1986 jetta problem need help!!!!

Well i posted in main forum but noone replied so ill try here i have a 1986 vw jetta gli with the 1.8 it has an over heating problem, but the thing is, that it will only do it sometimes, ok sometimes in tight traffic or just sitting and idling it will start to overheat and sometimes it wont, i was wondering if the thermostat would do that or what other things would cause that, but the fan does come on but not all the time, what could be causing it to overheat?.... PLEASE REPLY! I NEED TO GET IT FIXED!!! but i dont have money to take it to a shop i need to do it my self

has the antifreeze been flushed and filled lately?

...if not, start there; but wile doing so, might as well change t-stat at the same time. go with a good (CarQuest or NAPA) brass 180-195 deg thermostat.
also, with those miles racking up on that classic, if the engine has never been worked, cylinder head water passages might be somewhat gummed up. so a good flush will help.
I know my '86 Jetta was picky with oil filters as well...
would ocassionally overheat with a fram or generic oil filter;-
- but put a Wix or an OEM Bosch on, and she was happy again, with no flashing led light.
...you might check the temperature sending unit as well.
if it is original; it might be faulty and sending incorrect signals, since you say the fan is intermittent.

post back, or mail me with more precise info, and myself and others can assist,

[email protected]
ASE cert.instructor