Volvo RWD 140-160 Forum

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'72 145e brakes+low idle or cut out mystery 140-160 1972


Hallo,
Thanks again for all your help before.

But now...
When I step on the brakes the idle dips way low and when the engine is cool can cut out. At night, with the lights on (or fan) this is especially bad.

I am assuming that this is caused by a leak somewhere in the vaccuum system...as the brakes are connected to intake manifold etc. (d-jet). How would I go about finding out the culprit? And how to fix, perhaps?

Also, could be related, but there is a sound eminating from the brake pedal, not the pedal itself, mind you, but where the pedal pushes through the fire wall into the master cylinder. The noise sounds like TV "snow" or white noise and stops when I depress the pedal and engage the brakes. Could this have anything to do with the idle problem, or a seperate problem all together, or even be a gremlin?

When I bought the car the driverside carpet was soaked (still is) with a greasy reddish liquid...until now I assumed someone was trying to drive and drink a bottle of olive oil unsuccessfully...hmm now methinks she had problems before if what is in the carpet is brake fluid...anyone have any ideas?

indebted to any gurus
-samuel








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'72 145e brakes+low idle or cut out mystery 140-160 1972

Normally when you add air to a FI system your system adds the proper
amount of fuel and your engine speeds up, unless you are adding a LOT
of air.

I think you have a problem with both your brake booster and your master
cylinder, especially if the greasy stuff smells like brake fluid or will
wash out with hot water. First guess is that you have a hole in your
booster diaphragm so that your idle is based on how much air comes through
the diaphragm rather than through the idle adjusting valve. When you step
on the brake it pretty much stops that and then your idle dips because
that air isn't coming in any more. One way to test this is to disconnect
your brake booster and plug the line, adjust the idle to a normal speed
and then hook the booster back up. If it idles a lot faster, that is the
problem.
If you have a bad rear seal in your master cylinder the front of your
booster will partially fill with brake fluid.
If you then add a hole it the booster diaphragm, when you step on the brake
the fluid in the front is forced through the hole. When you get off the
brake the fluid comes out the vent where the actuating rod goes in the
back of the booster and ends up on your floor.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma







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