Hydro boost brakes awful sound after finishing motor swap

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Ryanbrown36

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I have just completed a Oldsmobile diesel to sbc 355 swap and on my first start every sounded great but the first time I pushed my brakes in it make a grinding noise, and would go away when I let off, I’ve had the truck running about 10 times since then and would come on randomly at idle, now comes on about 5 seconds after the truck starts, the brakes and power steering still work and the fluid is full, anyone have any ideas?
 
PrairieDrifter

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Have you tried bleeding it at all? Just finished as in never driven or really ran? Sounds like air in the system. I'm not fluent in the hyrdoboosts though.
 
legopnuematic

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My hydro boost experience begins and ends with my Dodge, but I believe the systems are reasonably similar. They both use Saginaw pumps and steering gear, the hydro boost units themselves might even interchange (to some extent).

Anyways, mine took quite a bit to get it bled out, lots of turning the wheel lock to lock (in the air), pumping the brake pedal while running. Checking and adding fluid as needed.
 
Ryanbrown36

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PrairieDrifter said:
Have you tried bleeding it at all? Just finished as in never driven or really ran? Sounds like air in the system. I'm not fluent in the hyrdoboosts though.
Click to expand...
I haven’t tried yet, the truck was running with the diesel and everything worked properly until I did the swap so air would definitely make sense, I’m going to bleed it and see what happens, I just didn’t think air would produce that much noise but starting to seem like that’s what it is
 
Ryanbrown36

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legopnuematic said:
My hydro boost experience begins and ends with my Dodge, but I believe the systems are reasonably similar. They both use Saginaw pumps and steering gear, the hydro boost units themselves might even interchange (to some extent).

Anyways, mine took quite a bit to get it bled out, lots of turning the wheel lock to lock (in the air), pumping the brake pedal while running. Checking and adding fluid as needed.
Click to expand...
Thank you, will try this tomorrow when I’m off school
 
PrairieDrifter

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Ryanbrown36 said:
I haven’t tried yet, the truck was running with the diesel and everything worked properly until I did the swap so air would definitely make sense, I’m going to bleed it and see what happens, I just didn’t think air would produce that much noise but starting to seem like that’s what it is
Click to expand...
A "dry" fluid pump will make very many noises. Pretty loud usually too. Haven't you heard all of the 90's-2000's fords whining everywhere they go? lolol
 
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I am troubleshooting mine for the same thing. Replaced the hydrbooster, all lines, power steering pump, and master cylinder. Spent hours upon hours bleeding and still does the same thing.
 
Ryanbrown36

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jwconnelly said:
I am troubleshooting mine for the same thing. Replaced the hydrbooster, all lines, power steering pump, and master cylinder. Spent hours upon hours bleeding and still does the same thing.
Click to expand...
I didn't get around to doing a proper bleed tonight but while messing with the carb and had it running for a while I took the cap off for about a minute and forgot about it totally, but now thinking back the sound went away. not sure how long it took to go away but it’s not there currently.
 
Ryanbrown36

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jwconnelly said:
I am troubleshooting mine for the same thing. Replaced the hydrbooster, all lines, power steering pump, and master cylinder. Spent hours upon hours bleeding and still does the same thing.
Click to expand...
Is yours almost a grinding noise or a whistle?
 
K5 Blazer

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I installed a hydroboost on my 1973 K5 Blazer while doing a LS swap. First I jacked up the front end and with the motor running, went lock to lock about 10 times.That purged a majority of the air.
 
Ryanbrown36

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K5 Blazer said:
I installed a hydroboost on my 1973 K5 Blazer while doing a LS swap. First I jacked up the front end and with the motor running, went lock to lock about 10 times.That purged a majority of the air.
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Oh ok, mine only ever had one line off so wasn’t much air. Mine was almost a grinding noise but slowly went to a whistle and now nothing. But I assume I didn’t have much air in the system which is probably why it was so easy to bleed
 
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Mine is a loud squealing when steering hits the stops. Same when you push hard on the brakes.
 
PrairieDrifter

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K5 Blazer

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Hopefully with the air purged, you are good to go. I differently like the feel of the hydroboost versus vacuum.
 
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