1987 Dodge Dakota height sensing proportiong valve

1987 DODGE DAKOTA

ALXX72

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Brakes problem
1987 Dodge Dakota 6 cyl Two Wheel Drive Manual 187k miles
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I bought this truck (87 dodge dakota 2x4 for $300, pretty good condition, considering the year and climate. However, the brake system did not fare as well as the rest of the truck. In particular the HSPV. It is badly rusted and 2 brake lines have snapped off in the valve, so I either get a new one at $289, replace the lines and prorobly the wheel cylnders and calipers( those bleeder screws look bad too)
By this time I'm looking at close to 2x if not more than I paid for the truck.
I came up with the idea of bypassing the HSPV. I would connect the primary line directly to the metering valve on the rear axle, and simply plug the bypass line at the differential/metering valve up front. After which I would adjust the rear brakes so as to try and prevent them from locking up as much as possible. I know this is not recommended, but my question is.....would this work??

Apr 29, 2008 at 3:21 PM

MERLIN2021

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It might...but why don't you just cut the line off as close to the end, and use a socket to remove the flare nut portion?

Apr 29, 2008 at 3:25 PM

ALXX72

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The line broke off flush with the valve

Apr 29, 2008 at 3:40 PM

ALXX72

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basically i wanna know that as long as i plug the bypass line up front i will get pressure to the rears?

Apr 29, 2008 at 3:42 PM

MERLIN2021

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What you would have to do is get a new brake hose long enough to mount it on the rear axle to eliminate the valve, Then branch off to the wheels...if you block it near the Master you wont get fluid at the rear. if the line broke at the valve, the nut is still there...I would do the above proceedure?

Apr 29, 2008 at 3:48 PM

ALXX72

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I think you are missing a part here. I have a preportiong/metering valve up front, 2 lines, a primary and a bypass line go down and just before the rear wheel there is a "height sensing proportioning valve" the 2 lines go into it, but have rusted away and broke off into it. Then 1 line goes to the metering valve on the rear axle. the valve on the axle (tee) is ok. The height sensing proportioning valve is what i am looking to bypass. I hope that helped

Apr 29, 2008 at 3:58 PM

DUSTYR26

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I just had the same thing kind of happen to my HSPV. Mine, all the lines are good, I just replaced them last fall. Now I noticed another leak on the back side of the HSPV. It's not leaking from the bleeders nor where the lines are coming in. Looks like there is a hole on the back side. Someone told me that the hole might be there for when the valve goes bad it will leak out of the hole?????? I too looked into replacing the HSPV. Same prices too!!!! I believe I am going to bypass the HSPV and run direct to the splitter on the rear axle. My question is which one is the back line and which is the return line. The front spllit has one line directly straight back to the HSPV and one comes out of the bottom of the Front Proportioning valve and goes to the back HSPV. Anyone know which line to leave and which line to Plug???? I'm thinking the bottom one is the return line.
Thanks in advance, Dustyr26!!!

May 2, 2008 at 10:04 AM

MERLIN2021

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The line out of the combination valve is the one to keep, block the other one.

May 2, 2008 at 1:22 PM

DUSTYR26

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Thanks,
The combination valve has the two lines coming back to the HSPV. I guess I'm just confused on which of the two to plug at the combination valve. I am assuming it should be the one coming straight back off the end of the combination valve. The other line which I would plug would be the one on the bottom. I will look a little closer once I get under the truck and try to get at it.

I probably will detach both lines back at the HSPV and then press on the brake to see which line shoots the brake fluid out, then that will be the one to connect to the line heading to the tee that goes to each rear tire. I would assume the other would then be the return line and plug that at the front at the combination valve.

Thanks again for the help. It's reassuring to pretend like I know what the heck I'm doing!

Thanks
Dustyr26

May 2, 2008 at 3:18 PM

MERLIN2021

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It really would not matter which then, both will do the job! Choose the easiest one.

May 2, 2008 at 3:29 PM

ALXX72

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Yeah Dusty, that's exactly what I'm doing too. I would've been done already, but the weather here has been rainy...no chance to work on it.

May 2, 2008 at 9:41 PM

ALXX72

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MINE WORKS!!!! ANY ?'s I'LL TRY TO HELP

May 4, 2008 at 1:30 PM

DUSTYR26

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Did you end up plugging the line straight back or the line that comes out of the bottom.

Good to hear yours works!

Thanks in advance.

Dustyr26

May 5, 2008 at 8:57 AM

ALXX72

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i plugged the 1 coming out the back (larger fitting) and ran a line coming out of the bottom all the way back to the tee on the rear axle

May 6, 2008 at 7:50 PM

DUSTYR26

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Thanks, I really appreciate the info. My mind set was to do it the other way. No real reason for my madness, but your info will save me from doing it the wrong way. Thanks a million again.

Dustyr26

May 7, 2008 at 8:12 AM

ALXX72

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no problem

May 7, 2008 at 12:33 PM

ALXX72

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Also, if in the process of bleeding your brake sys. you happen to snap off a bleeder screw, just replace the wheel cylinder(s), shoes and springs...it's well worth it while you're there. also if they are rusty dont bother trying to loosen them before you heat them up! really!
good luck

May 7, 2008 at 12:41 PM

DUSTYR26

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Thanks again, Actually I changed all the brake lines and got the bleeders loose last year. Only have 70,000 miles on my rust bucket. All the brakes look really good otherwise. This latest deal with the proportioning valve is the main problem now. Brakes worked fine for this last 8 months. Good to be able to bypass that piece though. Good to know I'm not the only one with this stupid problem!!!
When I get to doing this I'll let you know how it turns out. Probably won't be for a week or two.
Thanks again,
Dustyr26

May 7, 2008 at 1:43 PM

ALXX72

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ok, kool, let me know.

May 12, 2008 at 4:27 PM

DUSTYR26

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Had time this weekend to work on those brakes.
I tied directly into the back tee and plugged that line coming back out of the front splitter. Bled the lines and everything is working good.

Funny the plug piece only cost me $1.49.
Priceless.

Thanks to everyone with the help on this.

Have a good One!!!

Dustyr26

May 13, 2008 at 9:09 AM

MERLIN2021

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Very good!

May 13, 2008 at 3:50 PM

TC7

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I wonder if Dusty or Alxxl are still around to give an update on how their bybass is working?

I tried to work this out about 5 years ago. I talked to mechanics, service managers and engineers and they all said I would be crazy to try it. Glad you figured it out. Now I have no choice because the lines have corroded and split and the valve is a mass of rust.

So help me get this straight:
1. you block off the back port which goes straight (in-line) with the front proportioning valve. How did you do that because that is a wacky looking fitting! (large nut with small tube opening) Where did you find a plug?
2. Then you run the line which branches off the bottom of that same front proportioning valve and route that back to the Tee on the rear axle.
3. The line that used to come off the rear of the front proportioning valve to the HSPV is completely eliminated.

Is that it? I wonder what that other (bypass?) line was for?
Hope you guys are out there.

Mar 4, 2009 at 5:06 PM

TC7

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I thought I would add to the success list for anybody researching this problem. I bypassed the height sensing valve just the way it was described by Dusty and Axxl and it seems to work great. Rear wheels locked up a couple of times during a rapid stop when the roads were wet. But all-in-all it was a good way to eliminate this annoying and expensive problem for just a couple of bucks (brake line and brake fluid fluid).
Thanks guys.

Mar 8, 2009 at 7:01 PM

MERLIN2021

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OK, Your welcome.

Mar 9, 2009 at 11:27 AM

MENO19

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Great posts guys. Ends up I have the same problem as well. I have an old 87 Dodge Dakota that I am working to get back on the road. I did the HSPV Bypass and blocked off the return on the main proportional valve. Everything seems to work great and have decent pressure in the brakes but I still have the brake light on my dash. Now is this light on the dash related or is this pointing to another issue. My thing is I am trying to get a NYS Inspection done but need to get the light to go off. Any ideas on what it could be, is it because of the HSPV bypass, or is it something else. What would cause this light to trigger?

Jul 20, 2009 at 7:46 AM

MERLIN2021

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If it's the red light check the parking brak lever, the switch there may be stuck/defective, or you actually are low on fluid or have a leak still.

Jul 20, 2009 at 1:10 PM

MENO19

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[quote="merlin2021"]If it's the red light check the parking brak lever, the switch there may be stuck/defective, or you actually are low on fluid or have a leak still.[/quote

Yup it's the red brake light on the dash. For the longest time it was the parking brake lever that was messing up. It no has been on constantly. I even tried disconnecting the parking brake sensor wire to see that would get the light to go out and it didn't change anything. Now would doing the HSPV bypass and plugging the return line on the main proportional valve cause the light to go on?

Jul 20, 2009 at 2:15 PM

MERLIN2021

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Let me ask you this, was the light off before you did the valve bypass? If yes, I would say you may have something to recheck...the combination valve that you ran the line from, does it have an electrical connection to it? If so, try opening a front bleeder, and pressing down on the pedal, close the bleeder, and step on the brake, does the light shut off now? It's an off centerd valve...recenter it using this method. Then again, if your hieght sensor was leaking fluid and you ran the master dry, you may just need to bleed more air out!

Jul 20, 2009 at 2:29 PM

MENO19

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[quote:8dc5560b6d="merlin2021"]Let me ask you this, was the light off before you did the valve bypass? If yes, I would say you may have something to recheck...the combination valve that you ran the line from, does it have an electrical connection to it? If so, try opening a front bleeder, and pressing down on the pedal, close the bleeder, and step on the brake, does the light shut off now? It's an off centerd valve...recenter it using this method. Then again, if your hieght sensor was leaking fluid and you ran the master dry, you may just need to bleed more air out![/quote:8dc5560b6d]

Yes the light was on before I ran the bypass. I bleed both back drums but did not bleed the front and yes the proportional valve does have wires connecting to it at the top. Could the light be going on cause air could be in front half of the system? If I bleed the fronts do I need to bleed the rears again?

Jul 20, 2009 at 3:03 PM

MERLIN2021

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If all air was removed from the rear, bleed just the front...Good pressure at rear?

Jul 20, 2009 at 3:35 PM

MENO19

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[quote:2c5173709f="merlin2021"]If all air was removed from the rear, bleed just the front...Good pressure at rear?[/quote:2c5173709f]

Yeah they actually work now. If I jam on the brakes the back can lock up. I'm going to head home and try bleeding the front to see if it is as simple as that.

Jul 20, 2009 at 5:02 PM

MENO19

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Well I went to bleed the fronts and the left one bleed fine but the bleeder valve on the right snapped right off. So for now I cant bleed the right one. Either way it didn't turn the light off. I tried doing the reset procedure by holding down the brake pedal with the Ignition turned to AC and that didn't work. In the end I just went to the proportional valve and removed the sensor wire. That turned the light off. Hopefully that will get me through inspection.

As for later I still have an issue, correct me if I am wrong but either the proportional valve/metering sensor is not working correctly and needs to be replaced, air could still be in the system, or I have a short in the sensor wire going to the brake light. Any other ideas on what it is. Also thanks for the advise thus far all good stuff.

Jul 20, 2009 at 7:54 PM

MERLIN2021

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I did ask if the pressure to the rear brakes is good? You might need to use the other line out to the rear...block the one you are using...You can still blleed the caliper by removing it from the mount, put a block of wood in between the pads, turning it so the banjo bolt the hose attaches with is at the top, and crack it open...remeber air rises to the top!

Jul 21, 2009 at 2:51 AM

MENO19

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No the rear brakes do have good pressure now. Yeah I didn't think about bleeding from the banjo bolt very good point. I'll give the system another full bleed to see if it's still got air in it. For the rear port in the back of the proportional valve the one I blocked was the return. This truck is old and needs alot of work. Heck of a project that I decided to take on haha.

Jul 21, 2009 at 6:14 AM

MERLIN2021

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As long as the brakes hold! If light is out at inspection station, I doubt they will inspect the wiring!
SERVICING METERING VALVE 1. On disc brake equipped vehicles, the metering section of combination valve must be held open before pressure bleeding. 2. Hold metering valve open while pressure bleeding front brakes. To loosen front mounting bolt and install pressure bleeding tool on combination valve, valve stem should be fully extended or depressed. NOTE: Never reintroduce brake fluid that has been drained from hydraulic brake system or that has been allowed to stand in an open container for an extended period of time. Also, do not use fluid that contains a petroleum base. Petroleum based fluids will cause swelling and distortion of rubber parts in hydraulic system.Even if you didnt use a pressure bleeder, it might be worth a shot to hold the valve open while bleeding the fronts...

Jul 21, 2009 at 3:57 PM

MENO19

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Since I removed the HSPV everything has been fine but I was thinking or replacing or upgrading the main proportioning valve. Does anyone know where I can get one that is compatible with the 1987 Dodge Dakota or would I be able to utilize an aftermarket proportioning valve? I am just airing on the side of caution and would like to pretty much rebuild my brake system in the car.

Sep 4, 2009 at 7:46 PM

MERLIN2021

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I always say if it aint broke, dont fix it. That's just me. But get a valve for a cysler van or car that dosent have the HSPV and the lines should match up.

Sep 5, 2009 at 6:57 AM

MENO19

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[quote:237771b9e5="merlin2021"]I always say if it aint broke, dont fix it. That's just me. But get a valve for a cysler van or car that dosent have the HSPV and the lines should match up.[/quote:237771b9e5]

So basically I can just swap one in that is for a car with front disk and rear drums without a HSPV. Didn't know if you had to get a specfic sized valve or if you could just swap one out. Problem I'm having is the rear plug I am using is leaking ever so slightly. The brakes work but still feel a bit soft just trying to firm them up some more.

Sep 5, 2009 at 8:24 AM

MERLIN2021

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Remove the leaking piece, plug with a rubber plug so you don't loose all your fluid, or press the brake pedal down a feww inches ant hold with a rod and clamp at the steering wheel, this will put the MC piston past the ports and stop all leaking, then take that piece to the parts store and buy a brass plug and use the brass plug! This will eleiminte the problem at a fraction of the cost!

Sep 5, 2009 at 8:49 AM