Brake pedal sinks every so often

[NaSJohnny]

Hey guys, I have a slight problem.

Just bought my 92 EX, and everything is great on it inside and out.

Just a few minor problems I saw, one being the brakes.

Every once in a while, when I press on the brake pedal, it will get pressed down more than usual to stop the car. I figured it may be the brake booster or needing to bleed the brakes of air? Looking for a second opinion. It doesn't happen all the time, but does happen.

Any help is appreciated
Thanks!

[thumping_accord]

Sounds like you air in your system, or brake hose getting ready to say bye bye. Do they feel spongy, or do they just take more force to stop?

[deevergote]

Your master cylinder could be developing an internal leak as well.

[NaSJohnny]

Sounds like you air in your system, or brake hose getting ready to say bye bye. Do they feel spongy, or do they just take more force to stop?

It's spongy. Not stiff at all when it sinks. Figured the best case scenario is I just have to bleed the brake lines. Just needa find time to check for myself.

[NaSJohnny]

Your master cylinder could be developing an internal leak as well.

Didn't think about that. Thank you for the input. I'll put that on the list of possibilities to check over. At least as far as I see, it doesn't seem like an expensive fix if I have to replace parts. Lol.

[hiptech]

I definitely agree with deevergote your master cylinder is failing... don't wait too long

[Raf99]

I have this with the Acura. Randomly happens, doesn't affect the brakes at all as it always happens at a stop sign/red light. Always felt like a vacuum leak. If it was the MC leaking the fluid would drastically drop as "disappears" behind the plunger. But the fluid level never drops, i was told it's a vacuum leak or read it was just the pressures leveling off.

[Fleetw00d]

The master cylinder can be leaking past the piston internally, it stays in the system so the level won't drop. If it was only air in the system, it would likely be spongy all the time. Replace the master cylinder.

[Losiracer2]

I had this happen on my 91 LX Coupe. Your MC has blown its internal seal. It is very dangerous and I would get a new one ASAP.

They sell them new at Autozone for 50 or a remanufactured one is I think 25-30.

If you can, get a 4th gen. Prelude VTEC 94-96 MC, they're 1" in diameter vs. the 15/16" diameter for the Accord EX, not much but still an upgrade. They bolt up the same and no other modifications are necessary

[Raf99]

The master cylinder can be leaking past the piston internally, it stays in the system so the level won't drop. If it was only air in the system, it would likely be spongy all the time. Replace the master cylinder.

Current fluid level is from the piston forward. Behind the piston is nothing but air and the push rod, springs, etc. Also bad seals usually result in fluid leaking in by the pedals inside the car. But there is a chance the fluid is making it past the piston cups and not past the rod seal and in this scenario one would see a very slight drop in fluid in the reservoir.

[NaSJohnny]

You guys are all awesome. I may be replacing the MC this weekend if I have the time. Does not seem like it is a hard procedure.

[Losiracer2]

You guys are all awesome. I may be replacing the MC this weekend if I have the time. Does not seem like it is a hard procedure.

just make sure to bench bleed (fill reservoir and purge air prior to intalling on car) it first before installing and you'll be set.

[Accrdwgnguy]

This has happened to just about every Honda I've owned. Just replaced a master on my gf's Accord a couple months ago. Telltale sign is that the brakes seem to work fine but when sitting and holding the pedal (like at a stop light) the pedal slowy sinks and you gradually lose brake pressure until the brakes release. You let off the pedal and hit it again and you have pressure, until it sinks again. Also I've noticed the fluid seems to seep out the piston seal and drip down the booster stripping the paint off in the process. Very very slow leak however unless it gets real bad and at that point I'd suspect you'd have no brakes!

I've always bought new masters, don't take your chances with a crappy reman! The new ones are cheap enough, around $40 shipped on Amazon for a quality made in USA Centric master. I've used that brand almost exclusively on my Hondas and never had an issue.

When you do this you are going to end up bleeding out your whole system, which assuming the rest of your braking system is in good shape (pads calipers and rotors), it's going to feel like a new car in terms of brake feel. I usually bleed bleed bleed at each corner until I have a steady stream of clean fluid. It's worth the whole bottle to do this, and it should be part of your maintenance schedule.

[deevergote]

Centric makes good stuff, for sure.

If you're interested in an additional upgrade, pick up some braided stainless steel brake lines. They'll be about $100 today (front and rear.) Techna-Fit makes a decent, affordable product. StopTech does as well (StopTech is a Centric brand... they make very good performance brake rotors... another thing you may want to upgrade while you're there!) You'll be bleeding the system anyway, so there's no better time to get it done!