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  #1  
Old 10-25-2008, 12:22 AM
zeke's Avatar
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Location: The Alamo City, TEXAS
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brake rubbing

Ok, so I continue to try and find my lost mpg in my 240D

I think my brakes are in fact rubbing. My rubber brake lines were rotted (esp. in the rear), so I replaced those. Someone on here had said that old brake lines can cause the brakes to tighten and rub.

Unfortunately, replacing the rubber lines didn't seem to change the way the wheels spin.

All the pads look great with minimal wear. How do I deal with rubbing brake pads?

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Current Mercedes
1979 maple yellow 240D 4-speed


Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT
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  #2  
Old 10-25-2008, 01:40 PM
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Join Date: Jul 2008
Location: S.E. PA
Posts: 447
I enjoy watching mileage troubleshooting on here, I am working on regaining mileage on my 240D as well.

How clean are your rotors? I did the same thing with my 240D's brakes lines and the rusty rotors are still making their "poop" colored mark on my mileage.

I noticed that the faster the wheel was spinning the less drag I can feel. Brake drag may not be as parasitic as we think?

Also, I noticed that with the engine running I feel a lot less drag, but how does that work out? Also my brakes drag less when my car is warmed up than cold.

How new is your brake fluid? If it's 4 years old for mine used to be you might have some algae going on. Should of checked brake drag difference when I changed mine..

Hope this all helps out,
-Nick
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  #3  
Old 10-25-2008, 02:05 PM
zeke's Avatar
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Location: The Alamo City, TEXAS
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Well, maybe.....
I completely replaced the brake fluid yesterday when I changed the lines.

I can't feel the drag at all when I am driving, though I can hear a gentle whoosh whoosh whoosh that depends on the speed if I turn off my radio and stick my head out of the window.

If I turn the wheel by hand with the car jacked up, I can feel and hear the faintest rub of rotor on brake pad. Maybe the problem is out of round rotors?

All in all It isn't binding so tight that I can't turn it or that I feel it, But the whel doesn't spin like a bicycle tire, either....
__________________

Current Mercedes
1979 maple yellow 240D 4-speed


Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT
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  #4  
Old 10-25-2008, 03:58 PM
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i think some rub is part of the design with disk brakes. if you let them back off then there will be some delay in performance. I know the old drag racers used to put drum brakes back on in the late 60's because drums dont drag, not sure if hearing the whoosh of the drag translates to MPG losses. it really comes down to basic driving technique and above all going slow.
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1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
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1962 Corvette LS1 (to go in style)
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  #5  
Old 10-25-2008, 04:07 PM
zeke's Avatar
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It does seem like there is no way that the slight drag I describe could account for a 10-12 mpg drop, but neither could my driving style....

I am talking about a 4-speed 240D getting 18-20 mpg

On to checking chain stretch and timing, though I have no smoke, stutter, or other signs of improper timing
__________________

Current Mercedes
1979 maple yellow 240D 4-speed


Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT
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  #6  
Old 10-25-2008, 04:13 PM
lutzTD's Avatar
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Quote:
Originally Posted by zeke View Post
It does seem like there is no way that the slight drag I describe could account for a 10-12 mpg drop, but neither could my driving style....

I am talking about a 4-speed 240D getting 18-20 mpg

On to checking chain stretch and timing, though I have no smoke, stutter, or other signs of improper timing

wow, that is low. did it happen all at once? one tool for trouble shooting is identify the time the effect occured and also any changes you or the environment made to the car previously, along with extimates of how long the changes would need to have effect. for a car most changes would show immediately since there is no stock delay. so did you get different diameter tires, try some exotic fuel, change a filter or line etc....
__________________

1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)
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  #7  
Old 10-25-2008, 04:16 PM
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just a thought, but my best milage increase to date was replacing all of the return lines on the head. they were weaping fuel down the side of the block, but not in any one place so I did not notice it right away
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1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)
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  #8  
Old 10-25-2008, 04:24 PM
zeke's Avatar
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Location: The Alamo City, TEXAS
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Hmm, return lines are on my to do list, but I haven't noticed them weeping....

This has been the my mileage since I could check it when I fixed the odo about a year ago.
Over that year I have replaced all fuel lines (except injector return lines), both filters, and have run D2 from several different companies as well as B100.

It may have slipped 1-2 mpg over that time.

Everything on the car is stock. I took a water separator out of the fuel line b/c/ I thought it might be leaking, but no change.

Like I said, the weird thing it that it runs great. I have no complaints about the speed of the 240D, and that is even compared to my 300TD which has the turbo. No smoke, no performance problems at all.
__________________

Current Mercedes
1979 maple yellow 240D 4-speed


Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT
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  #9  
Old 10-25-2008, 07:48 PM
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Location: Nova Scotia, Canada.
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Well gentleman both of you should read and think about Cervans current rack damper pin thread. It is worth checking the fuel pressure present in my opinion. Especially on a 240d.

Eighteen to twenty miles per gallon is especially really poor economy. If the fuel feed pressure checks out okay I would have the injectors checked next. With the injectors out inspect the balls in the prechambers and general chamber condition. Double check before anything that you odometer is not slipping. Yout car would not be the first one.

Now to the disk brakes. When driving a fair distance try coasting to a stop. Get out and feel all the four wheels. If all are equally cool forget the brakes. On the other hand if one or two wheels are noticably warmer than the others you may have dragging calipers.

Disk brake pads do not retract like drum brakes. Springs actually pull the linings back from the drum. Basicallty with disk brakes there will always be a small amount of runout in the disks and perhaps a little give in bearings etc. This pushes the pads back a little and pushes the caliper piston in a very small amount. If those calipers are semi seized they will not push back far enough and the brake pad friction will heat the rotor with the heat being transfered to the wheel over a distance. I kind of suspect you might have one draging caliper by the noise you are hearing. The disk should drive the pads slightly away from the rotor. Even if only a few thousands. Make sure of course you do not have a rubbing back plate as the rubbing sound first.

Another strong clue to a possible dragging caliper is examining the brake pads. Basically most people change both sides of the same axle at the same time. So wear on both sides should be about equal. If it is not that caliper or rubber hose feeding it becomes suspect. Actually on these two piston caliper it would clearly indicate the exact sticky piston. The one with the pad worn down far more than the others that is.

You have to be a little careful diagnosing the rear brakes as a defective emergency brake could drag as well. Generally if youy can push the car by hand on a level surface by yourself real brake drag is not present.

Last edited by barry123400; 10-25-2008 at 08:00 PM.
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  #10  
Old 10-25-2008, 09:29 PM
zeke's Avatar
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Join Date: Sep 2007
Location: The Alamo City, TEXAS
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Great post, thanks!

I will try the coast thing, but from what you said, I don't think my brakes are really dragging. Brake wear is minimal and perfectly even on all 4 wheels. Also, I can easily push the car on a level surface. In fact, when I was tightening the lugs, my chock had slipped forward without me knowing it, and I was able to roll the car forward with the lug wrench

I will check out Cervan's post you mention. Actually, injectors are on my to-do list for next month, after I check the chain stretch and fuel timing.

It is hard for me to believe that I have a significant fuel delivery problem though, as the engine sound better than my 300TD which has one injector that nails a bit when cold but gets 26-28 mpg.

Like I said, no smoke, no twitching, easy to start, and runs powerfully and strong.....

Anyway, thanks for the post barry, I feel much better about the slight friction I feel.

__________________

Current Mercedes
1979 maple yellow 240D 4-speed


Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT
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