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On my car I put my foot on the brake, start the car and the pedal drops to the floor but the brakes stay on. Pump them and it will still do it. This never happens when driving strangely.

Today I have noticed a vacuum leak. I can hear the hiss over the engine noise. Brakes still work and pedal still does the drop to the floor routine.

Checked the vacuum at the vacuum pump, in excess of 25"
Disconnected vacuum hose to brake servo leaving all other hoses attached, excess of 25"
Reconnect vacuum hose to servo and remove branching hose, hiss is present and vacuum is about 5"
Press the brakes, hiss goes away, vacuum goes from 5" to excess of 25"

I am assuming that the vacuum should always be about 25" and the hiss and low vacuum at the servo is telling me there is a problem there, either in the brake amplifier (the plastic doohickey that connects the vacuum hose to the brake servo unit) or in the servo itself.

I believe the low vacuum is causing turbo actuation issues as well.

Any ideas? I'm thinking Balderdash's problem may be similar.
 

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Hi...you must start your own thread even when you have a 'similar'problem!..I ve done that for you! You also need to explain how your problem first started and most importantly WHAT model you have...I assume its a 406 but you dont say...let me know if it not.You will now get answers to your problem..oh and welcome to the forum I hope ive helped you...
 

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From the description 1 of the servo seals is not doing its job this will indeed cause boost issues as low vac will affect turbo control IF its a 110 or 136 hp engine.

That would not explain the pedal dropping to the floor though thats a separate issue.
 

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Discussion Starter #4
From the description 1 of the servo seals is not doing its job this will indeed cause boost issues as low vac will affect turbo control IF its a 110 or 136 hp engine.

That would not explain the pedal dropping to the floor though thats a separate issue.
That's what I'm thinking - that there is some seal somewhere thats leaking in the servo.

How is the brake amplifier removed? I don't want to try and pry it out and break it and then have some way bigger problem on my hands.

Yesterday was the first time the brakes almost didn't work and I nearly had a prang. The brakes have always done the sink to the floor routine even after the dealer did the brakes and all the fluid was renewed. I don't think it is an issue with the hydraulics at all because I would then expect it to happen every time I put on the brakes, not just idling at a stop and then not all the time. It has just passed it's warrant of fitness as well, with the brakes having an excess of stopping power. That's why I think it has to do with the vacuum somehow.

Hermano
 

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Check non return valve in servo pipe these do fail with similar issues

Sent from my SM-G935F using Tapatalk
 

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Discussion Starter #6
Brake servo repair

So, I've traced the hiss and vacuum leak to the rear of the brakes servo, likely the rear seal. This would account for all of the issues I am having including the loss of turbo boost at low revs.

Does anyone know where to get the seal repair kit that I have seen reference to?

Being in New Zealand makes obtaining parts hard. I really don't want to, nor can I afford to, junk the car because of a $10 seal that should be easily obtainable and replaceable if it is so critical to both the safe operation (brakes) and performance (turbo operation) of the car.
 

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Discussion Starter #8
Where in New Zealand?
Dunedin.

I have checked just about everywhere - dealer N/A, CBC ("can't tell you if we can repair it until we take it apart." WTF?), wreckers I could find on Trade Me and internet search, etc.

Speed can deliver one in three weeks at $500. "Is it the right one?" I ask. "It's the one that comes up under that VIN." "What happens if it isn't the right one?" "It's the one that comes up under that VIN." Knowing that there are two different ones used in the same model year makes me nervous.

I have contacted URO Parts in the US, they make seal replacement kits for many ATE boosters.

If you have any leads at all, I would be grateful. Thanks!
 

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Ok, I am a long way away near raglan in the wops. May be able to help you with s/h one but need your vin and a pic of your booster might be useful if there are any part numbers visible. You can PM me with the info.
 

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Discussion Starter #10 (Edited)
406 brake booster

Ok, I am a long way away near raglan in the wops. May be able to help you with s/h one but need your vin and a pic of your booster might be useful if there are any part numbers visible. You can PM me with the info.
I can't PM you here because I haven't posted 20 messages yet. I also can't post any links here either because I'm not ranked high enough so it will have to be via email. Send me a message to and I'll reply with the images. Replace the & with @ - I can't post email addresses either!
 

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Discussion Starter #12
Fixed!!

Well, that was one hell of a job!
All problems have now ceased, these were:
- weird braking action (scary at times!)
- dramatic loss of power (no turbo below 2200RPM)
- spongy brakes

How I did it:
- purchased 2nd hand brake booster from a member here which unfortunately had the same fault.
- found a booster plunger seal on eBay
- installed the seal in the 2nd hand booster (this is a bitch job) and made a new air filter from and old small engine air filter
- removed the brake master cylinder and brake booster
- installed the re-sealed 2nd hand booster
- installed the old master cylinder which didn't seem to be leaking but there are none available new and no rebuild parts anyway so I had no choice.

I have two videos on UToob showing the brake booster rebuild and listing the seal supplier here: https://youtu.be/5Dj8668qJ8o

While I was in there I cleaned out the disgustingly grungy intake manifold and disabled the EGR system (another post.)
 
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