Hard brake pedal no vacuum from pump

hello,

My background:26 years as a professional auto tech. ASE master tech.

Just told you that so we can get into this and move fast if possible.

Problem: wife was driving on highway in traffic and panicked because she couldnt stop. Brake pedal suddenly hard as a rock. Luckily it was low speed. We just slowed down from 70 mph and brakes were normal. We switched seats in the middle of traffic and i drove home with paddle shifters for engine braking and two feet for brake pressure. Ridiculous pedal effort.

Got home and found no vacuum at booster. Hard plastic line at vacuum pump has no vacuum at the pump. I am not working in a shop at the moment but borrowed an alldata account. No tech info or diagrams on this at all.

I did see a vacuum switch and pump but have little tools at home and no diag info. Does anyone have techninfo on troubleshooting this system? Component info and what the switch does? What supplies the signal to the switch? The EBCM or brake switch?

I can diag this but really would like diagrams or someone at a dealer who can share tech info.

Thanks,
Nick

Can you tell us which model version (Dynamic, Prestige, Pure, HSE etc) and year?

I'm thinking the clue's in the name...

(15-06-2016 03:44pm)Pete Wrote:  I'm thinking the clue's in the name...

There is a mechanical Vacuum pump on the back of the engine powering the Vacuum assistance chamber

I believe the Vacuum switch is directly controlled from the Engine Control Module.

   

Okay sorry guys for not posting the year and make that was kind of silly. All data showed a vacuum switch but apparently it doesn't included in the model that I have it's just a straight vacuum hose from pump to booster. The vacuum pump was taken off and I found it to be frozen. The bad news is that there's a bolt in the end of the camshaft that has a slide in it where the vacuum pump and gauge is it to turn it. That bolt sheared off when the pump froze. Extracting a broken bolt is not a problem even though it would be difficult in this spot. The problem is is that when the pump froze in the bolts sheared it kept grinding against the edge of the camshaft and ground the surface down a little bit so it's no longer flat. I'm thinking about modding the vacuum system installing an aftermarket hella electric pump. If I leave the broken bolt out and reinstall the Frozen pump it will seal the oil into the head and the Frozen pump won't contact the camshaft because the broken bolt pieces not going to be reinstalled. The correct fix is to replace the cam but I'm not able to do that since I have a torn rotator cuff and bicep. I do have a friend that is able to help me install this electric pump until I can get this fixed the correct way

Not a nice failure to take out the camshaft, if you have pics of the installation and damage it would be useful, electric pump will probably do the job.

Hi,

I know this was a while ago but my 2012 si4 prestige is doing the same thing but if i drive off properly and build the RPM and speed up then my brakes come back again and feel normal. I can slow down to a full stop again but then if i take my foot off the brake to let the car roll forward (like you would in a drive through) then when reapplying the brakes the pedal is hard again and the power assist is gone. I only picked the car up on monday and only found out about this as i was going through a drive through, luckily there was no one in front of me or i would have rear ended them :/

I am thinking it is either a vacuum pump/leak issue or a problem with the booster. Any help would be greatly appreciated.

Thanks, Jordan

Jordan I would think that you need to take the car back to the dealer if you only collected a few days ago.

Not that easy as they are 1000km away, I have spoken to them about it and it's booked in next week to be looked at closer to me so I can send them a quote. I'll definitely make sure they take care of it but I was just curious if it was the exact same issue or if once the car lost its brakes they were gone for good or if they came back again while normal driving like mine do.