Hydro boost leak - vent tube?

[Mquirin]

I’ve had my m998 for about 2 months. Over the past few weeks I’ve noticed what appears to be PS fluid leaking onto the floor behind the driver side tire. I’ve followed the leaking fluid up and it is coming from under the hydro boost. I used my phone to take a video, so I could get a good view. When I did it, I can see a vent tube and I’m thinking it’s coming from it. What would cause the fluid to start venting out of this tube (it hadn’t been doing it previously)? Is this normal? I’ve been continuing to add PS fluid as it gets low.

 

[Action]

Not thd cause of the problem, but exactly what fluid are you adding to it?

 

[Mquirin]

I'm adding PS fluid to the PS pump resevoir.

 

[juanprado]

Should be a red fluid and using dexron.

Are any of the lines going into the hydroboost leaking? If lines are clean and no leaks then:

To me that sounds like your hydroboost unit is leaking and you need a new unit. Does the brake pedal feel stiffer or harder to depress?

 

[Pierreab]

I’ve had my m998 for about 2 months. Over the past few weeks I’ve noticed what appears to be PS fluid leaking onto the floor behind the driver side tire. I’ve followed the leaking fluid up and it is coming from under the hydro boost. I used my phone to take a video, so I could get a good view. When I did it, I can see a vent tube and I’m thinking it’s coming from it. What would cause the fluid to start venting out of this tube (it hadn’t been doing it previously)? Is this normal? I’ve been continuing to add PS fluid as it gets low.

Ok, I purchased my HMMWV with this same problem; I'm not privy to a vent line though !!! So these trucks sit for a really long time; mine is a 1986 so it did some sitting ! The hydroboost is a Bendix and it does not go bad, the seals go bad and you don't have to pay well over $400 for a new one; how about $25 for a seal kit ! They are fairly simple to rebuild and there is lots of YouTube videos on how to do it. Usually the seal at the front between the master or the seal at the rear called the figure 8 seal are the ones that go bad, you can tell by washing it down with brakekleen and running the truck, steering back and forth and stepping on the brake pedal several times, make sure your power steering pump is full and the belt is tight; that is very important to build full pressure. You should remove the splash shield to wash it down completely and you'll need it off to remove and rebuild the hydroboost anyway. Mine actually had two leaks, the second leak was coming from the pressure line on the top of the hydroboost it has a o-ring on the end that was bad; the rebuild kit has new o-rings for the lines also. I bought my kit on ebay and it came with a link for rebuilding instructions online.

Sent from my SM-T800 using Tapatalk

 

[NormB]

Ok, I purchased my HMMWV with this same problem; I'm not privy to a vent line though !!! So these trucks sit for a really long time; mine is a 1986 so it did some sitting ! The hydroboost is a Bendix and it does not go bad, the seals go bad and you don't have to pay well over $400 for a new one; how about $25 for a seal kit ! They are fairly simple to rebuild and there is lots of YouTube videos on how to do it. Usually the seal at the front between the master or the seal at the rear called the figure 8 seal are the ones that go bad, you can tell by washing it down with brakekleen and running the truck, steering back and forth and stepping on the brake pedal several times, make sure your power steering pump is full and the belt is tight; that is very important to build full pressure. You should remove the splash shield to wash it down completely and you'll need it off to remove and rebuild the hydroboost anyway. Mine actually had two leaks, the second leak was coming from the pressure line on the top of the hydroboost it has a o-ring on the end that was bad; the rebuild kit has new o-rings for the lines also. I bought my kit on ebay and it came with a link for rebuilding instructions online.

Sent from my SM-T800 using Tapatalk

do you happen to recall which particular kit you bought? There appear to be several.

Thanks.

 

[Pierreab]

do you happen to recall which particular kit you bought? There appear to be several.

Thanks.

I bought the kit that matched year of my HMMWV; they used this style Bendix hydroboost in many GM trucks with diesel engines of that era. Just look up a replacement hydroboost for your year and note the part number then match the rebuild kit to that part number.

Sent from my SM-T800 using Tapatalk

 

[911joeblow]

It sounds like a reseal to me too. Not too hard to do, just time consuming. Make sure to install the seals wet, not dry. Keeps them from being damaged as you reassemble.

 

[Mquirin]

This is the tube coming out of the bottom of my hydro boost that leaks PS fluid. Should this be plugged into something? Should this be draining PS fluid?

 

[sallystrothers]

Did you ever find a solution? I'm having the same thing happen periodically, was wondering if it related to an incomplete air bleeding or a different problem?

 

[Mquirin]

Did you ever find a solution? I'm having the same thing happen periodically, was wondering if it related to an incomplete air bleeding or a different problem?

I never figured this one out. Still happens from time to time and I just make sure to keep the Dex at the appropriate fill level.

 

[Mogman]

You should take those leaks seriously, most of the time it is a bad seal in the hydroboost, if that seal goes out completely you can loose all the PS fluid in a short amount of time, BTW all of the videos I have seen are wrong, you are installing a seal against the seal lips and to do it right you must use a seal lip tool like this.

Or like this one,

You use it to ensure the seal lip does not fold back on itself, every video I have seen they just cram it in and hope for the best, if you get it apart and have problems find an auto trans guy, they are very familiar with installing these types of seals.
Most of the "universal" seal kits for the late 80s GM trucks will have an assortment of seals, there is basically two different bore sizes and most kits have both seals, if someone would send me a bad one I would do a video on doing it the correct way.

 

[sallystrothers]

I understand why the fluid is leaking out of the overflow tube from the reservoir, however, I don't know why it looks like it is "boiling" the fluid under certain conditions. I've bled it twice now and there are no visible air bubbles, but when running it periodically does this:

Is this a hydro-boost leak? This was immediately after a full-cold start. What else could be causing the periodic "boiling" of the fluid

 

[Action]

I understand why the fluid is leaking out of the overflow tube from the reservoir, however, I don't know why it looks like it is "boiling" the fluid under certain conditions. I've bled it twice now and there are no visible air bubbles, but when running it periodically does this:

Is this a hydro-boost leak? This was immediately after a full-cold start. What else could be causing the periodic "boiling" of the fluid

Are you turning the wheel all the way to one side when this happens? If so, it is air bleeding out.

 

[Mogman]

Why are you running the pump with the cover off, fill it to the full mark (and then recheck again later) put the cover on and it everything works and it is not noisy or leaks then be happy!

 

[sallystrothers]

Are you turning the wheel all the way to one side when this happens? If so, it is air bleeding out.

It happens just before the steering hits a hard stop, but then goes away once it actually hits the hard stop, on both sides right and left. It could be air, and I might use the turkey baster method on the cooler to try and suck any air out if I can.

 

[sallystrothers]

Why are you running the pump with the cover off, fill it to the full mark (and then recheck again later) put the cover on and it everything works and it is not noisy or leaks then be happy!

It does get noisy and when it does, the boiling action occurs. I was running it with the cover off as part of a bleed procedure I was using, that specified after 40 cycles left to right with the cover off and engine off, then to center the steering and start it up with the cover still off to measure the fluid level. Upon doing this I noticed it was boiling the fluid, even while centered, while the glow plugs kick in/off. The boiling is what is causing the slow leak to happen as it accumulates in the overflow tube.

 

[Mogman]

It surly has to be air, if any of the fluid got hot enough to boil (around 400 deg.) it would be smoking big time.
If it only happens near hard stop then what you are seeing may not be an issue as you rarely get near hard stop during "normal" driving

 

[Action]

It does get noisy and when it does, the boiling action occurs. I was running it with the cover off as part of a bleed procedure I was using, that specified after 40 cycles left to right with the cover off and engine off, then to center the steering and start it up with the cover still off to measure the fluid level. Upon doing this I noticed it was boiling the fluid, even while centered, while the glow plugs kick in/off. The boiling is what is causing the slow leak to happen as it accumulates in the overflow tube.

What is the "overflow tube"
Call it bubbling, not boiling.
Where do you consider the fluid level to be full?

 

[sallystrothers]

What is the "overflow tube"
Call it bubbling, not boiling.
Where do you consider the fluid level to be full?

Its not necessarily bubbling, as there is no gas/air coming, its just dancing. The actual leak is from the tube in the nook of the wheel well, just barely peeking out in the center of this picture.