hello everyone i have the hydroboost brake system and have some problems. when i come to a stop i have all kinds of brake pressure as i sit there with my foot on the brake in drive or any gear the pedal seems to drop a little then a little more and so on and so on until i have no brakes and the pedal is on the floor. now i am going to check every thing for leaks (lines, calipers, wheel cyndlers, etc) but, i dont seem to be losing any brake fluid. the fluid level in the master cyndler is good and does not seem to change level. im going to try to bleed the brakes and see if that will help but, im not sure if thats it. i want to keep this system so i guess my question is has any one had this problem or any ideas on what it could be? do you think it could be the master cyndler? or the hydroboost brake booster? thanks in advance
losing Brake Power
- Thread starter turbogimp
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Hey John , I am having the same problem with my 85 also. The fluid level is ok but brake petal goes to floor at stop's longer than 1 minute. I had same problem about 5 year's ago. I replaced a seal inside the hydroboost about the size of a nickle. I got it from a place locally. It cost me then about $5.00 dollars for the seal. I needed the car running right away so I skipped the overhaul kit which they told me was $50.00. I will call them Monday and find out what they have available and post. Hal
thanks man. do you know if it is a pain in the butt to rebuild them personally? how long did it take you to put in the new seal? if it is easy enough i will just rebuild it other wise i will replace the seal then overhaul it a little later when i have more time. like a weekend. thanks again and please let me know.
Hey John , The brake master cylinder which is in front of the hydroboost does not have a seal in between. I called several auto part's store's and found out I could get a rebuild hydroboost for $150.00 or have my old one rebuilt for $100.00 or purchase the seal"s and rebuild it myself for around $20.00. The clutch & brake shop downtown told me that they think my mastercylinder is the culprit. Mine has never been rebuilt or replaced. The NAPA store ordered me a rebuilt for $30.00. I tore my mastercylinder & hydroboost apart last night. The mastercylinder fluid was contaminated and nasty looking. I used a friend's bleed tank when I replaced rear wheel cylinder's and I think it may have had moisture in tank. But anyway I guess I will put the new seal's in the hydroboost since I have it down. You might want to try just replacing your mastercylinder. Hal
what store are you getting the seals for the hydroboost from? NAPA? do you have a part number for the seals? autozone told me $120 for the reman hydroboost unit but, didn't have a seal kit for it. yeah my brake fluid is like black so i would not be suprised if the master cylinder is going. are you going to use DOT 3 brake fluid or some thing better? well thanks for the help and please let me know where you get these seals from. also how it turns out. thanks again.
Hey John, The place I got the seals from is called Tulsa Brake & Clutch. I noticed that they have no part #s on any of the seal's.If you want I can try and get you a set. It might be next week though before I get back down there. I will use Dot 3 for the brake fluid. I bet my problem is my master cylinder. The cups were pretty worn. Hal
Guys, relax. It is completely normal for the pedal to drop at a stop light. You see, Hydroboost is driven off of the power steering pump. When it idles, pressure drops along with your pedal. Initially, It may not do this, but as time goes on, it will. As engine speeds increase, so does pressure.
It does depend on how far the pedal drops, though. Alittle bit is ok, but if it goes to the floor, then suspect a bad primary piston seal in the master cylinder.
Hope this helps.
It does depend on how far the pedal drops, though. Alittle bit is ok, but if it goes to the floor, then suspect a bad primary piston seal in the master cylinder.
Hope this helps.
Hey John, Glad you fixed your brake problem. I went ahead and rebuit the hydroboost while I had it apart. I am really amazed at how little effort it takes on the petal to stop. Also the petal does not drop at all when I am at red light's for an extened time. Bye Hal
No problem at all, John. Just so you understand the problem you had:
The primary piston in the master cylinder basically pushes fluid to your rear brakes. The fluid also pushes on the secondary piston to push the fluid to your front brakes. When the seal breaks or wears, it allows fluid to flow past the seal. The primary piston has a fail-safe, however, just in case. It has a rod that will push the secondary piston forward so your front brakes do the stopping.
That is why your pedal dropped at stoplights. You had enough boost to stop, but when the fluid leaked past the seal, the pedal dropped.
Again, glad I could help.
-Chris
The primary piston in the master cylinder basically pushes fluid to your rear brakes. The fluid also pushes on the secondary piston to push the fluid to your front brakes. When the seal breaks or wears, it allows fluid to flow past the seal. The primary piston has a fail-safe, however, just in case. It has a rod that will push the secondary piston forward so your front brakes do the stopping.
That is why your pedal dropped at stoplights. You had enough boost to stop, but when the fluid leaked past the seal, the pedal dropped.
Again, glad I could help.
-Chris
Mine started going bad and I also hated it when I hit a water puddle and would lose my brakes. Probably because the belt on the power steering pump would slip. I did the vacuum conversion and it wasn't that hard. That's always an option for those who can't get theirs working. The cost was fairly minimal.
