Somebody please STOP me! :) (Brake question please...57 Hornet)

SkyDad

Whelp, 4 months into my 57 Hornet and I got the engine running like a top. Woo hoo! Is there any greater sound than hearing and feeling the car turn over and come back to life?! I had the entire brake system redone while working on the engine...cylinders, lines, master/booster rebuilt by Ed Strain, Inc (power brakes), pads, sending unit, bearings, etc. Now that I was able to run the car and bleed the brakes, I cannot seem to keep pressure in the system. The brake pedal when pumped will stop the car, but you can slowly just push the brake pedal all the way to the floor and the brakes no longer work. A few more pumps of the pedal (after it returns from the floor) and you can apply some brakes again.

There are no visible leaks anywhere. My mechanic thinks it is the master/booster, but I had that completely rebuilt and it looked better than new when it was installed. Ed Strain Inc did advise to only use DOT 3 Brake Fluid in the master but I was strongly advised to use DOT 5 instead since the new sending unit would have fewer long term issues. Could the DOT 5 versus the DOT 3 have caused an issue this quickly after putting the fluid in the system? (Only a few days ago). I'm baffled. I plan on removing the master/booster tomorrow but curious if anyone else has had issues like this or knows enough about the DOT 3 vs 5 impacts to the master/booster itself? I personally don't think it has anything to do with the brake fluid, but could use any other troubleshooting expertise. Thanks much in advance! Mike

Geoff

 It won't be the brake fluid. Most likely a faulty cup in  the Master cylinder.

Geoff 

SkyDad

I found the pic I took when the master/booster was returned from Ed Strain Inc... I do not remember a "Spring" involved when installing this...oh crud...

SkyDad

The car never ran before I removed the master/booster so I had it rebuilt completely and couldn't test it until I had the car running (just a few days ago).

Since I plan on removing it tomorrow, what is your advice on what to do now? Could I have done more significant damage than just having the master/booster rebuilt? Do you believe I need to have the master/booster rebuilt again? I am still not sure the DOT 5 caused any of these issues. It was only in the car for a few days and the fluid had been sitting in a box for several weeks before it was used. Several different Hornet owners advised me to use the DOT 5 because of the issues with the brake light switches. If I have the master/booster rebuilt, should I just use the DOT 3 that the rebuilder recommended or the DOT 4 LMA glycol you are suggesting?

I'm concerned with the extent of any damage I may have caused.

SkyDad

No sir. The mechanic working on my car had the cylinder in the car for a few months with no fluid in it at all. I would say it has been less than a week since the DOT 5 was introduced to the master or brake lines. I am quite certain there was no "bench bleed". Is it possible to remove the master/booster and have him perform the bench bleed and start the bleeding process over again? (I appreciate your help by the way...I'm reading every article I can find on this topic. Thank you.)

SkyDad

Thank you very much, Ken. I will give it a try and update tomorrow with "hopeful" good news.

SkyDad

Whelp...no success with the bleed. The mechanic said he did initially bleed the master before starting all of the lines. We even tried re-bleeding the entire system...same results. I removed the master/booster and I am going to send back to Ed Strain Inc for a closer internal look. Hopefully, it is something as simple as a faulty cup.

SkyDad

Amen! Thanks Ken.

SkyDad

I think I found the issue. When I removed the cap for the master reservoir, I noticed the little pin with the spring seems bent. Does anyone know if this rod should be perfectly straight? I am assuming it should be as the spring seems to create the seal for pressure to me. I have the unit all packaged up at this point to return it, but I am hopeful if this piece is the culprit that it is a relative easy (and inexpensive) fix.

SkyDad

Great pic to keep for future reference, thank you Ken! (Also a great reminder that I am in over my head on this one. yep...Ed Strain here I come. Have a Hudsonly Sunday!

SkyDad

Whelp...I received the master/booster back today and spoke with Ed Strain. Sure enough, it was the compensating valve. Ed replaced the bad valve and returned it. (He does fantastic work, by the way.) Before I reinstall the unit, I want to revisit the DOT Brake fluid question. Ken, I know your thoughts on the DOT 5 fluid, and I appreciate your feedback. Does anyone have a different opinion about DOT 3, 4 or 5. The unit says use DOT 3 only, but I received advice from several Hornet owners that swear by the DOT 5 and have not had any issues with it. I'm a bit gun shy on what DOT to use for this redo? I'm open to any opinions and will hopefully make the best
decision based on all input. Thanks again everyone. Enjoy the day.

Lee ODell

SkyDad
Just a suggestion. Visit all the New Car Dealers in your area. Take the time to ask each service manager what brake fluid is used by the dealership.

Something seldom mentioned is what a brake instructor told me, that DOT 4 over time will become DOT 3.

What ever brake fluid you choose will stop your car. They all work and they all have experienced failures. Proper preparation is essential.

That sums up my 50+ years in the brake repair business. Customer gets what he wants.

Lee O'Dell

onerare39

SkyDad,

I would ask Ed why he specifically says to use DOT 3.  There must be some reason that he is very specific about that.

John