Hey Guys,

I have had a break fluid leak for the better part of a year. It is quite slow at about 1" dropping from the reservoir every couple of weeks, though I do know it was much slower than that up to several months ago. I had my garage look at things and they replaced a section of brake hose (at $325 ( ). That did not solve the issue at all. I took the back drum brakes off and looked inside the wheel cylinders - no wetness. I checked the front calipers as well. I checked the brake lines myself and see no apparent wetness. Also, no drops onto garage floor after depressing brakes repeatedly. And, I see no wetness inside under the dash (I have the bottom panel removed, so I can see averything) nor near the master cylinder under the hood. So, I am at a loss at this point and really don't want to pay a garage several hundred more for this problem. Can the leak be inside the master cylinder and be unable to be seen from the outside? Any other thoughts? Thanks All,

blackdog48

 

If it's losing brake fluid, it's got to be coming out somewhere. The leak inside the car can be deceiving. There is sound deadening material and carpet in there that can absorb a lot of fluid. I recommend taking another look there. Lay on your back and look all the way up where the master cylinder pushrod attaches to the pedal.

 

Thank you for replying DaX. So, to be thorough, I did check under the dash again and looked right up to the pedal/master cylinder junction. There is little foam there anymore and the carpet is out. I do not see any leakage there.

Last night; however, I guess I disocovered the general area of where the brake fluid is pooling. To start a repair on my shifter linkage, I drove onto wheel ramps and then jacked the driver's side of my car up quite high (enough that the back wheel lifted as well). When I looked under the car, I saw a significant pool of brake fluid (looks clear on my finger and feels slightly oily - though my engine oil is getting dark). From the photos, it has dripped from the rear of the catalytic converter's shield. I am guessing that the angle of the car allowed it to move there from another location. Do you have other thoughts given this new information? Cheers,

blackdog48

 

Look closely at the fittings along the firewall, like the proportioning valve. It could be dripping from there and getting blown back towards the cat, under the car. Or, your hard lines could be damaged underneath the car.

 

Do you know of a diagram that shows the locations of all of the brake line fittings along the firewall? There does seem to be a lot of wetness present, but it is too abundant to pinpoint. Also, how do you feel about products that are designed to show fluid leaks, including ones that can be added to brake fluid? Such as: https://supercool.ac/product/total-d...0brake%20fluid.
It is a UV dye, so maybe that would make more sense than a simple colored dye (which could get lost in all the grease under my car)? And, a simple UV light can be purchased on Amazon for ~$12. Have you ever used such a dye or know if they are effective? Thanks again DaX,

blackdog48

 

You could try looking at the exploded diagrams on www.hondaautomotiveparts.com, but I don't think they will tell you very much. You have 2 lines coming off the master cylinder that go to the proportioning valve. 4 lines come out of that and go to each corner of the car (calipers in front and cylinders or calipers in the rear). Dyes are fine for coolant, power steering, , AC, etc, but brake fluid doesn't circulate, so unless you replace all your brake fluid (lines and reservoir) with dyed fluid, it could take a long time for the dyed fluid to make it to the leaking spot. If you do go that route, buy a 365nm UV light, as it fluoresces dyes MUCH better. Most cheap lights are 390-400nm wavelength and they don't work as well.

I would probably just clean everything on the firewall as good as possible with brake parts cleaner then check daily to see where the wet spot comes back.

 

Yes, I was thinking that and will take your last suggestion first. What usually goes bad with the proportioning valve that causes leaking (there is wetness below it, so I think it may be the problem)? Are there o-rings at each fitting? Thank you for all of your help DaX!

blackdog48

 

No o-rings, just double/inverted flare fittings. If it's leaking from the fittings, try tightening them. None of the lines look rusty, do they?

 

None of the lines look rusty up along the firewall DaX. There is some rust at the beginnings and ends of some of the lines underneath the car. These areas would be quite dififcult to acess, it seems. The line has been replaced in the in-between sections that are easier to access. Kind of makes me wonder how guys replace the entire brake lines on their cars. That's probably a bit beyond what I would want to do. I'm really just trying to get this old girl through the terrible current car market until prices come down. Then probably buy a Civic that's 2005 or newer (do you like generation 6 and newer as well as the 5's?). But we'll see.

Question, though, (in worst case scenario if I end up not being able to fix the leak): will a slow leak cause some air to enter the sytem over time resulting in loss of pressure and require recurrent bleeding of the brakes? Thanks again,

blackdog48

 

put a piece of cardboard under the suspect drip areas and leave overnight.

 

I prefer the 5th gen lines, but have owned 4th gens, and wouldn't hesitate to buy a 6th gen. I don't think you would draw in air unless the leak was rally bad. But I'm not sure.

 

Well, I do learn as I go, at least. Watched a couple videos (the only two I could find) on replacing/repairing proportioning valves. Learned there is a little port facing the passenger side that is usually covered by a little rubber cap. When the o-rings along the internal shaft start to go the fluid leaks from this little port to alert you. Anyone know how hard it is to get the PV off to replace the o-rings? Being there are 6 fittings going into it, I imagine it is quite the job! At least I have managed to learn that this is, indeed, my problem (it is visibly leaking from the port and the PV is wet below it). Wish the garrage had done that! . Thnaks again All,

blackdog48

 

Get a good quality flare nut wrench. It shouldn't be hard to replace.

 

HI Guys - new to this thread and site. We have a 1992 Acura Integra, my son bought from his High School auto shop for $500 last year. We are trying to replace the leaking brake proportioning valve- but difficult to find and discontinued. Is there a replacement part that is compatible? We would really love to see if we can get this car race ready to have a couple of track days on it this summer. Any help would be greatly appreciated! Thanks

Doug

 

For bolt-on compatibility, I would just try to find a good used one on eBay or another website. There are aftermarket proportioning valves, but you typically have to change the hard lines as well.

 

Would replacing the o-rings along the internal shaft work rather than replacing the whole unit DaX? Thanks,

blackdog

 

I've never taken apart a proportioning valve, so I'm not sure if they are serviceable or not.