Has anyone bypassed their load-sensing assy (proportional) valve on the rear brake lines? The result?

The car is stranded with a mechanic I don't know. He's saying this valve is located in front of the gas tank and rusted out - leaking brake fluid. Dealer says this is very rare and is likely the connections to the lines there. I'm not sure that what he is refering to even is a proportioning valve- the autozone link seems to indicate that it should be closer to the master cylndr. up front!

Problem is- dealer says it has to come from Japan (3 weeks- $300!) and I need my car on the road? It's not an easy part to get off a car being parted-out or I would go that route.

Mechanic says to bypass it. Any brake experts out there?
Thanks!

 

it's the rear brake bias valve.
he could just route around it.
it is EXCLUSIVE to the VE w/ ABS models which explains why you are having trouble sourcing it.

I'd go with the bypass personally, I doubt you will notice much difference as long as your ABS is working correctly.

 

I fear this may actually be the end of the car!! How very sad....
The actual part seems to be a load sensing assy-valve (part # 46400R in the diagram)
http://www.courtesyparts.com/betasit...1706_1711.html
located at the rear of the car.

Has anyone ever done a bypass?

I don't think the abs is working any more.

 

What Brian said there.................. I would also bypass the sucker - BUT BOTH OF THEM since the FSM shows 2 of those suckers individually controlling the rear wheels independently, and if you only do 1 side, an emergency brake session may actually guarantee a spin.

Personally I must say I am rather surprised that the ABS equipped cars have that regulating valve and the non-ABS vehicles don't - one would think that with no ABS on a vehicle, the control of the rear braking force would be much more critical to prevent wheel lockup whereas the ABS cars would easily in theory be able to prevent that situation by design.

 

I believe they did it to get the car closer to the point of lockup so it could stop better
all I know is that with the abs deactivated and them working, I didn't care for the drive. though new front struts helped
something to do with the car's weight shifting when you brake which caused the load valves to change the way the rear brakes react.

 

BTW:92 se with antilock brakes, 5 speed.

Mechanic bypassed part mentioned. Frankly I can't tell the difference in braking efficiency. I have in the few days that have passed experienced ice, snow and dry. Happy so far... no brake lock-up or any symptom that I can notice.... maybe it hasn't been working for awhile. Note: both sides were bypassed (rear). Thanks to all who posted thoughts on the subject!

 

so....do GXE's or cars without ABS not have a proportioning valve? I was interested in this awhile back when I was doing the rear disk swap, because I've heard that a proportioning valve is intended for a car with front disks and rear drums. When you swap in rear disks and leave the proportioning valve it could cause there to be a constant bit of pressure on your rear brakes. True?

 

I'd think it's opposite. Disc braakes require more pressure than drums. I always wondered how swaps work on any car since the rear disc arent getting as much pressure as they should.

 

Well Bluetoof seems happy with his brakes and hes always at WOT or full brakes :P

~Alex

 

sigh....foreign drivers........

 

there is more than one proportioning valve.
there is the common type that our cars have in the master cylinder that adjust the pressure for front vs rear brakes (rear drum brakes require residual pressure to work effectively)
the rear valve adjusts pressure depending on suspension position.
the rear load sensing valves were ONLY used on 92-94 SEs with ABS. all other years trim levels did not get it. (excludes other makes/models)

 

So, if doing a swap, can the valve at the master be adjusted to accomodate the new disks? Should it be adjusted? I feel like the car still noses downward on hard stops...and if the rear disks aren't getting as much pressure as they should then I'd like to improve that. If a simple turn of a screw will put more pressure on the rears and even out the bias that I still have (Even with a BBK), then I want to know about it.

 

if the car is actually nosediving, you need struts and/or springs.

so far I don't think anyone has bothered to replace their MC when converting to rear disk

 

Well...definetally don't need springs/struts. My B&G/Koni combo is doing quite well for now. I'm mostly talking about the bias I feel when making hard stops. Though it's better than stock, the fronts are using more force than they need to.

It would be nice to hook it up to some kind of meter and see how much each caliper is actually stopping the car. Perfect would be 50% front and 50% back, probably. Mine feels more like 60%-40% respectively...maybe worse. Does such a meter exist?

For all I know my distribution could be something more like 34%FR, 29%FL, 20%RL, 17%RR. Those numbers are completly made up though....

 

you may not have enough dampening on the front koni's so they are allowing the nose dive.

 

If you are able to stop the vehicle in a straight line then there is very little "wrong" with the brake pressure distribution between the left and right of the car if the brake lines are connected where they should be and if they are able to pass fluid - the design of the MS and the engineering sizing of the wheel calipers/cylinders and drum/disk diameters actually guarantees that by design. The design of the MS also is responsible for the F to R brake force distribution based on the weight distribution characteristic (engineering parameters on the bench) of the car.

Other than a proportional valve on the rear axle, there is very little you can do with the standard hardware present on the vehicle - the proportional valve, when present, takes the pressure the MS sends to the rear wheels, and depending on vehicle load on the rear axle, modulates the maximum pressure per wheel to (mechanically and crudely) try and ensure no rear wheel lockup.

In general - most vehicles on the road operates with around 70/30 F/R brake force/effort since it has to be assumed the vehicle spends most of its life traveling forward and apparent weight transfer when slowing down via the brakes on the wheels is a fact of life/science - if you want/need independent control over every corner of the vehicle your only real answer is some form of ABS.