Anyone have an issue with blue brake fluid?

[SteveTheTech]

I had an interesting problem today at work and I was wondering if this is something to keep an eye out for.

The car was a 2004 G35 with 97k. It was recently purchased with a small list of mods already installed. Kinetic intake, JW popcharger, SS brake lines and blue synthetic fluid.

The only complaint on the ticket was the SLIP, BRAKE, and VDC light illuminate sometimes. I thought it would have been the usual...front pads and rotors....but this one was a little different...the DTC was for a pressure sensor not low brake fluid. The only fix for this is replacement of ABS pump unit! This costs about $1800 plus a few hours to install. I was not convinced the sensor was bad, at least convinced enough to try to sell a pump to someone. So I dug a little deeper.

If you look in the book the there isn't really much of a diagnostic test that includes seeing what the sensor is actually doing. Using the line graph capability of ConsultII I was able to watch the sensor output. After stepping on the pedal about 5-10 times the pressure reading stops returning to zero.
The computer sees the brake light switch is working, so the pedal is not applied the pressure should be 0 bar but it is actually hovering between 1-2bar. That is not an insignificant amount is about 20psi (+-about 8psi) of apply pressure. When I first drove the car in I thought it might have a sticking rear caliper because when it was in Drive there was no creep with my foot off the brake. A further inspection showed some drag from the brakes.

Although I was reluctant to proceed as the amount of damage might might be pretty big, and if we open this can of worms it might have compromised the braking safety of this vehicle. Although the brakes have been dragging for some time. The client already approved the 1 hr of my time so adding a brake flush was only a matter of buying the fluid. It actually took 2 quarts of fluid to entirely purge the system. Or at least to the best I could get it, realistically. After the first quart I inspected the reservoir and found the tell tale oil and water mixture....I was not pleased to see this.

I knew at that point what I was removing was a synthetic DOT 5 brake fluid. This cars' brake system was designed for a DOT 3. We replace with DOT 4 typically but DOT 5 is not at all the same.

When the second quart was completely flushed through the system the pressure sensor was retested using the same graph in ConsultII. Over about 30-40 application cycles the sensor always returned a reading of 0 bar.

I do not know who installed what type of fluid that is why I am going to put this hear, just in case someone googles this type of issue or has had this problem in the past. I am very curious if the rubber seal retain their integrity or how this was resolved in other cases...should there be.

[Fezzik]

Wow. that is very intresting. Never heard of this at all before. Glad you did what you did to find out the true issue! Good job!

[Amays U G37S]

isn't the synthetic german high temp brake fluid blue?


I was told to never run this in our vehicles.

[RED_DET]

isn't the synthetic german high temp brake fluid blue?


I was told to never run this in our vehicles.

That is what I use but it is not DOT 5. I have heard of issues with DOT 5 fluids and they are not recommended for street driven vehicles. I have never had any issues with ATE super blue.

[AZhitman]

I ALWAYS ran ATE Super Blue in my G35 Coupe, and now in my C5.