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I went and did a track day in my '15 Scat Pack this week, and while the car performed really well I did lose the break pedal by the end of each 20 minute session (the pedal was on the floor by the end of the first session and almost there after I used less brake in the next two sessions). I'm not a track day noob, but this was my first time out with this car. My last ride- a 2017 Taurus SHO- had DOT-4 brake fluid from the factory as part of a performance package and I never had this problem despite it being a similar size and weight. Anyways, I want to upgrade to DOT-4 fluid in the Scat Pack and after doing some research on the forums here's what I understand to be the case:

1. A traditional bleeding of the "base" braking system will result in a mostly complete fluid change except for....

2. There is some fluid stored in the ABS system reservoir that requires a pricey scan tool to cycle during the bleeding process in order to get both systems filled with the new fluid.

So, my question is:

If I were to simply fill the "base" braking system with DOT-4 by performing a typical brake bleeding, is the amount of old DOT-3 fluid that remains in the reservoir enough to dilute the DOT-4 fluid that I will be putting in once the ABS is activated and the fluid cycles through the rest of the system?

If it isn't too big of a deal to leave it in there I'm not opposed to just bleeding the brakes again in the near future after the ABS has been engaged a few times and the fluids have mixed... any advice or experience with this would be appreciated.

Thanks! (Here's my car...and my kids.)
997812
 

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Not really necessary unless the system ingests air. BTW if you get alfaobd ($50 android or PC software) and a compatible BT OBD interface like OBDlink MX or MX+ you can use the active diagnostics section to cycle the ABS solenoids to completely bleed the system.

997831


Oh and welcome to the forum.
 

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When I did my wilwood conversion, I didnt bleed the abs. Now granted, changing out the entire calliper might have introduced air even with as careful as I can be, I was dilligent on not letting the fluid go down all the way....

Well in the end when I took off, my pedal definitely did not feel normal.

Came back and discovered the abs bleed. Only had me do the passenger side for the cycle, and behold my brake pedal was back.

If you are just going from dot 3 to dot 4, I hear it's fine if they mix. But if you are a real stickler and want all the fluid flushed, gonna have to get over to a mechanic shop with a scan tool, go the alpha obd route (which can come in handy more then once) or borrow a buddy's scan tool.


Something tells me there may be a manual way to activate the abs pump....although I have no idea what that is lol
 

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The DOT 3 fluid is not the problem. The problem was you went to the track and didn't bleed the brakes beforehand.

Porsche recommends the brakes be bleed every 2 years and I can tell you my experience -- with the clutch hydraulic system that shared fluid with the brake system -- 2.5 year old brake fluid was no damn good. Now while the brake hydraulic system and followed by the clutch hydraulic system flush/bleed made a big difference in clutch action I could not detect any change in the brakes. But this on the street. I'm sure had I ignored the advice of my auto tech buddies from years ago -- when I auto crossed -- and taken the Porsche to the track with that 2.5 year old brake fluid the brakes would have manifested similar behavior to what you experienced.

Always when tracking the car show up with fresh engine oil and brakes recently flushed and bled.

Remember too that even fresh fluid has a limit. When you start to detect brake issues just call an end to the session and give the brakes (and the rest of the car) time to cool down.

If you run heat resistant fluid you can run longer but the rest of the brake hardware gets hotter and hotter and you can still damage the brakes.

BTW, if you go with Dot 4 fluid you are not supposed to use Dot 3. So if you take the car in for service and as is often the case vital fluids are checked/topped up a tech might add Dot 3 to the Dot 4 fluid.
 

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The Pork Wagon (‘14 Cop Charger)
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Something tells me there may be a manual way to activate the abs pump....although I have no idea what that is lol
Simulating a scenario in which the ABS system would normally engage activates the pump - get the vehicle’s speed up to highway speed, slam on the brakes and bring the vehicle’s speed down to zero or almost zero.
 

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Simulating a scenario in which the ABS system would normally engage activates the pump - get the vehicle’s speed up to highway speed, slam on the brakes and bring the vehicle’s speed down to zero or almost zero.
While that would work, that's a pretty brutal technique to cycle brake fluid through the ABS system. On dry pavement I have had to apply the Hellcat brakes in a semi emergency fashion and the car even from speed can slow down quite rapidly and I have not felt the ABS activate. (The best activation of an ABS system I ever experienced was when I pulled out of a car wash bay and pointed the car (not the Hellcat another car) down a short drive which intersected the road. I forgot about it being dead of winter and cold and the drive was a sheet of ice from the water vehicles had dripped on the pavement. A pick up truck was coming and I applied the brakes. When the ABS kicked in then it all came to me that I was in a world of trouble. I could do nothing but press the brake pedal as hard as I could. The ABS was vibrating like a machine gun. But it did its job. Best ABS system ever! The car stopped short of the road and a certain collision was avoided.)

Anyhow if one is successful at gettng the ABS to operate any this just expels the old fluid out of the ABS system back into the regular brake system and replaces the old fluid with fresh fluid.

Better would be while bleeding/flushing the fluid to have some way of activating the ABS system work the pump and replace the old fluid with new fluid.

The techs that worked on my other cars had a factory test computer which had an ABS activation feature. I'm sure the Dodge techs have this. The question is what can the DIYer get a hold of that would allow him to do this?
 

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Discussion Starter #7
If you are just going from dot 3 to dot 4, I hear it's fine if they mix. But if you are a real stickler and want all the fluid flushed, gonna have to get over to a mechanic shop with a scan tool, go the alpha obd route (which can come in handy more then once) or borrow a buddy's scan tool
Since I try to go to the track a few times a year I was hoping that it would be a simple enough DIY procedure. Unfortunately I do not have anyone to borrow a scan tool from.

While I’m not necessarily a stickler, I just want to make sure I don’t mess anything up or negate the “upgrade” by diluting the potency of the DOT-4 by leaving the old DOT-3 in the ABS reservoir.

Does anyone know how much fluid is in there?
 

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Since I try to go to the track a few times a year I was hoping that it would be a simple enough DIY procedure. Unfortunately I do not have anyone to borrow a scan tool from.

While I’m not necessarily a stickler, I just want to make sure I don’t mess anything up or negate the “upgrade” by diluting the potency of the DOT-4 by leaving the old DOT-3 in the ABS reservoir.

Does anyone know how much fluid is in there?
How much does the scan tool cost, or a "tool" that you could use to activate the ABS system during a fluid flush/bleed?

If you track the car a few times a year this scan tool I think needs to be part of your tool box. Or just arrange to get the brakes flushed/bled at the dealer some week or so before the track event. However, I dare say in this case the tool would pay for itself PDQ.

Almost certainly you will cause the ABS system to activate when on the track. If you leave any old fluid in the ABS system this old "water laden" fluid then will be in the hydraulic lines and the water it contains will boil if the fluid gets hot enough and it will. This can be enough to affect braking action.

The other problem is you have Dot 4 in the system, which has a higher boiling point that Dot 3 fluid. But the Dot 3 fluid in the ABS system when it gets with the Dot 4 then will boil at a lower temperature.

BTW, my info is the boiling point of DOT 3 and DOT 4 both "dry" and "wet" (wet being with some water in the fluid) is: DOT3 (401F dry/284F wet) or DOT4 (446F dry/311F wet).
 

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The scan tools that can cycle the ABS system run $185 and go up from there if they have more features for other functions

I'd bleed the entire system - I'd make the analogy of changing the oil but leaving the old filter (and its contents). You'd have new fluid and still have some old fluid mixing in.

side note: in the old days, (60s) I have service manuals that note that oil filters were changed every other oil change...its not like oil filters were that expensive
 

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The scan tools that can cycle the ABS system run $185 and go up from there if they have more features for other functions

I'd bleed the entire system - I'd make the analogy of changing the oil but leaving the old filter (and its contents). You'd have new fluid and still have some old fluid mixing in.

side note: in the old days, (60s) I have service manuals that note that oil filters were changed every other oil change...its not like oil filters were that expensive
I’m willing to pick one up. Is there one you recommend or have experience with?
 

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The scan tools that can cycle the ABS system run $185 and go up from there if they have more features for other functions

I'd bleed the entire system - I'd make the analogy of changing the oil but leaving the old filter (and its contents). You'd have new fluid and still have some old fluid mixing in.

side note: in the old days, (60s) I have service manuals that note that oil filters were changed every other oil change...its not like oil filters were that expensive
In the OP's case I think even the bare bones $185 scan tool that can cycle the ABS system would pay for itself in no time. (What other features the higher priced scan tools offer means these need to be considered. A more expensive scan tool might be the smarter buy over the longer term.) The alternative is to not bleed the ABS along with rest of the system or have the brakes bled at the dealer or some shop. Several times a year would easily cover the cost of the scan tool.

I agree that bleeding the entire system when changing from Dot 3 to Dot 4 is advisable. And I would say it is advisable even doing brake system flush/bleed services to ensure fresh fluid in the brakes.

In the old days... I can recall back in 2002 when I bought my Boxster the factory called for 15K mile oil changes and 30K mile (!) filter changes. The filter was not as cheap as say my Hellcat's filter but over all represented a rather small fraction of the total parts cost of the oil change. 'course, I ignored the factory with regards to 15K mile oil changes and 30K mile filter changes and changed both at 5K miles. And when I took the car in at 15K miles to have the oil changed the service manager told me they ignored the factory and changed the filter every oil change.
 

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The tool I have seen mentioned here frequently is called a Millenium 90. Look it up on Amazon. I recently received the one below as a birthday gift. Haven’t done the bleed yet, but will be soon. Please post up again after you do this and run the car hard again to let all know if it was a success or not.

 

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Just to clarify

Just by activating the abs while driving isn't enough to bleed the pump, as the air is still in the system.

You must activate the pump while stationary, and once it pushes the air out, you have to crack the bleeder on the calliper, and in sequence. Air will always make its way back into the system if it's not properly bled

Challytatum mention alpha OBD tool which have interfaces starting around $50 and up. All you would need is a compraeble laptop and some know how
 
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