2023-05-18 Thu 09:32 AM ![[Pasted image 20230518114905.png]] - My van is a 2016 Ram Promaster 2500 159 inch wheel base. - I bought it used - The previous owner had done something with the brakes which caused the two brake sensors in the front to be disconnected. - I had the van looked at when I bought it, and my guy said it's fine — you can just replace the sensors if you want them next time you get the brake pads done. # 2023-05-18 Thu 12:09 PM Situation - I've put about 10k miles on it over the last 10 months. Complications - When I'm working the brakes hard eg when coming down a mountain, I sometimes get a "brake fluid low" warning. - This is alarming when it happens, as once in high school with the old Cougar I had the hand brake slightly on without knowing it, and I wound up losing brakes while moving at high speed. Had to swing the car into a gas station to avoid a collision. - So what I do is park until the system cools off and the warning goes away. Then I drive again until the warning comes back on. - Other thing I do is switch into is, when coming down a mountain, switch to triptronic mode and use engine braking to manage speed so that I don't have to ride the brakes. - In addition, I've begun to hear more squeaks coming from the car while driving. - Notably, this is while driving, and not specifically while braking, so I'm not sure that it has anything to do with brake pads. Plan - Take it to a shop, - Ask they can look up when the car last had fluid changed - get fluid changed for $100 if I need to - Check pads - Replace them if I need to, at a cost (parts and labor) of ~$170 per axle Result - 2023-05-18 Thu 15:52 PM - Pads are fine all around. - They're at about 7mm all around, need to replace at about 2mm. - Les Schwab replaces calipers as well as pads — - Just replacing pads is what he called a "pad slap". They don't do it because problems with the caliper accrue - tehy also look at the rotors and machine them or replace them - Sensors — - known issue: right front is severed, left front is frayed. - replacing: the sensors come with the calipers, so no sense replacing now; would need to buy the whole caliper - Fluid level is good - Brake fluid low warning - No problems with fluid or pads; might be that frayed or severed sensor? - Could snip or cover the exposed parts with electrical tape. # Learning - How does the brake system in a Promaster work? What are the key parts? - Pads - Rotors - Calipers - Fluid - Sensors - etc This video did a fine job giving the basics: https://www.youtube.com/watch?v=6H7nwlT_qNY - Is there a straight mecanical (via fluid) connection between pedal and calipers? Or is there a computer involved to modulate the pressure? - Called "Power assisted brakes" - Can be either way. Not sure if I have power assisted brakes - But mostly it's lever action. You move your foot maybe 6 inches, but each caliper (on each of 4 wheels) only needs to move a much smaller amount (though you do lose mechanical levarge by spreading that force to 4 wheels) - 2023-05-18 Thu 15:58 PM Yes the van does have power assisted brakes — you can feel the difference by pressing the brakes with just the battery on vs with the engine on. - What would happen if you had a total sudden brake fluid evacuation, like if a line burst. You'd have no brakes? - Yes, you'd completely lose your hydrolic brakes. - You'd probably still have hand brake, which is probably on a different mechanism, - And you can still do engine braking. - But not a good situation. - Why does brake fluid behave differently as it heats up? (apparently) - >Brake fluid gets hot as it us used to push against the hot brake discs. If the brakes have been used long enough I.e down a long mountain road rather than using the vehicles gears the brake fluid actually boils. When it boils gas is compressible to causes the brakes to initially feel spongy and eventually stop working all together. When you apply the brakes they get hot. The heat from the brakes travels into the Brake Cylinders which in turn heat up the Brake Fluid. When the Brake Fluid gets to boiling temperatures- the braking gets less effective as the boiling brake fluid generates gasses. The brake fluid has very high boiling temperatures - so it is very difficult for this to happen - but if you are going down a hill with heavy loads -this an happen - and as soon as the brakes are allowed to cool down - it all reverts to normal. Hence keeping the car in lower gears to let the engine do a bit of the braking is a good idea.—https://www.quora.com/How-does-brake-fluid-get-hot-How-does-it-affect-braking - Why might my fluid be low? - One possible reason: very worn pads. it takes more fluid to fill the brake chambers to get the calipers to close the distance when the pads are gone. - Another possible: leak (but unlikely, esp for me because it's fairly stable) - Why does brake fluid warning come on when going down a big hill? - Could be angle of vehicle causing the fluid to move and not trip the sensor, but unlikely because this would then happen immediately when I got the car at enough of an angle. In my case it only occurs after riding the brakes for a while. And it goes away after I let it cool for a bit, even if I'm still at the same angle. - Does brake fluid need to be changed as part of routine maintenance? Why? How often? - Idea is that it can pick up bits of debris from all the mechanical action, and it can pick up water. - It can also pick up water through normal operation. - Change it every few years, about every 45,000 miules - What does a brake sensor car do? How does it work? - There might be other kinds of sensors, but one is just a brake pad sensor. - > The pads have a built in sensor that simply grounds out to trigger the brake alarm. It will turn off by itself with the new pads, or if it's left unplugged. https://www.promasterforum.com/threads/brake-pad-warning.96439/ - How to eyeball my brake pads? - Hard to do with the wheel on, but this guy gives an instruction https://www.youtube.com/watch?v=Mfxef0vgC60 - Which replacement pads should I get and how much should they cost? (parts and labor) - Parts: This guy tested a bunch and found different performance characteristics. But for cost, the cheap ones wore out something like 40% faster https://youtu.be/DZ8O2tJOGLE?t=441. So get the mid-tier ones at $40. But is that $40 for all 4? each one? Okay looks like it's 2 pads per wheel, so 8 pads needed if you're replacing the whole car, and they're sold in packs of 4 for either the front wheels or the back wheels. So est $80 for parts. - Labor: $80-100 per axle https://brakestogo.com/blog/brake-pad-replacement-cost - So if I'm getting the whole car done, should be ~$170 per axle, ~$240 for the whole car - How much should it cost to change brake fluid? - Average $100 for parts and labor - I think that I requested it on the initial work I had done when I got the car, but guy checked it in the computer and told me it wasn't time yet. - Can ask. - So if I need the whole thing for the whole car, ~$340