is not absorbed by silicone as in the case of DOT 3-4 fluids, and will remain as a separate globule sinking to the lowest point in the brake system, since it is more dense.

Fluid boiling point
DOT 4 glycol based fluid has a higher boiling point (446F) than DOT 3 (401F), and both fluids will exhibit a reduced boiling point as water content increases. DOT 5 in its pure state offers a higher boiling point (500F) however if water got into the system, and a big globule found its way into a caliper, the water would start to boil at 212F causing a vapor lock condition [possible brake failure -ed.]. By contrast, DOT 3 fluid with 3% water content would still exhibit a boiling point of 300F. Silicone fluids also exhibit a 3 times greater propensity to dissolve air and other gasses which can lead to a "spongy pedal" and reduced braking at high altitudes.

DOT 3 and DOT 4 fluids are mutually compatible, the major disadvantage of such a mix being a lowered boiling point. In an emergency, it'll do. Silicone fluid will not mix, but will float on top. From a lubricity standpoint, neither fluids are outstanding, though silicones will exhibit a more stable viscosity index in extreme temperatures, which is why the US Army likes silicone fluids. Since few of us ride at temperatures very much below freezing, let alone at 40 below zero, silicone's low temperature advantage won't be apparent. Neither fluids will reduce stopping distances.

With the advent of ABS systems, the limitations of existing brake fluids have been recognized and the brake fluid manufacturers have been working on formulations with enhanced properties. However, the chosen direction has not been silicone. The only major user of silicone is the US Army. It has recently asked the SAE about a procedure for converting from silicon back to DOT 3-4. If they ever decide to switch, silicone brake fluid will go the way of leaded gas.

Brake system contamination
The single most common brake system failure caused by a contaminant is swelling of the rubber components (piston seals etc.) due to the introduction of petroleum based products (motor oil, power steering fluid, mineral oil etc.) A small amount is enough to do major damage. Flushing with mineral spirits is enough to cause a complete system failure in a short time. I suspect this is what has happened when some BMW owners changed to DOT 5 (and then assumed that silicone caused the problem). Flushing with alcohol also causes problems. BMW brake systems should be flushed only with DOT 3 or 4.

If silicone is introduced into an older brake system, the silicone will latch unto the sludge generated by gradual component deterioration and create a gelatin like goop which will attract more crud and eventually plug up metering orifices or cause pistons to stick. If you have already changed to DOT 5, don't compound your initial mistake and change back. Silicone is very tenacious stuff and you will never get it all out of your system. Just change the fluid regularly. For those who race using silicone fluid, I recommend that you crack the bleed screws before each racing session to insure that there is no water in the calipers.

New developments
Since DOT 4 fluids were developed, it was recognized that borate ester based fluids offered the potential for boiling points beyond the 446F requirement, thus came the Super DOT 4 fluids - some covered by the DOT 5.1 designation - which exhibit a minimum dry boiling point of 500F (same as silicone, but different chemistry).

Additionally, a new fluid type based on silicon ester chemistry (not the same as silicon) has been developed that exhibits a minimum dry boiling point of 590F. It is miscible with DOT 3-4 fluids but has yet to see commercial usage.

[is.chowa]

As an afterthought you also may want to check the ABS sensor if it is melted after the fire.

Steve