are my back brakes dragging?

1693 Views 16 Replies 8 Participants Last post by Oregonwinger, Dec 5, 2005

avnsteve

Discussion Starter · Jun 23, 2005

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My question is 60mph @ 3000rpm in top gear normal?

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Tonys96

· #2 · Jun 24, 2005

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Dragging brakes will not cause the revs at speeds to change, that'd be a slipping clutch.

Your brakes could be worn out, or the piston may be failing to "relax" back into the bore after releasing the brakes.

When was the last time you bled your brakes...

What does your brake fluid look like...

Any moisture in the brake fluid can corrode the caliper internals.

Check you pads for remaining material thickness.

You should be able to hear the brakes if they are "dragging" by rotating the tire while on the center stand.

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exavid

· #3 · Jun 24, 2005

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avnsteve wrote:

My question is 60mph @ 3000rpm in top gear normal?

Doesn't sound too far off, my 1200 used to run around 3600-3700 at 70mph. The 1500s are higher geared by about 500 rpm at 70. Or therabouts. Check your rear caliper, they do occasionally stick and then your brake will drag a bit. It should be free enough to move back and forth a bit with light hand pressure. If one pad is worn a lot more than the other that's a symptom of a stuck caliper.

avnsteve

Discussion Starter · #4 · Jun 24, 2005

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today:

caliper rebuild kit (rear)

new pads

pumped new dot4 through the entire rear system, then bled

also topped off and bled the r/front

are you sure that something dragging wouldn't cause the motor to run at higher rpms to achieve the same speed?

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Tonys96

· #5 · Jun 24, 2005

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avnsteve wrote:

...are you sure that something dragging wouldn't cause the motor to run at higher rpms to achieve the same speed?

Yes

johnmac

· #6 · Jun 24, 2005

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My '85 1200 runs at 3600 RPM at 70 MPH. With a clutch and standard transmission (not automatic) the engine can't rev up to make up for a dragging brake. You can test this by stepping on the brake a bit while trying to hold a steady speed. The tach will read the same if the speed stays the same.

avnsteve

Discussion Starter · #7 · Jun 24, 2005

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ok, thanks, i've got it sorted out now.

GWEddie

· #8 · Dec 5, 2005

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What was the problem? Dragging brakes would just hold both the speed and the engine revs down. Slippy clutch would bring the revs up.But 3000rpm at 60mphdoesn't sound unusual.

Oregonwinger

· #9 · Dec 5, 2005

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3k at 60. About right. My Toronado is doing about 1500 at 60. Quite a difference. But at light throttle, it pulses. Very annoying. Put a switch in the lock-up to kill the surge. Hurts mileage, tho, and it runs about 2k w/o lockup.

Hawker22

· #10 · Dec 5, 2005

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GWEddie wrote:

What was the problem? Dragging brakes would just hold both the speed and the engine revs down. Slippy clutch would bring the revs up.But 3000rpm at 60mphdoesn't sound unusual.

If you have a brake that is dragging to the point where you get performance indications, it will not be long before you get heat buildup, then warping, then FIRE. Friction causes lots of heat.

Oregonwinger

· #11 · Dec 5, 2005

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Not to mention no power, and very bad mileage.

twisty

· #12 · Dec 5, 2005

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Oregonwinger wrote:

3k at 60. About right. My Toronado is doing about 1500 at 60. Quite a difference. But at light throttle, it pulses. Very annoying. Put a switch in the lock-up to kill the surge. Hurts mileage, tho, and it runs about 2k w/o lockup.

Oregonwinger, those older GM vehicles lock the converter solid when in TCC lock up,, the newer GM vehicles pulse width modulate the converters to allow slight slippage depending on the vehicle speed & load & throttle opening.

You might try putting a TEE in the EGR vacuum hose with a .012" orifice in the open end of the TEE then placing an old small paper fuel filter over the open end to filter the incoming air..

That takes some of thevacuum signal off the EGR at low speed high load & takes most of that surging out when it TCC lock-up..

Twisty

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Oregonwinger

· #13 · Dec 5, 2005

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This is a "diesel" Don't laugh. I have it very reliable. What a pain it was in the beginning. None of the fuel system is original, except nozzles, and inj. lines. Cat bolts on the heads, and mains. Had a few of them break. Got rid of the troublesome, unreliable glowplug system. Just have a set of limiting glow plugs, and a return to center toggle switch. So, it's like starting a D-8, or such. Very reliable. Still no power, tho. It does have a EGR. Think that might work on the diesel? I thot about blocking it off. Don't have to do I-M anymore.

twisty

· #14 · Dec 5, 2005

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Oregonwinger wrote:

This is a "diesel" Don't laugh. I have it very reliable. What a pain it was in the beginning. None of the fuel system is original, except nozzles, and inj. lines. Cat bolts on the heads, and mains. Had a few of them break. Got rid of the troublesome, unreliable glowplug system. Just have a set of limiting glow plugs, and a return to center toggle switch. So, it's like starting a D-8, or such. Very reliable. Still no power, tho. It does have a EGR. Think that might work on the diesel? I thot about blocking it off. Don't have to do I-M anymore.

Oregonwinger, yes, that original low voltage fast rise glow plug system was a real pain as the plugs burnt out quickly. What is your glow time now before cranking?

On the EGR for surge on a diesel? I don't know,, it would be easy to block it off & see if it helps. If your exhaust system is plugging even a little it doesn't take much EGR opening to really skew the low speed runability.

Twisty

exavid

· #15 · Dec 5, 2005

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Man I'm glad I have on old Dodge Cummins, no electronics, direct crankcase venting, no glow plugs and the intake preheater is 16 years old and still works fine. Original untouched injectors. Did replace the waterpump though. 203,554 miles and running fine.

Oregonwinger

· #16 · Dec 5, 2005

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Twisty. I do believe the exhaust is plugged, as the sound is a steady "SHHHHHH", for lack of a better term. The 28 degree morning, this morning, took about 40 secs. Hit starter, then a cppl more 10 sec jabs on switch, and it's good to go. The egr valve is right on top of the air intake crossover, and if anything, it's in the way of air volume. I might take it off, one of these days, when it warms up. BRRRRR. Foggy, right now.

Oregonwinger

· #17 · Dec 5, 2005

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Paul.

Those 5.9's are tough. We have a lot of them in Timbco feller bunchers, the engine-up design, they tip over often, radiators are continually plugged with brush, needles, moss, etc. They just keep going, despite abuse. The biggest trouble we had with them, was fuel transfer pump, and the belt tensioner. They're run full throttle all day. Seen them with 10,000hrs, and still running great. The rest of the machinewill bejunk. Only had to re-bearing one, and that was in a Timberline delimber. Don't remember the hrs., but a lot. Lot better engine than that Joke of a "3116" Cat. And we are the Cat Dealer. The 3126 Cat is a big improvement. (Electronic) It's a C-7, now. Very fine engine. Giving the 5.9 a run for it's money. Cat didn't like us "dealing " in Cummings, and made us get rid of the Timbco, and Timberline lines.

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