Mopar Brake Fluid Exchange vs ABS Bleed

[JJ_WA]

I took my 23 Willys to the dealer today for a WAVE oil change and tire rotation. I asked if they could do an ABS brake bleed, based on a couple of threads in the forum, discussing spongy brakes and how to improve the braking. They said they could.

When I picked it up the invoice indicates they did a brake fluid exchange service, but nothing about the ABS bleed. The brakes feel marginally better (or it's my imagination), but still require a couple of pumps to bring them to the top of the pedal.

For those in the know, what is the difference between a fluid exchange and an ABS brake bleed?

Thanks.

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[carlos c]

There is a procedure to be done with the computer after we change the oil or a caliper.
We have to follow the massager on the computer.

 

[NWJeepr]

The ABS bleed involves flushing the fluid from the lines and reservoir, then activating the ABS bleed procedure with the scan tool to exchange the fluid in the module with the newly filled fluid. Then, the system should be flushed out and refilled again because it contains the fluid cycled out of the ABS pump.

I did mine at roughly before the 2 year mark but wasn't able to activate the ABS pump (DIY home job). The fluid in the reservoir still looked clean, but the fluid at the wheels was very dirty when I first began flushing. IMO, still worth doing, but a complete flush would include the ABS pump. Had I kept the vehicle, I would have had it done professionally. Supposedly a home user can do the ABS pump procedure using JScan.

It would be worth asking the dealer about the specific procedure they use - actually discuss with a tech. Because it is important.

 

[dabolay]

I'm not an expert, but I did a bit of research and came up with the following.

The brake fluid exchange is also known as a brake fluid flush, which involves pushing out the old brake fluid and replacing it with new brake fluid. Question... was all the old brake fluid in fact pushed out or does some contaminated brake fluid still remain in the system separate from the ABS module or in the ABS module if it wasn't thoroughly flushed and contains air?

A fluid exchange typically does not require activation of the ABS system with special tools unless air is suspected within the ABS module.

Because the ABS module has valves and pistons controlling brake fluid flow for anti-lock operation, air can get trapped and cause a spongy brake pedal.

To properly bleed the ABS system, a scan tool or bi-directional OBD2 device is usually required to activate the ABS pump and valves to cycle the fluid through the unit.

Durinig an ABS bleed, the bleeder valves at the calipers are opened to let trapped air and fluid out while the the ABS module cycles fluid internally.

This process is more technical and sometimes must be done separately after a fluid exchange or brake bleeding if air is still suspected within the ABS module.

If the brakes still feel spongy and require a couple of pumps to bring the pedal to the top, it can suggest that there is air trapped in the braking system, potentially inside the ABS module. This is especially likely if the sponginess persists even after a standard brake fluid exchange or bleeding of the calipers and lines.

Other issues to consider and check could be an internally bypassing master cylinder, degraded or leaking brake hoses, or contaminated brake fluid. But if those parts have been checked or replaced and sponginess remains, the ABS module trapping air is a strong possibility.

Hope that helps.

 

[58Willys]

An ABS bleed, would be simply bleeding the ABS module. What you want is a “brake fluid flush”, which is removing all the fluid and replacing it with new, then bleeding entire system.

 

[JJ_WA]

Thanks to you both. I have a call in to my service tech to find out what/how they did the service.

 

[QwikKotaTx]

An ABS bleed, would be simply bleeding the ABS module. What you want is a “brake fluid flush”, which is removing all the fluid and replacing it with new, then bleeding entire system.

That sounds like draining the lines but you may just be wording it differently. You want to do whatever it takes to avoid getting air in the lines. The lines need to be continuously fed fresh fluid to avoid air. A power bleeder will help with that and they sell adapters to replace the master cylinder cap.

 

[toothirtyj]

Can anyone advise how much brake fluid it takes to flush the system? I checked my manual on Alldata and could not find a number. I'm planning on doing a system flush, including my clutch slave cylinder, (minus the ABS bleed because I don't have JScan) and was wondering how much fluid to plan on using.

 

[JJ_WA]

Thanks to all who contributed to this thread.

Update: I was sent the Stellantis Survey, which I filled out, along with my comments about the services I received. I was contacted by my original service advisor the very next day with an apologetic text. We arranged for me to take it back in today for an ABS burp/bleed - it had NOT been done before.

The mechanic who performed the service checked a number of the new Wranglers on the lot and indicated the feel of the brakes were comparable to mine. They did the service and I picked it up. There is a measurable improvement in the pedal play. It is now much better than when I first took it in and again after the fluid exchange.

The brake pedal feels firmer than before. I'm a much happier camper now.

 

[Aonarch]

I'm glad you got it sorted.

You have to use the dealer diagnostic tool (Or JSCAN/ OBD tool) to enable ABS Bleed mode. You then follow the instructions on the tool, it has you bleed a corner at a time, while it pulses the ABS pump. This is required to solve that mushy feel you were encountering, on top of a regular flush and bleed.

A flush doesn't take a lot of fluid and there is no preset amount. It is all around the fluid color and bubbles coming out of the line. You can do a flush on 3 year old fluid with as little as 500 ml of fresh fluid. I prefer to use at least 1000ml. Draining and filling the reservoir first is the best trick to minimizing time and maximizing effectiveness.

 

[iklo]

What is the prescribed brake fluid change interval? My Owner's Manual will not say...

 

[azjl#3]

No more than 3 years is recommended, 2 is better

 

[SAJN]

What is the prescribed brake fluid change interval? My Owner's Manual will not say...

Good question. At my last oil change, they recommended a brake fluid flush at 30K, and mentioned that my fluid was getting a bit brown. The cost was a little over $200. I also checked my owner's manual maintenance recommendations, and there was nothing there concerning a brake fluid service.

 

[Heimkehr]

What is the prescribed brake fluid change interval? My Owner's Manual will not say...

The brake fluid in our three vehicles is flushed (replaced) at the dealer every 3 or 4 years. Never longer than every 4 years. They've the equipment to do it right, with regard to anti-lock brake systems.

I'll perform the same service on my motorcycles myself, using similar service intervals...or whenever I install new brake pads, as I did last May on the Suzuki. I'll also install Speed Bleeders to make the work easier and faster. They're nifty little things.

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