'71 Power Brake Booster Check Valve (and thermal sensor)

[French demon]

Please, help me finding a brake booster power check valve for my Demon

My current booster check valve has been rubber coated by a previous owner, probably to plug an air leak. It works, but it's ugly.

I would like to replace it, but not sure about the one to order.

I found this valve in the Rockauto catalog, but it has three hose nozzles and mine has only two.
1971 DODGE DART 3.2L 198cid L6 Power Brake Booster Check Valve | RockAuto

What the frontal nozzle utility? And if I plug it, will the valve work?

Aesthetically, I would prefer to find a twin nozzles (or maybe my old rubbercoated valve had originally three nozzles? I don't know)

Need your help, thank you

Francois

 

[toolmanmike]

Please, help me finding a brake booster power check valve for my Demon

My current booster check valve has been rubber coated by a previous owner, probably to plug an air leak. It works, but it's ugly.
View attachment 1715906914
I would like to replace it, but not sure about the one to order.

I found this valve in the Rockauto catalog, but it has three hose nozzles and mine has only two.
1971 DODGE DART 3.2L 198cid L6 Power Brake Booster Check Valve | RockAuto
View attachment 1715906916
What the frontal nozzle utility? And if I plug it, will the valve work?

Aesthetically, I would prefer to find a twin nozzles (or maybe my old rubbercoated valve had originally three nozzles? I don't know)

Need your help, thank you

Francois

A plug should be fine. You can start a parts wanted thread here for a used one.

 

[French demon]

Ok Mike, but what does the original OEM valve look like? Two or three nozzles?

 

[toolmanmike]

Ok Mike, but what does the original OEM valve look like? Two or three nozzles?

What does the small vacuum line feed? It looks like you only need a source line (the large one) and a supply line to ??? Depending how original you want to be, the small line could be hooked to the carburetor. Just guessing but it may go to the heater/AC controls.

 

[French demon]

Hum, hum, I don't remember...

Found out this picture :

I think that the large hose go to the valve cover and the small one to the carb, but not sure.
I will check tomorrow. Night is coming here

Francois

 

[Hellrats]

The large hose goes to the back of the carb or the intake manifold. It is your vacuum source. The small hose goes to the heater control in the air cleaner NOT the valve cover.

 

[French demon]

So, I have had a look this morning

The big hose goes to the intake manifold
The small one goes to the carb base.

I don't know why two vacuum lines are required (or maybe because I have a Midland dual-diaphragm booster?).

Unfortunately, I don't have the 1971 service manual, but in 1970, there is only one hose on the brake booster check valve :

Hiltopautoparts seems to sell the correct dual-port check valve, but it's NOS.... and the price

NOS Mopar Power Brake Check Valve 1970-1 Plymouth Dodge Chrysler W/ Midland Ross - Hiltop Auto Parts


Francois

 

[CFD244]

My '71 has 2 nipples. The big one goes to the intake manifold vacuum source, and the small one has a rubber plug over it. I have a V8 and no A/C.

Edit: I would hazzard a guess to say that your PCV valve should be plumbed into the carb base not the booster. With that gob of silicone, you can't be sure what the OP did. I'll look at my '71 manual today and get back to you.

 

[French demon]

Hi Troy
My PCV valve is also plumbed into the carb base. On the right side (yellow arrow).
The other breather, in rear, is plumbed onto the air filter.

Yes, if you can post the '71 diagram of the power brake assembly, it would be fine.

After some researches, I found that '68/70 Mustangs and Cougars has the same Midland brake booster. So, I took the risk to order a dual-port check valve for this booster.
It's a very low depense (less than $20.00 including the grommet and shipping)

Francois

 

[CFD244]

S

Hi Troy
My PCV valve is also plumbed into the carb base. On the right side (yellow arrow).
The other breather, in rear, is plumbed onto the air filter.
View attachment 1715907342
Yes, if you can post the '71 diagram of the power brake assembly, it would be fine.

After some researches, I found that '68/70 Mustangs and Cougars has the same Midland brake booster. So, I took the risk to order a dual-port check valve for this booster.
It's a very low depense (less than $20.00 including the grommet and shipping)

Francois

So where does that little hose from your booster go? The big one should go to the intake manifold.

 

[French demon]

The little hose goes from the check valve to the carb base (left side), the big one to the intake manifold.

I will take some pictures with the air filter housing removed.

 

[French demon]

My brave little 1bbl Carter Ball & ball

 

[townsend]

Take a look at Raybestos cv89021 on eBay.

 

[CFD244]

My brave little 1bbl Carter Ball & ball

View attachment 1715907470

View attachment 1715907471

View attachment 1715907472

View attachment 1715907473

So the line that is connected from the booster to the carb base shouldn't be there. I think that fitting on the carb base gets attached to the heated air sensor (yours looked blocked off) underneath the breather. When it's cold, the sensor opens and allows vacuum to the trap door inside the breather snorkel directing warm air from the stove (tin shroud on exhaust manifold).

Basically, booster just gets connected to manifold vacuum, and the other port gets plugged. My pic from the '71 manual shows the same config as yours from the '70 manual. Here are the pics associated with your question. Here's my booster for my '71. The green tape fitting gets attached to manifold vacuum. PM me if you need clarification

 

[lemondana]

Wake up everybody! The large hose goes to manifold vacuum, usually a fitting behind the carburetor, The small hose goes to the Cruise Control Servo, or Speed Control Servo. That was only available on the 1975 A Bodies, so unless you've added factory CC, you don't need the small fitting. I can't believe nobody got that before now. But I guess if you've never been around C Bodies, you might not have seen where it is supposed to go.

 

[French demon]

So the line that is connected from the booster to the carb base shouldn't be there. I think that fitting on the carb base gets attached to the heated air sensor (yours looked blocked off) underneath the breather. When it's cold, the sensor opens and allows vacuum to the trap door inside the breather snorkel directing warm air from the stove (tin shroud on exhaust manifold).

Basically, booster just gets connected to manifold vacuum, and the other port gets plugged. My pic from the '71 manual shows the same config as yours from the '70 manual. Here are the pics associated with your question. Here's my booster for my '71. The green tape fitting gets attached to manifold vacuum. PM me if you need clarification

Hi Troy

I think you're right.
I'm going to plug this sensor onto the carburetor base... and to plug closed the check valve little nipple. No need for a dual vacuum line on the brake booster
I still have the tin shroud between the air schnorkel and the exhaust manifold, but not sure that the sensor works

 

[French demon]

Wake up everybody! The large hose goes to manifold vacuum, usually a fitting behind the carburetor, The small hose goes to the Cruise Control Servo, or Speed Control Servo. That was only available on the 1975 A Bodies, so unless you've added factory CC, you don't need the small fitting. I can't believe nobody got that before now. But I guess if you've never been around C Bodies, you might not have seen where it is supposed to go.

Thank you for this clear explanation

Francois

 

[French demon]

Troy, thanks to you, my air filter sensor vacuum line is now correctly re-routed.
I also plugged the little nipple on the check valve.

 

[CFD244]

Troy, thanks to you, my air filter sensor vacuum line is now correctly re-routed.
I also plugged the little nipple on the check valve.

View attachment 1715907963

View attachment 1715907962

Now, make sure that the valve is closed when it is warm or else you'll draw heated air all the time from the exhaust heat stove. Basically, when it's cold, the valve ALLOWS vacuum to get to the trap door, and when it is warm it DOESN'T ALLOW vacuum to get to the trap door. The have been known to fail.

 

[French demon]

Yes, I will check... It seems possible to replace a defective thermal sensor and it's easily available (Mopar #3514168).
I have also to check if the shnorkel door isn't stuck or rusty.

 

[French demon]

Ok, I disassembled my air filter housing. Visiblely, the parts are original but no rust of the flap door, nor on the shnorkel diaphragm.
I did re-assemble and aspire with my mouth and the flap raised up. Just a little bit because my mouth isn't as mighty as my carburetor.
Then, I tested with the engine running and the flap raised up too. Slightly more, but seemingly suffiencently to aspire the air coming from the exhaust manifold.
Also, maybe that the flap closure wasn't complete as the ambient air wasn't cold (15°C, 60°[email protected])

With an hot engine, the thermal sensor close the vacuum line and the flap goes down under the diaphragm spring pressure.

A perfect 51 years old operating system, Chrysler Corp. is the best.


Francois

 

[French demon]

About the brake booster check valve, as Mopar parts seem to be gold plated, I tried something else.

Some Fomoco cars (Mustang, Cougar) were equipped with the same Midland-Ross brake booster than Mopars.
So, I ordered a two nipples check valve from "West Coast Classic Cougar" (I was customer at them when I had my '69 Mustang)
They sell this valve for $12.87 including the grommet.
Check Valve - Power Brake Booster - Midland - Repro ~ 1967 - 1968 Mercury Cougar / 1967 - 1968 Ford Mustang

Perfect fitting
Now, just have to replace the clamp with a correct one.

François

 

[67Dart273]

OP if you have not done so,-- wander over to MyMopar. There are many years of both service manuals and parts manuals which you can download -- for free. Some of them are there because of guys from here. The parts manuals are a PITA to navigate. You may have to settle for Dodge vs Plymouth or vice versa

 

[French demon]

Thanks for the tip. I already have downloaded the '70 and '71 service manuals.

Here's my brake booster with the new clamp
I think this spring clamp is correct for 1971, is it?

François

 

[AJ/FormS]

AFAIK, no vacuum line on any A-body from 1967 to 1980 ever had a clamp on it, NOR were they covered in a mesh thingy. Vacuum lines for the booster and the PCV are thickwall offerings to withstand the vacuum. Fuel lines will collapse especially as the heat comes up. Vacuum lines are all slip-ons. They stay on, even if the engine suffers a back-fire, usually.