I have a '00 Dodge Ram 1500 with the 5.9L engine. Recently, I’ve noticed a brake fluid leak, and I’m having trouble locating a replacement part. This may be partly due to my not knowing what the part is called. In my mind, I would call it a “sending unit manifold” or “sending unit assembly.” The part is a machined block of aluminum with 4 brake lines - 2 in, 2 out - attached to it (no, it’s not the ABS module, but it’s next to it). As best as I can determine, this block serves no purpose aside from housing the brake light sensor. The problem is that there is a rubber plug at both the top and the bottom, and the bottom plug appears to be leaking. I figure I need to replace either the “sending unit manifold” or the rubber plug in the bottom, or both, but I can find neither through parts suppliers. Can anyone help me with this?
Untill Rick or Gary t shows up, let a parts counter person give it a try. It might be the proportioning valve. Go to a dealer, bring the VIN to help narrow the search. Some dealers have parts systems with many photos or drawings to help figure what you need. Good luck and let us know what it was.
Since I don’t know what YOU know about cars, (ie you may have ruled certain things out first), but WHERE is the part you are looking at. My first guess when you said machined block of aluminum was the brake master resivoir. But two in two out wouldn’t be right. It would have 4 out. (two to the front brakes and two to the rear). And it would be right about on the other side of the firewall from the steering wheel. So is this part under the truck, burried in the engine, towards the back, towards the front? Is it always leaking? Only leaking when the truck is running, only when you apply the breake?
Have you tried going to an AutoZone and asking them, they tend to be pretty knowledgable there.
It sounds like the Combination Valve, which houses the Pressure Differential Switch. Apparently it’s also called a Pressure Metering Valve and a Brake Proportioning/Combination Valve, not to be confused with the Height Sensing Proportioning Valve in the rear axle area.
I don’t know why my info shows those different names for it (presumably supplied by Dodge). It’s what I would normally call a proportioning valve, as Booker57 suggested.
I can buy 2 in and 2 out. It is probably a brake failure warning valve. (exact terminology may vary) 2 lines in from the master cylinder, and two out to the ABS hydraulic unit.
IANADPE (I am not a Dodge parts expert) with most cars this waring valve is probably not available aftermarket. You will probably have to get it from the dealer.
Head over to the dealer’s parts department with the info you posted here AND THE VIN (you may not need it, but be a Boy Scout and be prepared)
Describe to them where it is, and that you have been told it may be a warning valve. if the parts counter guy calls it anything other than a warning valve write this info down That is the unit’s proper name.
Anyway either buy the unit or go shopping for a better deal (using the proper name).
Once you have it in hand the fun begins.
You will need a flare nut wrench to undo the brake lines. But wait, you say, they just look like 7/16" (or 3/8") nuts with a brake line in the middle. No they are not just like regular nuts. if they are tight (and Murphy says they will be way fucking tight) and you use a regular wrench you will turn that 7/16" 6 sided fitting into a really nice circle that nothing will remove. Buy flare nut wrenches, they are way cheaper than having your car towed to a dealer to have the brake lines replaced. Ask me how I know this.
Undo all four brake lines. Remove the unit. Start by hand all four brake lines. Do this before you secure the unit to the car. If you cannot screw the brake lines in by hand, you may have them crossed threaded. A cross thread is not a leak proof thread. Get them in straight. Don’t fuck this part up. If you do fuck this part up see my comments above about the cost of towing the car.
When you are 100% sure the lines are not cross threaded, tighten the unit to the car and tighten the lines.
Now comes the really fun part.
Fill the master cylinder with fresh brake fluid (I use nothing but Castrol GTLMA) Get an assistant to sit in the car. You will need a socket or a wrench that fits the bleeder screws on the wheels. [guessing] 3/8"[/guessing]
Position yourself under the right rear wheel. Yell for your assistant to pump up the brakes. At the pump it up command your able assistant should pump the brake pedal 3-4 times quickly and on the final pump hold the brake pedal down. At the yelled acknowledgement that then goddamn pedal is down, you open the bleed screw and close it again quickly. You will at first get a splurt* of air. Then after a couple of splurts you should start to see fluid. When you get all clean, clear with no bubbles fluid move to the other rear wheel. When both of those are done go do the front wheels.**
When you are all done, the pedal should feel rock hard, and should not travel to the floor when it is applied. If it feels spongy you still have air in the system. See the above instructions. Lather, rinse, repeat until the pedal is hard.
*technical term used in auto repair, should not be used by amateurs
** after 7 or 8 splurts assistant sould leap out of truck and check and top up fluid in the master cylinder as necessary.
As usual while I am writing the great American novel on auto repair Gary Tslides in with a post that is short and too the point. :smack:
Pressure differential switch is just another way of saying warning valve. 
(Subject for GQ: Why do I spend 3 paragraphs to explain what Gary T does in 3 sentences? 
)
Thanks for the info, guys. From my online searches, it looks like this part may only be available from a dealer, in which case, I’ll have them go ahead and replace it and do the brake bleed, too.
Rick, yep, I know all about flare nut wrenches and bleeding brakes…did a couple of brake jobs on my old Ford pickup back in high school and college, and also had to do it when I replaced the rear axle and differential gearsets - twice. I can do this work - but I’d prefer not to.