G4 Quicksilver won't restart after warmup.

Quicksilver 2002, 800 MHz, 1 Gig Ram, 80 Gig Master(w/OSX10.4) and 250 Gig slave(w/OSX 10.4)

I bought this Mac about a month ago. It starts up fine. After it warms up the fan goes up to high. If restarted or shut down and started, it will go to a gray screen, with a gray apple, but no pinwheel. After a couple of minutes the gray apple turns to a O with a \ through it. If restarted with the option Key down, it shows both HD's with blessed OSX 10.4 on each and if installed, it also shows the emergency DVD. But no matter which disk is selected, it goes to O\. After unpluging to shut it down and waiting a couple of hours(it seems to have to cool down), it starts right up.
I've installed a new battery and zapped the pram.
I've used Techtools Pro 4.5.2, and Disk Utilities, everything passed. I've used Hardware Monitor 4.11 but this Mac only shows temp sensors for the two internal S.M.A.R.T. hard drives and nothing else.
I've installed Tempreture Monitor, but this mac has ATA built in and the app does'nt see the sensors.

Can temp( ATA)sensors be replaced or reset? Any way to check cpu temp? How can I check the heatsink? What is heat sink grease and where can I get some?
Anything you can think of would be of help, Thanks.

Welcome to Mac Forums msmasters!

I am sorry to hear that you are having troubles.

Once the fans kick in to high, does the machine continue to run, or does it eventually crash?

Have you opened the case and inspected? Could the fans be clogged with dust? This is a frequently reported happening.

Heat sink grease, by the way, is the stuff you put on top of a chip before you mount the heat sink onto it. It ensure good thermal coupling between the chip and the heat sink.

You do appear to have a heat related problem, so after ensuring that nothing is mechanically clogging the cooling system, inspecting and potentially replacing the heat sinks(s) would be a sensible next step.

Good luck! Please report back about the dust question.

Inside of the case is spotless. Fans are both running fine. Heatsink feels cool.
Machine never crashes.
I am having some software problems, I think this is OS related. I received this Mac with OS X 10.4.0 freshly installed. I received no disks with it. I have ordered 10.4.8 and should receive it today and will do a fresh install to see if that takes care of software problems.
Thanks for the reply, Manuel

Great, glad to hear that the machine is clean at least. I will keep my fingers crossed for you that the new OS load resolves your problem.