Disc and pad change, need to bleed brakes or not? Lexus RX45
Discussion
I'm thinking of changing the front discs and pads on my Lexus RX450h myself. It's a long time since I did any brake work myself and cars are more sophisticated than ever, so want to make sure I'm doing this right.
So assuming I successfully remove the old discs OK,can I just very slowly push the pistons on the calipers back in with a spreader tool and not have to bleed the system? Does the brake cylinder cap need to be off at the time?
Reason for asking is that I understand that bleeding the system, or changing the fluid over, needs to be done using Techstream. When it gets that involved, it is time to use a mechanic.
I would get the fluid changed over in the near future as part of a service anyway, but this would not be done by Lexus anyway if I went to them for pads and discs.
I reckon I can save around £200 doing the job myself.
Thanks
So assuming I successfully remove the old discs OK,can I just very slowly push the pistons on the calipers back in with a spreader tool and not have to bleed the system? Does the brake cylinder cap need to be off at the time?
Reason for asking is that I understand that bleeding the system, or changing the fluid over, needs to be done using Techstream. When it gets that involved, it is time to use a mechanic.
I would get the fluid changed over in the near future as part of a service anyway, but this would not be done by Lexus anyway if I went to them for pads and discs.
I reckon I can save around £200 doing the job myself.
Thanks
Check I don’t think you need to change the fluid just because he you are changing the discs and pads.
If I am changing both I normally pry the pads open with a big screwdriver as the disc is going to be changed anyway. I do ta key the cap out of the brake fluid reservoir but probably don’t need to. Pry the them open slowly, no damage done and all set. If I have already removed the calliper then I use a tool to press the piston back.
If I am changing both I normally pry the pads open with a big screwdriver as the disc is going to be changed anyway. I do ta key the cap out of the brake fluid reservoir but probably don’t need to. Pry the them open slowly, no damage done and all set. If I have already removed the calliper then I use a tool to press the piston back.
TUS373 said:
So assuming I successfully remove the old discs OK,can I just very slowly push the pistons on the calipers back in with a spreader tool and not have to bleed the system? Does the brake cylinder cap need to be off at the time?
Reason for asking is that I understand that bleeding the system, or changing the fluid over, needs to be done using Techstream. When it gets that involved, it is time to use a mechanic.
No, you don't need to bleed the brakes when changing pads/discs, cap off is never a bad idea, obviously keep an eye on the level in case it has been topped up since the pads were changed last.Reason for asking is that I understand that bleeding the system, or changing the fluid over, needs to be done using Techstream. When it gets that involved, it is time to use a mechanic.
AFAIK there is no need to use Techstream to do a fluid swap either, although others may know better, you should be able to bleed old-school, I don't know of a car that this doesn't work on.
You might need to use a piston windback tool - which pushes the caliper pistons back but also rotates them, this is to not stress out the seals too much. It depends how much you need to push them back, which obviously relates to how worn the pads (and discs) are. If its a short distance, you can just push it, and if its a bit more, push it then twist a bit, then push it etc. Its much easier with the proper windback tool though.
And if you push back a lot, you might need to remove some brake fluid from the reservoir - a syringe is handy for this.
I'd have to look at it, or look it up on Alldata, to be sure for your car though.
You don't need to change brake fluid for a disc/pad replacement. But if the fluid is due a change or deteriorated (you can buy a tester for a couple of ££) then you can but its a different job which could be done at a different time etc. So long as you don't let it go dry, no need to get too involved with service tools or bleeding ABS etc but you might need to pressure bleed it (tool costs about £20)
And if you push back a lot, you might need to remove some brake fluid from the reservoir - a syringe is handy for this.
I'd have to look at it, or look it up on Alldata, to be sure for your car though.
You don't need to change brake fluid for a disc/pad replacement. But if the fluid is due a change or deteriorated (you can buy a tester for a couple of ££) then you can but its a different job which could be done at a different time etc. So long as you don't let it go dry, no need to get too involved with service tools or bleeding ABS etc but you might need to pressure bleed it (tool costs about £20)
Thanks everyone for taking time this Sunday morning for your replies. Very much appreciated.
Consensus then, is do it slowly, the old fashioned way and I should be OK. I have piston tool but not the wind back variety - its more like a pair of paddles with a ratchet in between. I am thinking that will be OK for the front discs, but it may be different if I ever come to do the rears - which I myself probably would not.
I will be careful to transfer trims and clips over methodically and ensure no mixing up.
One further question please - what do people currently recommend/use for greasing up the sliders and rear of the pads? I think I used to use Copaslip back in the day, but see that there are silicone lubricants, ceramic etc. I don't want to increase any brake squeal if it was preventable in the first place.
Incidentally, the discs and pads that I am changing are the originals from the factory. 72,000 miles - not bad at all. I will use the genuine Toyota parts as replacements given this.
Consensus then, is do it slowly, the old fashioned way and I should be OK. I have piston tool but not the wind back variety - its more like a pair of paddles with a ratchet in between. I am thinking that will be OK for the front discs, but it may be different if I ever come to do the rears - which I myself probably would not.
I will be careful to transfer trims and clips over methodically and ensure no mixing up.
One further question please - what do people currently recommend/use for greasing up the sliders and rear of the pads? I think I used to use Copaslip back in the day, but see that there are silicone lubricants, ceramic etc. I don't want to increase any brake squeal if it was preventable in the first place.
Incidentally, the discs and pads that I am changing are the originals from the factory. 72,000 miles - not bad at all. I will use the genuine Toyota parts as replacements given this.
Worth looking up the official procedure for the hybrids. Carcarenut on YouTube has some. But I think you’re supposed to pull the abs and brake actuator relays because if something wakes the system up, such as opening the driver’s door, it’ll run the pump. If you have your fingers in the way of the pistons having taken the pads out it’ll use them as surrogate pads. Or pump the pistons out, and then keep pumping till it’s emptied the system. None of these things are desirable outcomes…
Edit to say the same feature is actually incredibly helpful for bleeding the brakes once reassembled if you wish to do so as the system is it’s own pressure bleeder. Just make sure the reservoir is full before starting.
Edit to say the same feature is actually incredibly helpful for bleeding the brakes once reassembled if you wish to do so as the system is it’s own pressure bleeder. Just make sure the reservoir is full before starting.
Edited by Grenadier_45 on Sunday 16th February 11:29
Thanks. That is off putting!
I saw a YouTube video that made it look simple and did not mention pulling relays. It did make me wonder if dis-connecting the auxiliary battery was a decent precaution. It is located in the boot. Tailgate is electric so I think I would have to keep tailgate open (it does not like being closer by hand and resists this, and no idea of how it opens again if there is no battery connected).
I saw a YouTube video that made it look simple and did not mention pulling relays. It did make me wonder if dis-connecting the auxiliary battery was a decent precaution. It is located in the boot. Tailgate is electric so I think I would have to keep tailgate open (it does not like being closer by hand and resists this, and no idea of how it opens again if there is no battery connected).
Grenadier_45 said:
Worth looking up the official procedure for the hybrids. Carcarenut on YouTube has some. But I think you’re supposed to pull the abs and brake actuator relays because if something wakes the system up, such as opening the driver’s door, it’ll run the pump. If you have your fingers in the way of the pistons having taken the pads out it’ll use them as surrogate pads. Or pump the pistons out, and then keep pumping till it’s emptied the system. None of these things are desirable outcomes…
Edit to say the same feature is actually incredibly helpful for bleeding the brakes once reassembled if you wish to do so as the system is it’s own pressure bleeder. Just make sure the reservoir is full before starting.
Why would opening the door cause a hybrid to apply the brakes? I can't think of a reason why it would need to do this or even why this would be linked to it being a hybrid. Edit to say the same feature is actually incredibly helpful for bleeding the brakes once reassembled if you wish to do so as the system is it’s own pressure bleeder. Just make sure the reservoir is full before starting.
Genuine question here, interested as maybe it's something I should be concerned about with other vehicles too.
Richard-D said:
Why would opening the door cause a hybrid to apply the brakes? I can't think of a reason why it would need to do this or even why this would be linked to it being a hybrid.
Genuine question here, interested as maybe it's something I should be concerned about with other vehicles too.
I don't know how/when it decides to run its pumps, but as a GS450h owner, I can confirm that it does run the brake accumulator when it feels like it, whenever you unlock and open up, or shut the system down after a drive. It doesn't always do it when the driver's door is opened and closed, but it seems as though that certain actions prompts it to self check based on criteria unknown ...Genuine question here, interested as maybe it's something I should be concerned about with other vehicles too.
Assuming it is very much like the RX400h I had last year. It is pretty much as per a normal car. The only issue you have is if you leave the key in the ignition it will take up any slack in the calipers, so make sure the car has shutdown, which takes a few minutes as you will observe if you just stand and watch after you have locked it. It will buzz and whir away to its self.
I did 2 sets of disks and a good few sets of pads in my 400 over the 120k miles I covered in it. You will need to wind back the handbrake adjuster in the rear disks to remove them. And the sliding pins, especially on the rear can seize as they don't see as much use as you would expect due to the regen braking.
I did 2 sets of disks and a good few sets of pads in my 400 over the 120k miles I covered in it. You will need to wind back the handbrake adjuster in the rear disks to remove them. And the sliding pins, especially on the rear can seize as they don't see as much use as you would expect due to the regen braking.
TUS373 said:
I don't know. What I can say from experience is that the two Lexus hybrids I have do make a lot of noises before and after start up. Hence my hesitation before piling in and swapping brakes like a man in a brown coat 40 years ago.
Modern cars all like to make a load of whirring and clicking noises when you unlock them but I'm not aware of any of that relating to applying the brakes.Grenadier_45 said:
I don't know how/when it decides to run its pumps, but as a GS450h owner, I can confirm that it does run the brake accumulator when it feels like it, whenever you unlock and open up, or shut the system down after a drive. It doesn't always do it when the driver's door is opened and closed, but it seems as though that certain actions prompts it to self check based on criteria unknown ...
Do you know that it is applying the brakes when it does this? I'm dubious as if accumulator pressure meant force was applied to the pads and the accumulator topped itself up when low then surely you wouldn't even be able to remove the calipers in the first place?Won't be far different to Landcruisers of the noughties onwards, ie an electric powered brake accumulator pump instead of vaccuum assistance.
The only time you should need techstream is if air has entered the ABS unit and /or the master cylinder has been disconnected/replaced, other than standard bleeding proceedurs will be fine...note i didn't use my ever faithful Gunsons easibleed on my Prado sized LC because no brake cylinder cap adaptor in the kit fits, standard up down routine with t'mrs pumping as instructed did the job fine when i replaced the front calipers.
Talking of front calipers, if your RX has Toyotas large 4 piston jobbies on the front, make sure to exercise the pistons in their bores well, the inside lower piston is the one that usually seizes first on those.
The only time you should need techstream is if air has entered the ABS unit and /or the master cylinder has been disconnected/replaced, other than standard bleeding proceedurs will be fine...note i didn't use my ever faithful Gunsons easibleed on my Prado sized LC because no brake cylinder cap adaptor in the kit fits, standard up down routine with t'mrs pumping as instructed did the job fine when i replaced the front calipers.
Talking of front calipers, if your RX has Toyotas large 4 piston jobbies on the front, make sure to exercise the pistons in their bores well, the inside lower piston is the one that usually seizes first on those.
I'm not saying you have to follow Lexus workshop processes, and I'm not saying that when the brake accumulator runs it's always doing so in order to bring the pads to the disks/self calibrate. What I am saying is that there is a proper process which is safe, and if you're not going to follow it, you need to be aware of the fact that the car is capable of doing things you wouldn't typically expect of a car with a vacuum brake servo, to be aware, and to take extra care. For example, put the key well out of the way, and certainly not in your pocket/on your person, and avoid opening doors.
Sadly Britprius is no longer with us, but there's an old thread on the Lexus forum the OP might find interesting. Obviously not an RX, but as another poster suggested, I doubt there are too many fundamental differences between the models.
There's a copy of some of the repair manuals on a Russian site here , if it helps.
Sadly Britprius is no longer with us, but there's an old thread on the Lexus forum the OP might find interesting. Obviously not an RX, but as another poster suggested, I doubt there are too many fundamental differences between the models.
There's a copy of some of the repair manuals on a Russian site here , if it helps.
Grenadier_45 said:
I'm not saying you have to follow Lexus workshop processes, and I'm not saying that when the brake accumulator runs it's always doing so in order to bring the pads to the disks/self calibrate. What I am saying is that there is a proper process which is safe, and if you're not going to follow it, you need to be aware of the fact that the car is capable of doing things you wouldn't typically expect of a car with a vacuum brake servo, to be aware, and to take extra care. For example, put the key well out of the way, and certainly not in your pocket/on your person, and avoid opening doors.
Sadly Britprius is no longer with us, but there's an old thread on the Lexus forum the OP might find interesting. Obviously not an RX, but as another poster suggested, I doubt there are too many fundamental differences between the models.
There's a copy of some of the repair manuals on a Russian site here , if it helps.
Yes it's always worth understanding the risks of skipping steps in a procedure, agree with you entirely.Sadly Britprius is no longer with us, but there's an old thread on the Lexus forum the OP might find interesting. Obviously not an RX, but as another poster suggested, I doubt there are too many fundamental differences between the models.
There's a copy of some of the repair manuals on a Russian site here , if it helps.
You say above though that it will push the pistons out by itself (obviously crushing your hand it it's in there) when the system is triggered by non related actions. I'm trying to understand why it would do that or if it does do this at all. Your earlier post sounded pretty definitive and I wanted to understand why you believed it to be the case.
edit: I'm not saying you're wrong here. If you have information about how and why the system does this I'm happy to be educated. Always keen to learn if there's something I've been blissfully unaware of whilst working.
Edited by Richard-D on Sunday 16th February 14:31
I think at a very basic level , its because the brakes are not connected directly to the peddle via hydraulics like normal cars, the car has to decide whether to use regen or real brakes when you press the peddle, this is done by a magic box so the car wants to calibrate or check it once in a while.
ARHarh said:
Assuming it is very much like the RX400h I had last year. It is pretty much as per a normal car. The only issue you have is if you leave the key in the ignition it will take up any slack in the calipers, so make sure the car has shutdown, which takes a few minutes as you will observe if you just stand and watch after you have locked it. It will buzz and whir away to its self.
I did 2 sets of disks and a good few sets of pads in my 400 over the 120k miles I covered in it. You will need to wind back the handbrake adjuster in the rear disks to remove them. And the sliding pins, especially on the rear can seize as they don't see as much use as you would expect due to the regen braking.
That makes more sense and I suspect may have been misinterpreted/chinese whispered at some point. I would imagine that a few modern cars do something similar, nothing to do with it being a hybrid.I did 2 sets of disks and a good few sets of pads in my 400 over the 120k miles I covered in it. You will need to wind back the handbrake adjuster in the rear disks to remove them. And the sliding pins, especially on the rear can seize as they don't see as much use as you would expect due to the regen braking.
Richard-D said:
Yes it's always worth understanding the risks of skipping steps in a procedure, agree with you entirely.
You say above though that it will push the pistons out by itself (obviously crushing your hand it it's in there) when the system is triggered by non related actions. I'm trying to understand why it would do that or if it does do this at all. Your earlier post sounded pretty definitive and I wanted to understand why you believed it to be the case.
edit: I'm not saying you're wrong here. If you have information about how and why the system does this I'm happy to be educated. Always keen to learn if there's something I've been blissfully unaware of whilst working.
I'm not a Toyota Master Tech, so pay no attention to me.You say above though that it will push the pistons out by itself (obviously crushing your hand it it's in there) when the system is triggered by non related actions. I'm trying to understand why it would do that or if it does do this at all. Your earlier post sounded pretty definitive and I wanted to understand why you believed it to be the case.
edit: I'm not saying you're wrong here. If you have information about how and why the system does this I'm happy to be educated. Always keen to learn if there's something I've been blissfully unaware of whilst working.
Edited by Richard-D on Sunday 16th February 14:31
https://youtu.be/jpiXOBRkZs4?si=R9TydrM6zD-6I0YV&a...
11 minutes in in case the link doesn't work properly. An old video on brake fluid changes from the Car Care Nut, who is a Toyota Master Tech. His latest videos are much fancier, but in this one, he's pretty definitive for the hybrids about not opening driver's doors, putting keys away from the car, and if you want to play things totally safe, disconnect the 12V battery. Why? Because there's a risk of the pump activating if you open the driver's door while you've got a bleed nipple open, and you ending up in a lot of trouble.
He's talking about it from the point of view of the pump activating unexpectedly while you're trying to bleed fluid, but clearly if it activates when you open a door, or touch the door handle with your hand with the key in your pocket which activates the lock/unlock mechanism, the pump likely can't tell the difference between bleed nipple open, pads removed, fingers in the way, or normal operation and just a bit of slack needing taking up, so it pumps till it feels a bit of resistance.
Richard-D said:
edit: I'm not saying you're wrong here. If you have information about how and why the system does this I'm happy to be educated. Always keen to learn if there's something I've been blissfully unaware of whilst working.
In my dim & distant memory there's something about Merc having a safety system that's activated by the door opening, the purpose is to check brake operation before you drive off. Possibly the same.Edited by Richard-D on Sunday 16th February 14:31
Not something you want when the pads are removed but can't recall how it's disabled ?
OBD socket ..Rings a bell.
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