I had heard issues with sealed hub bearings where the seals would pop off due to the grease getting hot and expanding, is that what is happening here?

I took the Fiero out at CMP (Carolina Motorsports Park) and during the second 20 minute track session, I came back in with no dust caps. The bearings were fine and gave me no trouble for the remaining 5 sessions.

86 GT. Thanks!

In general, Bearing cover/cap can pop mainly for 2 reasons.
1. Cover is bent up etc over time from remove/replace for bearing/brake work.
2. Too much grease + heat = push out the cover and/or seal. Grease problem Likely shouldn't you problem... Fiero seals are very weak and won't seal any pressure. Many if you stuff the cap w/ grease.

add 1 more for racing case...
3. autox etc + heavy brake use could make the hub area on rotating part to expand just enough so bent up cover can't hold.

Dorman etc have covers but often the catalogs are useless. problem is 1 cover often fits thousands of cars/trucks.

Many stuff the cap and area between bearings w/ grease. That is wrong.
Only coat those areas and spindle so they don't rust.
Why? Correct grease will not move at all. What grease are in the bearings after packing them are the only lube needed.

(ETA-> ) Best way to drive new caps is to find metal/plastic pipe etc so driving effort is loaded on the bent area that stop you to drive too much. 1.5 plastic pipe should drive the cap w/o any problem.
See my Cave, Front Bearings

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

[This message has been edited by theogre (edited 05-18-2015).]

Quick question?
This car is an 86?
It does not have a sealed hub.
The dust caps are on the outside of the spindle.
The sealed hubs were on the 88 only and are toward the inside of the knuckle.
You would probably never see them missing unless you explored.

Thanks for the responses. Makes sense. After a cooldown lap, the front rotor was still over 300 F when measured with a temperature gun. I also noticed that some generic cheap grease got really watery at high temp and would sling out of the bearing. While I am not generally a fan of Lucas products, their Red n Tacky grease was true to the name and stuck to the bearing.

For future reference, the correct replacement dust cap is Motormite / Dorman / HELP! part # 13976.