Hydroboost issue

[eze_1978]

I have a CPP hydroboost installed on my Nova. Seem like when I back up I can feel the brakes are still slightly engaged. If I’m on the hill of my drive and turn the steering wheel back and forth it seems to release the brakes. When I put the brakes on it will stop and seem to keep the brakes engaged a little bit until I start to move the car. I get a noise what seems to be comes from the rear brakes when I’m in reverse, looking at the calipers on both side it looks like the e-coating is still present on my passenger rear while drivers side is completely removed. Once I get moving forward everything seems fine and brake good.

Brakes are new wilwood 12.88 4piston in the rear and 12.88 6 piston up front. Can anyone point me in the direction of what may be occurring. Since it’s going to be a street driven car I do like how quickly it will stop with the hydroboost but I was given advice to get rid of the hydroboost and just go Manuel brakes. Any suggestions or input would be greatly appreciated.



I have a low vacuum engine so I could run power booster and don’t really want to go the route of a vacuum pump.

[HBHarleyman]

Sounds like there's fluid pushing into the rear to engage the brake. Try check the rod length from the hydro unit to your pedal. Disconnect it and jack up the rear and spin the wheels. If it's not engaging and spinning free, your problem is likely the rod length/adj.

[eze_1978]

Sounds like there's fluid pushing into the rear to engage the brake. Try check the rod length from the hydro unit to your pedal. Disconnect it and jack up the rear and spin the wheels. If it's not engaging and spinning free, your problem is likely the rod length/adj.

Sounds good. I’ll give that a try. Thanks

[WallaceMFG]

How do you have all the steering lines run? There's three lines going to the HB, pressure in, pressure out to steering, and a "leak" line. If the leak line does not have it's own line running back to the reservoir then it can cause issues with the brakes sticking on. A lot of people say to run the leak line with a T into the return line from the steering box, but this can cause the issues you are having. Pressure from the steering return line pushes into the leak fitting and can apply brake pressure without pedal input.

We had a similar issue on our Chevelle with the rear brakes sticking on, and changing the line routing cured it. It mostly did it when cold, and got better as the fluid warmed up.

Also, I'm assuming you got rid of the factory check valve for the rear drums? Just making sure as some people forget to remove those when they swap to discs.

[eze_1978]

How do you have all the steering lines run? There's three lines going to the HB, pressure in, pressure out to steering, and a "leak" line. If the leak line does not have it's own line running back to the reservoir then it can cause issues with the brakes sticking on. A lot of people say to run the leak line with a T into the return line from the steering box, but this can cause the issues you are having. Pressure from the steering return line pushes into the leak fitting and can apply brake pressure without pedal input.

We had a similar issue on our Chevelle with the rear brakes sticking on, and changing the line routing cured it. It mostly did it when cold, and got better as the fluid warmed up.

Also, I'm assuming you got rid of the factory check valve for the rear drums? Just making sure as some people forget to remove those when they swap to discs.

Yes, the rear check valves were removed when I I installed the new brakes and new 9in rear end. I also just installed all new lines with a new power steering pump as well. I thought that may have been the issue. I actually used a Y AN connector instead of a T connector.

[Kraftwork69]

Yes, the rear check valves were removed when I I installed the new brakes and new 9in rear end. I also just installed all new lines with a new power steering pump as well. I thought that may have been the issue. I actually used a Y AN connector instead of a T connector.

From what I've read I feel your "Y" is way too close to the Hydroboost Unit. Return fluid from the steering gear could be entering the Hydroboost.Looks like if a "Y" or "T" adapter is to be used it should be as close to the power steering reservoir as possible. For the best installation, putting it directly back into the reservoir is widely recommended. I disassembled the pump assembly, drilled a hole for a bulkhead fitting, and dumped it right back into the reservoir. Wasn't hard just gotta make sure everything is perfectly clean prior to reassembly.

[eze_1978]

From what I've read I feel your "Y" is way too close to the Hydroboost Unit. Return fluid from the steering gear could be entering the Hydroboost.Looks like if a "Y" or "T" adapter is to be used it should be as close to the power steering reservoir as possible. For the best installation, putting it directly back into the reservoir is widely recommended. I disassembled the pump assembly, drilled a hole for a bulkhead fitting, and dumped it right back into the reservoir. Wasn't hard just gotta make sure everything is perfectly clean prior to reassembly.

I was think about adding a return line at some point. I’m also thinking about just going manual brakes and eliminating the hydroboost. I did just installed new lines and prior to installing new lines there was a T installed and was closer to the pump, and I still had the same issue. I’m going to check the pin engagement first and see if that is the problem. Do you think it could be possible the master cylinder is bad? I was thinking about changing to a wilwood MC.

[Kraftwork69]

I was think about adding a return line at some point. I’m also thinking about just going manual brakes and eliminating the hydroboost. I did just installed new lines and prior to installing new lines there was a T installed and was closer to the pump, and I still had the same issue. I’m going to check the pin engagement first and see if that is the problem. Do you think it could be possible the master cylinder is bad? I was thinking about changing to a wilwood MC.

Definitetly remove the master and measure the depth of the piston to the mount surface. Then Do the same at the hydroboost. Make sure when the master is installed and weather or not your using a slug that there's a very small gap and there's no pressure on the master cylinder piston with no pedal applied. Was the master cylinder bench bled before installation? Air in the master could be a contributor. If the master is fairly new chances are it's something else. Not a very complex part. I use a wilwood master and very happy with it so far. At this point I would also rebleed everything is case it's an air in the line problem that expands with heat.

[Hydratech®]

Looking at the images, it is the way the low pressure return line is plumbed. To prove it out, get a AN-6 female cap, disconnect the low pressure return line connection at the "Y" and than cap that nipple. Then rig up a temporary hose from the low pressure return line port on the brake unit to go into the PS reservoir (with the fluid fill cap removed). You could also run the temporary test hose into a windshield washer or similar jug. The only time you will see any particular flow out of this line is when you release the brakes, usually exhausting a tablespoon or two of PS fluid - the harder you press on the brakes, the more fluid will exhaust when you release the brakes. Anyway, if you immediately see a considerable difference in the way the pedal releases, then you have proven out that the "Y" connection is the culprit. If you want to drive it, you can get a replacement PS cap and modify it to accept the end of your temporary bypass line so that you don't risk splashing PS fluid out of the pump on a test drive. "Y" fittings have caused countless amounts of people headaches. I strongly believe it to be the case. Installing a bulkhead adapter into the PS pump housing will be the best RX for the situation. This is what we use:

https://www.summitracing.com/parts/rus-670850

This can be installed anywhere it suits you best into the PS pump reservoir, as you are only discharging small amounts of fluid (from the brake unit back to the PS reservoir) at a time when you let off of your brakes. Naturally watch out to make sure you do not allow any metal shavings to get loose in the pump. We flip the pump upside down, drill it (using a step size bit), counting on gravity to bring the shavings downward, then take it over to the parts washer (while it is still upside down) and liberally hose the insides of the reservoir out thoroughly with brake cleaner spray, then blow it out with compressed air. Or? You can carefully remove the reservoir, but re-assembly can be tricky to provide a leak free installation on some pump designs.

The other problem that could also be a factor is that CPP uses the late model stock GM MC pushrods which are .060" longer than they should be. This .060" usually causes preload of your MC pistons - some MC's aren't bothered by this much MC piston preload, but most are. The quick test to rule this out would be to place a washer behind each mounting ear of the MC to temporarily space the MC away from the face of the brake unit. If this cures your problem, then you need to either make a shim (that looks like a metal thermostat housing gasket) to space the MC further out, or remove the MC and take a round carbide burr on an air motor and buzz the backside of the MC piston deeper to remove the preload. Attempting to shorten the MC pushrod in the brake unit is not something that usually goes well... Or? Get the Wilwood MC, as it has the deep MC pushrod hole provided with a spacer slug to convert for use with short MC pushrod design power brake boosters. You could then take Wilwood's aluminum slug / plug / bullet and carefully grind a few thousandths off of the front rounded end at a time until all preload is eliminated. You should be able to place the MC flush against the face of the brake unit casting cleanly without feeling any preload or seeing any air gap between the MC and the brake unit. Our target is .020" air gap to make sure there is no preload when everything is hot. No way can anybody feel .020" air gap in the brake pedal, so better to have a slight air gap than a slight preload. Wilwood MC's are especially sensitive to MC piston preload...

Let us all know what you find!

[Hydratech®]

Looking at your pictures again, I see another problem - you have a PS filter installed. That's great, but these can cause a restriction to flow, which can back pressure the low pressure return lines you have plumbed at the steering gear (before the filter). If you want to give it a shot, you could install a T fitting AFTER the PS filter - between the filter and the pump's return line nipple - that may also clear up your issue without having to install the additional return line connection on your PS pump housing. Do also note that Borgeson has PS pumps that have two low pressure return line nipples for use with hydroboost:

https://www.borgeson.com/xcart/produ...productid=1716

Their flow rates are a bit high though, as we prefer to see 2.2 - 2.6 GPM (gallons per minute)

[eze_1978]

Thanks for looking into all of that. I’ll try a few of the easy things first and see if it clear up my issue.

[Hydratech®]

The simplest test to do would be to temporarily install washers of equal thickness underneath each MC mounting bolt ear (shimming the MC further out by the thickness of the washers). If your issues clear up, it would point to excessive MC piston preload (as CPP supplies units with the GM late model MC rods that are .060" longer than appropriate for use with most older / aftermarket MC designs), or can indicate that your Y fitting arrangement is as discussed above.

Ditching the hydroboost and going to manual? You will end up having a much cleaner installed appearance of just a MC bolted to the firewall, but will have to run a small bore 7/8" MC and get used to looooong pedal travel and muuuuuuch higher pedal effort to make it stop.

[ponchoblue]

i had the same problem i removed the cooler i had and put a Y fitting in instead of a T fitting and problem solved i'd like to put the cooler back in to see what was the cause the T or the cooler

[eze_1978]

I don’t think the issue was the Y fitting, prior to me changing out the power steering pump it had a T fitting and was doing the same thing. I may not get a chance to work on this issues for a little while. I just had surgery and the. After I’m recover we are going to move to Florida. So hopefully I’ll get into it this summer.

[Hotwire]

Good luck with the recovery man. If it was a substantial surgery get Ensures (The chocolate ensures are the best, get them ice cold and chug them (one every morning)) and a good one a day vitamin. Your body needs fuel to heal and the foods we eat nowadays don't contain the nutrients needed. I use GNC Megaman vitamins, they're stupid rich in everything needed. That advice comes from the top surgical oncologist at Wake Forest Baptist Medical in Winston Salem, NC. Dude has had me opened numerous times and I bounce back great.

As for the car, how old is your rear rubber line from the frame to rear?

[eze_1978]

Good luck with the recovery man. If it was a substantial surgery get Ensures (The chocolate ensures are the best, get them ice cold and chug them (one every morning)) and a good one a day vitamin. Your body needs fuel to heal and the foods we eat nowadays don't contain the nutrients needed. I use GNC Megaman vitamins, they're stupid rich in everything needed. That advice comes from the top surgical oncologist at Wake Forest Baptist Medical in Winston Salem, NC. Dude has had me opened numerous times and I bounce back great.

As for the car, how old is your rear rubber line from the frame to rear?

Thanks it was a pretty big surgery, but doing well. The car has new brake line. Just replaced when the rear end was replaced.