Cat 312BL hydraulic heating problem.

Hello everyone,

Cat 312BL excavator serial number 8JR...

We had a hydraulic heating problem since some time. Replaced two hydraulic fitters but nothing changed. Looked at fan belt, cleaned the radiator,sealed the gap between radiator and oil cooler, didn't inspect the return filter(big one) near the hydraulic tank yet.

Normally when we work continuously 5-6 hours hydraulic oil temperature gauge sits around 6th band of its indication on monitor. But now after about 4 hours of work it rises to around 8th band and if we work further more it rises up all the way until warning lights comes on.

If we idle the machine for about 5 minutes when it reached to around 8th band of hydraulic temperature gauge, it will drop to 6th band within that 5 minutes.
It implies me that hydraulic cooling system works fine.

When we do heavy work engine doesn't get load at all. Though we operate control levers until it reaches to its release pressure engine runs very well with out loosing it's rpm badly.
This seems to me as hydraulic horse power is within its limits and prv also works fine. As I think more power means more heat.

Finally what we did was we increases the voltage level to the PRV Solenoid though it seems works fine using PRV calibration mode.
And now machine works normally.
My question is how this adjustment affect the hydraulic temperature ? Because before the adjustment also engine didn't load or stall at all under heavy loads. At that time it seems to me PRV is works fine.

So I would like to here our experts opinion on this issue.

Thank you.

I'm not so up on CAT-speak these days. PRV is what exactly?

92U 3406 said:

I'm not so up on CAT-speak these days. PRV is what exactly?

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PRV means Proportional Reducing Valve Solenoid. In other words it is the pump solenoid. It sends the power shift pressure signal (using pilot oil) to the pump regulators to destrok the pump according to the pwm signal sends from the controller. And this prevents the overloading of the engine. This is act as a under speed control or I think we can say as "anti stall function".

Could this thingy be bad?

185-9063

heymccall said:

Could this thingy be bad?
View attachment 234865 View attachment 234866
185-9063

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Is this the part you have mentioned? If i am correct bypass check valve and slow return check valve are both inside this unit.

We have the same machine and have had the same issue. It was the valve that heymccall has showed you . It controls the flow to the rad. Something inside the valve fell apart didn’t need any parts just reassembled it . We have also had issues when doing demolition work with it the fine dust plugs up the rad and the only way I’ve found to wash it out is to swing the air con rad out of the way remove the hydraulic rad , wash it while it’s out , wash the engine rad in place and reinstall the rest . Tried air , hot water wash but the only way is to do them individually, don’t have any problems till we tear a house down then it starts

Hanco said:

We have the same machine and have had the same issue. It was the valve that heymccall has showed you . It controls the flow to the rad. Something inside the valve fell apart didn’t need any parts just reassembled it . We have also had issues when doing demolition work with it the fine dust plugs up the rad and the only way I’ve found to wash it out is to swing the air con rad out of the way remove the hydraulic rad , wash it while it’s out , wash the engine rad in place and reinstall the rest . Tried air , hot water wash but the only way is to do them individually, don’t have any problems till we tear a house down then it starts

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In your case did you idle the machine for about 5 minutes after it reached to the very high hydraulic temperature to see whether it drops down the temperature to a acceptable level.

Because I am asking this, i think if the temperature drops down to acceptable level ( by about 2 bands of temperature gauge on monitor ) by placing the machine on idle for about 5 minutes, as I think if I am correct it implies me that the hydraulic cooling system works fine.
I think the part you and senior member "heymccall" mentioned is within the hydraulic cooling system.
As I above said if I am correct and can guess as hydraulic cooling system is good then this part you mentioned should be working properly.
Correct me if I am wrong.

More or less yes that’s what our machine did , the machine at an idle the flow though the rad is good but as you work the machine the flow is the same it doesn’t change there for no extra cooling . Not sure that’s exactly what is happening but it’s close to what it is .

By increasing the current for the prv you have decreased the hydraulic power output and that's probably why it doesn't overheat anymore.

I'd look at temps before and after the hydraulic cooler with an IR temp gun to make sure you get a good temp difference over it.
Also compare the temps of the flow to the radiator and the bypass that goes straight to tank.

You could have a bad relief that opens to early, that will create heat, check by stalling each function and verify pressure.
A worn main pump creates heat as well, had several machines that was cured by replacing rotating group in the main pump.
Even a swivel with bad seals can cause overheating if the machine is tracking alot.

Per Eriksson said:

By increasing the current for the prv you have decreased the hydraulic power output and that's probably why it doesn't overheat anymore.

I'd look at temps before and after the hydraulic cooler with an IR temp gun to make sure you get a good temp difference over it.
Also compare the temps of the flow to the radiator and the bypass that goes straight to tank.

You could have a bad relief that opens to early, that will create heat, check by stalling each function and verify pressure.
A worn main pump creates heat as well, had several machines that was cured by replacing rotating group in the main pump.
Even a swivel with bad seals can cause overheating if the machine is tracking alot.

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Sir,
Thanks a lot for your reply. Really good points to look at. I will check those quickly And tell you the results.

I need to clarify one thing, after machine get heats up if I idle the machine for about 5 minutes about two bands of temperature gauge goes down. From this judgement can i think that the cooling system is good.

anuradha said:

I need to clarify one thing, after machine get heats up if I idle the machine for about 5 minutes about two bands of temperature gauge goes down. From this judgement can i think that the cooling system is good.

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No, that proves nothing. Measure temperature at top, then at bottom, of hydraulic cooler.

Go out to machine at night, and place lamp inboard of radiator. Now, look at radiator (& cooler, obviously) and can you see light cleanly?

heymccall said:

No, that proves nothing. Measure temperature at top, then at bottom, of hydraulic cooler.
Go out to machine at night, and place lamp inboard of radiator. Now, look at radiator (& cooler, obviously) and can you see light cleanly?

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Sir thanks for correcting me on this issue. I will check tempreture difference & will check the radiator as you mentioned as well and let you know.

anuradha said:

Sir thanks for correcting me on this issue. I will check tempreture difference & will check the radiator as you mentioned as well and let you know.

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Just wondering did you solve your overheating problem & if so what was probable cause? Thanks