brake pressure regulator...missing?!

herr_sparky · Post by **herr_sparky** » Sun Feb 15, 2009 4:35 pm

it looks to me like its been removed and a hard line made to run directly to the T-fitting. should i replace it? how critical is it? where can i find one? the brakes always worked OK, just not great. i always figured it had more to do with a leaky MC and worn shoes, but could the system ever work well without the regulator?

Post by **david58** » Sun Feb 15, 2009 5:32 pm

Ok what is a brake pressure regulator?

herr_sparky · Post by **herr_sparky** » Sun Feb 15, 2009 5:45 pm

it adjusts pressure so that braking force is applied to the rear brakes proportional to the front...basically, it ensures that the front brakes do more work than the rear.
the Haynes manual describes it as ensuring "that the pressure to the rear wheels increases at a lower rate than that to the front wheels."

Lahti411 · Post by **Lahti411** » Sun Feb 15, 2009 11:03 pm

I know couple of guys who have removed it completely. I think it was adjustable, but still, it never worked properly. I have lots of period test drives and all of them had complaints that the rear wheels didn't brake actively enough. And Variant (square back) versions never had the regulator anyway. I guess the Variant had heavier tail so there was even smaller risk for the rear wheels to lock under heavy braking.

Lars S · Post by **Lars S** » Mon Feb 16, 2009 12:47 am

What happens if the rear brakes locks and the front does not is that the car suddenly wants to turn 180 degrees, guess thats what the regulator should prevent...quite important...but if the regulator normally works after 35 years I dont know.

LarsS

Lahti411 · Post by **Lahti411** » Mon Feb 16, 2009 9:13 am

Yeah, that's what the regulator was ment to do, but in a type 4 case i think the regulator was a bit exaggerated. I a type 4 the front wheels locked wery easily due the lightweight front and it was very difficult to lock the rear wheels as the tail was so heavy. In a period test drive i red the drivers even said that if (and when) the front wheels were going to lock you could easily push the brake pedal even harder and safely brake with the rear wheels as they were never going to get locked... I guess in a type 4 the pressure regulator should have been for the front brakes... hehe...

herr_sparky · Post by **herr_sparky** » Mon Feb 16, 2009 9:20 am

i never had any problems with the rear locking, and i've always had about 150lbs in the trunk (poor bastard lowering kit) so the front never locked up either. i wonder about using a regulator from a different car/model?

Lahti411 · Post by **Lahti411** » Mon Feb 16, 2009 9:33 am

I just noticed that you have a 412 estate (Variant, Squareback etc...) I thought you had a 2-door sedan... The estate versions never had the regulator. Ofcourse there might be differences between countries and states, but as far as i know VW never installed the regulator for the estate.

herr_sparky · Post by **herr_sparky** » Mon Feb 16, 2009 1:17 pm

i dont think thats true for the States...all my books show it, and i can see the brackets on the underside that it should be attatched to...anyone know for sure?

Lars S · Post by **Lars S** » Mon Feb 16, 2009 10:09 pm

The Haynes 411/412 manual says "not fitted on all cars".

Lars S

raygreenwood · Post by **raygreenwood** » Tue Feb 17, 2009 7:53 am

Yes, the 411 and 412 wagons never had the regulator. Only two and four door models did.
This regulator was the exact same model the 914 used. Yes...they work well. Yes they are adjustable. You will need a guage that reads about 600-700 psi.
I rebuilt two of them sometime back using new seals I had made for them. They were very hard to rebuild because the seals I had were CNC machined of a harder durometer rubber than stock (nature of the machine process). I went through 5 seal cups just installing the single seal. It worked well.
I would simply buy an aftermarket adjustable one and be done with it.

http://www.pegasusautoracing.com/produc ... RecID=2653

http://www.pegasusautoracing.com/produc ... RecID=6047

http://www.pegasusautoracing.com/produc ... RecID=4889

http://www.pegasusautoracing.com/produc ... oduct=3528

http://www.hrpworld.com/index.cfm?tpc=W ... on=product

Any of these products will do fine depending on how you plumb it. Generally right under the rear seat area on the left...is the single line from forward to a "T". The valve goes right before the T. Ray

herr_sparky · Post by **herr_sparky** » Wed Feb 18, 2009 8:06 am

thanks... if it wasnt there in the first place i'll just forget about it. the idea of having an aftermarket ajdustable unit does sound pretty cool, though. they're cheaper than i would have guessed, too.

raygreenwood · Post by **raygreenwood** » Wed Feb 18, 2009 11:37 am

The variant is heavier in the rear. They probably also figure that if you own a variaent you will probably have a bunch of junk in the back too.
In two situations I have needed the regulator....and thats how I knew that Mine had stopped working. Once it happened in my 411 wagon and once in my two door.

The issue is that as you brake hard, the enertia shifts forward. Pressure is taken off the rear end. the pressure can easily cause the brakes to lock because the lowered enertial weight/pressure needs less brake pressure to stop the wheel.
Without a regulator...especially in two and four door saloons, you can easily have just one wheel lock if you are braking in a curve and the body also has a enertial shift to teh outside. This can and will throw you into a wild skid.
Get a regulator. I have been there twice. Even for wagons . Ray

herr_sparky · Post by **herr_sparky** » Wed Feb 18, 2009 9:41 pm

i can certainly see the reason for having one. how does one calibrate it? you mention a gauge capable of 600-700psi...does that mean that there is a "target" pressure in that range when the rear circuit is retarded?

raygreenwood · Post by **raygreenwood** » Thu Feb 19, 2009 6:34 am

Yes...its actually in the Haynes manual IIRC in the brake specs. I will look tonight. It may have been in the 914 book or Clymer.

In short, there is a single inlet line from the master cylinder and two outlet lines, one to each wheel cylinder. When the valve operates...there is an audible or feelable clunk or pop.
So....disconnect the master cylinder line. Screw in a "T" fitting, install gauge. Bleed brakes well.
Have someone step on brakes while you have your hand on the regulator under teh car. Watch inlet presure from master cylinder rise on the gauge. Note the pressure on the gaugewhen you feel the "thunk" from the regulator closing. I just mark it quick with a grease pencil. Open locknut and get 4mm allen wrench and make adjustment. Repeat until it is set.

Now......Since every car has different tires with different grip...and slightly different weight distribution, take it out to a large parking lot , get it up to about 50 mph and slam on teh brakes for a second. Make note if teh rear wheels lock up. If they do....get out, reach under and tweek teh regulator with the allen key again. Repeat until you get no more locking up. Then when you get home repeat your first chekc and make note of the pressure that your regulator required along with the tire combination you are using.
Remobe the "T" and gauge...rebleed. Done. Ray