fuel economy just plummeted...

barley00 · **Posted:** Tue May 05, 2015 5:16 pm

My fuel economy just took a 20-25% drop. no idea why. Brakes aren't dragging, I don't notice any difference in RPMs, driving habits haven't changed, switched to 2nd gen fuel head a while back hopefully ruling that out...anyone had this problem? Any ideas where to start looking for the culprit? Thanks.

Mountainman · **Posted:** Wed May 06, 2015 12:31 am

bigger tires and a lift could cause such a thing, but I can't imagine anything else causing this unless you have some symptoms like blowing smoke or rough running. Unless you're just getting a bogus reading from the Evic?

hmm, then again. Viscous heater or AC clutch stuck as engaged, but even those would be more like 10-15% I think...

tire pressure a few percent. Bad fuel maybe some %.

What's your hand calculated mileage, and what are your driving speed and conditions?

Oh, and the thermostat is a big one at something like 15%. Maybe it just failed and your viscous heater is now stuck on? That would be a major change

Mountainman · **Posted:** Wed May 06, 2015 12:33 am

well, with the GDE tune the viscous heater 'shouldn't' be a problem, but maybe your brain is acting up? hmm

barley00 · **Posted:** Wed May 06, 2015 10:13 am

I religiously use Fuelly to calculate mileage. The motor runs like a top, sounds perfect. I haven't made any mechanical changes recently other than front diff mounts, front drive shaft u-joint and exhaust but all that was back in March and the mileage drop started a month later. I haven't seen a change in operating temp., it's always been about 2 ticks short of middle. Funny though I actually pulled my viscous fan to see if that would affect temp around the time I saw the mileage drop so I put it right back in and haven't seen a difference.

I'm wondering if there are some joint/bushing/tie rod issues as I have been hearing some knocks and creaks.

thermorex · **Posted:** Wed May 06, 2015 11:03 am

Dragging brakes? Pretty common on liberty

flash7210 · **Posted:** Wed May 06, 2015 12:08 pm

barley00 wrote:

I religiously use Fuelly to calculate mileage. The motor runs like a top, sounds perfect. I haven't made any mechanical changes recently other than front diff mounts, front drive shaft u-joint and exhaust but all that was back in March and the mileage drop started a month later. I haven't seen a change in operating temp., it's always been about 2 ticks short of middle. Funny though I actually pulled my viscous fan to see if that would affect temp around the time I saw the mileage drop so I put it right back in and haven't seen a difference.

I'm wondering if there are some joint/bushing/tie rod issues as I have been hearing some knocks and creaks.

My MPG took a hit back in NOV when I got bigger tires with a more aggressive off-road tread.
It took an even bigger hit during a cross-country trip where I had about 200 lbs of stuff packed on the roof.

Maybe you got some bad fuel?
Bad wheel bearings?
Tire pressure low?
Clogged catalytic converter?

Mountainman · **Posted:** Wed May 06, 2015 12:48 pm

So what's the MPG's you're getting?

flash7210 · **Posted:** Wed May 06, 2015 1:33 pm

barley00 wrote:

I'm wondering if there are some joint/bushing/tie rod issues as I have been hearing some knocks and creaks.

Since you mention it, if you haven't already checked and/or replaced your ball joints, you might want to do that. They are known to fail prematurely.

barley00 · **Posted:** Fri May 08, 2015 6:53 am

Brakes aren't dragging, that's the first thing I checked. The first tank that showed a drop in mileage was 15.3, down from what should have been 20+. I then drove about 100 miles, filled up again and got 16.8. Since that fill I've been watching the needle an I used to get around 125 miles out of that first 1/4 tank and I just got about 80... Maybe bad fuel...maybe bad bearings...maybe clogged cat, I'll check all that out, thanks folks.

Mountainman · **Posted:** Fri May 08, 2015 12:53 pm

Just 100 miles here and there won't give you a decent reading. Also, especially with diesel, it's really tough to get consistent fill amounts due to all of the froth. Test a few complete tanks, and use a flashlight to fill the tank to the exact same spot (takes a lot of patience waiting on the bubbles to die down), and I think you will find that your mileage hasn't changed. You'll get obvious symptoms if your mileage drops 20% all of the sudden.

barley00 · **Posted:** Fri May 08, 2015 3:25 pm

I hear ya Mountainman, I was hasty on that one 100 mile re-fill but I was anxious to see if there was much of a difference. I can already see on the tank that I'm on that the mileage hasn't gone back to normal as the needle is dropping awfully quick. I'll keep an eye on that froth and try the flashlight method. I know the guy that runs the Shell where I fill up so next time I see him I'll ask if he's heard anything from other diesel drivers about funky mileage. Thanks again.

Mountainman · **Posted:** Sat May 09, 2015 12:30 am

anytime

Disclosure: I haven't tried the flashlight method, but read about it on ecomodder. Not certain if you'll be able to see the fluid level on a CRD at a point that you can note, and keep consistent, but you'll know as soon as you try. Read on ecomodder about the fancy devices they get to give true fuel consumption readings. I've though about getting one, but they're spendy.

thermorex · **Posted:** Mon May 11, 2015 1:16 pm

When my Brakes were dragging, they didn't heat to the point of being obvious. I just went and removed the rubber boot that's on the guiding pin per forum suggestions and I gained couple mpg instantly.

RenKJ · **Joined:** Sat Jan 24, 2015 4:45 am **Posts:** 96

thermorex wrote:

When my Brakes were dragging, they didn't heat to the point of being obvious. I just went and removed the rubber boot that's on the guiding pin per forum suggestions and I gained couple mpg instantly.

Doesn't this expose the pin to corrosion /losing its grease? I might try it, suspect a mild drag

SargeIndustries · **Posted:** Mon May 11, 2015 2:48 pm

What's wrong with just taking pins out and greasing them? Did that with mine and brakes stopped hanging up. They were dry and corroded on one side.

SFHLibertyCRD · **Posted:** Mon May 11, 2015 3:38 pm

thermorex wrote:

When my Brakes were dragging, they didn't heat to the point of being obvious. I just went and removed the rubber boot that's on the guiding pin per forum suggestions and I gained couple mpg instantly.

Having never touched brakes before (except maybe in high school auto shop), can someone be a little more specific about what is involved here, and maybe a pic of the rubber part that sometimes sticks and location of the pins that need greasing?

Cheers.

barley00 · **Posted:** Tue May 12, 2015 6:58 am

thermorex wrote:

When my Brakes were dragging, they didn't heat to the point of being obvious. I just went and removed the rubber boot that's on the guiding pin per forum suggestions and I gained couple mpg instantly.

Very interesting, not aware of this, will try it.

thermorex · **Posted:** Tue May 12, 2015 10:42 am

The caliper itself it's sliding through 2 pins through the caliper bracket. The rubber boot (one per caliper) is located inside and on one of the sliding pins (I think is the lower one but not 100% sure) , you can only see it when you slide out the caliper. That one tends to swolen up and create a slight drag, even if it is properly greased. Keep in mind I'm not talking about the 2 dust covers that are cylindrical "acordeon" type that are visible without removing the caliper. Those 2 are required in there and are not to be removed. The purpose of that one rubber boot that's on the sliding pin is to prevent any knocks and clicks when the caliper works, as I know.

It's item #6, the right pin in the link below that has the boot.
http://www.jeep4x4center.com/jeep-brake ... iberty-kj/

Btw, the pic for #6 should only have one black rubber boot listed, not 2, a quick examination shows that just one pin (right) can accept it.
And sure, adding some ceramic high temperature Grease on the pins is a good idea.

SFHLibertyCRD · **Posted:** Tue May 12, 2015 2:12 pm

Thanks for this. I'll have to look into it.

RenKJ · **Joined:** Sat Jan 24, 2015 4:45 am **Posts:** 96

thermorex wrote:

The caliper itself it's sliding through 2 pins through the caliper bracket. The rubber boot (one per caliper) is located inside and on one of the sliding pins (I think is the lower one but not 100% sure) , you can only see it when you slide out the caliper. That one tends to swolen up and create a slight drag, even if it is properly greased. Keep in mind I'm not talking about the 2 dust covers that are cylindrical "acordeon" type that are visible without removing the caliper. Those 2 are required in there and are not to be removed. The purpose of that one rubber boot that's on the sliding pin is to prevent any knocks and clicks when the caliper works, as I know.

It's item #6, the right pin in the link below that has the boot.
http://www.jeep4x4center.com/jeep-brake ... iberty-kj/

Btw, the pic for #6 should only have one black rubber boot listed, not 2, a quick examination shows that just one pin (right) can accept it.
And sure, adding some ceramic high temperature Grease on the pins is a good idea.

Appreciate the info, is the best way of removing that hidden bottom pin boot, taking the brakes apart?

fuel economy just plummeted...

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