Bypass the anti-lock brake module?

[Declaration Day]

I have a 2005 Chevrolet Silverado 2500HD.  The anti-lock brake module is leaking.  It's a slow leak, but I have to bleed out the front calipers every 3-4 days, because it is letting air in the front half of the system.

I've called all the local auto parts stores, and none of them can get the abs module.  It appears to be a dealer part, and probably costs a fortune.  This truck is not my pride and joy; it's a work vehicle and I just want to keep it operating safely, and as cheaply as reasonably possible.  I don't like buying mechanical parts from a junkyard, and even if I did the nearest one is about 20 miles away.

The vast majority of vehicles I've owned haven't had ABS.  I don't need it.  So I am thinking about simply bypassing the ABS module.
The module has two input lines coming from the master cylinder.  One for the front wheels, one for the rear wheels.  It has three output lines.  One services both rear wheels, and there's a separate one for each front wheel.  I have already identified each line's function.

I am thinking of buying one fitting to connect the line coming from the master cylinder to the single line running to the rear wheels, and a 3-way T connector to connect the front input line to the two separate output lines that run to each front wheel.

Does anybody see a problem with doing this?  Any other advice?

[Nick1911]

I don't see a problem with it, unless there is some kind of balancing valve, or restriction orifices built into the ABS unit.

[zxcvbob]

You might need to remove the ABS fuse too, so the computer knows it has been disabled.  (I do that in my truck in the winter anyway, it's about time to put it back for the summer)

[Declaration Day]

I just called a Chevy dealer.  That module costs $557. 

[Declaration Day]

Ok, I just spoke to a trusted mechanic who told me I cannot do that.  The ABS module contains proportioning valves.  Not having them = bad.

I guess I'll just have to live with bleeding out my front brakes frequently, for now. 

[Tallpine]

Ok, I just spoke to a trusted mechanic who told me I cannot do that.  The ABS module contains proportioning valves.  Not having them = bad.

I guess I'll just have to live with bleeding out my front brakes frequently, for now. 

They've had those proportioning valves for a long long time.  I think my 1976 has it.

I wonder if you could substitute a p-valve from a pre-ABS GM pickup ...? 

[Brad Johnson]

Exactly where is the valve leaking?  Maybe it's fixable.

Brad

[Declaration Day]

Exactly where is the valve leaking?  Maybe it's fixable.

Brad

I'm trying to determine exactly where the leak is coming from.  I hosed the unit down with brake parts cleaner and will go back out there in a bit to inspect it.

In the mean time, thank God for Speed Bleeders.  They're a bit pricey, but worth it.

[CNYCacher]

Ok, I just spoke to a trusted mechanic who told me I cannot do that.  The ABS module contains proportioning valves.  Not having them = bad.

Can't imagine in what way.  Aside from ABS functioning independently on the fronts.

Although, I seem to remember non-ABS vehicles usually having separate lines for the front coming right off of the master cylinder, so perhaps there is a trick to it.

The only essential brake-proportioning I know of is you can't apply more brake to the rear than the front.  If the rears lock up you are in big trouble.

[Declaration Day]

The only essential brake-proportioning I know of is you can't apply more brake to the rear than the front.  If the rears lock up you are in big trouble.

And that is the function that a proportioning valve serves.

[Hawkmoon]

Ok, I just spoke to a trusted mechanic who told me I cannot do that.  The ABS module contains proportioning valves.  Not having them = bad.

I guess I'll just have to live with bleeding out my front brakes frequently, for now.  

I would physically remove the ABS module and plumb new hard lines directly from the master cylinder to the front wheels and to the flex hose on the rear axle. My pickup truck had a proportioning valve for the rear. It exploded in a panic stop several years ago, and since the truck was almost 20 years old at the time no replacement was available. I eliminated in completely and I don't notice any problems due to lack of proportioning. In fact, the brakes work better now than they ever did.

Dump the ABS. If you find that the rear brakes consistently lock up prematurely, you can get a Wilwood manually adjustable proportioning valve from a local speed shop or on-line from Summit Racing and add that to the hard line going to your rear wheels. The Wilwood valve (if you decide you need it) should cost you about $75.

[roo_ster]

https://www.partrequest.com/

Looks like ~$200 here:
http://www.rockauto.com/catalog/x,carcode,1431132,parttype,1592,a,www.google.com%2BSearch%2Bfor%2B2005%2BCHEVROLET%2BSILVERADO%2B2500%2BHD%2B6.6L%2B400cid%2BV8%2BDIESEL%2BFI%2BTurbo%2B%25282%2529%2BOHV

Good luck.

[Declaration Day]

https://www.partrequest.com/

Looks like ~$200 here:
http://www.rockauto.com/catalog/x,carcode,1431132,parttype,1592,a,www.google.com%2BSearch%2Bfor%2B2005%2BCHEVROLET%2BSILVERADO%2B2500%2BHD%2B6.6L%2B400cid%2BV8%2BDIESEL%2BFI%2BTurbo%2B%25282%2529%2BOHV

Good luck.

jfruser, that might just do the trick, thanks.  I am going to see if I can get a part number off the leaky one to be sure.

[CNYCacher]

And that is the function that a proportioning valve serves.

Correct, but is this not built into the master cylinder?

[Declaration Day]

Correct, but is this not built into the master cylinder?

Good question.  The mechanic I spoke to said it is likely part of the ABS module.

[CNYCacher]

Good question.  The mechanic I spoke to said it is likely part of the ABS module.

With separate lines coming from the master cylinder, how is it possible for the proportioning valve to be in the ABS unit?

Even with ABS, the front and back system are separate, and there will even be a baffle separating the fluid reservoir on top of the MC.  This keeps a leak on the back brakes from depleting all the fluid in the front brakes (or vice versa).

If there is a proportioning valve in the ABS unit, I suspect that it is some sort of controlled valve that allows the ABS system to continue braking one front wheel while it decreases the brake pressure on the other front wheel because it locked up.

[Jim147]

http://www.summitracing.com/parts/WIL-260-11179/


Set your brake bias anyway you want to.

jim

[Declaration Day]

With separate lines coming from the master cylinder, how is it possible for the proportioning valve to be in the ABS unit?

I don't know!  This is why I'm asking you guys!  

The truck's brake master cylinder does have a baffle in the reservoir, and as mentioned has one line going to the rear, and one to the front.  Are you saying that the master cylinder is designed to send more pressure to the front?  That makes sense to me!

In any case, bypassing the ABS module will cost only a few dollars.  I can safely test the truck on the streets in my neighborhood.  If it does not work out, I am out a few dollars and a couple of hours of work.  I think it is worth a try.

So my next question is, does anyone know where I can find data on the size and thread pitch of the brake line fittings?  All five of them that connect to the ABS module are identical.

[Jim147]

I'm not sure on the threads,may be 10 x 1.0, but I think they are still using inverted flares on the lines. You need brake fittings.

jim

[Declaration Day]

Here's the module, in case anyone wants to see what I'm dealing with:

[Declaration Day]

Ok, I've decided to attempt the bypass.  It will only cost a few dollars, and is reversible if it does not work.

However, it won't be today, or this weekend.  I have too much going on to be without my truck in case something goes wrong.

Thanks for all the advice.  I will resurrect the thread once I accomplish the repair.

[zahc]

Please do; I would probably try to bypass it just with hardlining it with no fancy proportioning or anything.

[Gowen]

Try car-part.com see if you can find it. Another idea is to see if you can find someone parting out a Silverado.  I know you didn't want a junk yard part, but $550 is a lot of money.

[sanglant]

is this it? $302~ will an older non abs unit fit? and how much will your insurance go up without abs? inspection problems?
edit: that's the wrong one $310~(google lists that one as, 2005 CHEVROLET SILVERADO 2500 HD Electronic Brake Control ABS Module)

edit: had an not in there where it didn't belong,

[RaspberrySurprise]

is this it? $302~ will an older non abs unit fit? and how much will your insurance go up without abs? inspection problems?
edit: that's not the wrong one $310~(google lists that one as, 2005 CHEVROLET SILVERADO 2500 HD Electronic Brake Control ABS Module)

Luckily the state doesn't do inspections on vehicles here in Michigan, at least not as far as I know.