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Old 03-19-2015, 02:02 PM   #21
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

http://www.jegs.com/i/JEGS-Performance- ... 6/10002/-1

That one even comes with a switch to automatically turn it on in the event of a low-vacuum condition.
I think I'd wire up an annunciation light to tell me when the electric pump kicked on.

Now we need a tee to split the vacuum connection to the rest of the vacuum system and a check valve between each pump and the tee so that either pump can pull but a failed mechanical pump won't leak air into the system.
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Old 03-19-2015, 04:31 PM   #22
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

That's interesting and worth looking into. Thanks
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Old 03-20-2015, 05:09 AM   #23
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

I'm not the least bit familiar with the diesel power brake system so forgive me if I'm off-base here.

Were failing vacuum pumps for the brakes even a semi-common failure mode I'd definitely install the 12 VDC auxiliary pump, have it plumbed into the existing boost chamber with appropriate check valves etc---those of an industrial quality rather than the "automotive" or light truck type.

Further I'd have nothing less than a direct reading gauge in the cabin monitoring the engine driven pump. Loss of vacuum could be detected and the auxiliary pump engaged quickly enough to restore full brake boost, temporarily or long term.

A super-sophisticated stand-by system could also include a sensor to trigger the auxiliary pump when present vacuum drops enough to affect brake operation. Additionally a reservoir equal in size to the brake booster chamber would give immediate and almost seamless engagement of supplemental vacuum in the case the engine-driven pump failed without warning.

Sounds scary to me---would hate to be without brake boost on a loaded van, up OR downhill.
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Old 03-20-2015, 03:57 PM   #24
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

Quote:
Originally Posted by Viva
Sorry to interrupt, but maybe someone else wondered too...
I did. Thanks Viva.

Brent
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Old 03-20-2015, 04:48 PM   #25
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

Quote:
Originally Posted by JWA
Further I'd have nothing less than a direct reading gauge in the cabin monitoring the engine driven pump. Loss of vacuum could be detected and the auxiliary pump engaged quickly enough to restore full brake boost, temporarily or long term.

A super-sophisticated stand-by system could also include a sensor to trigger the auxiliary pump when present vacuum drops enough to affect brake operation. Additionally a reservoir equal in size to the brake booster chamber would give immediate and almost seamless engagement of supplemental vacuum in the case the engine-driven pump failed without warning.

Sounds scary to me---would hate to be without brake boost on a loaded van, up OR downhill.
I'd be more comfortable with an alarm that would catch my attention. Even with idiot lights I've driven miles before I realized my ABS light was on. Same with gauges although if it shows the vacuum slowly dropping into the yellow zone going to the trouble of adding a gauge might be of value. In my situation I didn't see any indication there was a problem until I tried to stop. Still it's the fastest I've ever drove through a gas station and at least nobody was in front of me or they would have got to know my Aluminess bumper very quickly.

But one thing I don't want to do is to create a complicated system that might cause more problems. Cost is also a factor. I thought going with a hydroboost setup would be better and although you might loose braking from a failure, I thought that the idea was you have better braking even if the engine shuts down. Or am I wrong on this?
There can be more than just a vacuum booster failure to cause a loss in braking. If the cost to switch is similar to a full blown 12v backup system, I'd be looking at switching to the hydroboost. What are the cons to going that way?
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Old 03-20-2015, 06:46 PM   #26
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

With the myriad of codes the Scangauge reads, one would think there would be one for a brake boost failure?

But maybe by the time the gizmo picks up the code, it's too late. I guess all we can do is make sure our horns are in good working order.
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Old 03-20-2015, 07:54 PM   #27
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

Cons of Hydroboost:

1) If you are not very diligent with routing the extra hoses (i.e. anything other that a full OEM setup) you risk rubbing through and bursting a hose.

2) When you lose boost, it actually requires more effort to stop the rig, compared to losing vacuum. Now, you do get about 3 stops off the accumulator, but beyond that I would consider it undriveable. I would not coast down a hill with the engine off. This is because the Hydroboost setups use a larger master cylinder bore, which they counteract with the extra boost pressure from the hydroboost unit.

Plusses of hydroboost:
1) Failures are very rare, and usually involve a power steering system defect (worn pump) that makes a bunch of unpleasant noises before it goes out.

2) Hydoboost makes more assist

3) The larger bore size of the M/C will improve pedal feel, as it move more fluid-volume/stroke-distance.
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Old 03-20-2015, 08:44 PM   #28
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

Thanks, just the info I needed.
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Old 03-20-2015, 09:17 PM   #29
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

I have a good one you guys. I went to leave for the desert and the brake pedal started to just go to the floor and would stop you but you had to pump it to stay at the light. So first thought is the brake master is bad and replaced it and no better. Looked on the web and see that the abs unit might be the issue although I have no code or light so we bypass it and it's better but still will go down just not as fast and drivable but not ideal.

So is it a bad new master or a bad booster ?

Fluid is good and no leaks.
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Old 03-20-2015, 09:52 PM   #30
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Re: Power Brake Vacuum Assist Failure on Diesel Vehicles

Kelly, I had similar, but did see a small leak where the front passenger side brake line was rubbing against something behind the wheel and finally wore a hole thru the stainless tubing. Sorry that's not necessarily the solution you seek. Not a vacuum system issue either. Maybe you need a good system bleed if there's air in there. Good luck.
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