Only 15 mpg and hot to touch front hubs!

[Grantshire]

Get your hands on a laser thermometer from Harbor Freight or somewhere else for cheap. After a 30min drive hit every hub with the laser thermometer in the same spot and record the temps. Let us know what they are.

I have an infared temperature gun I use at work so I will do this next week and post the numbers.

Thanks everyone for your input and insight.

 

[StrykerPez]

My $.02:

First, if your daughter made a heavy stop getting off the freeway and then checked the temp of the lugs soon after, they would be normally too hot for comfort. See if the problem persists before continuing.

Second, I'm going to trust that your mechanic friend was right in all he said and did, (but keep in mind, mistakes can be made when working on old iron)

So, the calipers are new, they're not the problem.
The bearings are good, and packed. Not the problem.

Possible culprits:

Rear brakes may need adjustment.
Soft lines may be collapsed.
Driver of vehicle might have been riding the brakes.

Less likely culprits:

Master cylinder needs replacing (not saying they don't go bad, but when they do its usually different symptoms than hot brakes)
Proportioning valve stuck.

Recommendations: I would replace the soft lines unless they are BRAND NEW and you know it. It sucks hard when one of those blows out on you.

 

[dependable]

Sometimes the flex lines for the front brakes collapse internally. so when you press on the brake, fluid goes in, but is slow to release. This gives the same symtom as a hung caliper. looks fine from outside. Easy to test . Jack up wheel , spin, apply brake. If wheel dose not spin as well as before braking, you probably have bad brake lines or calipers. It is most likely the lines, unless someone mixed alchahol based D O T 3 based fluid with the original silecon D O T 5 . Then you should replace calipers. Do the flex lines while you are at it.

 

[Grantshire]

Sometimes the flex lines for the front brakes collapse internally. so when you press on the brake, fluid goes in, but is slow to release. This gives the same symtom as a hung caliper. looks fine from outside. Easy to test . Jack up wheel , spin, apply brake. If wheel dose not spin as well as before braking, you probably have bad brake lines or calipers. It is most likely the lines, unless someone mixed alchahol based D O T 3 based fluid with the original silecon D O T 5 . Then you should replace calipers. Do the flex lines while you are at it.

Everything is new except rotors and wheel bearings (checked and repacked). I am putting 4" lift springs on it within the next few weeks so we went ahead and installed the new, longer, braided brake lines front and rear.

I will see what my temperature gun reads this week after she drives it home (38 miles, mostly interstate) and post the numbers when I return next week (headed out of town on Thursday for a week).

 

[WarrenD]

I'm finally remembering some of my brake troubleshooting ideas from many yeras ago. I used to take a long highway drive after letting the truck sit over night. I had a route where if I was careful, I could get to the highway without touching the brakes. I'd run 20 miles to an exit with an upgrade ramp and coast to a stop. I'd feel the hubs, lugs and rotor (careful with that last one!) for heat. If everything was cool, I'd eliminate the bearings/hubs from the suspect list. At this point in your quest, after eliminating driver issues, I'd look at the proportioning valve.

 

[Grantshire]

UPdate on mileage and hot hubs

We've been monitoring this issue for a couple of weeks now and tracking fuel mileage so here is an update.

Hub temperatures have moderated and are no longer an issue. My guess is the new brakes, hoses and lines have "settled in" so hot hubs are a thing of the past.

I have been running BFG 35x12.50x15 AT tires on the rear (can't put them on the front until I get the lift installed) and fuel mileage is steady at about 15.5 mpg. Last week I swapped down to 33x12.50x15 AT's and milegae went up to a solid 17 mpg. I will check for about two more tanks and then we will swap the 31x10.50x15 AT's back on and check mileage. I am guessing that the lousy fuel mileage with the 35" tires is a combination of the 3.08 gearing and aged fuel delivery components (IP, injectors and/or glow plug). Several of you have responded you get good fuel economy (20+ mpg) with stock gearing and larger tires so I am assuming mine is not getting full power.

I am going to post a seperate topic on how to restore/clean injectors and make sure the fuel delivery system is in top working order but please feel free to offer any suggestions or insight on the above.

At some point I want to upgrade to a 700R4 transmission and 3.73 gears using different axles. I also have a set of Dana 44 axles with 3.53 gears that could easily be swapped under the Oh-9 to offset the large tires.

 

[4bogginchevys]

If your real handy you can pop out the pistons in the caliper and use some very fine emery to clean them up...I believe you can still buy that big o-ring for them too. by the way, you'll get great results from synthetic grease