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'97 K2500 hydro boost power brake Leaking ???

S

schiker

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My frame is wet below the master cylinder and my power steering fluid was low so I think my hydro boost is leaking. The firewall is damp and the bottom of the hydro unit is wet.

One quote came back at $1220 for new booster, master cylinder, and replace fluid/bleed ouch :(. Even if I buy a motive power bleeder checked bleeder nipples and gallons of fluid I still think I would save a few hundred $ doing it myself.

How hard is it to replace the hydro power booster? Looks like 4 bolts holding it to firewall, pedal linkage, and power steering lines. Take off master first a couple of mounting bolts and brake lines. Doesn't look like a terrible nasty job only one special tool.

The special tool looks like to measure the booster rod for master cylinder stroke? If I buy a new AC delco hydro boost unit I wouldn't think I would need the tool?????

Bleeding appears to be the only part that takes much know how.

I read a few posts and it doesn't sound too bad but I haven't ever done it.

Sounds like I can take off power steering return line while existing booster is still on the truck to flush the old power steering fluid out. How fast is it and do I need to rig up a supply to the pump to draw from (the other side of the return line too)? Should I turkey baster the majority of the power steering fluid out first?

Then replace the booster. Quick bleed same way and the power steering side is done. Do you have to pump the brake pedal to bleed the power steering fluid?

For the brake fluid side I thought about buying the bleeder nipples with a check valve and a Motive Power Bleeder to flush the old out. Then one or 2 bleeds of traditional pedal pump ~3x, hold, bleed.

Can we discuss some tips and particulars....

With the Motive power bleeder do I do one wheel at a time or front then back then one wheel at a time last???

Should I system flush the brakes through the old master cylinder first also just be as clean as possible to start?

What to look out for? How hard is it actually to unbolt the hydro unit under the dash?
 
Oh, that is how they work I watched a Youtube video on Motive style power bleeders one wheel at a time from farthest to nearest no need for speed bleeders.

Opinions on order of things.

1. Siphon out PS fluid from pump fill with new.

2. Disconnect hydro return flush hydro booster system.

3. Motive power bleed flush brake system

4. Take off master cylinder.

5. replace hydro boost install lines.

6. install new master and fill.

7. Bleed power steering hydro boost

8. Motive bleed brakes.

I am torn on #3 brake flush first might not be necessary but feel hydro boost flush before R&R is good idea since that is the problem. It might take a lot of brake fluid to purge the air from brake lines so not dirty fluid flush first? what would you do ???

What about order of brake bleed vs hydro bleed 7/8?
 
As long as your brakes are working properly, just the hydroboost leaking, the MC may not need to be changed. A couple years ago my hydroboost started leaking, very similar to your description. I was able to change just the hydroboost without opening the brake lines. No need to bleed any brakes and two years later my brakes are still working the way they were designed to.

Unbolt the MC from the Hydro without breaking loose any brake line connections. Very carefully pull the MC slightly forward (the brake lines will provide support). Under the dash, remove the clip that holds the brake pedal pivot pin to the rod that goes into the hydro unit.

Removing this clip was the toughest part for me. Tight quarters to work in, and a very hard to remove spring clip. Make sure you have a spare clip on hand in case the old one gets damaged during removal, or goes "sproing" into the unknown. There is a special technique to this removal, but I don't think I can properly describe it as I learned about it the hard way after the fact. Maybe you can find a you tube video of it.

Now the hoses on the hydro unit itself need to be removed. There will be some oil mess here, but hard to avoid. Once the hoses are loose the hydro unit itself can be removed. There are four nuts on the inside of the firewall, that hold the hydro unit to the firewall, that need to be removed. Tight quarters again, but a good ratchet and extensions are your friend here.

At this point the hydro unit can be removed and the new one put back in place by reversing the removal process. There is a way to bleed the hydro unit, but since mine was the first and only one I've done I don't remember exactly what I did. Find a you tube video for the process.

Replacing the hydroboost unit without having to bleed brakes means a lot less work.

Don
 
My master cylinder reservoir seeps a tad bit and has 200K + miles. I figure its due and while I am there might as well do it. Also figure its time to flush the brakes too. The little extra room removing the MC and benefits I hope will offset the extra work. If it was younger I might try to keep the OE MC.

I see a gasket listed for the hydro booster what is it for / where does it go ? Or is it for rebuild? Did you need one ? Does one come with a new hydro booster?
 
Ok went back to youtube and watched a few more videos on power steering and hydro boost flushes.

It appears the hydro boost will spurt a couple of ounces of fluid each brake pump and no need to attach a jug to return line to feed the PS pump just check it does not run too low on fluid. Is that what ya'll have seen with the 6.5's?

First thing to do is flush power steering fluid before replacing hydro booster.

1. Siphon out as much PS fluid from reservoir as I can. Refill with new.
2. Lift front tires up turn lock to lock slowly a few times with engine off and double check fluid level.
3. Siphon out mixed fluid and refill. Turn lock to lock engine off. Check fluid level to be safe.
4. Take off hydro boost return line and put clear hose to a container. With motor at idle a slow short pump of brake and check just a few ounces of fluid comes out. Checking fluid doesn't get too low pump brakes and flush until cleaner fluid comes out. Turn lock to lock a few times and repeat brake pump flush. The fluid should be clean and clear.

When I install new hydro unit a few pumps of brakes before re attaching PS return line.

One guy used about 4 quarts on a Ford 6.0/7.3. If I siphon out old I assume I probably could do it with 2 quarts ?
 
My pickup had in the neighborhood of 230K miles when the hydro started leaking, requiring replacement. I'm not the original owner so I don't know if this is the original MC or not, just assuming it is.

My new hydro unit didn't come with any gaskets. It was leaking from the front, there is a weep slot built into it. Because of this I never even thought about needing any gaskets. I've never since even come up with any reason to need a gasket.

I'm assuming when you say it's seeping from the reservoir that you are talking about where the reservoir mounts onto the metal casting part of the MC.

Have you checked to see if new rubber seals for this location are available? Rockauto shows a new reservoir available with new seals for $83 (ouch!). But, a new AC Delco MC for a hydroboost system is $164, so it may be worth while to replace the reservoir to get new seals. I just hate to throw away a MC that is working good when it is a known fact that even new replacement parts are not as good of quality as what came on these vehicles from the factory.

Doing a brake fluid change is always a good idea, especially if you don't know when it may have been done in the past.

Don
 
Yes, it appears to be seeping around the grommet / O-ring type seal the reservoir plugs into. I have used the master cylinder for support changing the fuel filter one too many times I guess.

Yeah, its a judgment call buying new reservoir and seal kit for about half of new part and worry about fitment and leakage vs. buying the whole new MC.

I hear you on new parts.
 
Finished the job earlier in the week and so far so good no leaks. Wasn't that hard of a job. The hardest part was the little clip on the brake pedal. I ended up getting it with a precision screw driver and prying it off. The brakes feel better but doesn't necessarily stop better just the pedal feels a little more firm. The Motive power bleeder seemed to work great on bleeding the brakes and flushing the old fluid out and any air in the lines from opening the lines.

This is what I did:

1. Vacuumed out old fluid from PS reservoir.
2. Refilled (about 5/8-3/4 of a quart) and drove a day or 2.
3. Repeated.
4. Took off old MC.
5. Took off old hydro boost.
6. Installed new hydro boost except return line.
7. Bench bled the new MC.
8. Installed MC.
9. Used Motive power bleeder to flush system and bleed air out of brake lines.
10. Vacuumed out PS fluid again, refilled, and pumped brakes (turned wheel back and forth a little) and flushed a last quart thru new hydro boost to expel air from hydro boost. The fluid looked pretty clean by now.
11. Reattached return line topped up PS fluid.

I bought my parts from Amazon dot com and fluids from Oreiley's Auto parts. Saved about $400 I think which works out to about labor but have a fluid extractor and motive power bleeder as extra tools for other projects to boot.
 
Well crap my new hydro booster may be leaking. Not 100% sure yet but other than a new part bad out of the box why would this happen? Could it be any technique in my install/bleed.

I had the MC a little over full and some brake fluid between the gasket and cover and for the first time parked it nose up on a slight hill. Hopefully that is it and not the hydro unit. I cleaned it up (again) and will watch it.

Bleeding the booster I left the return line back to the pump/reservoir off and put a length of clear tube on the nipple at the hydro booster. I cranked the truck up and slowly pumped the brakes and let it surge out into a bucket when I let off the pedal. When the fluid looked like it cleared a good bit of the snot out ( probably still had some air but was looking pretty clear) I reattached the return line. Should I have done this initial hydro bleed cranking the truck and not letting it crank up as to not surge so bad on the seals?

I googled a little and saw some pages that mention a while back circa 2002 ??? the Duramax trucks and some Astro Vans had leaking hydro boosters and they changed the part number for the Duramax. I doubt ours are the same but did GM spec the seals poorly or material and I bought a new old stock part :rolleyes5:.

Anyone hear of a parts change on the booster for service parts or other changes on GMT 400's boosters?
 
I just skimmed through this thread...

When flushing & beading the booster you should have the front tires off the ground, you should go from lock - lock each way slowly..

Did you rebuild the hydro, or purchase?
 
Brand new AC delco OEM No. 15192200 but I bought it off Amazon dot com and not sure when it was mfg'ed.

At some point I sawed on the wheel a little back and forth during the bleeding to try and flush out a last quart or so but I did not turn lock to lock. I would let a few squirts out then refill the reservoir. It never growled like it was low or had bad air.

I have read a few things on the net about leaky ones. This new one seems to be seeping from the weep hole.

Maybe since cleaned mine I noticed it and am sensitive to the issue and its somewhat normal. It developed a few drips and a droplet hanging on lowest point of MC after a few days.

One article......
http://www.thedieselpageforums.com/tdpforum/showthread.php?t=17968

Could it be it just needs to kinda purge out some of the initial blow by until everything got wet and sealed better???? Hopeful thinking and a bit miffed it might be an appreciable leak.
 
I would try cleaning it up a little and watch it a day or two. If it keeps "seeping" something is wrong, but worth a shot to se if a seal just needs to get wet. Or if the mc was overflowing.

If you do have to send it back, don't wait very long. I was talking with one of the AC Delco Engineers about other things a few months back and Amazon came up. AC Delco is gathering info to sue Amazon(if they have to) for the problems the customers are getting in warranty situations. He said call them up for customer service as they would rather have the headache and happy customers than the other option.
 
This is one of the things that is bad about Amazon especially and the net in general. I can't find a location for Amazon listings not even region. At least Ebay you know city or zip code where it is shipping from.

Say I need something quick but as usual no one stocks it everybody can order it so can I..... When I go to Ebay or other places too I can look to see if seller is at least in my region so I can expect quick shipping Amazon I have not figured it out yet.

Seems Amazon drop ships so to speak and/or many sellers don't disclose where they are located. I think several are unloading old new stock or outdated part numbers. I can gleam part numbers from several sources but don't always know if its the latest and greatest part number. We all know parts are getting poorer quality control and I guess the anonymity of the internet seems to encourage it.

Seems the other trend is house name brands and you don't know who made it and depending on lot may be different manufacturer.
 
You may consider running a "magnafine ps filter" on the return line of the PS box. (Better PS filters out there as some others have had issues with this brand.) Possible you have a bunch of debris in the system ruining seals.

Do not get a reman PS pump from from A1 Cardone, ever!
 
Good point. I did try and flush the system but doubt I cleaned it out 100%. I did read something somewhere to add a filter on return line when replacing hydro unit and that the hydro boost is sensitive to poor fluid and particle contamination. One article I read had it would benefit hydro boost units to have regular fluid changes but did not suggest service interval (its always variable anyway). Most everything likes a little TLC.

Does it have to have a filter? OE went 200K + miles with no fluid maintenance. I flushed it ok and the new one seeps within a week that is a pretty big difference.
 
Clean it good, use some spray stuff and stick the plastic spray thingy in the weep hole and blow it out good, and watch...

You should be able to tell if it's brake fluid or PS fluid by smell maybe help harrow it down.. could put a little AT fluid in the ps to color it also...
 
Fingers crossed it may have stopped. Why would cleaning out the weep hole have helped?

I am wondering if it was just some air entrapped in fluid from accumulator that was encouraging some blowby of the seals and once all air was out it wetted and sealed????????

The rest of the system was still wet so it's not like it ran dry.

One page suggested installing a hydro boost that was ported and not an eom type. Anyone know what they were talking about??????
 
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