Only 15 mpg and hot to touch front hubs!

[Grantshire]

Well, I am learning all the little quirks on my daughter's M1009. After three tanks of fuel it's only getting about 15 mpg, not near the 20 or more we were hoping for. In searching and reading older threads about mileage and other issues someone posted front brakes dragging could cause reduced mileage and lead to further problems. Yesterday when she got home from the horse barn I touched the front hubs and they were HOT! Bingo, just like the old thread said. So...

What all needs to be replaced and is their a parts list somewhere or do I just go to the Napa counter as look up an 86 K5 Blazer? The pads don't look bad but they are obviously dragging. Also, should I replace the wheel bearings, too? I have always been a Timken's fan but do not know if they are available for the military K5.

Figured I also should get new filters (fuel and air) but is there anything else I am missing that might contribute to the poor fuel mileage?

School starts next week so I got to get these parts on it this weekend.

 

[doghead]

I suggest you do a complete front wheel bearing inspection, re grease and reassemble. While apart, inspect the rotor and brake pads.
You may have tight or bad wheel bearings.
You may have brake drag caused by a sticking caliper, an internally swollen flexible brake line, a bad proportioning valve or even a bad master cylinder.

All the parts should be readily available at your favorite parts store.

 

[DaGlitch]

After three tanks of fuel it's only getting about 15 mpg, not near the 20 or more we were hoping for.

Yes, the brakes could be one of the issues to reduce the mpg. You may also want to throw a bottle of diesel treatment in a full tank as well. Also make sure you injection pump is properly timed, as this may be dumping more fuel into the engine then is really needed. Do you have any noticeable smoke coming from the exhaust?

 

[thedeliverator]

I had a similar problem with my 1009; in my case, it started drifting to one side, and the hub on that side was getting extremely hot. I thought brakes, but it turned out to be the wheel bearings. When I pulled it apart, I found nasty grease in there, and not nearly enough of it. The other side was similar. Two new sets of wheel bearings and new grease for them later, and it rode much better.

If you haven't already, hit all the zerks with your trusty grease gun, until you see fresh grease pushing out the old crud. If I had done that sooner, I would have found the u-joint in the driveshaft that was tearing itself to pieces. Bearings don't work well when ground to dust....

Almost everything on your CUCV can be had at the local parts counter, same as a civvy Blazer. Notable exceptions are the starter and alternators. You can still get correct replacements, but it may take a bit more digging. It helps to know the one guy (and there's only ever one per shop) that still knows how to dig through the parts BOOKS instead of looking it up in the computer.

 

[319]

Is that 15mpg city or highway? I get 15 in the city and around 20 highway.

 

[Croatan_Kid]

Your daughter drives an M1009? That's awesome!


I suggest doing the wheel bearings, probably just a clean and pack. Then throw some calipers and brake hoses on it. They're both cheap and you'll have piece of mind knowing that it'll last a good while.

 

[WarrenD]

My old 84 K20HD Civvie P/U had several brake issues, mostly caused by the calipher pins. They get gunked up with grease and brake dust and won't allow the calipher assembly to back away after brake application. Given the age, it could also be the brake pistons so it sounds like the entire brakes need to be gone thru. You'll have a chance to look at the bearings as you'll have to pull them and the hubs to get the rotors off.

 

[84cucv1ton]

that what im doing now. wheel bearings..

 

[Grantshire]

Thanks everyone for the input. I am headed to NAPA this afternoon and will pick up new bearings, pads, and brake lines. Am I missing anythings? Hope to get it all on this weekend.

Yep, 16 year-old daughter drives a stock M1009 and love it. I have a 4" spring lift, 35" tires, and a few other goodies for it but have not had time to put any of it on yet.

15 mpg is mostly highway and with larger tires. I think it should be more like 20-22.

 

[kipman]

My M1009 with new 31/10.5/15 mud tires gets 16 in town, 19-22 combo driving, up to 30 on long trip going 60mph.

 

[Grantshire]

My M1009 with new 31/10.5/15 mud tires gets 16 in town, 19-22 combo driving, up to 30 on long trip going 60mph.

I would be happy with that kind of mileage. I will keep you posted on any improvements address the brakes and wheel bearings nets.

 

[Grantshire]

My M1009 with new 31/10.5/15 mud tires gets 16 in town, 19-22 combo driving, up to 30 on long trip going 60mph.

Do you have a tach on yours? According to my rpm calculator 31" tires with 3.08 gears is about 2116 rpms at 60 mph (plus 100 or so for the TH400 automatic). From everything I have read about the 6.2 its best fuel mileage rpm range is supposed to be 1800-2200 rpms. With 3.08 and 35' tires my daughter's Oh-9 is turning about 2187 at 70 mph. I know the 35" tires are heavier and there is a little more wind resistance at 70 mph versus 60 but it seems to me she should be getting a little better than 20 mpg when most of her driving is Interstate.

 

[jrou111]

Not with gearing that tall. It's not just the RPM, the load is also a factor in MPG.

BTW, my absolute WORST mileage in my M1009 was 18 MPG while towing a 5000lb boat. I usually average around 22-25 if I can keep the truck in 3rd at 45-50mph. I don't drive it on the interstate much though.

 

[Croatan_Kid]

I need to find me a girl that drives an old military vehicle! It'd be love at first sight lol!


On a related note, I've gone all through my brakes. After the lift came the extended stainless braided brake hoses from ORD (best value I found), I turned my front rotors, put on new pads, and re-did the wheel bearings too. Just recently the rear brakes were leaking, turned out my hub seals were leaking on my M1008, so I put on some shoes, cleaned everything up and threw on some new hub seals. Good as new and will lock up all 4 tires at any speed

 

[Grantshire]

Not with gearing that tall. It's not just the RPM, the load is also a factor in MPG.

BTW, my absolute WORST mileage in my M1009 was 18 MPG while towing a 5000lb boat. I usually average around 22-25 if I can keep the truck in 3rd at 45-50mph. I don't drive it on the interstate much though.

I will be the first admit I don't know a lot about these vehicles or the 6.2 but I am learning. My M715 with the 6.2 isn't much help on comparing mileage because it has a NV4500, 4.56 gears, and weighs a hole lot more. I also know that 3.08 is a little too high for 35" tires (even though I found where others have posted good mpg with big tires) and re-gearing is in the game plan long-term.

I will address the bearings and brakes this week and check mileage again. I will also swap back to 33" tires and check it again. Don't have 31" other than the two on front or I would check that as well. Once the hot hubs are addressed I will post up how the mpg changes with tire size so stay tuned.

 

[Grantshire]

Update - New brakes and still hot!

Update on the hot hub issue:

Have a friend that runs a local auto repair shop and I was traveling on business so I took the Oh-9 to him to go through the front brakes. Ended up with new brakes (everything except new rotors), bearings were in great condition so they were repacked, and lockings inspected. First day or so no issues then last night when my daughter got to the horse barn (30 mile drive from school, mostly Interstate) she checked. The lug nuts were hot, hot enough she could not keep her fingers on them. What's up with this? I know everything was gone through, they even installed my New braided steel lines for my lift. Why are the lug nuts getting hot?

 

[WarrenD]

Could be the caliphers if the pistons are hanging. If they are new, that is doubtful. Next thing to look at is the rear brakes, are they working? If not, all the stress gets put on the fronts. If all is well, then the operator is the next place to look. It's a heavy vehicle, one must drive it accordingly, repeated heavy stops are going to heat up the best systems. BTW, most lug nuts get hot, they pull heat from the rotors. Have you discussed further with the local mechanic?

 

[jrou111]

Lugs are usually pretty hot, use the hubs to determine if it's too hot.

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.

 

[2deuce]

With a young driver, I think I would suspect a 2 footed driver. One foot on the gas and the other on the brake=hot brakes and bad mileage.

 

[4x4 Forever]

I agree with the lug nuts not being used as a temperature indicator as they are directly adjacent to the rotor.

If you can keep a hand on the end of the hub for 3-4 seconds before HAVING to remove it, the temp is ok. Ive done this for years and this was always my indicator to start digging into the front ends.

the old saying: one thousand 1 / one thousand 2 / etc..., works very well.