ZF BW190's low pressure at idle

[ageless]

recently BOTH gears started reading low at idle (120 port, 80star) without any performance changes. I noticed the star pressure sensor had oil seeping from the hole in the side of it. Reached out to ZF and received replacements, so I thought. I replaced both sensors and changed the oil, no seeping from new sensor. My first question is whether I actually replaced the pressure sensors or if it was the alarm sensors, rear (in the pic) is what was replaced.
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K

Thread 'Transmission low oil pressure'

Sep 18, 2024

I have 1988-67’-CPMY with 12v71s and ZF transmissions. The other day I noticed my port transmission pressure was low. With transmission disengaged and engines in idle (750 rpm) port trans pressure was 80 psi while starboard was 160 psi. Putting the transmission in fwd gear still at idle. The port trans pressure jumps up to 160 psi the same as starboard. With engine speed at 1300 rpm and transmission in fwd gear, the stb trans pressure was about 240 psi. The port transmission stayed at about 160 psi. The pressure did eventually get to 240 but it took some time. Today while docking I noticed...

• Kquaine
• Replies: 1
• Forum: Hatteras Tech Talk

I did find this former chat and followed Eric's recommends, as also recommended in the manual. Oil levels were perfect, It does appear controls have full travel and I removed filter screens and cleaned them. Just to make this interesting, if these weren't ZF I'd think I had a rear seal issue when I discovered the star oil was as black as Detroit oil. Weirdly enough it doesn't smell burnt, there's no visible shavings, and no "odd" sounds. I have not sent a sample off but will be. Spoke with my mechanic who recommended an "at idle" trial (after fluid change) which resulted in port gear reading 250 PSI, star 220 from idle to 1300 RPM's when engaged, back to 80 and 120 disengaged, neither gear temp exceeded 125*, no odd sounds, and no performance issues. Once the gen install is complete, I intend to open the gear and inspect the clutch's and will be replacing the actual pressure sensors, ASSuming I'm correct in my belief I replaced alarm sensors. If anyone has a part number for the actual sensors it would be greatly appreciated, the ZF catalog was of no help
Thanks, as always, for the great support

 

[Captain Ralph]

What is the green water temp? Real cold?
40W oil?

In the picture, the large sender (SW or VDO) would go to a display gauge.
The smaller black Nason sender will go to an alarm.

 

[ageless]

What is the green water temp? Real cold?
40W oil?

In the picture, the large sender (SW or VDO) would go to a display gauge.
The smaller black Nason sender will go to an alarm.

green water temp?

yes, 40w rotella
as I thought, I replaced the alarm sensors, now if I can chase down the pressure sensors--gauges are VDO

 

[Captain Ralph]

green water temp?

Raw or sea water. ☺
If it is real cold, your 40W oil may not flow to well and offer low oil pressure till it warms up.

 

[ageless]

Raw or sea water. ☺
If it is real cold, your 40W oil may not flow to well and offer low oil pressure till it warms up.

I'm in NE Fl and water temps have been unusually cold

 

[Teddyjensen]

New to the ZF world, the manual i hace for the bw190 shows an operating pressure of 25 bar, not sure how that equates to a psi, ive alway ran twindisc, where 350 was the norm

 

[drewread]

New to the ZF world, the manual i hace for the bw190 shows an operating pressure of 25 bar, not sure how that equates to a psi, ive alway ran twindisc, where 350 was the norm

25 bar = 362.594 PSI

 

[Briankinley2004]

tree fiddy sounds about right

 

[ageless]

tree fiddy sounds about right

ugggggg--In 8 years of ownership I've never seen my pressures at 350, typically 250-275. Maybe I've been destroying them all along

 

[Teddyjensen]

25 bar = 362.594 PSI

Ya i did the conversation right after i posted that lol

 

[Teddyjensen]

ugggggg--In 8 years of ownership I've never seen my pressures at 350, typically 250-275. Maybe I've been destroying them all along View attachment 89791

You definitely have the right gauge, psi on top bar on the bottom,

 

[drewread]

ugggggg--In 8 years of ownership I've never seen my pressures at 350, typically 250-275. Maybe I've been destroying them all along

No - reading that document 25 bar is a high pressure alarm situation.

Clutch neutral reading should be 7.5 to 10 bar. (108.8psi to 145psi)

You need to find "PKN" in your manual for proper running pressure +1.0/-0.5bar.

 

[drewread]

You need to find "PKN" in your manual for proper running pressure +1.0/-0.5bar.

PKN should be found as follows:

7) The nominal clutch pressure is specified in the binding, order-specific technical documents and also stamped on the type plate and in the control housing.

 

[ageless]

No - reading that document 25 bar is a high pressure alarm situation.

Clutch neutral reading should be 7.5 to 10 bar. (108.8psi to 145psi)

You need to find "PKN" in your manual for proper running pressure +1.0/-0.5bar.

View attachment 89795

this sounds more likely--why do the Germans have to make this so difficult? LOL. I've tried to get pics of the plates but the control units are mounted above them. I've got an email in to ZF for some support. Still concerned with the black oil

 

[ageless]

18 bar it is

 

[drewread]

View attachment 89862
18 bar it is

Sure looks like you are on the money...

 

[ageless]

Sure looks like you are on the money...

View attachment 89863

Port is on the money, starboard is running 13-14 bar when engaged. Waiting on a new gauge to arrive to check pressures as recommended by ZF.

Interestingly enough the only other recommend was clean the filter housing and screen. I will update when I check pressures

 

[Captain Ralph]

Any oil labs yet on the dark oil?

On my friends BW190s behind 12V71TAs, oil is still crystal clean as changed 2+ years ago.
260 PSI fast cruise.
My TD514s behind 12V71TIs still clear after 3+ years.
250 PSI fast cruise.

Oil labs may help determine what is that dark in the oil.

 

[Captain Ralph]

Oh; Do you have trolling valves?

 

[Briankinley2004]

Try turning that key on item 33 on the parts diagram. It rotates the screen and is supposed to expose new area. I would try that before removing it as it is simple to do