2nd gen 4Runner with rear ABS, suddenly got a soft pedal after hard braking (1 Viewer)

[ozarkmud]

Hey everyone.

I have a 2nd gen 4Runner with rear ABS. The ABS light will come on with the key in, but when it's started it goes back out.

I was testing the 4Runner in the snow going down my driveway, trying to lock and see how fast I could stop. I couldn't feel any pulsing in the pedal, which was strange. But after a few hard stops, my pedal got really mushy and would bottom out. I think it's the first time it's done that.

I looked at all four wheels and couldn't spot any super obvious brake fluid leaks. The fluid level was well below the minimum in the master cylinder, though. I don't know if it was above minimum or not before. I'm guessing it was, but I can't say for sure.

I decided to top up the master cylinder, but I'm concerned and not sure what happened or if there's something I need to look into. Would appreciate any suggestions you can offer.

Thank you!

 

[ozarkmud]

Alright, so I'm looking into this now and the system wants to take quite a bit of fluid. I still can't spot any leaks.

My theory is that it was bled last without bleeding the ABS unit. When I did the hard braking on the snow, the system tried to activate, introducing air into the system. Some of the extra fluid in the reservoir took the place of the air, until it went down quite a bit. Possibly far enough to introduce even more air into the system.

So far I've pumped from the middle line to below minimum a couple times. I'm thinking maybe I just need to hook up my master cylinder bleeder to it, put pressure, and crack the lines accordingly.

Does this seem plausible? I haven't done much brake work on vehicles without ABS.

 

[gnob]

pull the mc and made sure that you aren't leaking into the booster.
there are very few vehicles that have "special" bleeding for abs.
in actuality you should just delete it.

 

[ozarkmud]

Thank you!

I did actually find a leak... somewhere at the rear. It's a pretty serious leak. I must've blown something out.

I can't quite find the source, and the LSPV looks dry. I think maybe it had a small leak for a while before blowing out, but not positive. Do you have any ideas on where it might've blown out? Kind of hard to see under threre. This is in the right rear wheel well area.

Definitely fine with removing the ABS unit down the road, but right now it's not a priority. Just want to get the 4Runner back on the road for now.

 

[gnob]

if its actually not the LSPV i would suspect rusty line, judging by the pics.
get another body or put your phone under there and record it while you pump.

 

[ozarkmud]

It's surprisingly difficult to film in there. I wonder if I should approach it from the other side. There were lots of active drips -- I don't feel like I saw the source though.

If it is a rusty line, which would not be surprising given the rest of the rig, what options do I have? Is it possible to splice and replace a section of line, or does a whole line need to be run? I haven't worked with hard lines very much.

 

[jgranthevagrant]

I blew a line about 2 seasons ago. Was rubbing on the frame rail until it burst. Was on a very steep hill North of Whistler, B.C. I investigated my options like trying to splice with a flaring kit, but ended up replacing the whole line. Was still available at Toyota. Another tip: rocks, sticks, etc like to get stuck along the brake lines, which can exacerbate wear and tear, so I try to clean along the lines on the frame every now and again.

 

[ozarkmud]

I blew a line about 2 seasons ago. Was rubbing on the frame rail until it burst. Was on a very steep hill North of Whistler, B.C. I investigated my options like trying to splice with a flaring kit, but ended up replacing the whole line. Was still available at Toyota. Another tip: rocks, sticks, etc like to get stuck along the brake lines, which can exacerbate wear and tear, so I try to clean along the lines on the frame every now and again.

Wow, that's awful. I'm glad I blew mine out in the driveway.

----

Looking at it again, I'm still not quite sure where the leak is coming from. There's a hose (or maybe speedo cable?) going off the top of the differential. Do you know what that is? Little puzzling. Maybe speed sensor for the rear ABS?

It does seem like there's a safety issue with the LPSV, if I'm seeing it correctly. It looks like it has two lines going in and one line going out to the rear brakes. If you lose one of the lines, does the other line function? It was my understanding that front left/rear right and front right/rear left were supposed to be independent systems. It appears like this ties them together and if you lose pressure in one, you lose it in both. I may be mistaken, though.

 

[ozarkmud]

Doing some searches, it seems like this area is a common one to have problems in. The consensus seems to be that you either have to pull the gas tank to replace the line, or lift the body off the frame. Or just run brake line around the gas tank and leave the old lines.

Toyota-4Runner.org

The Largest 4Runner Community in the World

www.toyota-4runner.org

Toyota-4Runner.org

The Largest 4Runner Community in the World

www.toyota-4runner.org

I'm wondering though if there's a decent way I can disable whatever brake line is bad to get it to a shop safely, if this is something pretty involved to fix.