Hydraulic pressure, value too low

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finalfa
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Hydraulic pressure, value too low

Post by finalfa » Sun Oct 20, 2019 11:34 am

More problems with my Q4. Warning light for AWD lights up after a couple minutes of driving. The error code is Hydraulic pressure, pressure too low. Wrong oil was used in the system, so i changed the oil and flushed it twice. Still the same problem. Piston is all the time at 0%, and pressure reading is always 28-29 bar. I have tried bleeding the system with the alfa tester many times, no difference. The Viscomatic pipes were all remade a month ago. Ideas? :x
Alfa Romeo GTV 6 2.5 -83
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Alfan
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Re: Hydraulic pressure, value too low

Post by Alfan » Mon Oct 21, 2019 9:10 am

1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 270kkm
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55kkm
2011 Alfa Romeo Giulietta Multiair TCT Bianco Pastello 175kkm
2015 Alfa Romeo 4C Rosso Competizione 90kkm

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Mon Oct 21, 2019 9:24 am

Alfan wrote:
Mon Oct 21, 2019 9:10 am
Maybe this?

http://www.alfaromeo164register.com/vie ... f=2&t=1962
Could that be the problem even if i don't seem to have hydraulic pressure? Only around 30 bar at all times, no change when driving, or revving. I've read that the Coupling should engage even at around 20 bar.
I don't hear the coupling engaging
Alfa Romeo GTV 6 2.5 -83
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Alfan
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Re: Hydraulic pressure, value too low

Post by Alfan » Mon Oct 21, 2019 9:26 am

I don't have other suggestions. Otherwise you have to go through the trouble shooting in the user manual and take it step by step.

There are more threads about the 4WD here, where different things have been tried.
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 270kkm
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55kkm
2011 Alfa Romeo Giulietta Multiair TCT Bianco Pastello 175kkm
2015 Alfa Romeo 4C Rosso Competizione 90kkm

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Mon Oct 21, 2019 9:27 am

I noticed that the Recharge valve only gets 3.7V, so i fixed that and now it gets 12V. But still no difference in hydraulic pressure. At least that's what the tester's telling me.
Alfa Romeo GTV 6 2.5 -83
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Alfa Romeo 164 Q4 3.7 -96
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Alfan
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Re: Hydraulic pressure, value too low

Post by Alfan » Mon Oct 21, 2019 9:28 am

Also, does the light come on immediately when starting the engine, when driving and going above a certain speed or...?

If you erase the error code when driving, does the light come on again?

All of this can indicate where the problem lies.
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 270kkm
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55kkm
2011 Alfa Romeo Giulietta Multiair TCT Bianco Pastello 175kkm
2015 Alfa Romeo 4C Rosso Competizione 90kkm

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Mon Oct 21, 2019 9:30 am

Alfan wrote:
Mon Oct 21, 2019 9:28 am
Also, does the light come on immediately when starting the engine, when driving and going above a certain speed or...?

If you erase the error code when driving, does the light come on again?

All of this can indicate where the problem lies.
Comes on after approx. 2-5 min driving. Passes self check every time. Always gives the same error; pressure too low.
If i erase it, it comes on again after the same 2-5 min.
Alfa Romeo GTV 6 2.5 -83
Alfa Romeo 156 2.5 V6 -02
Alfa Romeo 164 Q4 3.7 -96
Alfa Romeo 164 Q4 3.0 -94

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Mon Oct 21, 2019 4:28 pm

Replaced the pressure sensor in Viscomatic group today. Now the pressure sank to 6 bar, and won't rise from there. Goes around 5-6 bar. Ideas?
Alfa Romeo GTV 6 2.5 -83
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Alfan
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Re: Hydraulic pressure, value too low

Post by Alfan » Mon Oct 21, 2019 6:07 pm

I don't have more details, can only refer to all the other threads and the manuals. But it seems strange that the pressure dropped after replacing the sensor.

If you haven't done it, I suggest to clean the plugs to the viscomatic box.

Even though it has become quiet on this site, some people might chime in with something else...
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 270kkm
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55kkm
2011 Alfa Romeo Giulietta Multiair TCT Bianco Pastello 175kkm
2015 Alfa Romeo 4C Rosso Competizione 90kkm

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AlfaWhiz
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Re: Hydraulic pressure, value too low

Post by AlfaWhiz » Mon Oct 21, 2019 6:40 pm

I'll be watching your thread and give it some thinking... I don't have a "pressure too low" error, but mine keeps getting "pressure fluctuation too high" error after some minutes of driving (30-60 mins slow driving or 5-10 mins above 90 km/h). I really wish we had more knowledge on this system as it's indeed very hard to diagnose properly.

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Mon Oct 21, 2019 7:55 pm

Measured today that the recharge valve gets 12V when connected. The voltage then drops to around 3V when the AWD light lights up. (Around 2-5 min after start up).
If i remove the fault code, it starts all over again.

Seems like the hydraulic group is getting some fluid atleast. Good thing i was wearing safety glasses when i opened up a banjo bolt for one of the lines.

The recharge valve clicks when i tried giving it 12V straight from a spare battery. So at least in theory, it should be ok.

All measurements are done by keeping the connector attachted to for example the recharge valve, and poking a hole in the isolation and measuring from there.

Does anyone know how much pressure comes from the 2 Stage pump to Hydraulic group? Just asking out of interest.
And if anyone knows any Ohm readings for the sensors, i would be very grateful.
Alfa Romeo GTV 6 2.5 -83
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Alfan
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Re: Hydraulic pressure, value too low

Post by Alfan » Mon Oct 21, 2019 8:43 pm

Your signature contains 2 Q4's :) Is the other one running? If so, you can put the tester on that and see the pressure level.

From memory the 4WD system goes up to app. 100 bar when fully functional.

All the values should be in the manual, which I assume you have downloaded?
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 270kkm
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55kkm
2011 Alfa Romeo Giulietta Multiair TCT Bianco Pastello 175kkm
2015 Alfa Romeo 4C Rosso Competizione 90kkm

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Mon Oct 21, 2019 8:49 pm

Alfan wrote:
Mon Oct 21, 2019 8:43 pm
Your signature contains 2 Q4's :) Is the other one running? If so, you can put the tester on that and see the pressure level.

From memory the 4WD system goes up to app. 100 bar when fully functional.

All the values should be in the manual, which I assume you have downloaded?
The other Q4 is a slightly bigger project, so no, it is not running. I have discussed this problem a lot with @Vehje, and he got at least around 80-90 bar on idle. I will have a look at the manuals again, thanks.

I will try again tomorrow measuring the values of the recharge valve and pressure sensor, and see if the change of pressure sensor has made any difference.
It's quite the system to work on this viscomatic.
Alfa Romeo GTV 6 2.5 -83
Alfa Romeo 156 2.5 V6 -02
Alfa Romeo 164 Q4 3.7 -96
Alfa Romeo 164 Q4 3.0 -94

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Mon Oct 21, 2019 8:56 pm

Worth noting, that i haven't got any difference made to the piston position. Still at 0% all the time. Unable to bleed the system due to the low pressure.
Another question, has anyone got experience with a white, almost foamy residue from the visco group? When i removed the sensor, it came out. But i think that it is only the fluid mixed with A LOT of air. (Due to not being able to bleed the system, thanks to the "low pressure". The previous owner had put wrong fluid in the system, but i changed it and flushed it real good, so it shouldn't be a problem anymore.
Alfa Romeo GTV 6 2.5 -83
Alfa Romeo 156 2.5 V6 -02
Alfa Romeo 164 Q4 3.7 -96
Alfa Romeo 164 Q4 3.0 -94

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Tue Oct 22, 2019 4:55 pm

Today i continued diagnosing my Q4, and i noticed that the hose from 2 stage pump to Viscogroup, has a small hole, and was twisted pretty badly. I will remanufacture a hose quickly, and see if this was the reason. Sounds pretty dumb now that i have spent many hours with an oscilloscope, and only now i realize there's a hole in a hose.
If anyone's wondering, i'm talking about part number 60605589.

Hopefully i will get it soon up and running on four wheels again. :P
Alfa Romeo GTV 6 2.5 -83
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Alfan
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Re: Hydraulic pressure, value too low

Post by Alfan » Tue Oct 22, 2019 8:37 pm

Be aware of this, it may be difficult to make.
viewtopic.php?t=1963

But it definitely is something worth checking, as that would restrict flow.
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 270kkm
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55kkm
2011 Alfa Romeo Giulietta Multiair TCT Bianco Pastello 175kkm
2015 Alfa Romeo 4C Rosso Competizione 90kkm

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AlfaWhiz
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Re: Hydraulic pressure, value too low

Post by AlfaWhiz » Tue Oct 22, 2019 9:52 pm

Good that you remembered Alfan, I've added a post in that thread just now to conclude the discussion, as I ended up getting 60605589 directly from Alfa Romeo which has solved my problem.

Reproducing was not successful in my case. I suspect flow restrictors have not been swapped out correctly which has caused a weird vibration problem.

But perhaps if you give it a try we will learn something more, who knows.

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Wed Oct 23, 2019 6:30 am

I will get a new hose manufactured by a local hydraulics shop today, so i will install it later tonight and see. If not, i think there could be a problem with the recharge- and/or proportional valve. According to the documents, the proportional valve is NOT PWM modulated, rather current modulated
"This is a distribution valve of the proportional type which causes a quantity of fluid to flow *which is proportional to the activation current supplying it*."

I have read that the proportional valve has 4 positions, but i have no idea at what current these activate, so it will be difficult to measure something of use.

The recharge valve clicks, but is there a way to ensure that it actually works and lets flow through? Just because it clicks doesn't mean it is working as it should.

I am assuming i am getting flow to the pump, so the components which could cause low pressure would be the recharge valve, proportional valve, safety valve and something else? Could the bleed valve be "stuck open" and cause no fluid being stored in the accumulator?

If the new hose does not fix this issue, i think i will try with another hydraulic block with "new" valves.
Alfa Romeo GTV 6 2.5 -83
Alfa Romeo 156 2.5 V6 -02
Alfa Romeo 164 Q4 3.7 -96
Alfa Romeo 164 Q4 3.0 -94

finalfa
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Re: Hydraulic pressure, value too low

Post by finalfa » Thu Oct 31, 2019 6:53 pm

Solved!!

Replaced all lines and fittings for Visco and power steering with teflon AN4 lines. Rather difficult to find all the correct fittings. Also replaced the male brake line fittings for supply and return from visco to hdyraulic block with banjo fittings.
Seems like the recharge valve was stuck, so by disassembly it and playing with 12V i got it working again. If anyone's wondering, it is rather easy to disassemble all the valves and sensors. So shortly said, the problem was in the recharge valve.
No error code, and i now have around 85-95 bar in the hydraulic system.
Everything seems good, and looks like the visco coupling engages and disengages as it should.
Tomorrow test drive! :lol:
Alfa Romeo GTV 6 2.5 -83
Alfa Romeo 156 2.5 V6 -02
Alfa Romeo 164 Q4 3.7 -96
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Re: Hydraulic pressure, value too low

Post by AlfaWhiz » Thu Oct 31, 2019 7:18 pm

Excellent news! And congrats on getting this fixed so quickly, it can be a real chore to deal with those problems but you really got it sorted very nicely. :mrgreen:

You've now inspired me to look into my 'pressure variations too high' issue as well.

Enjoy the test drive!

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Alfan
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Re: Hydraulic pressure, value too low

Post by Alfan » Thu Oct 31, 2019 8:49 pm

Great that you got it sorted 8)

Enjoy the test drive and if you have photos of the parts, please put them here as well.
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 270kkm
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55kkm
2011 Alfa Romeo Giulietta Multiair TCT Bianco Pastello 175kkm
2015 Alfa Romeo 4C Rosso Competizione 90kkm

finalfa
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Location: Espoo, Finland

Re: Hydraulic pressure, value too low

Post by finalfa » Sat Nov 02, 2019 8:42 am

Yesterday was test drive day. And boy did i have some fun. Visco works perfectly. I also bled the system with the tester, so now i have perfect pressure and piston movement!
Now i still have the ABS and airbag to crack next.
Alfa Romeo GTV 6 2.5 -83
Alfa Romeo 156 2.5 V6 -02
Alfa Romeo 164 Q4 3.7 -96
Alfa Romeo 164 Q4 3.0 -94

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Alfan
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Re: Hydraulic pressure, value too low

Post by Alfan » Sat Nov 02, 2019 11:49 am

:mrgreen: 8)
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 270kkm
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55kkm
2011 Alfa Romeo Giulietta Multiair TCT Bianco Pastello 175kkm
2015 Alfa Romeo 4C Rosso Competizione 90kkm

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