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Old 11-06-2018, 10:33 PM   #1
cleandmc
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Default ABS Reservoir Overflowing (not foaming)

My 1988 Legend LS is having a weird issue with the ABS reservoir.

The backstory:

I recently bought a 1988 Legend with 55K miles on it. The thing is pristine, and was actually well used the last few years by previous owner who put about 30K miles on it over 5 years, so worked out a lot of age issue maintenance items. I had no issues for the first 4K miles of ownership, but then noticed a brake fluid leak coming from the ABS reservoir/modulator.

My mechanic diagnosed that the modulator seal was bad. I took a modulator from my parts car and they installed that. I didn't want the ABS system active regardless, so I pulled the fuses. I noticed pretty quickly that there was still a leak, but this time it was coming from an overflow of fluid from the ABS reservoir cap. Not only that, but the fluid level from my regular brake fluid reservoir attached to the master cylinder constantly goes down. I assume the fluid is being pulled into the accumulator bladder that is underneath the ABS modulator, and that is somehow pushing it up to the ABS reservoir?

My only solution has been to use a turkey baster to suck the fluid out of the ABS reservoir when it starts to get too high. And I keep topping off the master cylinder reservoir. There is no leak if I continue to do this. But obviously I want to fix this and avoid having to monitor this every week.

My mechanics did the burping of the ABS system, but perhaps there is something they didn't do correctly? As a note, I did read two other threads that discussed something slightly similar, but those other threads discussed foaming. There is no foaming going on here, it is merely fluid being pushed into the ABS reservoir causing it to overflow.

Anyone that can help guide me on this? It would be great to point my mechanics in a direction to solve this.

Thank you.
T.
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Old 11-07-2018, 03:02 AM   #2
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The car's brake system is essentially two halves. One half is the service brake. The other half is the ALB. The Modulator is situated between both halves.

Both halves use brake fluid to operate. However, the fluid in both halves are not supposed to mix. Ever. The only way they get mixed is if there's an internal leak in the Modulator.

It's odd that your losing fluid on the service brake side and it's leaking to the ALB side. Usually, it leaks the other way around.

You might want to try to reconnect the ALB system, adjust the fluid levels in both reservoirs, find a deserted road with a gravel shoulder and exercise the ALB system by locking up the brakes two or three times - work the ALB system. Then see what happens.

BTW, how often do you have to empty out the ALB reservoir?

Does your mechanic have a Honda service manual?
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Last edited by paulo57509; 11-07-2018 at 12:47 PM. Reason: Spelling, Grammar
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Old 11-08-2018, 06:32 AM   #3
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I have a vague memory of a post showing some redneck engineering in which a hose was run between the reservoirs so that the overflow in one would simply flow back into the system that was losing fluid.

I couldn't find it on here, maybe it's on the old dot.commie.

-Kennon
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Old 11-08-2018, 02:49 PM   #4
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Quote:
Originally Posted by JKLedbetter View Post
I have a vague memory of a post showing some redneck engineering in which a hose was run between the reservoirs so that the overflow in one would simply flow back into the system that was losing fluid.

I couldn't find it on here, maybe it's on the old dot.commie.

-Kennon
I remember that thread too. But all I can remember is the hose barbs and hose. No details.
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Old 11-09-2018, 08:32 PM   #5
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Quote:
Originally Posted by paulo57509 View Post
...It's odd that your losing fluid on the service brake side and it's leaking to the ALB side. Usually, it leaks the other way around...
This must be because he disabled the system. It isn't building pressure on the ALB side and therefore can't bleed fluid into the regular brake circuit. But without pressure it allows the regular brake circuit to bleed fluid into the ALB side whenever the brakes are applied.

Here's a link to rebuilding an NSX modulator, which is very similar to a Legend modulator:

http://www3.telus.net/public/warshan...rebuld_v03.pdf

-Kennon
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Old 11-10-2018, 04:19 PM   #6
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Quote:
Originally Posted by JKLedbetter View Post
This must be because he disabled the system. It isn't building pressure on the ALB side and therefore can't bleed fluid into the regular brake circuit. But without pressure it allows the regular brake circuit to bleed fluid into the ALB side whenever the brakes are applied.

Here's a link to rebuilding an NSX modulator, which is very similar to a Legend modulator:

http://www3.telus.net/public/warshan...rebuld_v03.pdf

-Kennon
I thought the same thing about his ALB system being disabled. But fluid still shouldn't migrate into the ALB side. That's why I suggested enabling the system and exercising the system. Sometimes it helps, sometimes not.

Good link info. Hopefully, the o-rings for the solenoids would be the same in the Legend. The hard part is sourcing the cup seals on the pistons. Not impossible, but it would take hours looking through a seal catalog and perhaps some home make punches and fixtures.

I hoarded a couple of modulators years ago for evaluation, hoping to put together a seal kit. Or at least pirate the good parts from the three that I have to make one or two good ones. Maybe someday....

FWIW, here's the Modulator tear down for the Legend from the old online FSM. It's weird how these pages aren't part of the N. American version of the manual. Sorry no shared cloud storage link, just images.













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Last edited by paulo57509; 11-10-2018 at 04:23 PM.
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Old 11-11-2018, 07:37 PM   #7
cleandmc
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Yes, it is odd that I'm losing brake fluid from the regular side to the ABS side. This was happening before I pulled the fuses to the ABS system. I've pulled the fuses to my ABS systems in all of my previous legends, never have I had this type of issue arise.

The ALB reservoir is being emptied maybe once every two weeks. And the regular reservoir for the master cylinder is being filled around the same time as well to make sure it doesn't get too low.

Since I have my old parts car modulator in there now, I doubt the ABS system would even work if I tried.


Quote:
Originally Posted by paulo57509 View Post
The car's brake system is essentially two halves. One half is the service brake. The other half is the ALB. The Modulator is situated between both halves.

Both halves use brake fluid to operate. However, the fluid in both halves are not supposed to mix. Ever. The only way they get mixed is if there's an internal leak in the Modulator.

It's odd that your losing fluid on the service brake side and it's leaking to the ALB side. Usually, it leaks the other way around.

You might want to try to reconnect the ALB system, adjust the fluid levels in both reservoirs, find a deserted road with a gravel shoulder and exercise the ALB system by locking up the brakes two or three times - work the ALB system. Then see what happens.

BTW, how often do you have to empty out the ALB reservoir?

Does your mechanic have a Honda service manual?
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Old 11-11-2018, 07:39 PM   #8
cleandmc
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My dad was actually joking that maybe we could figure out a solution like this. Even if it is a bit ridiculous, at least it would cut down on worrying about it. I just have to believer there is a way to solve this. From the other replies below with service manual suggestions, I'm going to have to try and get the mechanics to walk through this a bit more.

Quote:
Originally Posted by paulo57509 View Post
I remember that thread too. But all I can remember is the hose barbs and hose. No details.
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Old 11-11-2018, 07:41 PM   #9
cleandmc
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Thank you for the below. Very helpful. Will be a few weeks until I can try anything as car is in Chicago and I'm back in Los Angeles for awhile. If I get this sorted, I will provide an update.

Quote:
Originally Posted by paulo57509 View Post
I thought the same thing about his ALB system being disabled. But fluid still shouldn't migrate into the ALB side. That's why I suggested enabling the system and exercising the system. Sometimes it helps, sometimes not.

Good link info. Hopefully, the o-rings for the solenoids would be the same in the Legend. The hard part is sourcing the cup seals on the pistons. Not impossible, but it would take hours looking through a seal catalog and perhaps some home make punches and fixtures.

I hoarded a couple of modulators years ago for evaluation, hoping to put together a seal kit. Or at least pirate the good parts from the three that I have to make one or two good ones. Maybe someday....

FWIW, here's the Modulator tear down for the Legend from the old online FSM. It's weird how these pages aren't part of the N. American version of the manual. Sorry no shared cloud storage link, just images.













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Old 02-10-2019, 08:01 PM   #10
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Default ABS bypass operation

I'm the 'redneck' (lol) who posted the instructions on how to do a 'bypass' operation that allows the fluid levels in both the regular and ALB reservoirs to equalize, and still allows the ALB system to operate. I couldn't find my thread here on this forum, but it was still on the 'other' Acura forum, so here it is. I have some photos somewhere, I could post them in anyone is interested.

THIS SOLVES THE PROBLEM OF ABS RESERVOIR OVERFLOW

Here's what I did: at a local hardware store, I picked up two (2) one-quarter inch brass "Hose Barb Connectors" ...two in package for $2.39. Also got a one-foot length of one-quarter inch (inside diameter) clear plastic hose at 29 cents a foot. Next, I drained both brake fluid reservoirs, using a plastic spoon fashioned from a 2-litre coke bottle cap, with a wire handle (you could also use a turkey baster, or any clean suction device ...not yer mouth!!). This allowed me to scoop out virtually all of the fluid. The remainder I soaked up with an absorbant, lint-free shop cloth. Each of the reservoirs is held in place at the bottom by two medium-size Phillips-head screws. The main reservoir comes off quite easy, but the ALB reservoir (the one nearest the battery) was a little tougher. Careful here: the screws go right thru the sub-base, and hold the sub-base to a main base as well. I suspect if the sub-base lifts, you'll get air in the system, and may have to do a complete system bleed. I carefully pried the reservoir loose by working a short, wide, flat-blade screwdriver between the reservoir and the sub-base. Once I had the reservoirs off, I stuffed a clean shop-towel in each one to keep dirt out. With the plastic reservoirs on the work-bench, on the ALB reservoir, I drilled a 3-eighths inch hole in the side, right at the MAX line. Drill a smaller pilot hole first ...then go for the 3/8ths hole. Drill slowly so the plastic doesn't melt. With the tank in place, and you standing by the driver-side front wheel, facing the engine, the hole should be in about the middle of the flat right-hand side of the reservoir. Simply thread one of the brass hose barbs into the hole. Its a perfect fit, and will not leak if you drilled a clean straight hole, and if you don't over-tighten the brass fitting. (while its clean and dry, seal around the brass fitting with some clear silicon just to be sure). Replace the reservoir, making sure there's no dirt in the sub-base where the reservoir seats. Put the main reservoir back in place to mark the location for the drill-hole. Once again drilling the hole at or near the MAX marking line. You'll need to mark it while in place so the brass fitting doesn't interfere with other existing hoses near the firewall of the car. Remove the reservoir and repeat the hole-drilling process, and thread in the brass fitting. Replace the reservoir tank. The 12 inch length of plastic hose should fit perfectly from one reservoir to the other, but do a trial fit (without actually pushing the hose onto the connectors) just to make sure. Lubricate the connectors with a bit of brake fluid, and carefully push one end of the hose onto each connector. Don't put too much pressure on the reservoirs ...they might crack, etc. Just to be sure, I put a small cable-tie over the plastic hose to ensure a tight fit with the brass ends. ALMOST DONE: simply re-fill both reservoirs with new fluid to the MAX line, and replace the caps. On mine, I started the engine and pumped the brakes a few times ...drove around the block, and put hard pressure on the brakes ...then came home to check for levels, and leaks. Levels fine, no leaks. There's actually not that much pressure in the reservoirs, so I don't anticipate pressure leaks at the brass fttings. It took me about an hour and half of my time ...and less than $6 in parts (fittings plus new brake fluid).

So, if you're at all handy with some basic tools, this is much more effective fix than spending $2500, or simply disconnecting the ABS.
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