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So I fixed a small leak in a brake line but realized they all need replacing!

Tiny
DJ123
  • MEMBER
  • 2000 DODGE CARAVAN
  • 240,000 MILES
So I fixed a small leak in a brake line but realized they all need replacing! I was considering buying bulk as I have a flare tool. The van has an HCU and I noticed the line nuts are larger there. But line is 3/16. Now are the lines double flare and can I do single flare using bulk line? Any other tips on bleeding too.
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Sunday, March 22nd, 2020 AT 8:51 AM

9 Replies

Tiny
KASEKENNY
  • MECHANIC
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I attached the info about these lines. If I am reading this correctly then you are saying the lines coming from the HCU are 3/16th? If this the case, I think that is not accurate. They are actually larger. Not by much but they are.

I highlighted a couple important parts that you need to notice when doing this job. Specifically, you can't use solid brake tubing on the entire length from HCU back due to vibration and shifting. Please read the attachment and then consider buying the pre made lines at least back from the HCU.

Let me know if you have questions about this, but I would not make the changes that you are talking about. Thanks
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Sunday, March 22nd, 2020 AT 9:10 AM
Tiny
DJ123
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Okay, so i'm the shade tree type mechanic making things work that don't always meet specs like you suggested! I don't see how and vibration is incurred by the master to HCU lines. It's all on the same uni-body structure? Any slight flex should be easily handled by the length of the lines? I have seen loops in lines before maybe that is to absorb movements?6mm vs 3/16? 6mm is like 1/4in I know lines are not that big? All hard lines look same size! I should add ABS not working.
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Sunday, March 22nd, 2020 AT 9:17 AM
Tiny
KASEKENNY
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I understand but there are some things that I will not try to re-engineer or shade tree repair and the braking system is at the top of the list. Not only are you risking your vehicle but those around you on the road as well.

I get that you may be able to change something and make it work but in the event there is a fatal accident and they find the brake lines are no longer original, they inspect them to ensure they are correct. And they do inspect them. It is on their check sheet when inspecting vehicles. When they find you did this repair, no insurance will cover what happened. Clearly this is extreme and probably will not happen but is it worth the risk?

You are decreasing the size of the brake supply line from the HCU to the rest of the system which is going to decrease the braking "power."

As for the flexible lines, I understand you may think the vibration is absorbed due to the length of the line but it isn't. They put rubber section in line for longevity. It may be fine for a while but how long will your hard lines last? The OEM has spent millions of dollars in R&R to know their design will last.

Again, you are looking at this from a shade tree mechanic standpoint and that is to just make something work to get it back on the road. I get it. Many things are over engineered but the braking system is not something I can recommend you take this approach on.
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Sunday, March 22nd, 2020 AT 10:02 AM
Tiny
DJ123
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Ya, I think it's over engineered like headlights! Product of college tuition rates! I'm going to mic line size. I was also thinking of replacing the HCU with non ABS block. And yes I do see your perspective as an official adviser. Interesting thing is auto parts stores don't make such an advisory or sell special lines. They just list regular line material for the year. Also on the rear proportioning block they use 2 different threads. Fine and course. The fine is very difficult to work with! Are they calling trained mechanics inept? Can't read instructions! Have to special thread it to prevent mistakes! And actually all lines have the flex section even the back! Yet that is not mentioned! Also they talk HCU cradle movement/vibration? Is it because of violent pulses of the HCU! Like I said it's not working anyway! I suppose they rubber mounted the hcu to cradle to cut down on noise in the car?
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Sunday, March 22nd, 2020 AT 5:06 PM
Tiny
DJ123
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For starters i'm just replacing master to HCU. I don't see that it will require any wheel bleeding. I'm going to loop the line by master to allow movement.
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Sunday, March 22nd, 2020 AT 7:06 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Always use the correct brake line diameter and also a double flare is mandatory for brake line repairs also the loops are used to help with vibration. Can you please shoot a quick video with your phone so we can see what's going on? That would be great. You can upload it here with your response.
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Monday, March 23rd, 2020 AT 11:30 AM
Tiny
DJ123
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For starters i'm just replacing master to HCU. I don't see that it will require any wheel bleeding.
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Monday, March 23rd, 2020 AT 11:52 AM
Tiny
DJ123
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Actually I have not started on this project probably until next week! And vehicle is located in another city.
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Monday, March 23rd, 2020 AT 11:53 AM
Tiny
KASEKENNY
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Okay. Thanks for the update. If you replace any portion of the lines then you will need to bleed it because just opening the system allows air in. Let us know when you are working on it if you need more info. Thanks
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Monday, March 23rd, 2020 AT 2:13 PM

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