Tech help, heat from hubs after rebuild...

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Mtbcoach

Mtbcoach

10 Year 15 Year
Joined
Jun 29, 2006
Threads
179
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4,391
Location
Carolina Beach NC
Guys,

To start off, continued thanks to everyone who helped me get the disc conversion/axle rebuild done on our 40. It is so great having this club and its members as a resource for everything related to these vehicles as well all things associated with being outside.

Now to ask for more help...

We got everything buttoned up after some frustration with finding some problems with some of the brake lines. Now that we have been driving it around, we are noticing some heat and "hot smells" that seem to be coming from the hubs. I can feel the heat coming off the hubs.

I'm concerned that I missed something. Could it be that the hub nuts are too tight, or that I didn't get enough grease in the knuckle or that this is just part of the "break-in" after the rebuild. I don't want to destroy all the work we put into this to have to do it again.

Thanks in advance for any input...
 
too much grease will contain heat, and too less will obviously create heat.
do the 40's have a cotter pin or a lock nut on the end of the axle??
 
There are several things that could cause heat, but I doubt it is the actual knuckles since they are spinning with little load. It is likely the wheel bearings or discs.

You can use the fish scale to check the wheel bearing preload. All that needs to be done is pull the wheel and caliper off. You can also check if the wheel bearings are too loose if you jack the tire off the ground and grip the tire at the top and bottom and try to rock in and out. Any wobble means the wheel bearings are loose.

The other possibility is that the heat and smell may be related to the rough condition of the discs and maybe the pads dragging. The smell could be from the rust or maybe not getting all of the grease off the discs.

I might be getting out later today and could make a trip to you to help check. Otherwise I could help inspect on Sunday.
 
Yeah so many possibilities, Jerry - if you need an assist w/ hands-on diagnosis, say the word............
 
Thanks for all the ideas and offers for help.

I think it is the brake calipers. On the way back from a quick trip to Lowe's, the brakes were not releasing and the pressure kept getting higher and higher. When I got home, I had to undo the brake line to get the brakes to release.

I took the calipers off to see what might be the cause of the pistons not releasing. After looking through the rebuild process and how to do it (thanks Clint), I gave the local Autozone a quick call. I ordered some re-man calipers for $30 each.

With the calipers off, the hubs turn easily and don't appear to be loose or sloppy at all. I'll probably get the rotors turned while I'm waiting for the calipers to show up, just to make sure I'm starting "fresh"...
 
I thought about our discussion about turning the rotors and had second thoughts... Since it will take you some time to pull both rotors, get them turned and reinstalled, you could wait to see if the rebuilt calipers fix the situation. Plus, since it will probably cost $15/rotor to turn (along with new inner wheel bearing seals) you could save the money for buying vented rotors later. Worst case if the rotor is warped it is usually just a nuisance with some vibration or pulsation while braking. Hopefully the new calipers will get the truck driving safely and you can focus on something else.
 
Another consideration regarding replacing the rotors is that it will require a press to remove and reinstall the wheel studs. I do however agree with clint in that you should consider switching to venter rotors. I would switch the calipers and see if that doesn't solve the heat issue you are having and then look into the rotors.
 
Thanks again for the info and advise. I'm hoping that the calipers take care of the issues. Once I get them slapped on, I'll follow up with how it fixed any of the issues.

The bottom line is that the whole process has made a big difference in its road manners and stability. I don't know if it was the tie rod ends, fresh bearings being torqued correctly or just all the little things put together, but it drives way better on the road. Once I get the caliper issues dealt with, I'm confident that it will be much better for Mikaela to drive around.

She gave her G-ma a ride to the store the other day and it was pretty funny watching my daughter drive my mother-in-law away in a '71 FJ-40. Not something I would have imagined seeing when she got her license...
 
southerncruiser62 said:
Another consideration regarding replacing the rotors is that it will require a press to remove and reinstall the wheel studs. I do however agree with clint in that you should consider switching to venter rotors. I would switch the calipers and see if that doesn't solve the heat issue you are having and then look into the rotors.
Click to expand...

Agreed on holding off on the rotor turning until later and switching to vented rotors. However, you don't really need a press to do the wheel studs. I did mine with a brass drift and a BFH. You'll probably WISH you had a press when you're done, but it's not absolutely necessary.
 
I have a 12ton here at the house any time anyone needs to use it.

Ramon
 
Just to follow up on this...I installed the rebuilt calipers, re-bled the lines and buttoned it all up...perfect. No more heating issues and I can now actually lock up the rear tires. I could never do that before but that might have had to do with the hole I found in the brake line that feeds the rear wheels (duh). It also drives much tighter with the fresh tie rod ends and I'm sure the fresh bearings don't hurt either.

Thanks again to everyone's help with this upgrade. Mikaela is now using it daily, still learning how to shift/brake/clutch with confidence...
 
Mtbcoach said:
Just to follow up on this...I installed the rebuilt calipers, re-bled the lines and buttoned it all up...perfect. No more heating issues and I can now actually lock up the rear tires. I could never do that before but that might have had to do with the hole I found in the brake line that feeds the rear wheels (duh). It also drives much tighter with the fresh tie rod ends and I'm sure the fresh bearings don't hurt either.

Thanks again to everyone's help with this upgrade. Mikaela is now using it daily, still learning how to shift/brake/clutch with confidence...
Click to expand...

Glad to hear it was just the calipers and it's driving much better....

Now once she figures out how to shift/brake/clutch with confidence on the road it will be time to start learning all over again on the trails....
 
southerncruiser62 said:
Glad to hear it was just the calipers and it's driving much better....

Now once she figures out how to shift/brake/clutch with confidence on the road it will be time to start learning all over again on the trails....
Click to expand...

That will be the goal for this summer, a bit of trail running in it for sure...
 
Next steps:

SOA
Orion Transfer Case (4:1)
H41 Non-US transmission
37x12.5 Krawler TAs
Longfields
CroMo rear shafts
ARBs (front and rear, of course)

That should hold for a while :)

R
 
Now, there I go assuming all is good.

Today, on the way home, the front brakes locked up again. Would not release until she took the hard line off the master cylinder. Good thing it happened close to home so she could walk home, get the tools and get it done. That part kind of makes me proud though.

Now I'm confused as to what it could be except the master cylinder. I bought it new and kind of made the mistake of assuming it would be fine. But, I can't imagine what else it could be.

Back to square one...
 
southerncruiser62 said:
Jerry, where did you purchase the Master Cylinder
Click to expand...

Cool Cruisers in TX, on-line, maybe stupid mistake. Bought the one for the FJ-40 w/front disk brakes.

More diagnostics...the brake pedal gets higher and higher as the pressure is building up until the front brakes are virtually locked up. The weird thing is that it was driving fine the past couple days then on the way home from school today, she couldn't overpower the brakes and called me that the "truck was stalling".

I asked the appropriate questions and gave her instructions to see if she could fix it (by releasing the pressure in the lines) and drive it the 1/4 mile home.

I hate to sound like such a moron. These "old" brakes are a simple system and I simply can't figure out what could be causing the brakes to build up so much pressure that the calipers won't release the pads off the disc... :bang:
 
Jerry, I couldn't imagine this being the case but if you are creating alot of heat near the master cylinder or even the brake lines, the fluid tends to expand and thus increasing the pressure on the caliper pistons. Another scenerio could be that the lines are slightly kinked and as you press the pedal you are forcing fluid through however as you release the pedal it isn't drawing as much fluid back through thus keeping the piston from fully releasing.
 
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