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Volvo L70F low brake pressure problem?

Eulb

Member
Joined
May 20, 2017
Messages
23
Location
United Kingdom
Replaced the accumulators still getting an error code,swapped sensors and still same.

Remove plugs off block under steps and comes up with error for fan and brake failure,fan must be slowing once warm as engine gets warm.

If my brakes were worn would excessive travel cause a low pressure fault?

Tia Eulb...
 

Ben Witter

Senior Member
Joined
Apr 3, 2013
Messages
263
Location
On the outside
What is the fault code? Are you just seeing the message on the display? Can you press the envelope key on the touch pad and get the fault code? While your friend was there you also should have had him erase the codes so you have a clean slate to look at.
Also tell us when the code appears and what are you doing when it appears.
 

Eulb

Member
Joined
May 20, 2017
Messages
23
Location
United Kingdom
What is the fault code? Are you just seeing the message on the display? Can you press the envelope key on the touch pad and get the fault code? While your friend was there you also should have had him erase the codes so you have a clean slate to look at.
Also tell us when the code appears and what are you doing when it appears.

Sorry not an error code,a warning message sometimes it beeps sometimes doesn't.

Only codes I have now are axle sensor codes (both sensors have the wires snapped off) and another for ambient temperature.
 

Eulb

Member
Joined
May 20, 2017
Messages
23
Location
United Kingdom
Got a video up on YouTube now. (Battery light is faulty on dash):rolleyes:


Every time I press the brakes the warning comes up.
 

funwithfuel

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Joined
Mar 7, 2017
Messages
5,519
Location
Will county Illinois
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Mechanic
I can see the brake pressure dropping like a rock just prior to the warning coming up. First thing I would do is check axle oil levels. One of them is probably gaining oil.
 

Eulb

Member
Joined
May 20, 2017
Messages
23
Location
United Kingdom
Checked axles and no lift in oil level.

If I press the brakes slowly the brake pressure lifts without the warning coming on,500psi just about throws you out the seat.

At the end of the clip I hit the brakes like normal and the warning comes up.

 

funwithfuel

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Will county Illinois
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Ok, 2 things.
First, oil pressure is not maintaining in the accumulator manifold. There is a one way check valve that holds oil. Yours is damaged. It should be on top if I remember correct. Follow hose from central valve up to brake manifold. That fitting will be the check valve. Take it out after you bleed down the pressure. Should not be able to blow through.
Second, the oil pressure drops fast, your axle not gaining oil says one or more accumulators has lost its charge. After you change the inlet check valve curl your bucket over relief to see what max brake charging pressure is. Then leave everything be and see if pressure drops on its own.
 

Eulb

Member
Joined
May 20, 2017
Messages
23
Location
United Kingdom
I’ve fitted a new check valve,accumulators are all new but doesn’t always mean they are right.

I’m thinking I’ve a fault with the footbrake valve.

87344EDC-8896-43E9-BA09-1DAEED51C56D.jpeg F8A6A5ED-8929-412F-ACB9-00987E471A0F.jpeg
 

funwithfuel

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Mar 7, 2017
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Will county Illinois
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Have you checked your brake charging pressure? The cut in should be 1780-1800. The cut out should be approximately 2200. Your max brake charging, (bucket over relief) should be 23-2400 psi. Are those values correct?
 

funwithfuel

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Joined
Mar 7, 2017
Messages
5,519
Location
Will county Illinois
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I’ve fitted a new check valve,accumulators are all new but doesn’t always mean they are right.

I’m thinking I’ve a fault with the footbrake valve.

View attachment 220476 View attachment 220477
While that's possible, it's not likely. You can't have a path to tank, simultaneously with a path to brake, you'd have such a leak.
 

Eulb

Member
Joined
May 20, 2017
Messages
23
Location
United Kingdom
Have you checked your brake charging pressure? The cut in should be 1780-1800. The cut out should be approximately 2200. Your max brake charging, (bucket over relief) should be 23-2400 psi. Are those values correct?

I did last time I messed with it and it was right.

Pressure does drop on its own so I’m going to check accumulators.
 

funwithfuel

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Mar 7, 2017
Messages
5,519
Location
Will county Illinois
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It's there to keep your accumulators charged. Otherwise the pump can never fully satisfy the brake circuit and will rob the oil from the fan motor. With the pump working its ass off all the time it will die in short order.
 
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