Val Kilmer had been dogged by rumors that he was a Hollywood diva and a pain to work with … but one costar and friend tells TMZ that’s a total crock.

Danny Trejo, who was among the star-studded cast of “Heat” with Val, tells TMZ … Val got a bad rap for being difficult to work with — but the icon wasn’t high-maintenance — he was a “perfectionist.” There’s a big difference, DT makes clear.

As you sadly know … the legendary actor died Tuesday at the age of 65 — his death sending shockwaves through Hollywood as most didn’t realize his health had deteriorated so severely.

Highlighting what a thoughtful dude Val actually was, Danny shared one of his favorite memories from their time on “Heat” — and it’s kinda a tear-jerker now.

One day, Val showed up to set wearing a fancy and obviously very expensive leather jacket — and Danny commented on how much he liked it. The next day, there was one in his trailer … a gift from Val.

Danny says the only issue he ever had with Val … his pal didn’t get nominated for an Oscar as Doc Holliday in “Tombstone.”