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The content is pretty much contained in the title. When I went to replace the brake pads, one pad was completely gone and the other was almost like new.

Now that I have replaced the pads, the wheel heats up quickly when driving even short distances.

I did notice that one of the guide pins seemed stuck - it did not move at all. Could this be the cause of the heat, and if so, what do I need to replace? Just the pins, or the caliper bracket as well?

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3 Answers 3

up vote 4 down vote accepted

If your guide pins are stuck, the caliper won't be able to slide properly.

With a sliding caliper, when you apply the brake, the piston pushes one pad against the disc (rotor), and simultaneously pushes back against the caliper (Newton's equal and opposite reactions), causing the caliper to slide along the guide pins, and pull the other pad against the disc. If the caliper cannot slide, the second pad remains forced against the disc, and you're effectively driving with half the brakes on on that wheel, hence why it gets hot. You'll find that if you jack up the the car, that wheel is much harder to turn than the other side.

Remove the caliper, and both guide pins. Clean them up until they both slide freely, re-grease and reassemble, using new gaiters if the old ones are damaged (which is quite likely, as that's the usual reason for them siezing). Do the same on the other side so that you know both calipers are in the same condition.

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Yes, that seems like the effect I am seeing. I attempted to get the pin to turn using a channel locks and a locking pliers. No luck. Then I tried putting a flat head screwdriver against the underside and using a hammer to force it out. Still nothing. This morning I plan on applying penetrating lubricant . Any other ideas on extracting the pin? –  ItsJason Jun 17 '13 at 12:44
    
Generally it's a case of 'brute force and ignorance'. You can usually get new pins if all else fails, as long as the caliper itself is OK. Last time I did one, it was a case of gripping the pin very firmly in self-gripping pliers, then tapping the handle of the pliers with a hammer to shock it free. Once it starts moving you can gradually work it out a bit at a time... –  Nick C Jun 18 '13 at 8:51
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This was it. I was able to extract the pin using the procedure described above, along with applying heat to the bracket using a torch. Installed new pins, and the wheel now runs like it should. Thanks! –  ItsJason Jun 18 '13 at 13:23

With the brake piston fully compressed the pads should have a little clearance, enabling minor "play." When replacing brake pads it is important to make sure that the caliper itself moves freely in the horizontal direction (i.e., perpendicularly to the disc.) If not, one pad will wear quickly due to the fact that it will maintain pressure against the rotating disc.

I'm not sure that stuck guide pins can yield a similar result, but your best bet - considering that your brakes are getting hot - is probably to remove the pads and make sure that all moving parts are ... moving.

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When replacing break pads it is incorrect and bad practice to simply push the piston back in, this will force brake back up into the master cylinder and sometimes even cause it to overflow. Just about everyone disregards this but it is very possible to damage the Master Cylinder this way. The "correct" way to do it is to open the bleeder screw, push the piston in (use a rubber hose & bottle to avoid making a mess), then close the bleeder screw. This will allow you to easily reset the piston. Also, this will not require that you bleed the brakes since you did not let any air into the system.

Also, using a wirebrush all slides and pins should be cleaned and then lubed. If the slides / pins are readily available or are included with the brake pads then it's recommended to replace them. Seeing that you were able to install the pads I'm going to say it's safe to rule out an issue with the caliper. I would take both sides apart and clean the slides / guide pins and calipers with a wirebrush and some Brake Cleaner. Then using some anti-seize lube all contact points between the caliper, slides, guide pins, and brake pads. This will ensure that there is unrestricted movement in the entire assembly. If the symptoms continue after you've done this let me know and I can help you start to look deeper into the system.

You should not drive the vehicle while it is like this. It's not only unsafe but it will further damage the braking system. If you have no choice then you have no choice but, try to keep it to a minimum.

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Have you got a reference for that first statement? Yes, it can cause the reservoir to overflow if it's been topped up since the last pad change, but I can't see how it'd be damaged, IIRC most master cylinders have a free path between reservoir and line when the pedal isn't pressed. –  Nick C Jun 17 '13 at 9:27
    
agcoauto.com/content/news/p2_articleid/202 & wikihow.com/Replace-Disc-Brakes (step 21) are are a quick 2. If you'd like more I'll post more. Both include the reasons why it's not a good idea to do it without opening the bleeder. –  cinelli Jun 17 '13 at 9:40
    
Ah, ok, so it's the ABS that suffers then. Fair enough! –  Nick C Jun 17 '13 at 9:43

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