John Deere 770G hydraulic overheating.

[NsiCat]

We got a Deere Grader that overheat under 15 mins of operation.
Check the filter, coolant (heat exchanger), the fan blows at its high speed it seems well.

CAT make like 12H and 140G don't even have heat exchanger and they are working fine.

Can anyone help me with the hydraulic schematic.
And what value should low standby pressure be.
What could be the cause

 

[mg2361]

Welcome to HEF NsiCat!

Temperature been confirmed with an infrared temp gun?

Standby pressure spec is 1775-1985 psi

 

[NsiCat]

We don't have the tools. It boils really fast and hot under 20mins of operation.
It melts the sight glass (oil level guage)

 

[Vetech63]

We don't have the tools. It boils really fast and hot under 20mins of operation.
It melts the sight glass (oil level guage)

YIKES!!!!

 

[mg2361]

Check your messages.

 

[NsiCat]

The machine now have knocking sound on starting followed by black smoke, until I bleed number 3 and it disappear both sound and smoke.
It's a common rail system.

 

[NsiCat]

I I've found what cause the ove within a short period of operation.
It's the cooling system.the fan go slow after some minutes.
I narrowed the issue to the fan control valve .
The fan Valve component are
1. Fan speed control solenoid (pressure reducing)
2. Fan direction solenoid
3. Pressure sensor
4. Check valves (4)

I will really appreciate if I get exact hydraulic schematic for this machine (cooling system)

John Deere 770G
Machine serial number DW770GX625056

 

[mg2361]

Check your messages.

 

[Welder Dave]

I'd guess MG gave him info and he figured out the problem.

 

[NsiCat]

Welcome to HEF NsiCat!

Temperature been confirmed with an infrared temp gun?

Standby pressure spec is 1775-1985 psi

Good day Friend
Please I'm having issues on John Deere Grader.
There is a constant pressure present in a load sensing line, this keeps the pump overworking that it begins to heat.
Constant flow from steering valve and both left and right direction control valve. I made some adjustment to flow-reducing-valve in the combination valve (hydraulic manifold) and steering valve became normal but the two control valve keeps producing pressure.
I also check load sense relief valve, I can't make adjustment to it, nothing moves and I don't know how it works - if it's stucked.



Machine plate number: DW770GX625066 Motor Grader
Anyone experience this issue or help me with the hydraulic Schematic? please your contribution is well appreciated.

 

[mg2361]

What are your specific pressures for Load sense, pump standby, and differential pressures?

Check your messages.

 

[NsiCat]

What are your specific pressures for Load sense, pump standby, and differential pressures?

Check your messages.

Immediately on engine start up, standby pressure increase to 1500psi and maintain the pressure.
It stays in 1500psi at the touch of lever (no changes under operation)
Im yet to measure load sense line though there is a high pressure present in the line - which I believe should be near zero.

Could it be;
1. Faulty load sense relief valve
2. Not-fully-center (close) control valve in the section - slightly operated..

 

[nikthewho]

We don't have the tools. It boils really fast and hot under 20mins of operation.
It melts the sight glass (oil level guage)

DAMNNNN

 

[mg2361]

Check for any partially stroked spools first.

 

[NsiCat]

I sincerely appreciate all the insights and support I received from the great minds in this forum. I’m truly glad to be part of this platform.

My heartfelt thanks to everyone who took the time to respond to my post.
I’m pleased to inform you that the issue has been resolved.

For anyone who may encounter a similar problem, here are the steps I took:

Connected a pressure gauge to the pump.
Adjusted the pressure reducing valve.

Observed the pressure drop from 1500 psi to 500 psi (system operating pressure was initially 1500 psi).

Adjusted the load-sense relief valve until it reached 2000 psi max operating pressure.

The machine is now operating perfectly.

However, I’m still curious about why Deere incorporated a load-sense relief valve into the system, as the adjustments above seemed to function similarly to tuning the load-sense and pressure compensator spool.

Thank you all once again.

 

[nikthewho]

I would like to document this. could you share images or anything helpful?

 

[NsiCat]

I would like to document this. could you share images or anything helpful?