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Intermittent Loss of Brakes

66 Sat

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My brakes are playing up. Car has a drum to disc conversion on the front, drums on rear, been driven for 2.5 years. no brake issues other than leaking wheel cylinders 6 months ago, all fixed.

Today driving in traffic and went to slow from maybe 10 mph but had no brakes and car felt like it was speeding up slightly. Pedal didn't sink to floor, just felt like no power assistance. Car did slow eventually (before I went up the rear of the car in front) and then lights changed to green. Brakes were normal for next 5 minutes until I parked at destination and I was thinking "did I hit half brake half throttle and that was the issue?"

Anyway, driving home again about half hour later had the same issue - hard-ish pedal but no power assistance and very little braking force, then a few seconds later back to normal. Managed to get home in one piece but obviously something is amiss. When it happens it will hardly even hold the car stationary at idle in Drive, which is a scary feeling.

Fluid level is fine in MC. Car runs normally except I thought the idle was higher than normal at times today, and last night driving home I was waiting at the lights and the idle seemed high, maybe 100 rpm higher than normal. Brakes were fine last night though. If the idle is intermittently high and it corresponds with the loss of brakes, then in Drive it would make the car feel like it was running away from me.

Can a vacuum leak be intermittent? If there was a leak in the brake booster could it be the cause of the high idle, or could the leak be anywhere and cause the issue with the brakes?

The booster is just one of those gold colored cheap ones that come with most of the conversion kits.
 
There should be a vacuum check valve where the vacuum line attaches to the booster. They can go bad.
 
There should be a vacuum check valve where the vacuum line attaches to the booster. They can go bad.
So the black plastic connector that goes into the booster contains a valve? Do you know how to check if it's ok, or is it just a "replace" item?
20210121_183348.jpg
 
Damn....that is a clean looking setup you have there.
The valve...It is cheap, probably less than 10 dollars to replace. They are supposed to be a one way valve but can fail. When they start going bad, you can have intermittent troubles. The booster itself may have a rupture forming inside. The check valve is cheap enough to be worth a try.
 
Damn....that is a clean looking setup you have there.
Thanks. Only 2 problems:
1. It says 318, not 440 or even better 426.
2. I painted the engine bay black in anticipation of painting the whole car black, but then kept the exterior Citron Gold. So now it's like a Chevy.

I'll try and get a valve locally tomorrow and hopefully that will be all it is.
 
With the engine being a Poly, it would be hard to fool a Mopar guy with any 440 nonsense!
Another thing....the vacuum hose can get sucked closed in REAL high vacuum conditions or if the hose is defective. It is unlikely but worth a mention.
 
I didn't mean a fake sticker, I meant a real 440 or hemi...

I'll have a good look at the hose too.
 
According to the Internet I can test the valve by removing the hose at the manifold and blowing into/sucking on the hose. If it's working it should not allow me to be blow air into it but allow me to suck air out of it. I'll try it in the morning.
 
Well, I tested the check valve in the booster and it felt fine. Sucked and blowed on it and it worked as it's meant to (I should have asked my wife to do it, she's out of practice...). Hose was fine too, no cracks or splits.
Then I started the car up and drove it up my driveway, brakes working fine. Let it idle and checked for vacuum leaks, none that I could find. Went through various routines with the brake pedal, turning the engine off holding the pedal down, pumping the brakes, starting with the pedal depressed and feeling it sink slightly etc - everything performing as it should according to my internet guide.
I thought I'd go for a short test drive around the block. Popped inside for a few minutes first and then when I started the car with my foot on the brake the pedal didn't sink at all...and the brakes were gone. Would barely hold the car in Drive or Reverse unless I was really standing on the pedal. Got the car back in the garage but no power brakes at all - they didn't come back at all while I was maneuvering the car into it's spot. I didn't check again to see if they were working again once the car was safely parked.
I'm thinking the Booster must be shot, and will probably buy a tool to check but any opinions or advice?
 
Booster working or not you should still have brakes.
The brakes do work...just. The pedal pressure is huge though to get them to work, whereas when they are working normally they only need a mild touch to work.
 
Brakes are fixed!
Took the booster to a local brake supplier on Tuesday, they took one look at it and said "Chinese crap, they fail regularly, and we don't rebuild them".
Instead they offered to supply a reconditioned Australian made booster from a recent Holden or Ford, adjusted to suit the dimensions of the Chinese one, so it would bolt right in.
I collected it yesterday and installed it this afternoon. Works perfectly and the pedal feels more progressive that before. It's also black and looks better than the gold POS that was on there before.
20210306_180536.jpg
 
They were 100% spot on, soon as I was your engine compartment picture I knew what was gonna be the problem... I try to tell folks but very few listen.... CHINA!!!! SUCKS!!!!
 
They were 100% spot on, soon as I was your engine compartment picture I knew what was gonna be the problem... I try to tell folks but very few listen.... CHINA!!!! SUCKS!!!!
Amen. I've begun my own quest to redo the drum setup on Fred and the Primary Directive in doing so is
that I will NOT accept any Chinese-sourced parts, period.
Wheel cylinders, shoes, hardware, hoses, master - NONE of it will be Chinesium, even if it means
exhaustive tracking down of older new stuff.
 
I check the manufacturing location for nearly everything I buy these days, and avoid China like the plague (or the Covid-19 haha).
I try to buy Australia Made first (obviously), but Made in USA gives a huge sense of confidence in an item. Just today I needed some dental floss. There was a cheaper brand, made in China, but then I checked the Oral B good brand and to my surprise was made in Ireland. I paid the extra dollar to keep our Paddy friends happy.
 
There was a cheaper brand, made in China, but then I checked the Oral B good brand and to my surprise was made in Ireland. I paid the extra dollar to keep our Paddy friends happy.

your custom is greatly appreciated. Your keeping my brother in a job. Now just drink Guinness and keep me in a job :lol:
 
your custom is greatly appreciated. Your keeping my brother in a job. Now just drink Guinness and keep me in a job :lol:
Yeah - I noticed some time ago the floss I buy is made in Ireland and always buy it cuz I can get btw my teeth without breakage. As for Guinness, always liked black & tan - drinking it straight is a bit too much since one beer is never enough.
 
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