Rear brakes mistery(please help)

N

napeHbNYC

Member
Location
NYC
Name
Dmitry
Hey, guys, I have a bit of a commotion here. 2004 FX35 AWD with 130k. Lately I started to get a weird shake after the car is driven for a bit, meaning it is perfect at first and then after about 5-10 min is comes in and stays until the car is parked. I thought it was a diff as after the car was on the lift, the rear wheels in N were almost impossible to spin. Upon further investigation, both rear rotors were scorching hot compared to front.

We waited for a little bit a the pressure on the rear brakes started to ease up allowing the rear wheels to rotate freely. I then pumped the brakes and sure enough the wheels are barely able to be turned. So it has to do with the brake pressure towards both rear wheel not being released and just building up.

Now the question is, I searched over and over with no avail, is there a valve or pressure regulator for both rear brakes? I followed the brake lines and so far the only thing I see is the connector peace behind the front wheel lining on the passenger side(it connects both lines, kinda like an x pipe function I'd say?). Is it the one that could go wrong?

It is my daily and I rely on it heavily, so I'd like to figure it out as soon as I can. Is it a common problem? The calipers are not seized as they release the pressure after some time and everything is perfect until after 5-10 min of driving. I tried searching brake lines diagram and came up with nothing. Hoping for some insight from here.

Thank you as always!!

---------- Post added at 10:17 PM ---------- Previous post was at 10:03 PM ----------

Both rear rotors are starting to go blue and there are no lights what so ever.
 
There is no proportioning valve in the brake line. The brake line comes off the actuator run straight to the calipers. I highly suspect that your caliper just starting to seized. I would check the caliper sliding pin to see if the caliper body is sliding freely. It not terrible expensive to buy one caliper and try it out.
 
Thank you, the problem is that it is happening to both at the same time, I will check the pins tomorrow, I guess it makes sense as far as not releasing properly the Pistons as pressure builds up.
 
Could it be a slip or VDC issue? Rear brakes are used when slip is detected. If something is wrong with the sensor, they may be engaged more. Rear brakes also engage first in braking to prevent dive. I believe all of that is part of the ABS system so there is no separate proportioning valve.
 
lube up those caliper parts - sounds like seized calipers starting to happen... salt probably got to them. Happened to both my rear calipers on my 05 FX35 around 75k...
 
Agree it sounds like caliper slider pins. But it could also be caliper pistons or even brake pad guides. I would definitely try servicing the calipers - remove the boots and inspect pins and piston seals. Clean everything and lube with fresh grease, then reinstall everything along with bleeding fresh brake fluid. If it is time for new pads, this would be a great opportunity.

If you are not doing this yourself, a shop might charge for a rear caliper rebuild and that would be appropriate.
 
+1 on the use of 3M silicon paste or any silicon based lube only. Petroleum based lubricants will cause rubber components to expand. Restricting movement especially with the slider pins.


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hum it could be also the caliper hoses it happen to me my hex 04 fx35 front brakes went to change rotors and brake pads and mechanic found that the caliper on the right side was unusually hard to move back the cylinder then when he went to do the left side the caliper was seized so we though new caliper that's when mechanic said let me check something out he disconnected the brake hose from the caliper and the caliper was working fine so he proceeded to change the two front brake hoses and problem solved the left side hose was broken inside and the right side one add the same problem
 
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So I finally got to checking everything, that was the last on my mind(not really a believer in coincidences, but both rear calipers seized at the same time, I guess recent few snows had to do with it. I replaced them and it is much better, now still tracking the whining sound-bearings I guess, I changed both front hubs, now waiting for rear bearings to come in, hopefully it will do it. I did change all the fluids(diffs, tranny.. ) with OEM ones when I bought the car in August. Thank you all for the help!
 
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