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My father has a 2003 Mitsubishi Montero which has recently had its brake rotors and pads replaced. It has been parked in a garage for the past few weeks, at which point we noticed that the brake fluid reservoir was overfilled. This vehicle has a Hydraulic Brake Booster-not a vacuum type. The procedure for checking the fluid level is as follows:
• Make sure the ignition key is in the OFF position,
• Pump the brake pedal about “40 times or until significant pedal resistance is felt,”
• The fluid should be at the MAX line. Add or remove fluid as necessary.
• Turn the ignition on and let the pump run. Once it is finished building pressure, check the fluid level again. It should be at or above the MIN mark.
• Start the engine and make sure that the brake dash light is not illuminated and that the warning buzzer is not sounding.I followed it exactly, yet when my father took it out of the garage yesterday, he said that the light came on and that there is a severe pulsation and chattering whenever the brakes are applied. He put most of the brake fluid back in and he says its better but not like it was before. This also means that the reservoir is way overfilled again. I’m at a loss about what is going on. I’m almost certain that it is not warped rotors, owing to the fact that they have been changed within the last 6 months. I really am having a hard time believing that just removing some fluid can do this to the system. Maybe there is air in the lines and they need to be bled?!
If anyone has ever had this problem or a similar problem, I’d greatly appreciate it if you would share what the cause was.
Thanks in advance.
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The only thing that can cause a brake pulsation is warped brake parts so don’t rule out a problem with the rotors as the cause even if they’re new, keep in mind it could also be coming from the rear. The hydraulic fluid is only for the assist and has nothing to do with vibrations. I suppose it could also be ABS activation but I don’t think so.
Quoted From EricTheCarGuy:
The only thing that can cause a brake pulsation is warped brake parts so don’t rule out a problem with the rotors as the cause even if they’re new, keep in mind it could also be coming from the rear. The hydraulic fluid is only for the assist and has nothing to do with vibrations. I suppose it could also be ABS activation but I don’t think so.
Thanks for the quick reply, Eric. I was wondering if it could be a problem with the ABS, but then again, the fluid still wouldn’t have anything to do with it. Is it just a coincidence that we played with the fluid level at the same time as something else was going wrong? The strange part is it hadn’t been driven in about 2 1/2 weeks and it was fine before that. Last question-I promise. 🙂 What could cause the rotors to warp like that besides heat? Could humidity/dampness play a part in that?
I’m assuming you used the right type of brake fluid, right? If it calls for DOT4 and you put in DOT3, you could create a boilover situation that would cause mechanical damage to your seals. If your fluid is ever low, just to be on the safe side, you should flush the entire system (you may have a leak) with the type of fluid called for in the FSM and the check the level over the course of the next few days to see if it continues to drop.
If it sat for a couple of weeks as you say and it’s a humid climate it could have been ‘flash rust’. This is rust that occurs on brake rotors sometimes after it rains or in high humid conditions, normally it doesn’t cause a problem if the vehicle doesn’t sit for too long but if it sits for a long period like this the rotor will get rusty everywhere except where the brake pads are causing a ‘clean spot’ which when the brakes are applied will translate into a brake pulsation. BTW this happens a LOT with cheep brake rotors.
Quoted From EricTheCarGuy:
If it sat for a couple of weeks as you say and it’s a humid climate it could have been ‘flash rust’. This is rust that occurs on brake rotors sometimes after it rains or in high humid conditions, normally it doesn’t cause a problem if the vehicle doesn’t sit for too long but if it sits for a long period like this the rotor will get rusty everywhere except where the brake pads are causing a ‘clean spot’ which when the brakes are applied will translate into a brake pulsation. BTW this happens a LOT with cheep brake rotors.
I also thought about that, though because brakes are kinda important and the truck is so big (our jack won’t lift it-too heavy-and tall-and it just about fills the entire garage when its parked in there)we’re gonna bring it in for our mechanic to look over. Will post the findings in a bit.
Well guys, got the truck back yesterday and it turns out it was indeed warped rear rotors. They were so warped in fact, that the pads were only really making contact in two places as the rotor spun. It was just a coincidence that we had played with the fluid at the same time.
Thanks for all your suggestions.
Cheers!Quoted From AVaneDew:
Well guys, got the truck back yesterday and it turns out it was indeed warped rear rotors. They were so warped in fact, that the pads were only really making contact in two places as the rotor spun. It was just a coincidence that we had played with the fluid at the same time.
Thanks for all your suggestions.
Cheers!We dealt with this a lot on Jeep’s at the shop, always warping rotors quick, I hope the shop you brought it too did a caliper service. Almost every car that I have ever had that warped rotors that fast was because the shop was cutting corners and never freed up the pins and lubricated them.
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