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> Turbo Boost Control Circuit Leak On V50 1.6d
CNogueira
post Feb 25 2013, 05:27 AM
Post #1


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Member No.: 114,699
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Location: Portugal
Drives: Volvo V50 1.6D



Hello.

I need some help here diagnosing an eventually leaking boost control valve on my V50 1.6D.
Recently it developed the following behaviour, aprox. 15min. after shutting off the engine, the brake peal becomes hard. Nevertheless, I’m sure the brake booster and respective (new) check valve are tight!
I developed some investigation on the problem I found that It looks like the turbo boost control circuit has a leak and is stealing vacuum from the brake vacuum line! They are connected to the same plug in the vacuum pump.
I reached this conclusion because I removed the turbo boost control vacuum tube and placed a rubber plug in its place. With the plug in place (and with no turbo L) the brake booster is normal again, I mean, it can retain the vacuum for more than 24h.

I got a mighty vac pump and applying it to the beginning of the turbo boost circuit, I found the following:

- With the engine shut down, applying vac up tp 500mmHg, the system starts to exhibit leak and it is not possible to go over 500mmHg because of (apparent) leak.
- During this procedure I was able to confirm that the valve breather is sucking air!
- I was able to confirm that vacuum reservoir, all vacuum tubes and the turbo actuator are tight and have no leaks. All it’s missing is the valve!

I’m not sure about how this valve works in detail, but to my understanding, with the engine shut down, the valve should be closed and tight, right?
If yes, the valve should be tight when vacuum in applied to the entrance, right? In fact it’s not!
If both previous sentences are correct, I shouldn’t be able to feel air being sucked through the valve breather in this circumstances right? In fact it’s sucking air…
Can someone explain me how to test this valve for vacuum tightness? I have the mighty vac pump…

Doe it look to you that all this troubles are caused by a leaking valve? Nevertheless the brakes are powerful (enough) and the turbo boost control function seems to be Ok!
All I feel strange is the fact that brake booster has no vacuum on it 15min after shutting of the engine and as I said, brake booster and its check valve are tight when I disconnect the booster control circuit and close it’s vacuum passage.

Thanks in advance.

CN
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danielm85948
post Feb 25 2013, 06:01 AM
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Location: glasgow uk
Drives: volvo 940 se turbo 1991



QUOTE (CNogueira @ Feb 25 2013, 06:27 AM)
Hello.

I need some help here diagnosing an eventually leaking boost control valve on my V50 1.6D.
Recently it developed the following behaviour, aprox. 15min. after shutting off the engine, the brake peal becomes hard. Nevertheless, I’m sure the brake booster and respective (new) check valve are tight!
I developed some investigation on the problem I found that It looks like the turbo boost control circuit has a leak and is stealing vacuum from the brake vacuum line! They are connected to the same plug in the vacuum pump.
I reached this conclusion because I removed the turbo boost control vacuum tube and placed a rubber plug in its place. With the plug in place (and with no turbo L) the brake booster is normal again, I mean, it can retain the vacuum for more than 24h.

I got a mighty vac pump and applying it to the beginning of the turbo boost circuit, I found the following:

- With the engine shut down, applying vac up tp 500mmHg, the system starts to exhibit leak and it is not possible to go over 500mmHg because of (apparent) leak.
- During this procedure I was able to confirm that the valve breather is sucking air!
- I was able to confirm that vacuum reservoir, all vacuum tubes and the turbo actuator are tight and have no leaks. All it’s missing is the valve!

I’m not sure about how this valve works in detail, but to my understanding, with the engine shut down, the valve should be closed and tight, right?
If yes, the valve should be tight when vacuum in applied to the entrance, right? In fact it’s not!
If both previous sentences are correct, I shouldn’t be able to feel air being sucked through the valve breather in this circumstances right? In fact it’s sucking air…
Can someone explain me how to test this valve for vacuum tightness? I have the mighty vac pump…

Doe it look to you that all this troubles are caused by a leaking valve? Nevertheless the brakes are powerful (enough) and the turbo boost control function seems to be Ok!
All I feel strange is the fact that brake booster has no vacuum on it 15min after shutting of the engine and as I said, brake booster and its check valve are tight when I disconnect the booster control circuit and close it’s vacuum passage.

Thanks in advance.

CN

the trouble can be your turbo bypass valve is leaking it is a diaphragm ,you can get pin holes or a spilt in it.
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CNogueira
post Feb 28 2013, 06:17 AM
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Posts: 3
Joined: 23-February 13
Member No.: 114,699
Status: Offline
Location: Portugal
Drives: Volvo V50 1.6D



Does anyone know if this boost control valve (vacuum valve) is of the ON/OFF type or if it is of pressure regulator type?

CN
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