Air in brakes?

[pcspinheiro]

Sorry for the quick shout-out, but today I changed the front discs and pads on my 2017 superb. I had them machined a while back but, while I've been happy with this service in the past, I think this time it was not properly done... 

 

Anyway, the job implied retracting the pistons a fair amount and, after some reading, I decided to open the bleed nipple and discard the oil right there instead of pushing it up through the system. I think it was a good choice since the oil wasn't exactly clean. However, since the process was going slow and I was alone at it, I opened the nipple enough to make it quite effortless. Despite being careful, I think this may have allowed a little bit of air to go back in before I got to fully close it because the brake pedal now feels a bit soft and if I keep my foot on it, it continues to go down veeeerry slowly for a while. The nipples were tightned correctly and there were no leaks after gently pressing the pads against the discs with the car still in the air and engine off. I haven't driven it out on the road but I'm wondering if it's dangerous to drive before bleeding out the air? The car is due for the last oil service at the dealership tomorrow and I need to drive it there. Seems to brake fine btw... And the only thing that I can think of that may have gone less well was the bleeding out of the oil to retract by the pistons.

 

Edited 28 July, 2022 by pcspinheiro

[ApertureS]

Yes it’s dangerous to drive if you’ve allowed air into the hydraulic system.

 

opening the bleed nipples without doing anything else is a terrible idea as all you’re going to do is allow air into the system. 
 

you now need to have your brake fluid flushed/changed to remove any air bubbles from the system.

 

also, why did you have the brakes machined? Is it really that cheap and worth the hassle, the price of discs isn’t too bad so why not just replace them?

[pcspinheiro]

Maybe I didn't explain properly... I opened the bleed nipples while pressing down on the pistons to retract them. I then closed them right away while keeping the piston pushed in. But now the brake pedal kinda feels a little soft? But I was also driving my old astra for over 1 week so maybe I had forgotten how they feel. I do get the feeling that the pedal keeps going down ever so slowly if it keep it pressed long. If there's a tiny bit of air it will be right by the bleed nipples, wouldn't bleeding the brakes do the trick? Why do you say flush the whole system? 

 

Oh, and yes, having the brakes machined was only 10€ each, new ones were almost 50€ each (bought brembo). But turns out it was 10€ lost because they probably didn't do it properly this time. Used them several times in the past with no issues...

 

Thanks!

Edited 29 July, 2022 by pcspinheiro

[Breezy_Pete]

It'll be fine to get to somewhere to do a brief pressure bleed on each side. 

[pcspinheiro]

I hope so. I could do it myself but no time before having to hand in the car....

[pcspinheiro]

Maybe I'll ask the dealer to bleed them, can't be that expensive... They'll have the car for an oil service and to look for an oil leak (probably front cranckshaft seal), so the wheels probably have to come out anyway.

[pcspinheiro]

Small update: it was breaking fine on the road, no more soft pedal feel. However, it was due for a break fluid renewal in September, so I asked for it now. All good, thanks for your feedback!

[pcspinheiro]

Haha, just noticed that my phone's spell check put break instead of brake pretty much everywhere. I type faster than I can see and trust the machine 😁 

 

Car's almost done, they did see the oil leak but it's mostly from the gearbox, have to wait for a lease plan (warranty extension) approval for repair. They also said that crankshaft main seal was clean, so I showed them again my own pictures taken days ago showing oil all over, and they agreed to include that in the approval request. 

 

Waiting for the painful s€rvice summary...

Cheers!

Edited 29 July, 2022 by pcspinheiro