M1009 Brake question

[Marschmallow]

My M1009 does the same thing, rear brakes grab hard and will easily lock up, but only in the morning, for the first two or three times I hit the brake pedal. It has been years since I have owned a vehicle with drum rear brakes. I seem to remember this same problem with cold damp drum brakes on a 1983 2wd pickup. We do have dew here in the morning in Georgia that accumulates on vehicles, we are also having warm humid nights. I have inspected my brakes all the way around and find nothing out of place. Brakes work fine after their morning warm up. I have over the years gotten spoiled by 4 wheel disc brakes.

 

[jrou111]

It's the hydroboost. When the motor is still cold so is the PS fluid. Since it's thicker when cold the pressure is higher in the hydroboost. Both my M1009 and my Ford do it when cold.

 

[2deuce]

If the pressure is higher wouldn't it also affect the front? and with lighter pedal pressure being required wouldn't that be the only issue. I have had 3 M1009's as daily drivers, I haven't noticed any grabbing with any of them, freezing winter weather or summer heat. I think something is wrong and this shouldn't be considered normal.

 

[firecontrol86]

My 1009 has this same issue from time to time, but I like to let my truck warm up for a few minutes anyway so the oil gets moving around and makes it less knocky when I'm driving. I assumed the same thing someone said earlier about cold fluids being less....fluid. One of these days I'm going to a brake overhaul and rear disc conversion anyway, so as long as I can still drive it safely I'm not sweating it too much right now.

 

[CycleJay]

Hi All,

I just got my M1009's brakes inspected at a reputable shop in my area.

They said there is nothing wrong other than a little wear, so I am good.

He did say that they were a little dry and could be lubricated, and that
could be a contributing factor to the grabby brakes.
So I am going to work on getting that done.

He also said the grabby brakes after a cold start is pretty much normal
for a diesel from that time period.

He even said the brakes all the way around were good and looked like they
were recently redone by someone that knew what they were doing.
And that were safe and had no issues to worry about.

He said just let it warm up for a few minutes before driving after a cold start.
That's all.

By the way, he did not find any dead mice in the calipers.

Thanks for all the information guys, you are great, it is much appreciated.
Feel free to keep commenting on this thread if you like.

Have a good day,

CJ

 

[2deuce]

Glad you had a good inspection. I'm surprised that grabby brakes are normal. Its odd that I haven't experienced it. It may be that I back down a 300' driveway or I use my truck everyday. I do know I use my brakes less than most people. I have a 79 ford pickup, I bought new that still has the original brakes and I have driven 500 miles without touching the brakes, just to see how far I could go. As for grabby brakes, I'll change my opinion to... your results may vary.

 

[67_C-30]

It's the hydroboost. When the motor is still cold so is the PS fluid. Since it's thicker when cold the pressure is higher in the hydroboost. Both my M1009 and my Ford do it when cold.

I agree. I've noticed this in several hydroboost equipped vehicles I've had. Not all of them do it, but my 2 current ones (my '84 M1009 and '67 C-30 with a retrofitted hydroboost) do it.

 

[87k5]

I have a m1008 and my truck does the same thing as described in the original write up, Just thought I would let everyone (cycleJay) know that his is not the only one with grabby brakes.

Charlie

 

[CycleJay]

Hello Guys,

Thanks for all the comments, especially about having trucks that do the same thing,
and that they are in good shape too.

It is something I will have to learn to live with, and the guy that did the inspection
said I just need to let it warm up for a few when I do a cold start.

That is cool, I can do that, not a problem.

He was also very thorough, he looked over everything, etc, and took a lil while...

So I was pleased.

Have a good night,

CJ

 

[akonitony]

I'm confoosed... Yer mechanic said the brakes were dry and needed to be lubricated? Not sure I follow him there. I do know a little oil on brakes or a clutch will make them super grabby. You might want to have the front disk rotors taken off and checked to see if they need to be turned. While they are off, you could have them ground a little to give them a nice non-directional finish, then do the same to the pads with a whiz wheel, and this will get you back into the land of new brakes as far as feel goes. Just a suggestion is all.

 

[akonitony]

Actually, on a little more thought, your mechanic might have been referring to the slider pins on the front calipers. They need to always have a nice coating of synthetic brake grease on them to keep them from sticking.

 

[Barrman]

There are also lubrication points on the rear drum brakes. Where the shoes slide on the backing plate.

My M1009 blew a drivers side rear wheel cylinder a few weeks ago. I fixed it and everything worked great. I drive the truck just about every day. Last week, I parked it on Friday evening and didn't move it until Monday morning. I had a 140 miles trip to San Antonio to make in it. The rear brakes grabbed some on the first few stops I made, but by the time I got to down town, they were normal. I recalled this thread and figured maybe that was what my problem was.

The truck sat in a parking garage from Monday mid day until Thursday evening when I went to leave. I checked all the fluids and everything including the brake fluid was full before I left. Going down 8 floors in a parking garage was torture. The rear brakes were grabbing like crazy. I actually stopped and looked for broken leaf springs or something like that since it felt like the axle was falling out from under the truck. I got out of downtown stop and go and onto the interstate by going very slow and not using the brakes much.

100 miles later of driving 62-63 mph without using the brakes I had to exit the highway. I slowed down as much as possible by just coasting, but had to use the brakes at the stop sign. No grab, no chatter and normal brake action. Hmmm...

I made it home with normal sounding and working brakes. The next day, I pulled both rear drums looking for gear oil or brake fluid. Figuring that something leaked out while the truck sat, got on the shoes and burned off as I drove. Rear axle lube was full, so was the master cylinder. Both drums, backing plates and such were dry. However, my drivers side shoes had some dark color to them. I used a can of brake clean on them, let it dry and looked at them again. All uniform color and felt fine. I put the truck back together and did a test drive. All ok.

The leaked out brake fluid from the blown wheel cylinder had gotten into the shoes. It was coming to the surface while the truck sat. Just something else to think about besides the evil hydroboost.

 

[Barrman]

I guess I need to update again since mine isn't fixed. I was stuck at another teacher conference until today in Ft. Worth. The M1009 once again sat all week in a parking garage. When I went to leave, the same thing happened going down the levels. The rear axle sounded and felt like it was coming off every time I hit the brakes. Hard braking was no big deal, just the very soft dragging brake action needed to keep the speed slow going down an incline.

Same problem in city driving. Once I got on the interstate, I got on the brakes pretty hard for a long slow down. Problem went away the rest of the trip. I still think it is junk in the shoes that is just rising up to the surface though.