39 Plymouth Brakes wont work

[likaleica]

Hi guys - would be very grateful for some guidance on sorting the brakes on my newly purchased 39 P7/P8 hybrid export model sedan. 

The brakes have been restored previously with all new brake lines, flexible hoses and judging from their appearance,  new wheel cylinders. But the foot pedal went straight to the floor with no braking action.

We've bled the system in the normal way and a good deal of air came out. Now the brake pedal is solid - there is no movement at all once the free pedal movement is taken up.  We've got the rear wheels jacked off the ground and we can turn them when the foot pedal is pressed down. Any advice would be well received as we're scratching our heads here in England!

Thanks guys

 

[Reg Evans]

Have you turned the brake adjusters until the wheel locks up and then back off a little ?

[likaleica]

Hi Reg - We were debating that and now you mention it we will give it a try. Unfortunately the car is out of the garage, it's after dark and raining here in England - so it'll be tomorrow before we can give it a go. Thanks and we'll let you know!

[Andydodge]

Have you got a workshop manual?........would strongly suggest you get one but a paper one, not those CD versions............andyd

[likaleica]

Hi Andyd - yes we have a paper manual but it's a bit vague. BTW I will take some pix of those vacuum wiper switches as soon as I can and post them.

[plymouthcranbrook]

Make sure the vent in the master cylinder is open. Several threads about this in the forum.

[likaleica]

Thanks all.  We followed all you guys' advice and still we had the problem. Then we noticed the fluid level in the master cylinder was dropping - tho we couldn't find a leak.  That is, until we removed the rubber boot from the piston rod on the master cylinder and fluid gushed out!  So we've removed the master cylinder and taken it for renovation to a specialist company just up the road from here who'll fit a stainless steel barrel liner and renew the internals.

It'll take around 10-14 days (and about $150!) so I'll let you know how we get on when we've re-fitted it.  Thanks again for all the help fellas.

[greg g]

When you install you renewed piece, make sure you have sufficient free play at the top of the pedal stroke. There are different specs through the years but there should be some free movement to the pedal before the actuator rod begins to contact the M/C piston. This assures that the system can fully dissipate the fluid pressure when the brakes are released. If free play is inefficient, the brakes can drag or even fail to release. Remember also to do the bleeding cycle starting at the wheel furthest from the master. Older technicians would also advise putting a thin wood block between the pedal and the floor to keep the mc piston from contacting the end of the bore when doing all the pumping during the bleeding process if you are doing it manually.

Look thoroughly at this site. There is a primer regarding the proper way toadjust the brakes. Without a proper adjustment you will not get a satisfactory bleed.

Edited October 31, 2014 by greg g

[likaleica]

Thanks for all that excellent advice Greg. I have a reprinted workshop manual that gives the correct free play measurements and it does say depress pedal half way down during bleeding - tho the block of wood sounds a sensible way of ensuring this.

 

While on the subject, the system had been filled with light pink coloured brake fluid which I suspect was dot 5 silicon. I'm old school and prefer amber dot 4 - can I pump out all the silicon and refill with this without changing all the seals (cups) in the wheel cylinders? I've read conflicting advice on whether Dot 5 and Dot 4 are compatible.

[Don Coatney]

DOT 5 is not compatible with DOT 4 or the more common DOT 3. Can you contact the prior owner and find out what brake fluid is in the system?

[Dodgeb4ya]

DOT 5 or silicone brake fluid is usually dark amber or purple  color as manufactured.

 

DOT 3 or 4 Glycol brake fluid is nearly clear when new. DOT 3 or 4 will also turn dark as it absorbs moisture and needs replacing.

 

DOT 4 has a roughly 40 degree higher boiling point and is 100% interchangable with DOT 3.

 

If you contaminate and intermix DOT 3 or 4 Glycol brake fluid  with DOT 5 silicone in any amounts the brake system should be completely and thoroughly flushed  or best taken apart and the rubber parts replaced with new.

 

I run into  Hmmm....what type of brake fluid is in a old car brake system in my work.

I take a small sample from the car and drop it into a clear jar with new DOT 3 or 4. If it sits as a ball or jelly bean in the bottom of the DOT 3 or 4,   it's DOT 5 silicone.

 

Be sure of what fluid type is in your old cars brake system if you are not sure. Most old cars still have regular glycol DOT3 in them.

[likaleica]

UPDATE:  Another plea for helkp I'm afraid!

After many trials and tribulations I had the wheel cylinders as well as the master cylinder remanufactured here in the UK -  stainless steel sleeves pressed in the barrels and all new seals etc. Lovely - except on the first road test we discovered a front brake drum is cracked

I've placed a wanted advert for a good replacement drum in the classified section of the Forum and PM'd a few members individually.

All help in tracking one down would be very gratefully received!

hanks as usual for all the kind help and advice, guys.

[Jerry Roberts]

Here is one source to try ...  www.vapinc.co    then go to mopar index , then go to brake drums . 

[likaleica]

Finally the brakes are sorted and the car is back on the road just today !  Thanks for all the help and advice.

Having been assembled in South Africa from crated parts, the brake drums appear not to be standard 1939 items - but pre-1938. But uncertainty preciselty which drums it has led me to double-check if the broken drum could be repaired here in the UK in spite of first being told it could not be.

An engineering shop successfully welded the cracked drum and machined it out. So after more than 16 months of ownership,  I drove the Plymouth for the first time today and it drove beautifully the 10 miles or so to the paint shop where its driver's side front wing it to be resprayed. I pick it up tomorrow and need to get it cleaned up ready for a car show literally 1 mile away from me on Saturdaty and Sunday. Thanks again for all the kind help,

[RobertKB]

Glad all worked out well. You will certainly enjoy driving it and taking it to shows. Sometimes the wait is worth it!