I have a 1966 Marlin .. 4 wheel drums , brake pedal has been trouble for awhile now.. long story ,,
everything is new on this car.. or in new condition.. but that doesn't mean it is working fine, and I may have to replace .. but I think it is just a matter of dialing it in..
so,, for some reason... and I can't imagine this would be correct... but the port on the master that is closest to the front of the car.. is marked REAR.. and the brake lines go to the front.
the port near the firewall is marked FRONT... and goes to the rear brakes.. strange mistake,, or a done on purpose,,,, or..... was the mechanic used to always putting the front lines on the front port.. and the rear lines on the rear port.. and did it wrong by habit..?
I dunno.. but I think I am going to change that.. so the front wheels come off the port marked front..
The pedal was / is very touchy..and it seems that the booster applies the brakes it self just at the point the pressure build in the system.. I have seen the booster issues before where starting the car would apply the brakes... this isn't the case.. the pedal seems correct.. then just as you can feel the brake application.. it goes FULL BRAKE!!! SQUEEEEEAAAALL ... front wheels lock up..
I pulled the master off the booster to check for fluid in the booster.. but I really can't tell for sure... it is very dry.....
I am in the process of full inspection and operation of the brakes ,, and I really think the master, or the booster has to be the issue.. but......
if I have to make changes.. I might just put front discs on.. and then I need to figure out the master/proportion valve/ combination
Here are my questions.....
1) how can I inspect the booster for fluid from a previous master leaking past the seal into the booster
2) does this car require a proportioning valve,, or is it built into the master.
3) should this car have a switch to turn on the dash light "BRAKES" ,, or is that light for parking brake.. and not a system pressure differential
4) can I block off the vac to the engine so it acts like manual brakes..and see if that stops the touchy effect,, then I know the booster has an issue?
Thanks for any help! .. I really don't need lectures on how important it is to fix the brakes .... and I have talked to local brake experts and they just don't know old cars.. I am a mechanic... I'd love to get the correct vintage combination back on this car so it works .,, but if it needs an upgrade.. then I'll go that way.
Jamie The first thing I would do is get the org. repair manual for this vehicle. It should have a diagram showing the whole system. You will find this manual will help you over and over. In the meantime you might find the diagram you need on the internet. Google is you friend. If that is the proper master cyl. then the brakes are plumbed wrong. The stock system should not need a proportioning valve unless the diagram shows it. If you have the correct master cyl. and once your brake lines are correct your problems should be solved.
Beautiful looking ride, I especially like the colour.
One other thing to check, there should be a rubber cone in each port, these are residual valves to keep the shoes close to the drums. They sometimes get overlooked when a rebuilt M/C is installed. If you don't have them, go to Brewers or McKerlies (whoops, living in the past) and get a couple. They just push in.
10 Lb residuals will never hold back 70 Lb return springs on a drum system . Their only purpose was to load the cup seals in the slave to keep them from leaking. The master should be a straight bore so front or back will make no difference . Most of the time the differential on drums was made up changing up the slave or the shoe width or size 2 1/2 front 1 3/4 rear. rock auto still has a good listing to compare what you got . check the simple things first . all 4 are releasing fully , shoes are not reversed. too much brake on a drum system is normally something not returning home.
Jim Rae in port perry is he still around ?? Big AMC Rambler guy might have info for you . Join , Frans AMC forum and Mike Luke,s amc drag racing free forum . There is a bout 20 Ontario guys on each of those forums
drum brakes locking up ?? fluid or grease on shoe lining , shoes on back wards ? rear wheel cyls seized , frt cyls doing all the work . for a test drive you could un hook and plug or clamp off the vac line to booster and road test it ..77.
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I,m as cool as Milner , but axeually a bit more like Beckwith
I had the drums off.. 1.75" rear ,, .2.5" front shoes .. both F&R are 10 in. drums, all shoes appear new.. shoes are not reversed.. leading shoe,, short and thinner, is the front shoe... longer and thicker shoe is the rear trailing shoe... all 4 are releasing fully , adjusters, and other spacers, springs appear ok, but I don't have a picture to compare to for sure.
i reversed the F&R lines at the master.. bled them without issue.. I am still not happy with the way the pedal feels in the booster.. so I have to inspect that a bit further..
I haven't had time to take it off the jack stands and test drive it yet... way toooo much nitromethane this weekend!! Smax captured the win for Leverich Racing 4.84 et 297mph @LeverichRacing #leverichracing
-- Edited by meester_jamie on Sunday 3rd of July 2016 06:48:46 PM
"10 Lb residuals will never hold back 70 Lb return springs on a drum system . Their only purpose was to load the cup seals in the slave to keep them from leaking. The master should be a straight bore so front or back will make no difference ."
Actually Slim, you couldn't be more wrong. Residual valves were never meant to hold back springs but rather to maintain fluid pressure in the lines, 2lb in disc lines and 10 lb in drum lines. This is even more important in a M/C mounted low to prevent the fluid from running back into the M/C. Every manufacturer specifies which line goes to which port, regardless of bore.
Drums always return to the fully retracted position so its impossible for any more fluid to run back unless you pull a vacuum in the master. The shoes are against a dead stop and the cups in the slave are spring loaded out against the stop. the 10 lb's was to keep the cup lip loaded against the slave bore. the spring loads the opposing cups in the centre the pressure keeps the rubber seal tight against the bore wall so the fluid stays inside. New seal design has helped reduce this effect . Disc's are a whole different animal and need the residuals because they are just floating in position .
one update. the wheel locking up is the pass rear wheel.... I don't have the answer yet.. I need to replace that rear wheel seal and the shoes as they have oil on them.. ,,, because the front end dives hard and to the pass side when the wheel locks up,,it was misleading everyone to think it was the front pass wheel locking up.. once I get the oil seal and shoes replaced.. I'll probably get a much better picture..
as for line size... I had a early 1985 Astro van that had very odd brakes ... I complained to Dealer about it.. they had a blank face,, no help... then circle of friends network,, a mechanic at the FORD dealer told me there was a TSB on the brakes... customer pays repair.. GM wouldn't admit issue.. but the "Kit" they supplied to appease the customer was more aggressive rear shoes etc... it was to compensate for undersize line to the rear axle... that was the antilock method they used .... too small a line to the rear wheels... the late yr 85 up van had larger rear brake shoes, lines and master cyl etc from factory... so I am not sure saying "1/4" brake lines should always be used because they are better than 3/16"" is a complete statement.. I would think the combination is part of the parcel....... simply increasing the line would not provide any real difference to a properly engineered system.. as the master would put out the same.. the slave would receive the same.. technically I am sure there is a theoretical change like the timing of the slave .. but as the way I understand bernoulli theory, you need to tell me more..
I think Petebil is just trying to make a funny. Hahaha, (what was your previous members name?)
If I go by what I've been reading in this forum, over the last few years.
Judgements have been passed on other members, due to there input, on specifically this "1/4" dia. lines".
Which had in turn been railroaded and taken out of context by other members, that likely get steered in the wrong direction from lack of knowledge, or just because...Speedway...Wilwood...
Do proper research, best of my knowledge, your Marlin didn't have 1/4" lines (no ABS systems, or metric lines(6mm), or .236" yet.)
So, the factory system is calibrated to 3/16" lines, front and rear. (best of my knowledge).
Some Fords (9"), late 50's early 60's did come with 1/4" lines at rear.
Once you get the new seals and shoes in, let us know how you make out.
Slim said:
Drums always return to the fully retracted position so its impossible for any more fluid to run back unless you pull a vacuum in the master. The shoes are against a dead stop and the cups in the slave are spring loaded out against the stop. the 10 lb's was to keep the cup lip loaded against the slave bore. the spring loads the opposing cups in the centre the pressure keeps the rubber seal tight against the bore wall so the fluid stays inside. New seal design has helped reduce this effect . Disc's are a whole different animal and need the residuals because they are just floating in position .
Drums return to what position? What's the retracted position of a dia.?
How is it impossible for fluid to run back?
Fluid can run back, (if there's a leak in the system). Otherwise the brakes would stay locked, same goes for disc brakes.
Jamie, you're on the right track...
Again, let us know how things are going.
Drums always return to the fully retracted position so its impossible for any more fluid to run back unless you pull a vacuum in the master. The shoes are against a dead stop and the cups in the slave are spring loaded out against the stop. the 10 lb's was to keep the cup lip loaded against the slave bore. the spring loads the opposing cups in the centre the pressure keeps the rubber seal tight against the bore wall so the fluid stays inside. New seal design has helped reduce this effect . Disc's are a whole different animal and need the residuals because they are just floating in position .
Drums return to what position? What's the retracted position of a dia.? How is it impossible for fluid to run back?
Fluid can run back, (if there's a leak in the system). Otherwise the brakes would stay locked, same goes for disc brakes.
Jamie, you're on the right track... Again, let us know how things are going.
your kidding right... The shoes are round but the force is linear from the slave... so retracted is what I meant or returned home Via large springs that hold them against a fixed end stop when you remove your foot from the pedal .So once the shoes are completely retracted against the stop no fluid is going any ware. 10 lb residuals are no match to hold back the return spring they will retract fully to the stop every time. If fluid is leaking on the ground I don't think they will lock up brakes are a sealed system in the static home position you would need to let air in for fluid to run out. so again going back to the purpose of the 10 lb residuals loading the cup against the slave wall. Again disc's float nothing but a puck with fluid behind it the 2lb residuals are the only thing keeping them in position. As long as all the air is removed you could run a 1" line without any real adverse effect undersize lines would make for far more interesting reactions. This is all basic stuff that anyone working on brakes should Know....
Jim Rae in port perry is he still around ?? Big AMC Rambler guy might have info for you . Join , Frans AMC forum and Mike Luke,s amc drag racing free forum . There is a bout 20 Ontario guys on each of those forums drum brakes locking up ?? fluid or grease on shoe lining , shoes on back wards ? rear wheel cyls seized , frt cyls doing all the work . for a test drive you could un hook and plug or clamp off the vac line to booster and road test it ..77.
Sorry to say but Jim passed away while at Hershey PA a couple of yrs. ago. Think nhis son is still running the parts end of business on a part time basis!!
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I can only please one person a day, Today is not your day!!Tomorrow doesn't look good either !!!!
Once you get the new seals and shoes in, let us know how you make out.
Jamie, you're on the right track... Again, let us know how things are going.
Oil problem resolved at rear pass side shoes... new shoes installed... and the locking up problem is gone..
so , front brake hyd lines connected to port marked front.. rear connected to port marked rear.. no oil contamination,, no air in lines. adjusters pretty tight.. reservoirs full... engine off .. pedal hard ,, start engine,, brake application ..pedal goes to floor.. and car "just" stooooooops ...
only a small bit of play at booster rod.. about 1/4" at pedal
I installed a Vac gauge in the booster line.. reads about 17 .. pretty steady.. and with brake application,, no noticeable change ... I am still sort of puzzled and not happy about amount of brakes .. or stopping power...... sigh
seeing as I had the vac gauge out... and it might be a bit low.. I thought I'd see about playing with the timing to see if I could get a bit more vac.. but I wanted to get a base line first
I checked : Dwell 28 deg,,,, 680 rpm idle..... vac 17 ,,,, i think the timing is at 5deg BTDC .. there is a middle line with a dot.. and a line on each side.. I am sort of assuming the dot is TDC.. and the other 2 are 5 deg BTDC and 5 Deg ATDC ... plug gap 0.035"
this is a 66 Marlin AMC... but the car originally came with a inline 6.. I am pretty sure engine is a 327 and I think it came from a rambler classic same era ....
Ok,,, I have to do some research...... I need to know the timing markings on the harmonic balancer pulley ....... I think I'll install a brake fluid pressure gauge ,, but I need a spec there ...
BobT ... yes, the org. repair manual for this vehicle would be a great asset ! ,,,, I am still looking.. any one have a lead ... 66 AMC Marlin
I need to top up the auto trans.. so I need to find what the correct fluid is ...
I am thinking I need to prove the booster is adjusted and working correctly as well.. but one nagging thing bothers me ,, apparently there are different brakes for the 6 cyl car.. than the 8 cyl ,, I can measure the drums to be 10" .. but seems weird to have 9" shoes.. which I can't really measure ... so I want to compare the shoes I have to the "other" set avail. and see if that shows up something..
along that point.. the wear is even on the shoes.. and I'd think that 9" shoes in a 10" drum would have center wear ,,, but these adjusters have a lot of exposed thread... as they are wound out a long way... seems like the adjusters should have little thread showing on new shoes ...
Update!
with the contaminated shoes replaced, no more wheel lock up... then the correct master cyl ports to the respective slave cyl., a little better braking.. but not acceptable... then I checked the booster push rod inside the master.... and it was 0.400" toooooo short..... it has a threaded end, so I adjusted it out 0.350" and the pedal is at the top.. and rock solid.. and the car stops like it should!!
Yippppppeeeeeeeeeeeee!
now, I am looking for a set of H78 - 14 with small white walls.. or.. something that will sort of keep the vintage look.....
