Do you get any error messages?
When did the problem start? Is your toner cartridge an HP one (part no. 92298A) ***or*** a third party or refilled HP? These can cause problems.
[[Topic:HP Laserjet 4|HP Laserjet 4 Service Manual|new_window=true]] Read through the manual
Is the leakage of toner just on the paper or is it inside the printer? If in printer you mast clean it up.
Possible causes of streaking:
[link|https://inkjetsclub.com/blog/why-toner-cartridge-is-streaking-leaking-and-wow-to-fix-it|Link|new_window=true]