Cat 924 G radiator fan doesn't turn

[DennisZ]

Good day

My 2001 Cat 924G is heating up because the radiator fan doesn't turn. Only on high engine revs. I checked oil supply to the little pump on the right side of the engine, has plenty of oil but none comes out the hoses to the fan at idle... Is that pump shot? Can there be something adjusted in the valve behind the pump, to the right on the picture?

Regards Dennis

 

[Nige]

The fan pump is electronically-controlled IIRC. There is probably a test procedure for it.
Serial Number..?

 

[kshansen]

Good day

My 2001 Cat 924G is heating up because the radiator fan doesn't turn.

Regards Dennis

As Nige says need a S/N.
Just as an example here is a list of the 924G's on SIS, and this is only those that show on my USA based SIS access. Also each of them may have one or more change in the Prefix's shown:

 

[DennisZ]

The fan pump is electronically-controlled IIRC. There is probably a test procedure for it.
Serial Number..?

3PZ00845

 

[kshansen]

Best I can do is these two forms. Seems the same pump that powers the cooling fan also supplies the brake pressure. There appears to be a "priority valve" that sends oil to brakes first then to fan. So if the pump was weak or "priority valve" was faulty it could cause the problem. Hope someone with more direct knowledge can chime in on this one. Does not appear to be electronically controlled, from what I see.

 

[Nige]

That machine has two accumulators on the brakes. The first thing I'd be checking is the accumulator charge.

 

[kshansen]

That machine has two accumulators on the brakes. The first thing I'd be checking is the accumulator charge.

Good point, if the pump is working full time to keep brake pressure up there would not be enough to run the fan.

 

[Nige]

I came across exactly that problem this week on a 938.

 

[DennisZ]

I came across exactly that problem this week on a 938.

Brake accumulators need to be filled/replaced as the brake light comes on as soon as you hit the brake pedal. But now brakes don't seem to work anymore either after yesterday unplugging some hoses...

I'm 2 weeks out from receiving it's predecessor, a 926M so I don't want to do to much on it. Also have a 924 K to do the work...

 

[Nige]

If the brake (accumulator) warning light comes on like you say then either the charge is low on one or both accumulators, or one of them has failed completely. The fact that the brake pump is frantically trying to keep up with the demands of the brakes means there is little or no flow capacity left for the fan motor, hence it is spinning slowly.

 

[heymccall]

Just went thru this crap on a Komatsu WA270-7 with 8k hours.
The regulator cartridge for the brake and fan supply oil went south (intermittently at first).
Symptoms...brake accumulator and fan rpm codes and little to no fan operation once the oil warmed a bit, but brakes always worked good.
You could test until you were blue and it would always test good.
Komatsu makes it harder to test as they use their own unique threaded fittings.

 

[heymccall]

And, a failed accumulator won't "dump" oil pressure. It will just lose the reserve capacity (repeated application will out run the oil supply). If you're not applying the brakes, the accumulators use no oil volume.

 

[kshansen]

And, a failed accumulator won't "dump" oil pressure. It will just lose the reserve capacity (repeated application will out run the oil supply). If you're not applying the brakes, the accumulators use no oil volume.

Not knowing the operating situation this machine is working under it maybe working in a way that brakes are being applied very often. Also if this has had an accumulator and or brake problem for some time maybe the pump is getting tired from constant use. Or could the accumulators not even be the problem and it is a problem in the priority valve or pressure relief valve?

I've heard of people going through all kinds of motions trying to fix something simple like a brake light that was not working only to find the problem was something the "new" bulb the put in to replace the original bad one was defective despite being new in the package or the ground circuit for the tail light was bad and they tested the "hot" wire to the brake light by hooking the ground wire for test light to some place that did have a good ground.

And who knows what other problems the machine may have that we have not been made aware of up to this point

 

[Nige]

HMC's right. A failed accumulator(s) won't dump system pressure. However if the accumulators are not up to snuff the pump will simply become overwhelmed when asked for flow for the braking system and the fan system at the same time, and with the Priority Valve set to supply the brake system first the fan will always suffer. These systems are typically specified with a pump flow way lower than system demand when the brakes are applied and depend completely on the accumulators to provide the makeup oil flow whenever the brakes are applied.

Dennis, if you start the machine up from cold first thing in the morning how long does it take for the brake system warning light (4) to go out.? Is it almost immediate after you start the engine or does it take a while.? If the latter, how long does it take.?

 

[John C.]

Just another thought. Hydraulic pumps don't fail from use. They fail because of contamination. While springs and seals have a defined life, a hydraulic pump operated within it's defined specifications will out live most of the other components on the machine. I'm guessing you don't do oil sample analysis or have regular hydraulic oil change intervals? Do you have a service manual for the machine? I've seen this scenario in the cook book troubleshooting section of the manual.

 

[DennisZ]

HMC's right. A failed accumulator(s) won't dump system pressure. However if the accumulators are not up to snuff the pump will simply become overwhelmed when asked for flow for the braking system and the fan system at the same time, and with the Priority Valve set to supply the brake system first the fan will always suffer. These systems are typically specified with a pump flow way lower than system demand when the brakes are applied and depend completely on the accumulators to provide the makeup oil flow whenever the brakes are applied.

Dennis, if you start the machine up from cold first thing in the morning how long does it take for the brake system warning light (4) to go out.? Is it almost immediate after you start the engine or does it take a while.? If the latter, how long does it take.?
View attachment 202399

At the moment it won't brake at all but I guess that might be due to me unhooking some hoses for troubleshooting. I phoned my dealer to come and fix it, but the quote they gave me made me decide to leave it. As I said I'm 2 weeks out on it's replacement

 

[Mobiltech]

It could also be the brake/fan charge relief valve. I would bet on the pump.

 

[pauw]

That machine has two accumulators on the brakes. The first thing I'd be checking is the accumulator charge.

hello how much pressure ?

 

[pauw]

on the accumulator

 

[Nige]

Please supply a machine Serial Number so that the appropriate testing procedure and pressure setting information can be located.

Edit. I found it on your message - 3PZ01130. Checking the system it recommends first checking the operation of the pump that powers the fan drive and brake system. I will try to post up this procedure first. There is no sense in going for the accumulator first if the pump is the issue.