Stuck brake proportioning valve?

ImKenNY · 02-14-2008, 10:02 AM

I determined my newly acquired 1985 MR2 has properly working front brakes but no rear hydraulic brake action.

I suspected frozen rear calipers but after further investigation I found brake fluid enters the proportioning valve (located at the front of ther car near the master cylinder) at both inlet ports but no fluid will pump through the rear outlet port of the proportioning valve with the brake line removed.

I havnt had a chance to take the valve apart yet (the valve is in great cosmetic shape with no surface rust) but I was wondering if anyone has ever had a similar experience?

2restomod · 02-29-2008, 01:32 AM

Yhep. Same thing. I didn't realize that I had no rear brakes until I went to DMV to get my car emissions test and the guy told me to put on the brakes and the rear brakes would not come on to stop the rollers! You're right on the fix as well. I just swapped another valve I didn't try to fix the existing one. Didn't know you could rebuild it?

Gairloch · 02-29-2008, 03:50 AM

The brake proportioning valve doesn't have any moving parts. Have you tried bleeding the system? Could be you've just got a whole bunch of air in there. Did you also make sure that the rear calipers are able to move on their sliders?

ImKenNY · 02-29-2008, 09:02 PM

Quote:

Originally Posted by Gairloch

The brake proportioning valve doesn't have any moving parts. Have you tried bleeding the system? Could be you've just got a whole bunch of air in there. Did you also make sure that the rear calipers are able to move on their sliders?

No air or fluid would exit the rear brake port of the proportioning valve before I took it apart. It didt matter if i applied light brake pressure or stood on the pedal

I took apart the proportioning valve and found the top spring loaded valve was stuck (No problem was found with the lower spring loaded valve)

I was able to to work it free and I put it back together with a coating of new fluid.

After reassembly,fluid would flow through the rear port properly and a 4 caliper bleed brought the braking to perfection.

Gairloch · 03-01-2008, 01:47 AM

Good job! Any chance you took pictures?

2restomod · 03-01-2008, 11:02 AM

^^Cool. I saved my old one. I'll have to take a look at it and see if I can save it as well. Thanks for the info.

willy swafford · 03-23-2009, 07:59 PM

yeah ive got the same prob in my 85.just bled the rears today,but barelly any fluid came out.guess im gonna rework mine.maybe i can come up wit some solution

02-14-2008, 10:02 AM	#1 (permalink)
ImKenNY No Skills Join Date: Feb 2008 Posts: 4 Thanks: 0 Thanked 1 Time in 1 Post iTrader Rating: (0/0% )	Stuck brake proportioning valve? I determined my newly acquired 1985 MR2 has properly working front brakes but no rear hydraulic brake action. I suspected frozen rear calipers but after further investigation I found brake fluid enters the proportioning valve (located at the front of ther car near the master cylinder) at both inlet ports but no fluid will pump through the rear outlet port of the proportioning valve with the brake line removed. I havnt had a chance to take the valve apart yet (the valve is in great cosmetic shape with no surface rust) but I was wondering if anyone has ever had a similar experience?

03-23-2009, 07:59 PM	#7 (permalink)
willy swafford No Skills Join Date: Mar 2009 Location: chattanooga/tn Posts: 12 Thanks: 2 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	having the same prob yeah ive got the same prob in my 85.just bled the rears today,but barelly any fluid came out.guess im gonna rework mine.maybe i can come up wit some solution

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02-29-2008, 01:32 AM	#2 (permalink)
2restomod msnusers.com/mr2projects Join Date: Apr 2007 Location: Queen Creek, AZ Posts: 377 Thanks: 23 Thanked 14 Times in 14 Posts My Google Map iTrader Rating: (3/100% )	Yhep. Same thing. I didn't realize that I had no rear brakes until I went to DMV to get my car emissions test and the guy told me to put on the brakes and the rear brakes would not come on to stop the rollers! You're right on the fix as well. I just swapped another valve I didn't try to fix the existing one. Didn't know you could rebuild it?

02-29-2008, 03:50 AM	#3 (permalink)
Gairloch Dreaming of apexes Join Date: Aug 2005 Location: Minneapolis, MN Posts: 5,313 Thanks: 139 Thanked 296 Times in 264 Posts Blog Entries: 4 My Google Map iTrader Rating: (7/100% )	The brake proportioning valve doesn't have any moving parts. Have you tried bleeding the system? Could be you've just got a whole bunch of air in there. Did you also make sure that the rear calipers are able to move on their sliders?

03-01-2008, 01:47 AM	#5 (permalink)
Gairloch Dreaming of apexes Join Date: Aug 2005 Location: Minneapolis, MN Posts: 5,313 Thanks: 139 Thanked 296 Times in 264 Posts Blog Entries: 4 My Google Map iTrader Rating: (7/100% )	Good job! Any chance you took pictures?

03-01-2008, 11:02 AM	#6 (permalink)
2restomod msnusers.com/mr2projects Join Date: Apr 2007 Location: Queen Creek, AZ Posts: 377 Thanks: 23 Thanked 14 Times in 14 Posts My Google Map iTrader Rating: (3/100% )	^^Cool. I saved my old one. I'll have to take a look at it and see if I can save it as well. Thanks for the info.