Jim Pivonka

This is in a 1999 V6 Coupe Accord.
First, the brake warning light turns on. Eventually the car will not start.
These conditions are caused by the brake fluid level sensor in the brake fluid reservoir, on top of the master cylinder, detecting low brake fluid.
Inspection _appears_ to indicate that the brake fluid is being lost because the plastic reservoir on top of the master cylinder has come loose from the master cylinder and is leaking, rapidly, there. It loses about 2/3 of a pint of fluid in an hour.
I have to add fluid to get the Accord to start.
The brakes still work, kind of. The fluid level, after all, does not drop below the level of the top of the master cylinder casting; it is only the reservoir that is losing fluid.
Who can tell me how the reservoir is supposed to be attached to the master cylinder, and how to reattach it so that it does not leak - if that is possible.?

belairbrian

The short answer is replace the master cylinder unit as a whole.

IIRC there are o-rings on the reservoir that seal the tank to the base. Those o-rings are not available separately.

Jim Pivonka

Apparently the O rings have failed, then. Aftermarket O rings seem to do that, if this an the gas cap are indicative. I wonder if Honda has a secret O ring formula, or the after market people are just chintzy.

belairbrian

what i've found is some after market rubber is junk. learned myself go with OEM. In my case I bought after market upper arms. The rubber seals lasted about 3 months.

I took a look and a master cylinder from Honda can be had for 50 bucks less than an after market from oreilly auto.

Jim Pivonka

That increases the likelihood that its the o rings that have gone bad. I'm 80+ miles from a putative Honda shop, at least 90+ from a credible one, and leak bake fluid at a rate of half a pint an hour, out of the reservoir. The rest of the system still has fluid in it, when the reservoir is empty, so the brakes still work, at least for a few braking cycles. Hours on the interstates.

But the electronic interlock prevents starting the car, if the fluid is that low, so during the drive to whatever shop I find to do the work, I will have to carry pints of the stuff with me, to add periodically.

The bad seals come as part of the MC body, not the reservoir, so replacing the reservoir would not be an option even if one were available.

As a stopgap I am thinking of taking the reservoir off the master cylinder body, cleaning the contact surfaces with brake parts cleaner, and using "ultra grey rigid high torque RTV silicone" gasket maker to seal the reservoir to master cylinder. I'll be shooting for enough driving time to get me to a dealer who can replace the aftermarket m c with the Honda OEM part, not anything fit for more than a few hours or days.

Any thoughts, comments, cautions, etc. on this approach will be much appreciated.

VeeSykkz

I wouldnt worry about taking it apart and cleaning it if you plan to replace it. That could introduce further contaminants into the system and is just a waste of time.

INSTEAD just seal the outside of the MC where it meets the res. Keep in mind there may be a conflict with ANYTHING you use that will come in contact with the fluid.

Jim Pivonka

Thanks for that advice. I just wiped the outside of the reservoir and the cylinder body with a brake parts cleaner dampened cloth, let it dry, and finger applied the permatex to the exterior, in hopes of sealing - at least partially - the leak. I used two chained 1/4" zip strips to apply a little compression to the join.

At 10AM Tuesday I have an appointment at Scholfield Honda, Wichita, 130 some miles to drive, to get a new cylinder installed and the system cleaned up. I'll be carrying 5+ pints of fluid with me, in case my sealing effort fails.

Thanks to both of you for your help!

Jim Pivonka

That worked like a charm. This morning I added enough brake fluid to the reservoir to turn the 'brake warning' light off and start the car, drove three hours to Wichita - apparently without losing a drop of brake fluid from the newly sealed reservoir/cylinder - and am waiting for Scholfield to finish replacing the failed aftermarket cylinder with a new Honda cylinder. (Parts & labor & tax ca. $475; that hurts but not so bad as a failed brake system.) The mechanics see no physical damage to the cylinder/reservoir and concur that the problem is a failed sealing ring in the aftermarket part.

VeeSykkz

haha awesome! Glad I could get you there safely and most importantly LEAK FREE!

I worked at Napa auto parts for 2 years and now am an engineer for Hilton hotels.

Jim Pivonka

Yep. I started the trip to Wichita wondering if I'd make it there, and finished wondering how far I might have been able to drive with the patched and bandaged MBC. Thanks again for that suggestion.

DCFIVER

There is no correlation here. The brake warning light circuit does not interact with the shift interlock. You have a separate issue with regards to the no start.




Has the brake fluid ever been flushed? If not, expect the new Honda MC to leak in due time as well.....