2004 5.3L Tahoe Proportioning Valve/ ABS/ Coolant leak

[KarenZ71]

Hello, I appalogize ahead if I'm in the wrong thread. I wanted to see if anyone could help figure out what these lines are and how I should go about replacing them. I'm not a mechanic by any means just try to do what I can to keep er' running.

Both lines from underneath the proportioning valve are soaked. I do not know what lines these are. Are they cooler lines? (I have a coolant leak and it looks like coolant on these lines.)

From above the brake booster looks wet as well but more from underneath. I saw a video once where the sensor on the proportioning valve was leaking and wasn't from the valve at all.

So just wondering if anyone would have any suggestions. Thanks all for your time.

Thank you

 

[rockola1971]

Those are your brake lines that feed brake fluid to the front and rear brakes. The whole purpose of the proportioning valve is to apply a certain percentage of braking pressure to the rear brakes and the rest to the front brakes. Remember when you were a kid and told to not ever grab just the front or step on just the rear brakes because your front wheel will lock up and send you over the handlebars or just the rears which will send the rear end out from behind you and try to roll ahead of you while doing it??? On a bicycle, dirtbike, atc, motorcyle....etc. Same rules apply to a automobile, especially a top heavy SUV.

 

[KarenZ71]

Those are your brake lines that feed brake fluid to the front and rear brakes. The whole purpose of the proportioning valve is to apply a certain percentage of braking pressure to the rear brakes and the rest to the front brakes. Remember when you were a kid and told to not ever grab just the front or step on just the rear brakes because your front wheel will lock up and send you over the handlebars or just the rears which will send the rear end out from behind you and try to roll ahead of you while doing it??? On a bicycle, dirtbike, atc, motorcyle....etc. Same rules apply to a automobile, especially a top heavy SUV.

@rockola1971 Hey Thanks for your reply, i do understand now lol. I've tried looking for YouTube videos on replacing these but haven't had much luck. I'll keep searching though. The fluid on the lines looks like it has a dexcool color tint to it. Do you think there could be a coolant leak spraying upward in that area or is that probably for sure brake fluid you think?

It got late and dark fast so wasn't able to get out and work on it but I will start early am.

 

[OR VietVet]

What @rockola1971 said is a great way to describe the effect from the proportioning valve. The front and rear brakes do not grab 50/50%. Anyway, I would bet the leak is from above. Make sure to get the correct size flare wrenches and make sure all threaded fittings at the proportioning valve are tight and also at the master cylinder. I am assuming you have a vacuum brake booster. If is leaking there, it is likely the back seal of the master cylinder and leaking out of that area where the master cylinder bolts to front of the vacuum booster. You can unbolt the master cylinder from the booster and move it off the mounting studs and look for the wetness at back of master cylinder and the front of booster. If bad enough, it can cause a problem with the internal diaphragm of the booster and cause a leak and then a hard brake pedal but that is extreme. This is a sample pic of where to look. That rust color in the pic is caused by lack of maintenance when brake fluid was not flushed, water builds in the fluid and causes rust and the rust eats away at seals.





I recently did a master cylinder and booster on an 85 F150 that showed the rust at the back but really showed the start of it all from inside the master cylinder.

 

[KarenZ71]

What @rockola1971 said is a great way to describe the effect from the proportioning valve. The front and rear brakes do not grab 50/50%. Anyway, I would bet the leak is from above. Make sure to get the correct size flare wrenches and make sure all threaded fittings at the proportioning valve are tight and also at the master cylinder. I am assuming you have a vacuum brake booster. If is leaking there, it is likely the back seal of the master cylinder and leaking out of that area where the master cylinder bolts to front of the vacuum booster. You can unbolt the master cylinder from the booster and move it off the mounting studs and look for the wetness at back of master cylinder and the front of booster. If bad enough, it can cause a problem with the internal diaphragm of the booster and cause a leak and then a hard brake pedal but that is extreme. This is a sample pic of where to look. That rust color in the pic is caused by lack of maintenance when brake fluid was not flushed, water builds in the fluid and causes rust and the rust eats away at seals.



View attachment 410033

I recently did a master cylinder and booster on an 85 F150 that showed the rust at the back but really showed the start of it all from inside the master cylinder.

View attachment 410034

@OR VietVet Yes, you are correct. I've never done a brake job on this Tahoe. I replaced the brake booster (used part) about 6 years ago but have been to afraid that the lines will break on me if I attempt a full brake flush.

Ok, so separate the 2 and see if it's leaking from there and make sure things are tight?

 

[OR VietVet]

@OR VietVet Yes, you are correct. I've never done a brake job on this Tahoe. I replaced the brake booster (used part) about 6 years ago but have been to afraid that the lines will break on me if I attempt a full brake flush.

Ok, so separate the 2 and see if it's leaking from there?

It is @rockola1971 that was correct, I was just agreeing with him and went from there. You leave the top on the master cylinder. Unbolt where the master cylinder attaches at the front of the booster. None of this will cause a leak. With all nuts off the mounting studs, just pull straight forward and when the back mounting plate of the master cylinder clears the studs, just keep pulling straight forward. Do not lay it over to the left or right or tip it down in the front, just pull straight forward. The lines stay attached at the master cylinder and will support it. Crawl in there and get a light and look at the back of the master cylinder and see if is wet. If is wet, it is leaking. A sure sign of this will be noticeable as wet right at the back area when bolted to the booster. That area and under that area, on the front of the booster, should not be wet. Lots of times, if is wet enough, the brake fluid will cause the paint on front of the booster, below the mounting point of the master cylinder, to peel and blister. Brake fluid eats paint. That would be a sure sign of the leakage I talk about and would not require you to unbolt the master cylinder and look.

 

[nonickatall]

You need to change your break fluid regulary, if you do not, your main break cylinder and your calliper will die very soon. Also, your abs block is in danger. You should change the fluid all 2 years. Its no big deal. You can do it with the "old times" method: (two guys and a hose) or with cheap DIY equipment sold in the internet..

As well do the other maintenance. Change transmission fluid, differential fluid, transfer case fluid, steering fluid. Check for oil pump o ring, pcv valve. Grease the axle components. Check for corrosion.

Give the lady attention. She will thank you with a long live.

German Rally driver Walter Röhrl once said:
You can't treat a car like humans, ar car needs love....

 

[rockola1971]

I personally would never change brake fluid every 2 years. Its not needed. But it definitely wouldnt hurt, heck if you want you can change the fluid out every 2 weeks. The owners manual specifies recommended maintenance interval on just about everything. Copies are always available online to look through or buy.

 

[OR VietVet]

IMO, it depends on the mileage in that two years, kind of driving, towing, humidity in the air and what the fluid looks like. On average, 2 years is a bit quick, IMO. Anywhere between 3-5 years is typically ok, but I do most of my decisions on the flush on the condition of the fluid. As you can see with the pic of the inside of that master cylinder, that I changed. The owner waited waaaaaaaaaaayyyyyyyy too long. The entire system has rust in it. He said he will get back to me about doing lines, hoses, wheel cylinders and calipers. I told him, no guarantee on the safety of the brake system and I said it in front of witnesses.

 

[nonickatall]

I personally would never change brake fluid every 2 years. Its not needed. But it definitely wouldnt hurt, heck if you want you can change the fluid out every 2 weeks. The owners manual specifies recommended maintenance interval on just about everything. Copies are always available online to look through or buy.

That is true me nether, but i wanted to keep it simple. I have a detector which can measure the amount of water in the brake fluid and i change it on demand.
But when i buy a used car my first action ist to change all fluids and do maintenance and check for corrosion. Especially transmission fluid and stuff like steering fluid is very often in lack of maintenance.... Not to speak of corrosion protection which very few people do.

And i am sure. If you take a car like our trucks which are reliable and you make a regular maintenance and repair immediately when there is a problem on the horizon, than you can drive this car a lot of miles. But if you don't change oil, brake fluid and don't do necessary maintenance, than you ride a gmt 800 in short term to the junk yard as well.