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How to lube door lock mechanism?

1999 Suburban

Although the key slides into the lock easily, it’s a bear to turn the key left and right. I tried squirting some graphite into the key hole and working it with the key but that didn’t do much if anything.

Is there a way to lube the internals that a homeowner–not mechanic–can do?


You might try the DuPont lock lubricant, it worked for me. I got it at Lowes:
If that doesn’t help then it might be something mechanically wrong with the lock mechanism. You may need to open up the door and see.

The linkage the lock cylinder attaches to is likely dry - I.e. no lube. Try a little white lithium grease spray (available in auto parts stores) with the spray tube attached. Stick it between the window glass and the outer seal with the window dropped a couple of inches. Point it in the direction of the lock and handle. Spray. You don’t need the whole can, just enough to coat all the lock and latch bits. Work the lock, the latch handle, open and close the door. If it gets a little better, try another shot. That should solve it.

okay, I’ll give the spray a look

Take that spray and squirt some into the latch mechanism on the side of latch. I like to work the lock mechsnism a bit as I spray to work in the lube.

Sometimes that happens with my truck, and I just spray a little WD 40 into the door lock mechanism using that thin red tube that comes with a can of WD 40. If that doesn’t work, I’ll spray some WD 40 on the key, and then put the key into the lock and work it around. Sometimes it takes two or three days of doing this, then it will loosen up.

Other times all that doesn’t help and I have to remove the inside door panel for a look-see to find what all is binding. Often it is a screw or nut that has come loose. One time I had to replace the lock cylinder, which meant replacing three lock cylinders, two for the doors, one for the ignition, since I wanted the same key for all three. That was a bit of a pain.

I think on a 99 model you are safer to only use a dry lock lubricant, not WD 40. I’m just saying what I use. My truck in 40 years old, so I’m ok with having limited expectations.

If you are up to it, remove the interior door panel which will expose the entire latch / lock mechanism and it’s rube-Goldberg connecting system of rods and bell-cranks that may need to be cleaned and lubricated…Squirting stuff into the key-slot is seldom effective…

I’d go with a spray lock lubricant instead of WD 40.

I’ve had excellent luck with the PTFE (Teflon) dry lubes like Texases suggested. I use the sprayer with the tiny spray tube to get in behind the little spring loaded “door” in the lock hole.

And, if you have an unworn key, try that one instead of your daily use key. 15 years of wear can disable a key.