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VK sedan braking issues

186565

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I am in the process of fixing up a VK (6 cyl Black motor) for my son and am having trouble with the brakes. I have replaced the rear wheel cylinders and rebuilt the front calipers and master cylinder (also tried a spare I have) but still have poor braking. About the only thing I haven't changed is the brake booster. I have also just rebuilt the carby (varajet - soon to be weber). There appears to be some vaccum assist from the booster but I suspect it has a slow internal leak but I havent ruled out low manifold vacuum as the problem. VK brake booster are few and far between and I don't want to pay 100 - 150 for a booster that may be in as poor a condition as the one I have and may not solve the problem.

Are there any later model boosters ( vl,vn,vp,vr,vs) that require little to none modification to fit ?

 

VK SL 3800

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Do your brakes pull to one side and do the fronts lock up if you press hard enough? You could replace the master cyl if you havent already and replace your brake hoses too if they look old, how easily did the brakes bleed? Whats the pedal feel like?
 

Lewie

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Very thirsty VT & VH project under way! YAY!!
There are plenty of threads on here on upgrading your brakes. I fitted a VS booster to my VH without modification. The VT master cylinder required a different flare on the end of the lines but that wasn't too hard. You might want to consider upgrading if you are going to replace things anyway.

For info: http://forums.justcommodores.com.au/vb-vk-holden-commodore-1978-1985/100012-vh-brake-upgrade.html

I'm unsure if you need to replace the calipers with this mod if you do go down this road.

Food for thought.
 

VK SL 3800

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I did the above, VT brake upgrade with a VS booster, absolutely fantastic brakes, highly recommend it but if you do do that you have to convert the rears to disc as well, which isnt too hard either.
 

vktorana

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Just wanna say........I had those same mags on my first vk! Sweet as lol. Only thing I got from that old girl now. Yea def got the upgrade spesh for ya son. Money be worth the piece of mind. Knowing the brakes will work if he needs em!
 

186565

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After some research and some more diagnosis I have solved the problem. The check valve on the vacuum hose was a bit dodgy and the vacuum hose had perished internally at the manifold end and had nearly blocked the hose. I was still getting some vacuum so I thought I had enough vacuum to run the brakes and it appeared that the booster was partially working. When I replaced the hose and cleaned out the valve (new one on order) the difference in the braking was profound. The old beast now stops on a dime. So thanx to all who offered advice and I may still look into the upgrade to later model brakes. I have always been impressed at how well my everyday ride (vs) stops. Thanks all. ;))
 

VK SL 3800

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What diff do you have under the back, if its a later VK it will have a borgwarner brand salisbury. the same as VN- onwards commys. So disc rear conversions are simple and parts are easy to get. The only bit you cant do your self is change the axle seals unless you have a press, and to do that you have to replace the rear wheel bearings as there pressed on after the seal. The bearing themselves are the same as drums but the seal is wider as the disc brake plate is wider so the seal is made wider to line up if that makes sense. It makes more sense when you pull it apart and have it in front of you :D
 
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