slyfox2062

Hi, is anyone familiar with the hydraboost, I purchased mine about 2 years ago and installed myself while getting the my 72 road ready, I'm almost there and took the car out today but the brakes are terrible. Is there a way to test the system? Pedal is hard not spongy and brakes have been bled, I just don't feel any stopping power. The master cylinder is standard, not Wilwood, and I remember the supplier provided a push-rod of a different length to match my master cylinder, something to do with the depth of the dimple in the piston??

Any ideas?? Regards Greg

spdrcr29

Sorry I don't really have much to add to this, but going to save this thread and watch for responses. I too just installed a Hydroboost system and am having few issues myself. M/C is a Wilwood unit, brakes have been bled as well as p/s system. After all that has been done, noticed a pretty hard pedal sitting in garage. Car hasn't been driven yet though. Also noticed that when pressing brake pedal, the pedal sometimes kicks back at me when trying to press down. Enough about that. This is about your question anyway, so hope others chime in and help get your issues figured out!

'75

Does the car have power steering and is it working?

slyfox2062

Yes I have PS and its working well which indicates PS pump is developing pressure that goes to the Hydraboost and then back to the power steering valve / actuator. I gather a higher pressure is developed in the hydraboost to apply to the brake MC. Regards Greg

'75

I presume you have the installation directions and have rechecked to make sure the hoses are plumbed to the correct ports. Does the engine pull down at all during a brake application (steering pump trying to make pressure)?

mrvette

Early sharks had a deep hole in the m/cyl and a long rod to fit in it from the booster, unsure why or the reason for the shallow piston with a divot in it and shorter push rod in the booster later on.....but the later setup more closely matched other GM products.....

I have '88-91 vette serp drive on my '72 and so just spliced the line, using the old '72 valving/regulator on the newer pump, because at the time I had stock steering.....I just spliced the lines with a brass plumbing fitting 3/8 compression on each end....still there 20 years later.....now the serp drive setup has a remote plastic tank for reservoir setting on the frame, under the m/cyl for my car.....

a couple years later I added my own rack winter 01-02......same as the kits, but way before any of that appeared....maybe I should tool up and market my rack conversion and sell it for 300 bux or so...

at any rate, some years later I added a Hydroboost, and so pump to HB, output to rack, and here we get specific I used a T 3/8 line coupling to the return lines and not thought a bit about it....the HB return goes through the top of the T straight out, the STEM of the T got the rack return line.....mine stops great and on a dime, steering has always been good....

There is many a comment that HB needs it's own return line not to be joined with the steering.....which MAY be true, depending on the arrangement at the T coupling, and the type of steering pump, if it is the stock type with reservoir integral to the pump, maybe have to mod the tank and run a separate line....comments on the spot to run it to also....above or below the fluid level in the tank, and to be honest I forget which on that point.....

pauldana

ok... here is the problem you have... the rod between the HB and the master brake cylinder is about 1/8"-1/4" to long. it will have to be shortened...

if you want to test this and make sure i am correct... which i bet i am... anyway, loosen up the 2 bolts between the MC and the HB, let it have a 1/8-1/4" gap/// if the lock up goes away.. that is the problem,///

slyfox2062

Thanks guys for all your suggestions. My engine has a 292 cam and I'm not too clever on camshaft technology but the idle was always very rough but with some tweaking of the ignition timing mainly by ear as I have no specs to go by, the idle is much improved and as a result the braking is much better. My car has today passed the Dubai Classic car club test and tomorrow I will be registered with Classic Car plates. I found some data on testing the Hydroboost which I will follow up on. But to answer some questions the engine does labour some on braking and a slight noise indicates increased brake pressure. Overall I think its working fine now. Thanks again chaps. Regards Greg

slyfox2062

Hi Guys, sorry I've been away a while. I have sorted out my rough idle and fuel mixture, the engine is pretty sweet now. I also redid my brakes new rotors, pads and calipers. Now I'm still suffering with lack of stopping power.

Will the rod length if incorrect between the HB and MC cause reduced braking power? I also notice that when braking the steering wheel kinda snatches a little, definitely feel something on the wheel when applying brakes. I don't think that is correct as the accumulator should apply brake pressure and not take it from the steering.

Is there a test to check the hydroboost operation?

Regards,

Greg

pauldana

Takes from 100-500 miles of driving to get the HB to settle down, get out all the air bubbles and pockets..

slyfox2062

So you don’t think it’s the push rod length? The pedal is really hard when engine off. When running it has some effect and pedal softer.

pauldana

Did you perform the test laid out in reply 7 that I ask you to do?

chevymans 77

You will feel it very slightly in the steering wheel when the brakes are applied, this is normal

The accumulator is charged with pressurized oil for when pressure is lost from the pump, when you crank the car and apply the brakes the accumulator will then charge with oil from the pump. If the booster is in good condition the accumulator with maintain the pressure for a good time but as they wear they will start loosing the ability to maintain the pressure over time and will re-charge when the brakes are used again, each time the accumulator re-charges you will feel it in the steering wheel as the pressurized oil for a split second will divert to the accumulator.

The peddle being hard when the engine is off is normal

The rod length is very important and yes it will cause braking issues, do as pauldana has suggested and see if it helps.

Neal

slyfox2062

thanks, are you referring to “ anyway, loosen up the 2 bolts between the MC and the HB, let it have a 1/8-1/4" gap/// if the lock up goes away.. that is the problem,///“

ive not tried this yet as car in for other work, will try on Monday. I thought this was to resolve brakes locking up, I seem to have lack of braking. Will come back on Monday with results.

slyfox2062

[QUOTE=chevymans 77;1599087640]You will feel it very slightly in the steering wheel when the brakes are applied, this is normal

Thanks Chevymans 77 for the description. I will try the gap between HB and MC on Monday when I have the car back. Regards Greg

slyfox2062

My MC with deep hole

My HB rod removed

Rod inserted

Rod length

slyfox2062

The rod is 114mm or 4.48 inches. I opened the gap between HB and MC by 1/4 inch and tried the brakes in the shop but no noticeable difference. Will try later on the road. Regards Greg

'75

The rod between the hb and mc can cause a low brake pedal if too short or brake lock up if too long. The rod from the pedal to the hb, if too long can cause problems also, make sure the pedal is not coming all the way up to the pedal stop, that the hb is limiting the upward pedal travel.

pauldana

Wrong rod

the small ~2”? Rod that is inserted in the master brake cylinder, this rod just falls out
nothing holds it in

slyfox2062

Thanks, Is there an adjustment at the pedal end to set length of the pedal pushrod to HB. I will need to revisit my car to check this.