Question about Dell Dimension 8400 PC Desktop

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Dimension 8400 will not boot, very loud fan.

Got me some BIG problems here with my 8400, 40 months old and well out of warranty. For the most part, she has run flawlessly, with the exception of a bad stick of RAM about 6 months ago. I replaced all (4) sticks of DDR2 512mb with (2) new 1gb sticks. All was well until 6 days ago when I got home from work. I hit the power button and got a solid amber power button light and a "rocket ship" for a fan. LoL. I thought the thing was about to fly to the moon. I've never heard a computer fan so loud in my life, it was akin to a vacuum cleaner. I couldn't power off via front button, so I had to pull the AC cord. Upon replacing the cord, unit "took-off" again w/o my pushing the power button. It was a combination of pulling the cord and pushing the button simultaneously before I could get the tower to stay off and be plugged in. When I attempted to start-up again, same rocket ship fan issue. I did get the thing to boot eventually by, again, some funky combination of pulling the AC cord and pushing the power button as well as some "jostling" of the tower. When it did finally start, I kept it running for (6) days while I removed data from it, saving music, pics etc. to an external drive. During the (6) day period it was on, I did re-start on (2) occasions, via Windows, not by turning off and on again. It re-started with no problem. Finally this morning, I turned it off and let it sit while I showered. Upon my return I attempted to turn on and you know it....amber light and rocket ship fan. Once again I was able to get it to boot with the funkiness of pulling, jostling, and punching the button. I have search online for similar issues and have found many with the same problem. It seems that all the others with the same problem have had 87 different ways to fix this. Does anyone have a sure-fire way to remedy this?? I've read about PS, MoBo, CPU, RAM just to name a few. Any help is greatly appriciated!!

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  • Jim
    Jim Apr 04, 2008

    Thanks PJ, Im going to do the PSU swap-out first, although my gut says there maybe something else wrong, You gotta start somewhere right? I have a buddy who has a spare PSU and I will give it a go. Keep in mind that with some screwball combination of pulling the AC cord and pushing to front power button, I can get it to start and run normally. My fear is that soon, very soon, I will not get the thing to start ever again.

  • Anonymous Apr 15, 2008

    If misery likes company, I am right in there with you! My Dell 8400 went off of warranty 11/07...And I am having the same problem. (Are we seeing a manufacturing issue here?! )



    When I press the on button, the Heat Sink fan begins to spin and gets louder and louder each second! In fact, it sounds like a hair blower! When I turned on my 8400 last week, I went to the other end of the room and I heard the fan, I thought my wife was drying her hair in the room.



    I have removed all adapters and memory and the fan still speeds up. I ordered and replace the PSU with one from Dell and that didn't help either. I was led to believe that it the cooling fan itself but that fan plugs into the motherboard and I won't be able to affored the cost of that.



    If there are alot of folks with this same problem, it sounds like something was wrong in the manufacturing process of these Dell 8400's.



    Any one else with this problem or resolution, please respond..



    Thank you!



    R2D2

  • Anonymous Apr 15, 2008

    I have the exact same problem. I bought a new 500w power supply and brand new ram....still sounds like a rocket ship and solid amber light. What is going on here????

  • brentholmes May 09, 2008

    Same issue here. Flawless Running till about 10 days ago. Same issues. My quirk was it would run while laying down on it side with the case open (for a while then would freeze. Extremely sensitive to vibration. After pulling and re-seating all cards, memory, cpu, mobo, and switching out the video card, it only does the amber light and turbo fan. I got a replacement mobo and going to try to replace that tonight.

  • Anonymous May 10, 2008

    Exact same problem. Dell 8400 belong in the landfill.

  • Anonymous Jun 06, 2008

    When I hit the power button I get a solid amber power button light and a "rocket ship" for a fan. I've never heard a computer fan so loud in my life, it was akin to a vacuum cleaner. I can power off via front button by holding it down for 5 seconds or by pulling the AC cord. Upon replacing the cord, unit "takes-off" again w/o my pushing the power button. Whenever I attempted to start-up again, same rocket ship fan issue.

  • jmarshall4 Jul 05, 2008

    Same problem. Fan sounds like a jet engine. After about 40 or 50 attempts at re-starting, I finally got it running, and have not shut it down for the last 2 months.



    When the computer will not start, the error codes indicate an overheat problem. however, I got the same error codes even when the machine had been off for a couple of days. Sounds like a problem with the temperature sensor, sending a bad signal that the damn thing is overheating???

  • Anonymous Sep 04, 2008

    I've only had a loud fan once, but all of a sudden it won't boot, yet power is on - can anyone offer suggestions?

  • dianelet59 Nov 09, 2008

    When I turn on my pc nothing happens other then a very loud fan motor. It sounds like my computer is going to launch. I have purchased another pc however I need my files, pictures and music off the 8400. my dimension has windows XP and my new computer has vista can anyone tell me how I can get my files off the 8400 dimension?

    Thanks

    Diane

  • Anonymous Nov 27, 2008

    I had the same problem. I unplugged all memory sticks, video and sound card, cleaned, reinserted and everything so far works fine. About 9 months now. I have 2 dell 8400's.

  • dingo925 Jan 23, 2009

    I have the same problem. Amber light, a fan that sounds like a jet is taking off, and I can turn off the power by holding in the power button for 5 seconds. What is the solution?

  • Anonymous Jan 25, 2009

    Same problem. I just removed heatsink, cleaned thermal compound, put new thermal compound on and resttached heatsink. It works!





  • 45xt3 Jan 27, 2009

    Same problem exactly. I was able to deal with this a couple of times in the past by opening the case and using compressed air to blow off the fan/heat sink. That didn't work this time.



    After reading the other posts, I figured that trying to close whatever gap there was between the CPU and the heat sink/fan was better than trying nothing. I opening the case (computer unplugged), put pressure on the green plastic fan covering toward the right side of the computer, and plugged in the computer while still putting pressure on the fan covering. I was able to then push the button on the front of the computer to start it up normally. Then, I backed everything up and now I'm going to get a new computer.

  • Anonymous Feb 20, 2009

    Dimension 8400 will not boot, very loud fan

  • Jim
    Jim Apr 19, 2009

    Howdy folks...it has been a year since I posted here and thought I would check in. I ended up scrapping the 8400 and built a new machine with some of the components from the 8400 i.e. vid card, sound card etc. The new machine...top notch. The old 8400, what's left of it, is in the closet collecting dust. It turns out to be a leaky cooling system that friggs up the CPU etc. Depending upon the extent of the damage, you may be able to re-seat the chip with new compound and get your beast working again. I opted for the new machine, building a mid-tower XFX mobo with CORE 2 Duo CPU, OCZ 2gb ram, new HD, old 8400 HD is in this tower as well, put the two disc drives from the 8400 into this as well for (3) drives, DVD-ROM, DVD±RW and a new DVD-RAM drive, stole the vid card & sound card from the 8400 and am using them also, a GeForce 6800 and an Audigy2ZS Soundblaster card. Yes these components are a tad old but they work like a champ. I wish you folks who are having this problem all the luck in he world, I absolutely hated dealing with this issue when it arose but am in a much better place now.

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Pc turns on and fan is very load and will not boot what can i do

Posted on Dec 12, 2009

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I own & operate a computer reapair store. I recently worked on a Dimension 8400 that sounded like a jet taking off. I removed the heatsink, cleaned the heatsink & cpu, applied thermal grease & reattached the heat sink. It booted up quietly...after testing it several times...the turbo fan, jet engine sound returned! I removed the heatsink and along the upper part of the cpu I could see where the heatsink hadn't made contact with the cpu! I added more thermal grease & reattached the heatsink. It started fine on several attempts before the jet engine sound returned. I tried applying uppward pressure on the heatsink so it would close the apparent gap between the cpu & heatsink and when I pressed the power button...it started up quietly! At least I identified the source of the problem...not sure how to fix it yet.

Posted on Nov 19, 2008

  • richarddanie Apr 28, 2011

    i got cofused when you said there was a gap between the heatsink and cpu so you applied upward pressure on the heatsink? i really dont understand why to apply upward pressure instead of pushing down on the heat sink. can you please give me some more details, please.

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I have a small business where I have worked on PCs for the past 14 years. I have had some of my clients that have brought me a few of these Dell 8400 to work on with the same problem. Will not boot and loop the start up, along with sounding like a leaf blower. After much trial and error i.e. Heat sink,cooling fan, power supply and motherboards. The first one I worked with by changing the heat sink, worked for about a week, then started doing the same thing. Replaced the Power supply with no results, same issue. Next was the Motherboard, still same issue. Last I pulled the processor out and found that the processor had over-heated and was damaged. In all I had well over $500.00 dollars invested and countless hours. Still the machine did not work, and still needed more work. Since this time I have had a few more of these machines cross my path. My suggestion is to scrap it and purchase a new PC. This is not one of Dell's better designs, and there is a tech issue from Dell related to this problem with the heatsink and the machine itself in the tech support on the Dell site. It states that they had a bad batch of heatsinks, but only replaced them under warranty.
Salvage what you can and build or have someone build you a clone.

Posted on Aug 07, 2008

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I had the same problem with my Dimensions 8400. I redid the thermal paste/grease but the problem continued. I discover that by getting more downward pressure on the heatsink unit fixed it (albeit by using an unorthodox method). I folded some tinfoil (the same surface shape of the top surface of the heatsink to the thickness of a few millimetres) placed on top of heatsink and so when the green cover for the heatsink is pushed back into place it helps to apply more downward pressure on the heatsink eliminating any gaps between heatsink and CPU.
The problem in the first place might be down to the bracket for the heatsink becoming weakened over time.
Did this last week and computer working fine and starting up without the racing fan.

Posted on Aug 18, 2009

  • richarddanie Apr 28, 2011

    sounds like a smart idea. i think im going to try that as well. thanks for the idea. my computer wont boot at all and i have to shut down the computer to stop hearing that terrible fan.

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In a follow up, my solution was a new mobo. I got a $80 older, 'compatible' board (long story on getting it in the case), but it been working fine since. IMHO and research, the problem comes down to heatsink, mobo, or cpu. My theory is the problem starts with the heatsink, either it goes bad or the conductive gel does (looked like it my case). If you are lucky and catch it early, this is all you have to fix. If not, then the heat damages either the mobo or the cpu, and then its a ****-shoot to figure out which it is. In my case, $80 and 4 hours of my time paid off. Now, I hope I can make it to tax-refund time to get a new primary machine, and this one can be back up. :-)

Posted on Oct 23, 2008

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Had the same problem. Replaced battery for CMOS on the motherboard. Computer works fine now.

Posted on Dec 06, 2009

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My 8400 is over 5 yrs old now,and i recently had the cpu fan go into leafblower mode,couldnt shut the thing down by holding in the power button so yanked the power lead out.The strange thing is that the pc was idling at the time,and had been on for a couple of days,no programs or games were running,so i doubt its an overheating issue.Also,since this happened i have been playing pretty demanding games (farcry2 & fallout3) with no issues.One thing i did notice while investigating this was that the molex plug to my graphics card was loose,i unplugged it and tried to boot to see what would happen if the card wasnt drawing power,and the fan was much louder than usual but no where near as deafening as leaf blower mode,so i think pjmarkert is onto something with the overvoltage theory,but what could make it occur at a totally random moment,and be ok after a reboot?Hmmm

Posted on Nov 22, 2008

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I have a dell optiplex gx240, once i push power, the cpu fan goes crazy, sounds loud like the pc is about to blow up, and nothing shows on the monitor, i took the cpu fan out and put some thermal compound on the heatsink/cpu and tried starting it up again and it still does the same thing, can anyone help me?! lol

Posted on Oct 23, 2008

I had this same problem and simply took the mem cards out then put them back in. After that it worked like a charm. However, once my fan kicks into "high" it won't downshift to any other setting, so it is loud most of the time.

Posted on Aug 29, 2008

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Same issues (no boot, loud fan and amber power).
NEED HELP

Posted on Jul 17, 2008

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Same issues (no boot, loud fan and amber power). Called Dell and they said they will send dispatch.

Posted on Jun 27, 2008

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The problem is the heatsink. The pipes have come unbonded or have leaked fluid which slowly evaporated. The CPU temperature sensor senses the heat and speeds up the fan. Been there, done that.

Posted on Jun 06, 2008

  • richarddanie Apr 28, 2011

    is there a way to check for a leaking heatsink fluid and how can i tell if the cpu is damaged in any way including by overheating?

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If the fans are rediculously loud, ie much more than normal high speed, there may be a serious overvoltage problem in th ps. If that is the case, you may fry everything in the box eventually, or start a fire. DON'T LEAVE IT PLUGGED IN TO POWER UNATTENDED. Try swapping out the power supply. A peripheral such as a disk drive may be shorting the 5V and 12V together. It is more likely that the 12V is going overvoltage since the fans run on 12V

Posted on Apr 04, 2008

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