Lost power steering and brakes? - Ford Powerstroke Diesel Forum
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Old 11-09-2012, 08:30 PM
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Lost power steering and brakes?

Hey, we'll today I went for a bit of a 4x4 with some mates in the rain, basically I was the only one to try this one rocky hill climb, I was stuck halfway up, couldn't get up a step up, anyway I kept trying for a good 10mins, eventually got up, when I got to the top my steering went hard, I lost power assist, we thought I might of overheated the power steering so let the truck cool down. Once it cooled down, it was still hard to turn, so I took the p/steer line off the cooler and started the truck, no fluid was pumping out, no big deal I thought I could drive home with no p/steer, until I went to drive off, brakes are ridiculously hard to press and sometimes jam on and you have to pull the pedal back, and the pedal is constantly vibrating/buzzing

Do you guys have any idea why I no longer have brakes, hoping I haven't stuffed the brakes aswell
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Old 11-09-2012, 10:36 PM
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You have a hydroboost system. The power steering pump is sorta like the vacuum pump on other vehicles but much more powerful. Once you fix that you will get your brakes back.
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Old 11-09-2012, 11:51 PM
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Do you still have fluid in the system? There are some high pressure hoses that like to wear through. As stated above power brakes and power steering are the same system on these trucks, so a failure in the system will disable both.
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Old 11-10-2012, 12:59 AM
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Yeah its got fluid, its just not pumpin through
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Old 11-10-2012, 01:03 AM
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Might be a stupid question, but is there any special reason why they run a system like this, ive never seen somthin like this and neithr have a few.of.my.mechanic mates, usually its all vaccumm, just curious
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Old 11-10-2012, 05:06 PM
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The 7.3 diesel engine does not have a throttle plate and therefore does not have a restriction in the intake path. As a result of not having a restriction, there is not really a "vacuum" that could be used to provide the brake boosting function. In addition, once the manifold pressure increases while under turbocharger boost, the vacuum booster would be ineffective.

Similarly, a lot of turbocharged vehicles rely on other means for brake boosting as well, since the "boost" from the turbocharger makes the vacuum booster ineffective (a check valve would be required to prevent the pressure from affecting/damaging the diaphragm).

I have a turbocharged car that has been converted to vacuum brakes, and although it works fine most of the time, it can be downright scary when going from full throttle (high boost pressure) to hard on the brakes, because there is lag between having positive pressure in the manifold to the manifold going back into vacuum and providing the boosted braking pressure.
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Old 11-10-2012, 05:18 PM
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What he said. Diesels dont create their own vacuum. This is why we all have small electric vacuum pumps. They dont do anything like brakes, just small things; the HVAC blend door and the ESOF.
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Old 11-10-2012, 06:53 PM
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Quote:
Originally Posted by Devil Car View Post
The 7.3 diesel engine does not have a throttle plate and therefore does not have a restriction in the intake path. As a result of not having a restriction, there is not really a "vacuum" that could be used to provide the brake boosting function. In addition, once the manifold pressure increases while under turbocharger boost, the vacuum booster would be ineffective.

Similarly, a lot of turbocharged vehicles rely on other means for brake boosting as well, since the "boost" from the turbocharger makes the vacuum booster ineffective (a check valve would be required to prevent the pressure from affecting/damaging the diaphragm).

I have a turbocharged car that has been converted to vacuum brakes, and although it works fine most of the time, it can be downright scary when going from full throttle (high boost pressure) to hard on the brakes, because there is lag between having positive pressure in the manifold to the manifold going back into vacuum and providing the boosted braking pressure.
Nice answer!

Travis T


Sent from my iPhone using Autoguide.com App
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Old 11-11-2012, 01:31 AM
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Quote:
Originally Posted by Devil Car View Post
The 7.3 diesel engine does not have a throttle plate and therefore does not have a restriction in the intake path. As a result of not having a restriction, there is not really a "vacuum" that could be used to provide the brake boosting function. In addition, once the manifold pressure increases while under turbocharger boost, the vacuum booster would be ineffective.

Similarly, a lot of turbocharged vehicles rely on other means for brake boosting as well, since the "boost" from the turbocharger makes the vacuum booster ineffective (a check valve would be required to prevent the pressure from affecting/damaging the diaphragm).

I have a turbocharged car that has been converted to vacuum brakes, and although it works fine most of the time, it can be downright scary when going from full throttle (high boost pressure) to hard on the brakes, because there is lag between having positive pressure in the manifold to the manifold going back into vacuum and providing the boosted braking pressure.
cheers for that, we were all curious just standing around looking at it hahah
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