Possible rear brake line leak?

[slimjim]

Got the dreaded C1252/C1256 error code today. Initially suspected it must be the infamous abs booster/cylinder combined unit finally giving up the ghost but upon closer inspection I suspect it might just be a simple leak; I also suspect it could just be a leak because of circumstantial evidence (see story below). The unit under the hood looks just fine externally (no obvious leaks) but as you can see in the pictures the rear driver rear must have a leak of some kind. The fluid doesn't have a strong smell so I'm reasonably sure its brake fluid.

Can anyone help me identify what appears to be going on based on the pictures? Where is the most likely place for the leak to be coming from? Rear passenger side picture included as a clean(er) reference. Do I need to replace the caliper? Flexible line? the copper crush gaskets and copper bolt on the flexible line (90430-10074 and 90401-10015)? If possible I'd like to get the truck back on the road ASAP as its hunting season and I'm depending on it. It's obviously just about time to redo the entire brake system as I believe its all original but I'm hoping to quickly/temporarily address this specific problem until hunting season is over. Any tips would be appreciated!

Bit of backstory: Recently mounted up some new wheels/tires and while taking it to alignment shop shortly thereafter I noticed an unusual pumping noise under the hood in the parking lot of the shop (before alignment was even performed). I was worried it might be the brake master cylinder acting up but decided to just ignore it and see what happens. A few weeks have gone by now, truck hasn't been driven much, and while running an errand in the neighborhood finally got the dreaded ABS light today along with the annoying warning tone (half mile from home thankfully, brakes kept working the entire time). I actually already have a replacement master cylinder ready to go thankfully but not the flexible lines or anything else. Really hoping I don't have to rebuild the entire brake system this week!

 

[2001LC]

I don't see a brake fluid leak. But I can't see the caliper. I doubt flex line leaking, although I can't see it all to be sure. But typically the brake fluid will travel back along flex line, as well as downward.

The oil on brake dust shield. May be gear lube. Will see rear diff gear lube pass the axle seal. It often show on lower half of brake dust shield. WITH TIME THE OIL (GEAR LUBE) TRAVELS UP, due to capillary action. You can look for more clues. By removing brake rotor. Or Remove wheel speed sensor. If any gear lube found in either. You have a axle seals, and bearing is bad or will be.

 

[Trunk Monkey]

Have you checked the brake fluid reservoir? Looks like it could be more of an axle seal leak than brakes.

 

[GTV]

Whenever you suspect a leak first clean the area and then monitor it closely. It can be difficult to find a leak through 20 years of grime.

Sharing the year, model and mileage of your 100 is helpful.

 

[slimjim]

capillary action

Did not know this was a thing, thanks! That hardline on the rear diff may be the culprit in that case (hopefully), trying to find the appropriate parts diagram now

Have you checked the brake fluid reservoir? Looks like it could be more of an axle seal leak than brakes.

Yes, as it currently sits its slightly above the max fill line (I assume because the accumulator is empty) but it could have been overfilled honestly just not sure

year, model and mileage

'99 LC 175ish

 

[2001LC]

That hardline on the rear diff may be the culprit

Hard line where it connects to flex line circled in red area, is dry as a bone. Not leaking.

 

[slimjim]

Hard line where it connects to flex line circled in red area, is dry as a bone. Not leaking.
View attachment 4032820

I meant the hardline on the diff (below the circled area), assuming it must be oil from the rear axle/diff. This 99 has an elocker in the rear and I can't seem to find that hardline on any of the diagrams... but as long as its not a brake problem I don't have to address it this week lol

 

[2001LC]

Punch in your VIN# at www.partsouq.com

Yellow arrow: Wheel speed sensor. Remove it, check for gear lube.

 

[slimjim]

Punch in your VIN# at www.partsouq.com

Yellow arrow: Wheel speed sensor. Remove it, check for gear lube.

Thank you! found it:
89545-60030 (rear right)
89546-60030 (rear left)
These things are surprisingly pricey hoping it's not necessary to replace

 

[2001LC]

Thank you! found it:
89545-60030 (rear right)
89546-60030 (rear left)
These things are surprisingly pricey hoping it's not necessary to replace

NO, NO and NO!

I AM NOT, saying you need the either of those parts (wheel speed sensors). Nothing you've stated or pictures you've posted, suggest you do.
I only gave you partsouq as a reference tool. So you can look at part diagrams, and see what all parts are. Since you mistakenly called the wheel speed sensor wires "hardline"

You also have called this oil spot on LH rear brake dust shield. "Brake fluid leak". Wrong, by all indication! No picture or clue (brake fluid above max line), indicates, you even have any brake fluid leak.

We're just identifying, your oil spot on LH rear brake dust shield. By pulling the LH rear wheel speed sensor. So you can inspect area inside of its port. This is just a check/inspection, to see if gear lube inside that port, that houses/holds the wheel speed sensor. If you find gear lube, than your LH rear axle seal is leaking. That would explain the oily appearance on LH rear brake dust shield. Then just put that old wheel speed sensor back in place. Gear lube leak here, has nothing to do with your codes (DTC): C1252 & C1265. Just one more thing (LH rear axle seal) on your list of repairs needed.

DTC:
"C1252 Brake Booster Pump Motor ON Time is Abnormally Long"--- Indicate a brake master pressure issue. Very likely leak at or within brake master ASSY
"C1265 Accumulator Low Pressure." -- May indicate: Weak motor, pump or accumulator. Also weak battery voltage to booster motor. May even be, leak in seal of master.

I HIGHLY SUGGEST YOU STOP TRYING TO DIAGNOSE BRAKE DTC C1252 & C1265. Take your 99LC w/175K mile. To a competent Toyota mechanic, not some INDY shops.

Your 99LC, likely needs a new brake booster w/Master cylinder ASSY (The whole brake master). But you've not giving any clues. That I can go on, to make the call with any certainty. Other than DTC C1252 & C1256. You could have even just had, low or dead battery for all I know.

What I do know. You have brake master pressure DTC. They must always, be properly diagnostic.

You may gain some understanding reading below thread.

Thread 'Brakes ...... Overdue write-up.'

Nov 1, 2020

First and foremost: Brakes should only be worked by those, with high level of mechanical abilities and experienced with brake systems.

With the age of all 100 series today, in our aging fleet. Any issue, with brake master assembly. IMHO, best and safest course of action. Have the whole brake master assembly, replaced with new. If you have to ask question, on "how to", your not qualified to work on the master.

My hope is below link will give better understanding as to what we can do to reduce brake failure and what to watch for. The info is from my experiences and my thinking, as to what...

• 2001LC
• Replies: 189
• Forum: 100-Series Cruisers

• 
• 

 

[slimjim]

Like I already mentioned I actually have a complete and brand new brake master cylinder unit to install, precisely because I knew this day would come, which I am doing now. Was trying to get help identifying what's going on with this back wheel to make sure I didn't miss something obvious. Anyways...

 

[OEMGUY0720]

That appears to be your rear axle housing seal.