Brake proportional 'valve' questions

[TechnoWeenie]

Yes, I tried searching, but didn't get the info I was looking for.

I picked up an M1009 that recently had both front and rear brakes serviced.

It stops on a dime (for a big SUV), however, I noticed a wee bit of a problem.


Under even moderate braking, the rear brakes lock.

They release immediately upon letting off the brake, but obviously, there is more braking 'power' going to the rear, than the front.

In modern cars, it's just a matter adjusting a set screw or similar.

In searching, I've seen there's some sort of lever or something, but haven't really been able to figure out *what the heck* is going on.

I also see info about a front valve and a rear valve, and everyone saying 'don't touch it'.. Which doesn't help me.

A little insight would be appreciated.

 

[BikerBi11]

Double check and make sure you don't have anything leaking back there. Gear oil on the brake shoes will cause those symptoms. I don't know if brake fluid will or not, but better safe than sorry. Hope this helps.

 

[TechnoWeenie]

Double check and make sure you don't have anything leaking back there. Gear oil on the brake shoes will cause those symptoms. I don't know if brake fluid will or not, but better safe than sorry. Hope this helps.

I had it on a rack yesterday. Looks like a brake line was replaced in the rear (recently).. There is no fluid visible.

I'm thinking that the person who did the job, didn't adjust the rear brakes. I'm a complete n00b when it comes to drums. Give me rotors any day, and I can do anything you need to them. The whole adjusting springs and crap is new to me.

 

[Sharecropper]

Ditto on what Biker Bi11 said.

Also, the rear proportioning valve must be properly adjusted in order for equal braking force to be applied to front and rear brakes. I provided details for this in post #75 of my rebuild thread.

Hope this helps.

 

[porkysplace]

When you say serviced what was done ? what parts are new , was it just pads and shoes ?
Knowing what parts were replace will help with diagnosis . Peoples opinion of a brake service varies widely , especially when putting one up for sale.

What kind of fluid did they use did they replace it with D.O.T. 5 , if it is mixed with D.O.T. 3 that could be your problem. If they are mixed it can gel up.
Brake fluid -how to tell which kind you have DOT 3 or DOT 5

 

[TechnoWeenie]

When you say serviced what was done ? what parts are new , was it just pads and shoes ?
Knowing what parts were replace will help with diagnosis . Peoples opinion of a brake service varies widely , especially when putting one up for sale.

What kind of fluid did they use did they replace it with D.O.T. 5 , if it is mixed with D.O.T. 3 that could be your problem. If they are mixed it can gel up.
Brake fluid -how to tell which kind you have DOT 3 or DOT 5

No service records. The seller said all fluids were done (trans, transfer, diffs,etc) and had 'brakes replaced', albeit no records. my mechanic confirmed that all the fluids were virtually brand new, sans the oil, and said the shoes and and pads looked new, with little to no wear on the rotors, but didn't check the drum itself.

Is there a manual that shows the 'proper' adjustment method? I see where it is, but the thread linked just had pictures with no real descriptions.

If I'm reading correctly.

Remove the arm, make sure the dot is facing up, then re-secure the arm?

Is there not a distribution valve in the front to control the amount of fluid sent to the rear?

The rears WERE NOT spinning freely, they had a hair drag to them. Not much, but enough to slow it down.

In addition, on light braking, there is a 'thunk' and a jolt, similar to when you're towing a trailer. Does NOT to it on decel, only on light braking, and there is no play in the driveline.

I'm thinking the rear shoes/drums weren't adjusted properly. I know generally speaking that there's a tension spring (similar to what's used on a parking brake on disc brakes) on drum based systems. Is that the case in the CUCV case as well?

 

[cpf240]

Please correct me if I'm wrong, but I don't think the M1009 has the weight proportional valve on the rear that adjusts the rear brakes based on load weight like the other CUCVs. Looking at the -34p TM, figure 119, most of those parts, including the valve, don't list the "209" UOC, but seem to list all the other UOCs for those parts.

 

[tankie88]

I did read somewhere that as soon as the rear valve was faulty the military removed them and never replaced them as they were rubbish.My M1009 has none.

 

[TechnoWeenie]

So if there is no REAR proportioning valve, where is the FRONT one?

 

[doghead]

What state is UTL?

The pictures in the parts technical manual show where they are(clearly).

 

[TechnoWeenie]

What state is UTL?

It's not.

The pictures in the parts technical manual show where they are(clearly).

I did look. I didn't see anything that regulates flow to the rear, from the front. Only the rear one, which I do not have.

I guess I should loosen the rear shoes then, so it requires more force to actuate the rear brakes?

 

[doghead]

You need to inspect then for sure.

You also need to put your state in your location, it's the site rules..

If you do not live in the USA, then show your country(at least). We want to know where you are to better help you

 

[porkysplace]

Follow the lines from the master cylinder they will lead you to the valve

 

[southdave]

check the cross member under the raditator, the valve dose go bad, however it is rare. Most of time the the valve is just crapped up from mixing DOT fuilds. Its my opinion, that the system needs a flush and adjustment. Note the valve"new" is about the only thing on truck that is really hard to find.

 

[Warthog]

As a noob I guess you missed the rule about foul langauge is not tolerated here. While we are not prudes, this is a family friendly site.

the f-bomb or any of it abbreviations will not be tolerated and will get you intro le every time. You get a warning this time.

 

[Warthog]

The proportioning valve is on the front crossmember of the CUCVs. It is non-adjustable/non-serviceable.

The pickups have a rear ride height valve the applies additional braking power if the bed rises.

 

[TechnoWeenie]

check the cross member under the raditator, the valve dose go bad, however it is rare. Most of time the the valve is just crapped up from mixing DOT fuilds. Its my opinion, that the system needs a flush and adjustment. Note the valve"new" is about the only thing on truck that is really hard to find.

Duly noted.

The fluid was grey, however there were no particulates and it did not appear gelled.

My mechanic said 'whatever it is, it's NOT DOT5', and sucked out the reservoir and replaced it with clean DOT3, it's not as sensitive now, but still does it occasionally so yes, definitely needs a full service/flush.

Appreciate the answers.

Nonadjustable? Ugh.

Can't complain too much, got the truck dirt cheap, knowing that I'd have to put a grand or so into it to get it perfect.