Hard braking question (1 Viewer)

Joined
Dec 20, 2008
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126
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Costa Rica
If I do a lot of continuous braking (heavy traffic) braking becomes very hard... almost like I have to physically stop the truck with my body weight :frown:

Thing is - which I don't understand - is this only happens when I'm not using the gas... for example it is worse downhill - brake and coast, brake and coast - and not noticeable uphill - brake and accelerate, etc.

If I'm going downhill, in neutral, but accelerating the motor the problem also goes away. :confused:

It's a 1979 BJ40 with original drums. No leaks that I can tell. Recently replaced the booster. Can anyone explain what's happening?
 
Joined
Dec 20, 2008
Messages
126
Location
Costa Rica
Tks! The problem should be somewhere in the picture then? I was wondering what the reservoir was... someone told me it was for emissions :doh:
diag_AHxmvx.png
 
Joined
Nov 23, 2008
Messages
690
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Los Angeles
 
 
Your brake booster (the cannister behind the master cylinder is bad or the line going to it is leaking.
 
Joined
Apr 2, 2008
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Victoria, BC
 
 
Some of the diesels have a vacuum pump (on e alternator) to create vacuum to assists the brakes. A dying pump could create enough vacuum when you're accelerating.

Just a thought.:D
 
Joined
Dec 20, 2008
Messages
126
Location
Costa Rica
Some of the diesels have a vacuum pump (on e alternator) to create vacuum to assists the brakes. A dying pump could create enough vacuum when you're accelerating.
Yeah, I have one of those... I'll check all the tubes and if everything looks tight I'll see if I have to service the vacuum pump...
 

bj40green

Tssss, tssss
Joined
Dec 13, 2010
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Atenas, Costa Rica
 
I have a '78 BJ40 with the vaccumpump on the altenator. From there the line goes to the vacuum cannister under the floor of the drivers seat, from there the line goes to the brake booster. Can be a leak anywhere.

Hope this will help a bit,

Rudi
 
Joined
Oct 26, 2008
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2 1/2 Hrs. from everything
 
 
I had the checkvalve on my booster crack where it goes into the rubber grommet causing a vaccum leak. Check the grommet and the check valve along with any vac. lines. good luck.
 

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