Thinkpads Forum

Hi,

I don't often look at the bottom of my laptop but today I did.

And I found ugly discolored "streaks" at various places. I wonder if it is normal? I really didn't notice them before

It looks like this (sorry for the poor quality):

http://s2.postimg.org/5ayw8jo6h/DSC_0060.jpg

Discoloration is most likely from a very hot area of your motherboard.
Is that spot directly under the CPU or GPU?

There are some under the DVD drive, so I wouldn't think it is from heat

I found some W520 bottom cover pictures on the Internet (not many of them) and some appear to have a similar issue. So maybe it is caused by a manufacturing process?

Some streaks are light (like in the middle of the picture) and some are dakrer (like those that are "flowing" from the vent holes).

AFAIK these laptop cases are made from a plastic-type of material, that is supplied in powderform to the manufacturer.
They probably mix other things with it, to reinforce it, or whatever.
My theory:
if the mixture is not correct, or they use a cheap knockoff material (most likely, since those parts are "Made in China"),
things like discoloration are bound to happen.
If the strength of the base is OK, I wouldn't worry too much.
But Lenovo-QC has not been greatly observed lately...

Here are some other pictures I found:

http://kevinjmorse.ca/sites/default/fil ... tall_1.jpg
...similar pattern like mine in the top left area near vent holes and one streak "connecting" the left side of the docking port with the corner of the battery bay (difficult to see on a photo but if you know where to look at, it is there).

https://d3nevzfk7ii3be.cloudfront.net/i ... wNqrI.huge
...similar pattern near the vent holes, light "patches" on the left side.

http://i01.i.aliimg.com/wsphoto/v0/3223 ... 4W1591.jpg
...the vent area again. It just "looks" like there was something leaking out of the vent holes.

I'm a bit calmer now that I know it probably was not caused by me. But I still wonder if there are some other people with similar issue

In case it really bugs me – how difficult it is to replace the bottom cover?

Maybe it's just the plastic wearing out.

I don't see any on mine, and I run mine at ridiculously high temperatures for prolonged periods of time:

Interesting. So some have it, some doesn't.

My W520 has some other issues with outer plastic panels (after a large drop) so when I'm at it, maybe I would replace them all to have a new machine again Is it easy to replace the bottom cover? According to manual it holds just on 4 screws.

You mean four screws, plus a bunch of other screws.

Those 4 screws are only the ones on the INside that hold the chassis to the bottom.
Just turn the machine over, then count all the screws you see in the bottom on the OUTside.
All of them have to come out first.
Draw a plan of where those screws are located, then tape them on that plan, so you know which screw goes where when you reassemble.
You'll also need to remove/disconnect the HD/CD/battery/dummy-card(s)/lid/antenna wires/etc.
My guess: about 40 screws.

I know, I've disassembled my W520 many times...I 've meant four screws inside that I didn't touch yet I thought it would be more complicated.