mehall

The initional post 2 weeks ago....I thought we got it fixed, for a couple of days!

>>NOW, I have a new thing. My wife mentioned that it started to "rumble" getting worse as she drove then suddenly sounded to her that it a plugged pipe had blown open (her description of the sound) and it ran fine.

Today, I took it out for some errands, all in town. When leaving the driveway, it seemed reticent to move, as if the brakes were hanging up. 3 stops, longest leg about 2 miles back to home. It's behaviour degraded to the poind that it felt like I had a flat tire complete with the tire flopping sound and the car was shuddering badtly. The last leg was about a mile on the hiway which I took slow, about 45, which was interesting.

I checked the wheels for heat - none, There was the smell of hot rubber...

No flat.

Where would you start? <<

mehall

3 mechanics told me that colapsed brake hoses would constrict the flow from the calipers when the pedal when the pedal is released, which in turn would cause the ABS to react as if the tires weren't stopping as it should. This could lead to the problems we were happening.

We installed 4 new lines using new copper seals and flushed the system with a couple of quarts of DOT3.

Ran great 4 days until this morning when it started doing it again. If I can start the car with minimal brake pressure and drive to avoid stopping, it does fine. When I must brake, it starts up. I tested this by parking where I could leave it for a few hours and then drive ~5mi at up to 70 mph. I exited and braked as needed and got back on highway and it started up again.

I limpted home and checked all 4 wheels. The front 2 were coool and back 2 were hot.

The car has a new (rebuilt) master cylindar with maybe 250 miles on it. Had it replaced as part of the purchas of thecar. It had a very mushy pedal. It also got new brake pads around and new discs in the rear.

Any ideas?

rome99LS

Check the emergency brakes in rear by taking the Rotors off.

billydpowe

iTrader: (1)

that is where I would look too..... but I might want to replace that master cylinder if the emergency brakes looked ok.

steve2006

As above but also check the rear caliper pins for partial or full seizure,check the parking brake cables are also free to move.

mehall

Today I put it on a lift and did all suggested checks and several others: pulled a caliper, forced the caliper open (easily), checked brake lines from MC to each corner, and some others. Cost $70 for the time.

With the exceptioin that the rear brakes were locked, we found no issues.

The only new thing we learned: the brakes were locked which meant that the fluid was NOT flowing back to the MC. We cracked the rear ciruit on the MC and fluid flowed onlto our rags; tightened the nut and pumped the pedal -> instant wheel lock. This told us that the ABS system wasn't at fault, proving even I can be wrong sometimes.

We decided that the re-man MC that was installed as part of the deal when I bouht it last mont. Now I am looking for a reliable source for an affordible MC.

And the saga continues...

mehall

I thought I had updated this thread. ): hear's an update.

We installed a rebuilt MC from RockAuto.com, the problem went away. We ended up replacing the UCA (2) and rear trailing bushings (4).

Wifey is happy and expecting the rest of the repairs & and upgrades.

mehall

My '94 has developed a new brake issue.

We had a problem that appeared to be in the Master Cylindar, which was replaced. It has worked fine for about a month - only a bit over a full tank used.

At first, the car runs great, rolls good, etc. Within a few miles and several stops/slow downs the brakes begin the drag. Soon, it's all the car can do to move; it will stop rolling down a fairly steep road rather than coasting as it should.

All 4 wheels are noticeably warm, the FL is quite hot.

The previous issue had both rear wheels locked up after a few minues of driving and would release in 30min or so. Meanwhile, the fromt wheels were cool to the touch.

Any suggestions? One retired certified mechanic mentioned that he would check the proportionary valve. Where is it, and would that be a good placed to start

Thanks in advance,

j2b4o

EDit: read The other thread I got nothing.

cndnate

I would second proportioning valve, which controls the flow to each caliper, I don't where it is located on a lexus, on my other cars it is bolted to the firewall, follow the brake lines!

cndnate

Read your other thread.. it says that you eliminated the abs unit as causing the problem.

I didn't follow your reasoning on that elimination. Have you tried simply pulling the abs relay?

mehall

My mechanic told me it wasn't the ABS 'cause the locked brakes stayed locked after parking.

I never considered it. I have a habit of driving older cars (currently mine is '87). I didn't know what would happen; no brakes, poor brakes, regulare brakes without ABS.....

Where & which relay it is?

I've never in all my cars had or even heard of these issues. I've been doing most of my basic maintenance since the mid '60s. [I am not a mechanic]

cndnate

Okay, if you are not comfortable/unsure your way around cars, maybe you should not pull the relay. Do at your own risk!

In other abs cars I have owned pulling the ABS relay stops the abs from modulating the pressure. If however there is a STUCK mechanical obstruction, obstructing the flow - this may not change anything.

Try it and find out?

To find - look at the back of the relay covers and or your manual. I'm not currently at my ls400 so I can't say for sure.

cndnate

On the mechanic opinion - I would say that is a sound judgement, unless there is something FUBAR in the pump mechanically, i.e. obstructing the flow.

I DO not have a FULL understanding of the system design on the ABS unit, so cannot advise fully.


Has anyone REMOVED the abs unit and brake lines direct?

mehall

I am comfortable working on cars, but I need to know more about the car. I've not had this one long ehough to be knowlegment to be comfortable with it. Working on my Porsche in easy because I've had it 3 years.

I just want to know where the relay is located and which one is it. I've not had time to even learn where the electical panels are.