Help diagnose G5 2.5 dual problem

[applegear]

I have a G5 2.5GHz Dual with a problem.

If left off for while, boots up, works normally for about 5mins
then goes to sleep.
istat shows fans at full speed, processors around 80 degree temp,
when gets to around 90 degree, shuts down.
Then usually does not even show video screen when booting up
next time. Blank, full fans.

I think is a power supply issue?
If video card taken out and booted, fans do not go full power.
Could it be power supply no longer outputting enough power to
handle all normal functions?
The fact it can boot and work normally for short while, to me
would say is a full working Mac, but without enough power to
function over time?
According to istat, the processors are constantly at a very high
temperature. There do not appear to be any leaks in the liquid
cooling system.
Have re-seated RAM, video card, reset PRAM.

I am looking at getting a new power supply for it, but want to
sure I'm not completely wasting my time.
Would there be anything to indicate is logic board or processor
issue?

 

[rabidz7]

I have a G5 2.5GHz Dual with a problem.

If left off for while, boots up, works normally for about 5mins
then goes to sleep.
istat shows fans at full speed, processors around 80 degree temp,
when gets to around 90 degree, shuts down.
Then usually does not even show video screen when booting up
next time. Blank, full fans.

I think is a power supply issue?
If video card taken out and booted, fans do not go full power.
Could it be power supply no longer outputting enough power to
handle all normal functions?
The fact it can boot and work normally for short while, to me
would say is a full working Mac, but without enough power to
function over time?
According to istat, the processors are constantly at a very high
temperature. There do not appear to be any leaks in the liquid
cooling system.
Have re-seated RAM, video card, reset PRAM.

I am looking at getting a new power supply for it, but want to
sure I'm not completely wasting my time.
Would there be anything to indicate is logic board or processor
issue?

It sounds like you are having an issue with the liquid cooling. You will need to check for leak.

 

[ybz90]

I agree. That it works and then fails seems more likely to indicate a problem that is heat-related than one that is power related. Even if no leak is apparent, it may be an issue.

Or, even if it hasn't leaked, it could be failing in some other way that is deficient. You mention the high temps -- how high are they? I don't know much about the specific cooling system in these G5s, but iirc, they use some sort of coolant that could have gunked up over time. That's why I prefer just distilled water in all my LC setups with a kill coil.

 

[666sheep]

istat shows fans at full speed, processors around 80 degree temp,
when gets to around 90 degree, shuts down.

You mean Celsius, I assume. If it's getting such temps 99% its the pump that has died (or it's totally clogged). Check in iStat if you have any fan @0 rpm. Pump is reported as fan in iStat.

 

[applegear]

I thought istat was farenheit? I thought was high number as I have 1.6 G5 which shows temp at half that.
Fans show 3200rpm

Edit: Is celcius. But goes to that straight away, can they get so hot so quickly?

 

[666sheep]

Download Temperature Monitor to confirm iStat reads. If they're true it would mean that there's no coolant flow. It works like in a car. Coolant must flow through waterblocks and radiator to spread heat properly. These CPUs are running hot. LCS is there not without a cause.
Check threads about LCS rebuilding here and on xlr8yourmac.

 

[applegear]

Download Temperature Monitor to confirm iStat reads. If they're true it would mean that there's no coolant flow. It works like in a car. Coolant must flow through waterblocks and radiator to spread heat properly. These CPUs are running hot. LCS is there not without a cause.
Check threads about LCS rebuilding here and on xlr8yourmac.

Computer only stays on for a minute then goes to sleep. Temps on both constantly climbing. CPU A got up to 107 degrees c, CPU B up to 91 degrees c. Heatsink around 48 degrees c.

 

[666sheep]

Try reduced performance: https://forums.macrumors.com/threads/1308165/ maybe it will last on a little longer. Anyway, you need to rebuild LCS to fix your G5. You'll find all neded info in LCS rebuilding threads on this forum.