This will be the last question on brakes. I'm having difficulty with my brake stopping the truck. I really have to apply a lot of pressure to stop it. It's seems like the booster is not working, but it is. I'm using the disc/ disc MC from a Chevy (I know....) could it be my lines are backwards. The front line of the MC is going to the front disc brakes. The middle of MC line is going to the drums in the rear. Should it be reverses. I'm also using an adjustable proportioning valve on the rear drums. Would adjusting that make any difference?

 

Ed

This is a little tough without being there. The lines could be flipped, but the truck should still stop half decent. Whats the specific donor? VERY hard brakes is often the booster. Can you adjust the pushrod? If not, try losing those little spacer gaskets. God help you with your friend if that fixes it LOL.

I'd start from the basics. Put the truck up on stands. Try to get a clue if all the wheels are trying to brake by applying just a little pedal pressure. You'll need an assistant. Also, with the truck not running, pump the brakes until the pedal is rock hard. Keep pressure on the pedal and start the truck. The pedal should soften and head down toward the floor some within a few seconds of start-up. If you can't feel a huge difference on start-up, start looking at the booster real hard.

You should get lots of input on this one. Plenty of brake wizards on this forum.

There, that should keep you busy for a minute.

 

Dewayne, thanks for the great advice. I did take the metal gaskets out when I put the new MC on, and now put them back to see if there is any difference. I guess it could be a number of things which makes it difficult. I'm not sure what you mean by the donor? The booster appears to work, however when I apply the brakes the engine is idling rougher and it actually makes a sound like an exhaust leak? It did that before the brake conversion and the brakes worked fine. I've replaced everything else, may as well be the booster now. Smile! I was concerned that maybe the lines were reversed going to the MC? I read an article somewhere, that the person had the lines in the wrong position, once the lines were corrected, the brakes worked great again. I'm starting to understand why people leave the brakes up to the professionals. Too many variables. (don't want to start with statistics here). I have a hard pedal, it seems like I'm putting too much force on the pedal to get it to stop. I may have to fool with the proportioning valve goint to the back drum brakes. I understand it's difficult to diagnose without being here or seeing what's happening. Sure sounds like the booster to me also. Good thing is I can remove the MC without disconnecting the brake lines to remove the booster. I'll wait to hear from some of the brake wizards in here for more advice.

I took it for ride around the block a few times this morning. Sure felt good to drive it again, it's been too long.

 

"I was concerned that maybe the lines were reversed going to the MC? I read an article somewhere, that the person had the lines in the wrong position, once the lines were corrected, the brakes worked great again."

Could be Ed, but I'm not going to pretend to know what each and every system would act like in this case. The front ot rear % would likely be wrong if you flipped them. If the disc side is pushing the wheel cylinder side I can easily see a stiff pedal. I haven't been following along close enough to know exactly what you got here. Any chance a rubber line is clogged or collapsed? Or are we dealing with new stuff? By donor, I meant where did the non-Ford parts come from? Might help if we knew if we're dealing with a 73 Monte Carlo, or a 93? The r stuff is pretty similar, no matter what brand. Companies such as Bendix and Kelsay Hayes manufactured systems for numerous different makes. They weren't Ford ***** like you and me.

 

If your MC has two different size reservoirs the larger should be plumbed to the front. Usually the rear reservoir is the larger. If you added residual (check valves) make certain they are installed with the flow in the correct orientation. It sounds more like you have a booster or hose problem. Applying the brakes should not have an effect on how your engine runs unless you have a vacuum leak when applying the brakes. I would check the line to the booster and the booster itself. Maybe when you have some help and its on the jack stands you can have the brakes applied and you can listen to determine where the noise like the exhaust leak is happening.

 

I replaced the gaskets between the MC and booster. The variation in idle is now much better (maybe the rod was too long?) I haven't driven it yet to see if anything is different. The MC is for Disc/Disc, Its from a Chevy and I assume a newer type. The reservoirs are of equal size. As for vacuum, I have new rubber and am running 3/8" aluminum hard line to the booster. (no leaks). All the hard lines were replaced. No residuals valves were used, only a proportioning (adjustable) one in the line going to the drum brakes. (Booster is mounted on the firewall). I noticed the front fitting on the MC uses a larger fitting than the middle fitting. MIddle fitting is standard 3/16" fitting and the front one is slightly larger but still uses the 3/16" line. I'm curious if the MC has a proportioning valve or residual valve built in on the front fitting (that's the one going to the brakes. The brake line hoses are all stainless braided lines. All the lines are new and clear. Maybe the brakes shoes need to be worn in? This is hard to diagnose????? I appreciate the suggestions since I'm pretty clueless when it comes to hydraulics and brakes.

 

Not to be petty, but what do you mean by "middle" port? It may be in the middle of the MC? but it's for the rear cylinder, right? There isn't a third port, is there? I think some ABS-equipped MC's have 3 ports ( 3rd is a return or something).

 

Albuq- No, the middle port meaning the second reservoir. There aren't 3 ports on this MC. Front brake line is going to the first fitting or first reservoir (front of MC) The rear brake line connects to next fitting which is the rear reservoir. The rear line is going to the drum brakes at the rear of the truck. My brake light switch and proportioning valve are on this line also. Sorry I didn't explain it better. I really should post some pics.

 

Sounds like your booster isn't working. There is an opening on the back where air gets in, sometimes with a felt filter; is it unobstructed? You didn't mention a check valve in the vacuum line, are you using one and know that it's not backwards? (you can't reverse most of them)

 

I've got a check valve in the line going to the booster. It's an aluminum check valve that splices into the line. I checked it out and it's functioning correctly. You can have suction, but won't allow you to blow air in. Not sure what you mean about the opening on the back where air gets in? Inside the firewall near the pedal/ rod? unobstructed? Where do you look for that or check for?

 

You mentioned the engine changing ilde and a hissing when the brakes are applied. Classic symptoms of a torn diaphragm in the booster. When you apply the brakes you open up the tear in the diaphragm creating the vacuum leak. I'd look hard at the booster.
Years ago you used to be able to rebuild the boosters, you could pick up a new diaphragm from the dealer for pretty cheap. Like most other things they are probably not rebuildable anymore.

Good luck
Bobby