GM hydro boost brakes for newbies like me....
- Thread starter chilliwak
- Start date
Larry
Bigassgas Explorer
Thanks for all the input guys. This is really what I need to understand the system. A member here on the board is getting me hooked up with a pedal assembly and such so that I can do my swap this summer. He is also the guy that has helped Larry. Cool to have people that can help you out...
Chilli, there are lots of videos on Youtube related to hydroboost that might help you understand the system. Basically, hydroboost uses hydraulic pressure from the power steering pump to operate the power piston inside the booster in order to provide brake boost whereas the vacuum booster relies on engine vacuum to operate a large diaphragm inside the booster to assist with brake boost. Not sure if that is what you were looking for with your comment in needing to understand the system.
Ridge Runner
Delta V
One thing I haven't heard anybody mention is how braking is while turning. I don't have any firsthand experience with the system, but everyone locally hates on it for that reason. Of course, I wouldn't exactly call most locals experts, either.
toddz69
Explorer
That's sometimes a problem on the Ford Super Duties and their less than stellar CII power steering pumps. I have 183k on mine now without any issues but I have read a lot of comments from people that have had problems.
I've never heard of it being an issue with the Saginaw pumps. I've run both Saginaw and Explorer (CIII) pumps on my Bronco without issue.
Todd Z.
AA1PR
Disabled Explorer
Chilli, there are lots of videos on Youtube related to hydroboost that might help you understand the system. Basically, hydroboost uses hydraulic pressure from the power steering pump to operate the power piston inside the booster in order to provide brake boost whereas the vacuum booster relies on engine vacuum to operate a large diaphragm inside the booster to assist with brake boost. Not sure if that is what you were looking for with your comment in needing to understand the system.
Curious to know more about that. I am not following what you wrote because that doesn't make much sense. If you lost a p/s pump you would lose brake boost (other than the few pumps the accumulator would provide) but if you lose a booster you wouldn't necessarily lose power steering unless there was a major fluid loss. If that was the case, it would be obvious power steering would be lost with no hydraulic fluid just in the way we would die without blood (to clarify, steering is not lost, but power steering would be lost). The part about vacuum comes off of the power steering pump is even more confusing. There is no vacuum being made in the p/s pump nor in the hydroboost system. It is a hydraulic system. Not sure what you mean there?
sorry it was late for me..., hydro-boost uses the hydraulic pressure from the power steering system to provide the driver assist in applying the brakes, so when the pump shaft broke/failed I had very little pressure to apply the brakes from it, so no matter how hard I applied the brake it didnt matter basically
let me see if I can find a web link that might help...here ~ http://www.brakeandfrontend.com/operation-diagnosis-and-repair-of-hydro-boost-power-assist-systems/
Larry
Bigassgas Explorer
Me neither and I've had my 8,000 lb. K10 running 35” tires in some pretty precarious positions while crawling around the Canyonlands back country where the engine was at idle (lowest pump pressure output) with the brakes applied and turning the steering wheel at the same time all on a 100+ degree day. No issues what so ever.
That said, as I've mentioned in the past, I work for a truck manufacturer where we built stripped chassis for the RV and commercial step van industry. Back before we moved to hydromax across the board we did have a few cases on class A RV's where owners complained of hard steering while slow speed steering with brake application such as backing the coach into parking spot with hydroboost. The actual cause was poor weight distribution over the front wheels (think how a shopping cart steers with 50 lbs of sand over the front casters) by the body company (RV house) but, if I recall correctly the fix was to add a washer or spacer behind the spring inside the pressure regulator/valve inside the pump to boost pressure. That particular generation of chassis still had the IFS front suspension (ugh, airbags to boot) with a 10,000 to 16,000 GVWRs and were all running Saginaw pumps and Saginaw steering gears. We moved to ZF pumps and ZF steering gears across the board a few years later on a chassis redesign. Never had another complaint after that. It is still my opinion Saginaw steering pumps have plenty of gonads to run hydroboost under most conditions us folks will run into but the RV story above is more of an anomaly in a unique application with poorly planned weight distribution.
chilliwak
Expedition Leader
Just a quick question for you Larry. Is there anything user specific to a 6.2 liter diesel set-up out of a military cucv that would NOT work with my old 79? Just so I need to know what to do to make it work. Hose lines being metric and my old truck being standard? I guess all the lines need to be either metric or standard when relating to the power steering pump, steering box, and booster? The only thing that does not matter too much is the return lines right?
Any info would be helpful...:ylsmoke:
Any info would be helpful...:ylsmoke:
Larry
Bigassgas Explorer
Chilli,
As far as I know the only difference would be the metric (CUCV) vs. standard threads on your existing power steering pump and steering gear. As mentioned above, you would also need the brake pedal if that isn’t already part of the CUCV bits and pieces you would be buying.
chilliwak
Expedition Leader
So Larry I can assume that if I want the metric threaded cucv system to work I will need the pump, power steering box, housing, and all the lines, or should i buy new lines that are standard threaded and make it work with a new housing that is also standard threaded and my existing steering box that I guess is standard as its from 1979 and then only get the pedal system so that it would work with the standard thread housing and lines? Any help would be greatly appreciated as this feels like a jungle...:Wow1:
chilliwak
Expedition Leader
Is there anyone that can help with the differences from a 1979 Chevy steering box from a half ton to a 85 cucv hydro boost conversion? How much do i need of the metric cucv system to convert my old 1979 system to the cucv hydro boost system? This is just a jungle for me so any help would be appreciated..
Larry
Bigassgas Explorer
Sorry Chili, somehow I missed your post from the other day. You could do a couple of different things to make the metric hose thread CUCV hydrobooster work on your standard thread p/s pump and steering gear. You could make your own lines as Todd mentioned in the other thread out of AN hose and fitting. If you went that way, you could just use the metric adapters and SAE adapters where applicable and not worry about changing your steering gear or pump. AN is good stuff but for me the hardest part about using AN stuff for projects is finding the right adapters and having the special tools to work with it (cutter, aluminum wrench, lube). You almost need to call some like Summit Racing to help identify the right fitting and adapter numbers as there are so many it is confusing to pick out the right ones. I've had good luck with AN on the only project I've used AN stuff on (automatic trans swap cooler lines) although it took me a few tires to get the right adapters/fittings.
The other option would be to change the steering gear and p/s pump to later pieces with metric fittings. That would add to the cost but at least all of the hoses, etc. are all off the shelf parts that could be purchased through any parts store if there is a problem down the road.
Here are Napa part numbers for a the two pressure hoses and p/s pump for a 1985 spec K5 blazer with hydroboost.
71784 Hose: Hydro-Boost to Steering Gear
P/S Hose End Type : 16 mm Male "O" Ring x 18 mm Male "O" Ring
Power Steering Hose Imperial Length : 49"
Power Steering Pressure Hose Thread Size : 16 mm -1.5 x 18 mm -1.5
76193 Hose: Pump to Hydroboost
P/S Hose End Type : 16 mm Male "O" Ring x 18 mm Male "O" Ring
Power Steering Hose Imperial Length : 55.5"
Power Steering Pressure Hose Thread Size : 16 mm -1.5 x 18 mm -1.5
381168 PS pump w/reservoir
Hose Port Type : O-Ring
P/S Pump Line Thread Size : M16 x 1.5
P/S Pump Shaft Type : Press-On
OR
381167 PS pump w/o reservoir (you would need to use a remote mounted reservoir with this one)
Hose Port Type : O-Ring
P/S Pump Line Thread Size : M16 x 1.5
P/S Pump Shaft Type : Press-On
391090 Steering Gear Box
# Steering Gear Box Turns : 3 7/16
Steering Gear Box Input Shaft Diameter : 1.25"
Steering Gear Box Output Shaft Diameter : .72"
# Steering gear Box Mounting Holes : 4
Hose Port Type : Metric
Power Steering Gear Box Line Thread Size : M18 x 1.5 & M16 x 1.5
Here is another thread brewing on another site on the hydroboost topic. Someone posted more pictures of pedals there. Check out the pics on page 2 of the automatic hydroboost brake pedal.
The other option would be to change the steering gear and p/s pump to later pieces with metric fittings. That would add to the cost but at least all of the hoses, etc. are all off the shelf parts that could be purchased through any parts store if there is a problem down the road.
Here are Napa part numbers for a the two pressure hoses and p/s pump for a 1985 spec K5 blazer with hydroboost.
71784 Hose: Hydro-Boost to Steering Gear
P/S Hose End Type : 16 mm Male "O" Ring x 18 mm Male "O" Ring
Power Steering Hose Imperial Length : 49"
Power Steering Pressure Hose Thread Size : 16 mm -1.5 x 18 mm -1.5
76193 Hose: Pump to Hydroboost
P/S Hose End Type : 16 mm Male "O" Ring x 18 mm Male "O" Ring
Power Steering Hose Imperial Length : 55.5"
Power Steering Pressure Hose Thread Size : 16 mm -1.5 x 18 mm -1.5
381168 PS pump w/reservoir
Hose Port Type : O-Ring
P/S Pump Line Thread Size : M16 x 1.5
P/S Pump Shaft Type : Press-On
OR
381167 PS pump w/o reservoir (you would need to use a remote mounted reservoir with this one)
Hose Port Type : O-Ring
P/S Pump Line Thread Size : M16 x 1.5
P/S Pump Shaft Type : Press-On
391090 Steering Gear Box
# Steering Gear Box Turns : 3 7/16
Steering Gear Box Input Shaft Diameter : 1.25"
Steering Gear Box Output Shaft Diameter : .72"
# Steering gear Box Mounting Holes : 4
Hose Port Type : Metric
Power Steering Gear Box Line Thread Size : M18 x 1.5 & M16 x 1.5
Here is another thread brewing on another site on the hydroboost topic. Someone posted more pictures of pedals there. Check out the pics on page 2 of the automatic hydroboost brake pedal.
underdrive
jackwagon
There's a 3rd option as well, at least as far as the PS pump is concerned. The fitting that the pressure hose threads into can be removed and swapped from one style to the other. On our FrankenFord we are running a Saginaw PS pump, for a while we used the metric fitting and a late-'90s GM 3500 pressure hose attached to it, then later we switched to the '70s double-flare setup with a different hose as that gave us better clearances around the other engine accessories. Pump even remained bolted to the engine the whole time, we just unscrewed one fitting and screwed the other one it its place. Most of the fluid leaked out in the process, and one also needs to be aware that inside the pump behind said fitting there is a spring-loaded valve, it won't try to fly out and kill you or anything but it's still a good idea to remove the fitting slowly.
chilliwak
Expedition Leader
Thank you for that super cool and detailed parts write up Larry. Are the old sae hoses for the 1979 and previous C30 trucks with hydro boost not available anymore? I was thinking that I could order an old school 1979 brake fluid housing that had sae thread and then get the hoses that fit so that I could run my existing power steering pump and steering box. Please let me know...:ylsmoke: