- This topic has 5 replies, 2 voices, and was last updated 10 years, 2 months ago by
.
-
Topic
-
Hi Everyone;
Got tired of digging on my Acura electrical problems and wanted to ask something about my project pickup here. Yes, the truck that pre-dates me by few years, but that’s why I just LOVE it. And its a great place to learn for a novice mechanic I think!
So here is a hopefully an easy one for you. This is Chev Pickup 1/2 ton from 1970. 350ci engine and Turbo 350 Transmission. As I have been told, a pretty solid drive train indeed.
Recently, I replaced the Carb with a rebuilt OEM one, what s difference! This Carb here is Pre-EGR days. There is no EGR system at all. There is 1 vacuum line from the Distributor vacuum advance and one to the PVC. THAT’s IT 😀 :cheer:
So engine starts and runs great, love the sound of those headers rumbling. 😛
What I am having issues with is brake booster/ transmission vacuum. On the back of the intake, behind the carb is a “T” port that has thick Air line running to the brake booster. Then the other side of that “T” was a loosely fit Vacuum from the transmission.
As I was checking those 45 year old airlines for the transmission,(its mostly metal tube and short rubber pieces at both ends) I noticed that the rubber ends were worn so I replaced them. WOW what difference in shifting!
(** Note for clarity — after digging around the web- I was told the the heavy turbo 400 transmissions had nothing but vacuum lines…And that the 350 turbo I have has the Vacuum line AND a kick down cable, AND some sort of electrical cable running from the side of the bell housing. Only thing hooked up on my pickup right now is the vacuum line. I have been told the kickdown not being connected yet is OK and not hurting the transmission)
So like I said, the Vacuum to the transmission is making it MUCH better. The problem was shortly after that, I lost all pressure in the BRAKES! :pinch: The pedal goes right to the floor. Before fixing (breaking? 😛 ) this, simply touching the brakes lightly put your head through the windshield almost. LOTS of pedal (almost too much)
Again, the 2 are related (I am thinking) because they both share a common T connector to the intake.
So here comes the questions:
1) Is this the proper setup for this? Is that “T” which gives full intake vacuum, proper for both transmission and the Brake booster..Or is there just not enough vaccum for both of these at that spot?
2) If not, Other vacuum sources for the transmission could be to “T”ed into the carb where the Vac advance goes into the front lower portion of the carb.(Have read the brake booster line should not be moved and makes sense since it is thicker than the carb lines)
3) Could this indicate the Brakes booster check Valve is clogged or broken? Would it have failed so quickly?
4) I also checked and no fluid lines seem to be broken to the brakes. Note that both front and back use drum brakes (yup OEM setup for these old guys)
Any road, just checking what would be a good test to see which system is at fault and what the proper setup would be. The truck is going on the road in the new year so I have some time to tinker. 🙂
thanks again guys:
3)
-
Replies
-
There should be no issue with the vacuum lines for what you’re describing. If you could stand on the brakes with both feet and it felt like the pedal was rock hard and barely moving, then you could be concerned about a brake booster/vacuum problem. Power brakes used to be optional back then. (My old 71 Chevy didn’t have power brakes and my right leg was really strong for it.)
Start with checking the fluid level in the master cylinder. I’m betting it’s low or empty in at least one of the reservoirs. Then pull the wheels off and look for leaks in the wheel cylinders. If your brakes leaked out fast enough, you might even have a tire that’s wet on the back side by now. That would make it easier for you to find an offending wheel cylinder. But, if they’re as old as the truck itself, now would be a good time to replace them anyway.
So If I hear you right Common;
– The brakes being very hard and stiff (as they were before “fixing” the transmission vacuum) could have been symptom of a faulty brake booster system in the first place?
– Now that the brake pedal goes to the floor and it only stops it a little, this could be the wheel cylinders?
I do tend to blab on a lot so I should clarify this maybe. After “fixing” the transmission line, it might have been 30 minutes later, and 3 city blocks of driving, that the brakes acted that way? (pedal to floor)
Does this makes sense then?
– Air leak to the booster at the T on the intake(it was like that when I bought it). So previous owner adjusted the brakes last time with this fault already occuring.
– I fixed the all other engine air leaks (new carb and base gasket) tested with carb cleaner trick.
– Once I fixed the last air leak (trans line) the brakes which were adjusted with the leak became over powered, more then they were used too.
– And quite possibly, the new weakest link in the system could be a bad wheel cylinder now that the system has better vacuum.
If this sounds logical, this does make a lot of sense and should help me troubleshoot better. I’ll check the reservoir as you said, then the wheel cylinders. Never saw any leaks of fluid on the tires, but I do know if the cylinder jolted or twisted and missing the top of the shoe somehow (had this happen on an old car in college, it had bad backing plates 🙁 ) then this might explain my bad brakes now.
I’ll let you know what I find! 🙂
[quote=”gsr-chick” post=116633]So If I hear you right Common;
– The brakes being very hard and stiff (as they were before “fixing” the transmission vacuum) could have been symptom of a faulty brake booster system in the first place?
– Now that the brake pedal goes to the floor and it only stops it a little, this could be the wheel cylinders?
I do tend to blab on a lot so I should clarify this maybe. After “fixing” the transmission line, it might have been 30 minutes later, and 3 city blocks of driving, that the brakes acted that way? (pedal to floor)
– Once I fixed the last air leak (trans line) the brakes which were adjusted with the leak became over powered, more then they were used too.
– And quite possibly, the new weakest link in the system could be a bad wheel cylinder now that the system has better vacuum.
If this sounds logical, this does make a lot of sense and should help me troubleshoot better. I’ll check the reservoir as you said, then the wheel cylinders. Never saw any leaks of fluid on the tires, but I do know if the cylinder jolted or twisted and missing the top of the shoe somehow (had this happen on an old car in college, it had bad backing plates 🙁 ) then this might explain my bad brakes now.
I’ll let you know what I find! :)[/quote]
Brake boosters seldom fail. Even for as old as your truck is. The problem with a hard brake pedal was in the vacuum lines you replaced. You solved that problem.
Yes. Now that the pedal is going to the floor, I’m really content on checking for leaking wheel cylinders. If your wheel cylinders all pass, then check the master cylinder for bypassing. (Bypassing is an internal leak in the master cylinder sealing cups. The master cylinder probably won’t be low on fluid in this instance.) Bypassing is still low on the list because you’d get a lower pedal, but you’d still have the same stopping power.
Remember that you’re dealing with a very old truck. It’s entirely possible that you just happened to have something else break after fixing another thing. (I have an S10 and a Blazer that are guaranteed to break right after I get done fixing something else.) In a general sense, shit happens like this all the time with cars of any age.
The operating principle behind the vacuum booster has nothing to do with how the brakes are adjusted at the wheels. The whole point of that vacuum booster is entirely so you can apply the brakes without having to stand on the brake pedal. If you can stretch some time for it, find a way to safely plug the vacuum line going to the brake booster on your Acura and then disconnect the end of the hose from the brake booster. Then get ready to hit the brakes really hard and have the scare that your car isn’t ever going to stop. (think roads less traveled for that test drive)
There could still be an issue with the booster, but it’s still really really far at the bottom of my troubleshooting list and I’ll explain it more once you get done checking out wheel cylinders.
Good luck.
UPDATE;
Well I thought I would share an update with you. Looks like I have low fluid in the reservoir for the brakes. The front chamber looks lower than the back. (see pic) . I am thinking I most likely have a leak somewhere. I’ll have to investigate the lines now. The do look quite sour.
I did get the rear tire off but I did not get to the drum. What I did notice is the slots in the drums. (look at the pick with the red arrows) Do you know what they are for? Are the for adjustments? Are they for pulling the drum off?
Since I didn’t have any brake fluid for the master, I decided to wait to troubleshoot the problem till I can top the system off. I’ll have to check the lines out very closely by the look of things.
I also think it might be a good project between now and January when I plan to put the truck on the road to watch Eric’s video about brake bleeding and replace the lines.
I’ll be playing more with this come the next dry day we have. I’ll keep you all posted.
In that first picture of the drum, those would probably be sight windows. Something you can look through to see the thickness of your shoes. Since you’re parked on the bricks, you might just be able to get away with pumping the brake pedal a few times and then check underneath for the fresh puddle. That is if it is indeed a broken brake line.
Thanks for the pictures. It looks rough, but far from hopeless. I noticed the coil spring has a little coil bind in the middle. Did somebody do some back yard lowering tricks on the suspension?
- You must be logged in to reply to this topic.