Me and wanda are having brake issues. Could use some advise.

Not sure if I missed it but is the vacuum fluctuating as it idles? That can be a sign of manifold leak if because vacuum would change when the cylinder with the leak fires. Could also be a sign of a flat cam lobe, but that won't affect your brakes.

Hi guys. Sorry im forst answering now. But im in Europe so the time difference is present.

There is no vaporlock canister anymore. My current setup is a new gm performance 290 horse 350 with edelbrock intake and edelbrock 600 carb. Im running Stock cast iron manifolds with the airholes blocked. They where blocked already when it Came to Denmark in 75.
Im not a fan of headders because of the leaking and noise i experienced. I have a set of stainless ramhorns i was going to install some day.
Everything is new including the hei dissy, wires and so on.
When i connect the vacum gauge it fluctuates a little in idle, not crazy but a little. That combined with the brakes loosing vacum after 3 push and the idle, makes me. Belive the vacum leak teory.

It idles in gear now ,and dosent try and Creep forward or stalls, as i did before is started playing with timing and carb adjust. However it does not have as smooth an idle in gear as i have seen others have.
But other than that is runs and pulls strong. And has plenty of power. And fires right up with a Nice idle. Only idle in gear has been a little problematic.

Only Real annoying symptom is the brake issue.

Im running a 700r4 and have just redone my rear with brand new 3:73 gears. I have changed alot of brake Lines and the brake Block on the frame. And made sure everything has been bleed and is in working order. So im back to the vacum issue as the only possible ansvar.

This weekend im going to try and locate the possible leak with brakecleaner and some leak tester. En of the mechanics at work gave me some waterbased leaktester that should be better near hot things.

Anyway im going to give it a shot and see what i will find. If it require for me to get new manifold gaskets and redo it, i will do that when time permits.

I also need to brake my new rear in and see if i did it correct. I hope did and it dosent make noise or whatever.

Ill get back with what i find. Thank you for all your help. Im happy i can always get good advise in here. Henrik.

I'm just going to throw this out there. Don't discount the cam as being a little big. Its a 222/222 @.050 cam in a low compression engine. I think if you look up reviews of that engine you'll find the same conditions you are experiencing. That doesnt mean you can't search for a leak, but it may be normal for that engine.

Don't forget the little piece of hose down at the vacuum modulator on the transmission. Maybe loose or a little slice in it. I've got that same cam It idles pretty good and no loss of pedal action one way or the other.

Ok i see what you mean. Ill leak test it this saturday and see what i will find.
I dont have a vacum modulator on the trans anymore, cause i changed it to a 700r4. But i have a Block off plate for the old style choke that could be a problem, and a myriade of other places to look.

So saturday i will see what comes up. And i will return with my findings. Thanks for all your help all of you. Regards Henrik.

If i dont find a leak and it is just because the cam is a little Big. Would a vacum reservoir be a good idea? It would not be a large problem to get it and install. I thought about it after Reading some use it with Big cam engines with poor vacum issues. What say the experts?

Regarding a vacuum reservoir, my Monte Carlo came from the factory with air conditioning (A/C) and has a spherical reservoir that looks like this…


It appears that your car doesn't have A/C so you likely don't have that reservoir.

There were lots of things added to, and upgraded on, cars that were ordered with A/C, for instance a better radiator, a fan clutch, a vacuum operated shut-off valve to prevent hot coolant from going to the heater core, more powerful alternator, and a return fuel line from the fuel pump to the fuel tank to prevent vapor-lock. You probably don't have any of that stuff but, then again, you have less stuff that can fail and needs repair.

It doesn't hurt to add a vacuum reservoir. They're inexpensive and easy to install. If that solves your brake boster problem then you're done and don't have to worry about messing with removing/reinstalling (RR) the intake manifold.

Regarding camshaft concerns, I have a CompCam 12-422-8 roller cam with 218° duration at 050 inch lift on the intake, and 224° on the exhaust. The only time I have power-brake issues is when I press the brake pedal repeatedly in quick succession at low idle (650-700 RPM according to the factory tach in the dash) like while the engine is idling and I'm running the A/C. When that happens, I either wait a few moments for the engine to develop vacuum, I hold the brake pedal down with my left foot and gently raise the RPM to just over 1000 for a moment, or I put the transmission in neutral and give it one good rev then put it back into gear.

I Read through your post, 15~18" vacuum is plenty to operate the brake booster. If i'm not mistaken, GM says a minimum of 14" for proper operation.

My '73 only has 11" at idle, even less when it's in gear. The pedal is a little hard but the brakes are excellent. The pedal is not hard enough to warrant a canister or external pump. I'm running the stock dual diaphragm booster which was standard on '74 ~up cars. Some of the 73 cars had a single diaphragm booster.

When I restored my 77 El Camino a couple years ago, I had similar brake issues. When I first got it running I had a very hard brake pedal. Just like it would feel with the engine off. Then I tested the check valve at the brake booster and it was not functioning at all, like completely closed. Replaced the check valve with another known good one, and fixed the problem. Never seen this before or since.

I have tried numerus check walves and different boosters. I have the same problem you described just now. The brakes work exelent until im parking and use the brakes 3-4 times at idle. Then the pedal gets harder like wacum is going away. Just a small amount of trottle and the brakes are back to normal.

Unfortunatly Many of the parts that are availeble here in Europe, are not wery good and Many times i have experienced getting faulty parts right out the box. I currently have a 11 inch booster original to camaro and its the best one yet. And my brakes work just fine driving around. However its annoying that i have to be prepared to Press harder when i park.

This weekend im going to leak test it and change the booster hose and check valve if i dont find a leak. If this do not work. I will install a vacum reservoir and see how that works, and Call it a day if im happy with it. The car runs Nice now and it is the only thing that annoying me.

I Got a restored original booster the first time i changed it, and i almost hit the Wall in the garage. Because it was not working at all. I warrentied it and Got another, still no good. So i bought one at summit and finally i have decent brakes. Although my Buddys 77 elco has better ones. His are super Nice and feels almost like a new car.

Same story with alot of other parts including check valses, fuelpumps and even a waterpump that Dell apart and took out my radiator and fan.

Im really frustrated with alot of the parts availeble. But i dont have a budget for hi dollar parts, cause it cost an arm and a leg to import parts from us to Denmark. Most cases it makes the part cost 3 times as much as you pay for them i us.

Anyway my gadeplan is to look it over this weekend and see what ill find. Maybe it is just my new booster that has a fault again even though it seems to work ok, exept when i use the brakes repeatedly.

Ill g back to you all with what i find when i find the solution. Im happy you all are helping me find a solution. Thank you regards henrik

Hs1973 wrote:Many times i have experienced getting faulty parts right out the box. … Im really frustrated with alot of the parts availeble.

I completely understand and share your frustration regarding faulty and defective parts as I mentioned in a post I made regarding rebuilt carburetors. Experiences such as these have forced me to become a self-sufficient expert on all things 1974 Monte Carlo (and 1968 Cadillac). In my garage, I have all sorts of spare parts "in stock" so to speak. Things like an extra alternator, power steering pump, hoses, belts, etc. I've also stocked up on rebuild kits for things like brake boosters, master cylinders, calipers, wheel cylinders, etc. The kits are less bulky and take up less space than the actual parts. The flip side of that is I've had to accumulate an assortment of special tools in order to rebuild the parts. Fortunately those tools are a one-time expense. Furthermore, the Chevrolet service manual and overhaul manual have all the information needed to do the actual work.

My advise to you is, after you're done tearing the hair out of your head from frustration (I've done that many times myself), turn that frustration into determination. You said you've received some defective parts. Well, those parts don't work, so, disassemble them and try to rebuild them yourself. What's the worst that can happen; the parts still don't work? What will likely happen is, because we hobbyists are methodical, meticulous, and thorough, the part will end up working perfectly. I used that approach on the first master cylinder I rebuilt. I bought it from a parts store, installed it, and it didn't work. Following the service manual, I took it appart and discovered that the "professional" rebuilder used the wrong seals when they reassembled it.   I got a correct rebuild kit with the right seals, reassembled it, and it worked perfect.

Dealing with the added challenge of being in Denmark, having to pay extra for shipping parts from the U.S., is far from enviable yet very admirable. Since rebuild kits are smaller and, more importantly, much lighter than the parts they're meant to repair, I would expect the cost of shipping them to be less expensive.

You are right. I Think i Might try and take the booster apart some day and try and see why it dont work. However i still dont understand how someone will ise time and money making or rebuilding parts, and then they dont work as advetised.

I mean i would gladly pay a little more if the parts where a little better.

Im not about to give up. I will make it work as i want it to, but im a little frustrated after trying to find a fault for a year now. But maybe it is just the Way this car is. And if i dont find a leak then i will install a reservoir and hope it helps. After that i Might consider installing something different. We Shall see. Ill return tomorrow with my findings. Thanks again for your time. Henrik.

So here is an Update on what i Found today. I did find a leak. The fitting i put in the manifold for the brake booster was leaking and somehow loose. I fixed that and now the booster is working every time even when i Press the brakes repeatedly.

However the brakes still had no bite and would not lock up the front tires. So i bleed all 4 corners again and adjustet the pushrod a little longer at the brake pedal.

So now it feels ok and like it has bite when brakes are applied. However for some reason they feel like they have more bite to them when i back up and hit the brakes. Going forward and braking is ok, but backing up and braking seems alot better???? Why i dont know maybe i just need to drive it and see how it feels.

I cant however drivende legally until march 15 due to insurence rules. But i did a little trip around the corner from where i live.

Wich brings me to my next question. I installed a new set of gears and followed instruktions on setup. And on my little trip ( maybe a mile) i thought i heard a faint noise coasting, like gears running. Not a bad or loud in any Way. I Might not have noticed if the radio had been on.
Is this ok if it comes from the rear? its a pretty loud exhaust i have so its hard to tell. Could it be the new gears need to break in to each other? Or did i screw up on setup?
The gear noise i heard, is so small most would not notice. But i am allergic to all new noises i dont remember hearing before. And of course i was listening Real close too.

Should i drive it some more and see if it goes away, or should i start over on setup???? Wich id rather not, since it is a bitch doing, pardon my french.

Advise is more than welcome. Regards Henrik.

Adding a vacuum canister will give you "about" and extra 2 pumps of the pedal. Its essentially just making the brake booster volume a bit bigger. Canisters are ok but Id lean towards a pump that way you have no brake issues. Vacuum pumps come in belt driven and electric models.

Hi Joe. I was hoping to hear from you. I solved the missing vacum issue. It was a vacum leak at the booster fitting in the manifold. So a canister is not necessery now. However im still fighting the lack of bite Feeling.

Im guessing it has to do with the pushrod length somehow. I put in a booster from a camaro and i Think that Might be part of it. I adjustet the lenght and i did help a lot. So it is much better. However i Think i still need to bleed the front brakes again. Ill mess more with it when i can drive it legally.

My rearend seems fine after gear change and setup. But i am not sure it is, since im pretty sure i heard a sound coasting. It sounds like a gear set working if that makes sense. Or something like a bearing noise. It is so faint i was not even sure it is there. I would have missed it if the radio had been on.

Did i do The setup Wrong ? Or is it only the gears Being broken in to each other. Do i just drive it some more and be Aware of it or do i need to take it appart again???????

It is so faint and does not sound anything like a howl or bad noise just like the gears on a bicycle rotating kind off. I cant hear anything when im on the trottle a bit, cause my car is kind off loud he he.

Great you found a vacuum leak and corrected it. I dont think anyone will be able to diagnose your rear axle without actually hearing it. Possibly the person who set up the gears might know if they were set a little too much or little in either direction for proper tooth mesh. And if the pinion bearing preload is correct.

I did the setup myself studying instruktions and so on. I did one previusly that worked fine. They where however a used set. This time a bought a new gear set from richmond and i used alot of time setting it up Being super nerd about it. I only Drove it about a mile and of course i was nervous if it was silent or howling. It was silent but i seemed to notice a wery small amount of sound, like a gearset on a bicycle working or a bearing whirring. It was so faint i almost did not hear it so im thinking it is the gearset getting used to each other, in lack of better terms.
Or is it just something in my head and i should just break it in and see if it keeps still or starts to be noisy when i drive it more. I cant legally drive it for 10 more days.
I feel im out on a limb and i dont know exactly what im doing. Im not a mechanic but know how to make things look pretty. I guess im starting to get tired of wrenching all the time and just want to drive it for a summer without worrying about things not working right.

Would you drive it more and see if the sound is getting louder( or even there, most would not hear it i Think)

Or take it to a Pro and have it redone for safety before i break something. Second time i drove it today it seemed it was gone, but i only Got up to around 40 mph.

I know i sound stupid and ask alot of questions. But i hate when i dont know what im doing and im trying Real hard to learn.

Questions are always good. Thats how we share information. Since the sound seemed gone, Id focus on other things until you can drive it more and have more time for it.

You are right. Im obsessing for no reason. I guess im somehow just afraid i have to use money and time doing the rear again, or paying someone to do it for me. I dont have alot of coin for hobby cars, so maybe thats why i Think i hear stuff.

I feel pretty stupid not double chekking myself, and Found that leak before. But im happy i can always get you guys to point me in the right direction. Thank you for al your help. Ill drive it some more and see how she behaves. Thank you all. Ill be back with an Update when i have driven it more.

No problem at all. Sometimes its good to just talk it through. Usually you get an idea that works out for you.

Again you are right. Sometimes it is good to talk with someone that knows more. Thanks and ill be back with more questions sooner or later.

Hs1973 wrote:So here is an Update on what i Found today. I did find a leak. The fitting i put in the manifold for the brake booster was leaking and somehow loose. I fixed that and now the booster is working every time even when i Press the brakes repeatedly.

Woohoo    

Hs1973 wrote:However the brakes still had no bite and would not lock up the front tires. So i bleed all 4 corners again and adjustet the pushrod a little longer at the brake pedal.

So now it feels ok and like it has bite when brakes are applied. However for some reason they feel like they have more bite to them when i back up and hit the brakes. Going forward and braking is ok, but backing up and braking seems alot better???? Why i dont know maybe i just need to drive it and see how it feels.

I'm assuming you fully bench bled the master cylinder before installing it. One thing I've learned over the decades is bubbles in brake lines can be stubborn and elusive at times thus making their removal troublesome. I've used a leather mallet to rap on the front calipers to help dislodge a stubborn bubble. One of the most troublesome places for me has been where the brake lines connect to the master cylinder. I've had great success clearing out a stubborn bubble using the following method; I remove the cover from the master cylinder then put a large C-clamp on the caliper to compress the piston into the caliper, as though I were going to remove the caliper and brake pads, thus forcing the brake fluid back into the master cylinder.

As you likely know, the way the brakes function are the rear brakes engage first but only a little, then the front brakes engage. You also likely know that the rear brake self-adjust when applying the brakes while driving in reverse.

Hi zucchi. I am pretty sure i have more air trapped. I installed a new brake walve Down on the frame. And i know from past experience air can be hard to get out. I did not know the rear brakes adjust in reverse. But i do now. I thought i was done with air, because the pedal felt pretty hard and ok, but now im sure there is more air in the front system.

The little button on the brake valve should also be pressed simultaniusly while bleeding right?? Or only if the valve is tripped??? ( light is not on in the dash)

The master was bench bleed prior to install. I tried to bleed the brakes myself using a airbleeder from the local autoparts store. but im sure now that i need to do it the oldschool Way Being 2 guys using the pedal. It Got better the more i bleed it, but i Think part of the problem is the airbleeder.

So im going to try doing it over the oldschool Way with my co worked mechanic. He is confident that the problem Lies in air in the lines to the front calipers.

Im sure that is also why the front brakes dont lock up.
Im no Way confident or experienced enough to diagnose mecanical problems right away. However im learning something new every time.

I feel stupid from time to time when you guys point out some things i should have thought of myself. But im happy i can find advise and get pointed in the right direction in here. And i wish i could tell you how much all of your advise actually helps.

One of the problems with owning a classic us car here in Europe, is the lack of experienced guys that know how to deal and operate on them. So i have to fight my Way trough varius problems every time. And every time i modify something it opens up a can of worms it seems.

Anyways i Thank you all for your help and i will Update with what the solution was, when it is fixed. Maybe someone Else can learn from my problems. I know i Laen something new every time i wrench on this thing. And im getting closer to it working like i always wanted it to. Looking good is one thing, working and running good is another ballgame alltogether.

So im happy i can ask all my questions in here,and who knows, maybe i will be vise enough one day to actually know a little about what im doing.

Wanda and Henrik.

It really helps to have the service manuals.

Hs1973 wrote:The little button on the brake valve should also be pressed simultaniusly while bleeding right?? Or only if the valve is tripped??? ( light is not on in the dash)

I think you're speaking about the proportioning valve. That's supposed to regulate the hydraulic pressure between the front and rear brakes and also act as a sensor when there's a failure, i.e., a significant difference in pressure between the front and rear. The purpose of the button is to restrict movement of the valve during bleeding operations to make it easier to bleed the system. I never noticed a difference between the times when I have pressed it and when I haven't. Mind you, I'm NOT saying it doesn't matter, only that in my case, I didn't notice a difference.

Understand that your brake system are two systems that are connected to each other only through a mechanical connection. The two systems do not share fluid between each other so, since your rear brakes are working fine, you don't have to fuss with them.

I've been doing repairs on my cars for more than 40 years. I've learned to approach each problem with what I hate to do being the last thing I'll want to do. In this case, I hate making a mess. Bleeding brakes can sometimes be a little messy.

Anyway, if I were in your shoes, I would do the C-clamp thing I described in my previous post. It has the least potential for making a mess. If the brakes still don't grab solidly, then we're going to have to get dirty.

To bleed the brakes, start with the passenger side first. There is a way to do it the old school way by yourself. You will need a sturdy hose that will fit on the nipple of the bleed valve. Have a tall jar handy that's about 1/4-full with brake fluid. Cut a finger off of a latex glove and cut a 2-3mm slit on the side about 3cm from the tip. Slip the hose into the glove finger you've just cut and slitted, then secure it in place with a rubber band above the slit. The purpose of the slitted glove finger is to create a check-valve; this will become obvious in a moment. Remove the master cylinder cover. Attach the open end of the hose onto the bleed screw nipple and place the other end into the jar with brake fluid. The end of the hose should be low enough in the jar such that the fluid level in the jar is above the slit. Open the bleed screw, get inside the car and slowly press the pedal down to the floor. What happens is fluid (and any air bubbles) goes down the hose and out the slit. After the pedal has gone all the way down, wait about 5-seconds then let it back up slowly. This is where the makeshift check-valve comes into play. You want fluid to be drawn down from the master cylinder while the pedal comes back up. Without the check-valve, fluid (or air) may get drawn back into the caliper. If you want to spend the money, you should be able to get a brake bleeder hose which has a check-ball in it.

The main reason to remove the master cylinder cover is to easily monitor the fluid level from inside the car while you're bleeding the system. If you press the pedal too fast, fluid may squirt out of the master cylinder all over your the place making a big mess. You may feel like a hard, fast press of the pedal may dislodge a bubble, which it probably would. No worries, simply place the master cylinder cover over the master cylinder to prevent squirting fluid from spilling when you do that. Check the fluid level after each pump of the brake pedal when you have the master cylinder cover in place.

Thank you for that. I will follow instruktions and rebleed the front brakes again. I know in teory how to do it. But now with your careful instruktions i am sure i will get it right. I just need the time to do it. I hope i get a chance saturday.

I will Update back to you when im done, and hopefully i wont need to mess with it anymore. Thank input for taking your time to write all of it up.

Regards Henrik.