Creases in paper

[MARKT]

I have a 4000T about 12 yrs old. The paper is creasing approx in the middle
beginning half way down the page.
Paper creases from all 3 input trays.
I am trying to run a half test ? but I cant seem to get any items to show
up once I get into the service mode.
I suppose I need to replace an output assembly.
Any suggestions or comments are appreciated.
Mark

[ptjeff1]

Do you print many envelopes? We have noticed this problem with the laserjet 4000 series when customers print lots of envelopes. It's a problem with the ceramic heating element in the fusing assembly. It gets slightly warped when running lots of envelopes. The problem was fixed with the LJ 4100 fuser which has three segments. My best advice to people running lots of envelopes on the laserjet 4000 or 4050 is to due smaller batches of envelopes to let the printer cool down a bit.

[MARKT]

Yes, I just ran 500 envelopes.
I had just replaced the fuser unit approx 5 months ago. Are you saying I have to replace the fuser unit again to fix the problem? If so, OUCH!!!!