FAQ |
Members List |
Social Groups |
Calendar |
Search |
Today's Posts |
#1
|
||||
|
||||
Low Vacuum
Been finishing up the loose ends on my 65 2+2. It's has a HO motor built by other? Working on adjusting the Power drum system. Only getting 10 psi of vacuum. Brakes when warmed up tend to grab. It's that a vacuum or adjustment type issue?
__________________
1965 Pontiac 2+2 421 HO auto 1967 Pontiac Grand Prix 428 4 speed- sold 1968 Firebird 400 auto - sold 1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold |
#2
|
|||
|
|||
That is a brake issue, not vacuum. If drum brakes, shoes may be rubbing or be contaminated [ oil or grease ]. These are most likely, but other things could also cause grabbing.
If disc, piston might be sticking. |
#3
|
|||
|
|||
Check and make sure your primary and secondary shoes are in their correct positions too along with the proper left and right orientation of the star adjusters.
|
The Following User Says Thank You to alleyCat For This Useful Post: | ||
#4
|
||||
|
||||
I will double check the shoes. Also a ordered a Crane Cam Vacuum canister. Watched so UTube videos on that. Will give more updates soon. Thx.
__________________
1965 Pontiac 2+2 421 HO auto 1967 Pontiac Grand Prix 428 4 speed- sold 1968 Firebird 400 auto - sold 1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold |
The Following User Says Thank You to 67GP428 For This Useful Post: | ||
#5
|
||||
|
||||
Low vacuum will make your brake pedal very hard to push.
__________________
64 Lemans hardtop 4spd, buckets |
The Following User Says Thank You to Lemans64 For This Useful Post: | ||
#6
|
||||
|
||||
The brake pedal is had to push at idle and get a little better when driving. Then gets harder to push coming to a stop.
__________________
1965 Pontiac 2+2 421 HO auto 1967 Pontiac Grand Prix 428 4 speed- sold 1968 Firebird 400 auto - sold 1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold |
The Following User Says Thank You to 67GP428 For This Useful Post: | ||
#7
|
||||
|
||||
If it's a vacuum problem, the pedal will good while the vehicle is in decal mode, but if using brakes lots going down a hill slowly the pedal will feel
hard, not enough to make it work correctly. The reservoir should help a little with that, but for grabbing, I would think you either have bad adjustment or bad shoes, shoe to drum contact bad. Does it pull left or right while doing this? I am assuming this is a 4 wheel drum system?
__________________
64 Lemans hardtop 4spd, buckets |
The Following User Says Thank You to Lemans64 For This Useful Post: | ||
#8
|
|||
|
|||
The vac tank does not increase vacuum, it just 'stores' what vacuum there is.
So hopefully you will have enough reserve before you go under the rear end of that semi.... |
The Following User Says Thank You to Geoff For This Useful Post: | ||
#9
|
||||
|
||||
The brakes do pull to the left. Brakes have no problem stopping the car. Do you feel the grabbing brakes when warmed up is due to being adjusted too tight? It is a new parts and I feel they need to break in and seat? I feel the vacuum canister will help at idle?
__________________
1965 Pontiac 2+2 421 HO auto 1967 Pontiac Grand Prix 428 4 speed- sold 1968 Firebird 400 auto - sold 1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold |
The Following User Says Thank You to 67GP428 For This Useful Post: | ||
#10
|
||||
|
||||
I used my temperature gun to check the temperature only all drums. Left was the hottest. Rears where cool. I bleed the brake system. Adjusted the right front and both rear drums. Road test this weekend.
__________________
1965 Pontiac 2+2 421 HO auto 1967 Pontiac Grand Prix 428 4 speed- sold 1968 Firebird 400 auto - sold 1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold |
The Following User Says Thank You to 67GP428 For This Useful Post: | ||
#11
|
|||
|
|||
Quote:
What I have found, even with my contemporary cars, is to ask for the base or inexpensive line of shoe/pads. They seem to have less metal, are softer, and stop way better. They don't chew up my rotors and I can/have put 3 sets of pads on 1 set of rotors on a former Toyota. I don't have much experience with the newer ceramic pads, but my 2015 Hyundai has them. They seem to wear well and they do stop good. I replaced my front's at 80K and they were at 1/2 life. Now I bought the car with 30K, so maybe they were replaced. Rotors looked perfect. But even 50K and 1/2 life seems good to me. So another car I just slapped new pads on with the original rotors. 130K miles and no issues. I did get ceramic front pads for the disc brake conversion I did on my '68 Lemans, but it is not road ready yet and will still be a few years to completion, but I thought I would try a set. |
#12
|
|||
|
|||
I don't want to be the dictionary **** but vacuum is measured in "inches" as in 17 inches of vacuum.
|
The Following User Says Thank You to flat-bill For This Useful Post: | ||
#13
|
||||
|
||||
Lol. Listen to mean not what I say. Still learning the correct lingo. I do have the more expensive shoes. The sure grab!!!. The shoes are installed correct. Probably try a cheaper style of shoes if my problem isn't fixed.
__________________
1965 Pontiac 2+2 421 HO auto 1967 Pontiac Grand Prix 428 4 speed- sold 1968 Firebird 400 auto - sold 1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold |
The Following User Says Thank You to 67GP428 For This Useful Post: | ||
#14
|
|||
|
|||
Shoes adjusted too tight can definitely cause the car to pull to one side. More likely to happen once the car is driven for awhile & the shoe[s] heat up.
Shoes that are rubbing on the drum can be caused by things other than adjustment. Corrosion in the wheel cyl might be preventing the piston from fully retracting, keeping the brakes 'on'. Sediment/sludge in a brake hose or line can cause the same thing. Weak brake shoe return springs. Rare [ but I have had it happen ] wheel brg comes loose in the hub & wears the hub; drum 'wobbles' & rubs on the linings. If you do not have automatic adjusters, well worth buying the kits. |
The Following User Says Thank You to Geoff For This Useful Post: | ||
#15
|
||||
|
||||
I have 100% new brake system, lines to springs and everything in between. Might just have to break in?
__________________
1965 Pontiac 2+2 421 HO auto 1967 Pontiac Grand Prix 428 4 speed- sold 1968 Firebird 400 auto - sold 1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold |
The Following User Says Thank You to 67GP428 For This Useful Post: | ||
#16
|
||||
|
||||
New drums as well?? Or just machined? New stuff can take a bit to match, causing pulls and such. How are you adjusting them?
Should adjust until they lock then back off till free, usually counting the number of teeth on adjuster to make the opposite side the same. For front it is critical. This is why most people convert to Disc brakes.
__________________
64 Lemans hardtop 4spd, buckets |
The Following User Says Thank You to Lemans64 For This Useful Post: | ||
#17
|
||||
|
||||
Four new drums also. I'm still getting the rub then spin easy when turning the tires. Witch makes it hard to adjust. Hoping a little more drive time will help the go away. What about going in reverse and braking so the self adjusters will help set the tension on the drums?
__________________
1965 Pontiac 2+2 421 HO auto 1967 Pontiac Grand Prix 428 4 speed- sold 1968 Firebird 400 auto - sold 1967 Bonneville Brougham 2 dr. hardtop. 1969 AMC Rebel SST wagon-sold |
The Following User Says Thank You to 67GP428 For This Useful Post: | ||
#18
|
|||
|
|||
Yes, driving in reverse & applying the brakes is how drum brakes with self adjusters adjust the brakes.
It would be a good idea to back off the adjustment slightly & then do the above self adjustment. This would ensure the brakes are not too tight. Grabbing when hot does sound like adjustment is too tight, especially with all new parts.' If the problem persists, you might want to swap left & right side brake shoes to see if the problem swaps sides. That would indicate faulty shoes or linings. You could also swap drums first in case one is out of round, easier to do. Nothing wrong with drum brakes. |
The Following User Says Thank You to Geoff For This Useful Post: | ||
#19
|
||||
|
||||
Trying to stop a 3700lb+ car with 10" of vacuum was just plain insane, I went to a Hella UP28 Pump and now at 21" of vacuum it stops incredible along with the brake updates too. Actual stops better than my 2009 Lancer.
Pump model and pic below, stopping is the best mod you can do for yourself, your car and others.
__________________
69 GTO Convertible, 4000lbs 462ci, 606tq/569hp - 93 oct @ 34 deg (207psi) 11.7:1, KRE H Ports, Lunati HR 282/290 w Johnson Lifters & 1.65 Scorp, E30, EFI, Holley HP + Dual Sync, 12-1 Crank Trig, 120lb Inj & 1000cfm TB, Torker II EFI Int & Rails, PTC 10", Ricks SS Gas Tank, Magna 4303, Aerom EFI Reg, Aero Front & Wilwood Rear Disc Brakes, Dougs 1 7/8" & Borla Pro XS 3", Alum Rad & Dual Fans, 12:1 Box, UMI Arms & Viking Berz Fr + Rear CO Shocks, Hella UP28 Vac Pump, 12 Bolt, 3.73, 33 Spline |
The Following User Says Thank You to GOAT8U2 For This Useful Post: | ||
#20
|
||||
|
||||
"Nothing wrong with drum brakes. "
Geoff, generally, I agree, however, back in the day when I had manual drum brakes, doing a panic stop from speed was very exciting after the first few seconds.......noticeable fade.... George
__________________
"...out to my ol'55, I pulled away slowly, feeling so holy, god knows i was feeling alive"....written by Tom Wait from the Eagles' Live From The Forum |
The Following User Says Thank You to george kujanski For This Useful Post: | ||
Reply |
|
|