Just put a hydroboost in my 1980 C3 corvette.

I have installed Hydroboost from a 94-95 Astrovan (Refirb) with a Borgeson Box and LS1 (not sure of the GPM), its a 2004 VY Commodore Gen 3 pump. New Wilwood 260-8556-BK MC (1.125" bore) Im getting kick back and then a slow return or slow shudder return... I did have to make my own kit and get a spring (76mmx25mm), retainer made from a 41mm OD pully puller tool with 10mm ID hole and a cut down 3/8" push rod pin (77mm long) for the hydroboost since the refirb doesnt come with them..



I have used Redline power steering fluid with wheel jack up off the ground and hard turn left then right 5x with 3x brake pedal (repeated this 50x) with a further 10x with engine running. Both times the PS res lid off (with towel over the top to stop splashing)

With engine off its a nice firm push of the brake pedal and smooth release back.
With engine on its a kick back - press the pedal in, it jerks back at me and then slowly returns rest of the way or sometimes shudders back....

Currently have no brakes due to separate issues of proportioning valve float being stuck so cant just drive it around and see if it will sort itself out.

Is it possibly my PS pump not having enough flow? or the spring and retainer i had to make as the refirb HB unit didnt come with any.

Push rod was cut as per instructions and 1/4 " gap between new MC before it was tightened up.

See pictures below of install. PSP = ls1 gen 3 power steering pump
HP SB = High pressure to Steering Box
LP Red = Low pressure from Hydroboost to PS Res
LP Blue = Low pressure from Borgeson steering box to PS Res








The position of the clevis gives Around 8-10mm before bump stop
5.25" from firewall with brake no engaged
5.05" at engagement point
2.6" at max engagement (Wilwood says min 1.5" from memory")



Self made, spring seats inside the bore, has a male union tap adapter cut down to center the push pin on either end and then a 41mm washer (had to use thick pulley presser and circlip to keep it in place.

 

I have to wait to get the proportioning valve bleed tool so i can correctly bleed brakes and then be able to drive to see if this sorts itself out.

I did make sure the return lines were below the level of PS fluid at all times and even run them separate back to res just to make sure there was no back pressure

Any suggestions?

 

I see a problem right away. It's not a good idea to join the LP return from the PS and the LP from the Hydoboost with the T section shown in the photo. The hydroboost cannot tolerate any backpressure on the LP return line. One flow problem is that the PS return line has a gusher of hydraulic fluid flow when you turn the steering wheel. The hydroboost return flow is on the volume of a few tablespoons. The Saginaw power steering pump on GM cars/vans equipped with the hydroboost have two returns on the power steering pump reservoir. One for the PS, one for the hydroboost. I suggest getting a pump reservoir (the miniture shapped ham can) from a salvage yard pump or a new pump. I bought a new pump, removed the ham can reservoui and installed it on the 70. I didn't want to use the whole new pump because it had a press on pulley and the 70 has a keyed threaded pulley pulley.
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The advice not to T the PS and hydroboost return lines is based on what I've read. I haven't driven the 70 yet. The fact that GM has two return fittings on their PS pump for cars/vans equipped for the hydroboost, certainly supports this no-T advice. Nice looking engine comartment.

 

Thanks for the advice, to reduce the complication of using a Tee i have used a Y (more flow) but even then since i got these issues i separated them both. Now the Borgeson steering box goes to the res fitting and the hydroboost unit line just sits directly inside the res submersed in fluid while the car is sat in garage being tested. Even without moving the steering wheel it is giving me kick back..

All i can think is
1. faulty HB unit (but its recon from summit)
2. the spring i used and retainer is too strong/not strong enough or long or too short etc
3. my PS pump is not providing enough GPM

My brother the same day just put in a HB unit in his patrol. Uses a Tee, no issues at all, worked from the start and we bleed it the same way. His was a kit and came with the pushpin already cut to size and spring and retainer.