Prefectca wrote:

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I remember in about 1977 I changed one on a 1973 Caprice and the new one from the dealer was brass and the original was cast iron (or steel, it was rusty). The replacement part fit fine.

Paul

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 Paul, the ones i am seeing out there all seem to be brass. The one on my car is so covered in 1974 under coat that i can not tell if it is steel or brass at this point but i know it has never been changed. 

4SPEED427 wrote:

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And by the way, do you know how to tell the difference between std and hd brakes on your car? 11" or 12" drums in the back?

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 Carl, my wagon has the HD brakes on it. Thank you very much for all this information. Greatly appreciated. 

long stroke wrote:

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4SPEED427 wrote:

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And by the way, do you know how to tell the difference between std and hd brakes on your car? 11" or 12" drums in the back?

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 Carl, my wagon has the HD brakes on it. Thank you very much for all this information. Greatly appreciated. 

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 Ok good. Sorry if I kind of stated the obvious there, I never know if guys know stuff like this about their cars or not! Although on here I shouldn't be surprised if guys know their stuff...

I know you know your stuff Cam. I'm just relaying the information in the GM parts book. For those who don't know their models -35 and -45 are wagons. The book lists either.

Interesting!

gparis7 wrote:

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john Stuart Power Brakes in Hamilton will rebuild your original. I had two 68-70 hold-off valves done there and they turned out well. 

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 John, this is good to know and i know they are reputable. Thanks.

George! Check those soft brake lines! I'll bet that is what is going on. They are probably coming apart internally. Check them!

long stroke wrote:

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JC2+2 wrote:

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George. What is actually happening with your valve? Ive never really heard of one act up. Pressure difference causes them to trip caused by a leak or bad master cylinder. And if it seized youd never know it until you lost pressure somewhere and it didnt trip. Just curious on the symptoms.

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 John, the very lightest touch to the brakes causes the rear wheels to lock up when driving slow to moderate speeds. I have removed the wheels and checked my brakes and there is no brake fluid leakage on the linings. Also there is no leakage of any differential oil on the linings as well. I know that this is a symptom of leakage usually but there is no leakage what so ever. I replaced the master cylinder about twenty years ago and it presently is not losing or leaking brake fluid in any way. The interesting thing though is that after driving it for 10 to 15 minutes and after using the brakes a few times it stops doing the rear brake grab. I know cars but i am always willing to learn more. I do not know what else could be wrong other than the brake combination valve (proportioning valve). I am open to any and all opinions on this matter. I appreciate any help from the C.P. brotherhood. Cheers. 

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 I had an S10 act exactly the same way years ago. Crazy as it sounds, all it needed was to remove the rear drums and give both the drums and the brake assembly including the shoes a thorough cleaning, problem solved. It's worth a try, nothing to lose but time and these days almost all of us have more of that than we need! If you do it, REALLY clean it up good, brake clean on the shoes, etc. 

JC2+2 wrote:

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Sounds you could be loosing pressure to the front. Your master cylinder doesnt have to leak externally to be bad. It could be bypassing internally. Does your pedal change any when this happens?

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 John, there is no change to the pedal what so ever, it is normal. Thanks.

4SPEED427 wrote:

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long stroke wrote:

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JC2+2 wrote:

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George. What is actually happening with your valve? Ive never really heard of one act up. Pressure difference causes them to trip caused by a leak or bad master cylinder. And if it seized youd never know it until you lost pressure somewhere and it didnt trip. Just curious on the symptoms.

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 John, the very lightest touch to the brakes causes the rear wheels to lock up when driving slow to moderate speeds. I have removed the wheels and checked my brakes and there is no brake fluid leakage on the linings. Also there is no leakage of any differential oil on the linings as well. I know that this is a symptom of leakage usually but there is no leakage what so ever. I replaced the master cylinder about twenty years ago and it presently is not losing or leaking brake fluid in any way. The interesting thing though is that after driving it for 10 to 15 minutes and after using the brakes a few times it stops doing the rear brake grab. I know cars but i am always willing to learn more. I do not know what else could be wrong other than the brake combination valve (proportioning valve). I am open to any and all opinions on this matter. I appreciate any help from the C.P. brotherhood. Cheers. 

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 I had an S10 act exactly the same way years ago. Crazy as it sounds, all it needed was to remove the rear drums and give both the drums and the brake assembly including the shoes a thorough cleaning, problem solved. It's worth a try, nothing to lose but time and these days almost all of us have more of that than we need! If you do it, REALLY clean it up good, brake clean on the shoes, etc. 

 

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 Carl, i have already done that. I gave my drums and linings a real good bath with brake cleaner on all four wheels. Thanks.