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1991 C4 intermittent brake failure


Vehicle Information: Model: C4; Year: 1991; Body Type: Coupe; Total Mileage: 82500;

At my a drivers event this weekend, I twice suddently lost pressure in my brakes even after pumping them. Some corners the brakes would work fine, but others they didn't, including the last time in which I ended up going off-roading and clearing brush along the runoff. A bit afterwards when driving back to the pit, the pedal then came back and was fine as I drove unnervingly another 200 miles home, albeit at much more relaxed roadgoing conditions. Over the prior few weeks, I've remembered that occasionally while idling in traffic, the brake pedal would also go to the floor but since I was stopped already, I must have been naive thinking this would not be a problem especially at track speeds. I've been reviewing your posts which indicate that perhaps some white vaseline goo may have formed throughout the braking system due to contaminated, old hydroscopic brake fluid. The previous owner said that he had similar problems and replaced the master cylinder, hydraulic pumps, ABS unit etc. but he also had some of these problems. He said it may have been an intermittent hot/malfunctioning relay which doesn't really make sense to me. I've never gotten any warning lights when I had my off-road excursions and know that these lights work on starting the ignition.So my question is about the process to remove this type of goo. You mention flushing the system with DOT-3 brake fluid as it may have some solvent properties for this goo, then waiting a week and then re-flushing it again with DOT-4. Using some basic chemistry principles, do you think it may be helpful to warm up the whole system by repetitive braking, in essence trying to boil the fluid, or warm up the new DOT-3 fluid someway so that it may dissolve this goo a bit better and then immediately flushing with DOT-4 so that it doesn't get a chance to precipitate when the fluid cools? Or would that make it worse if warm fluid may cause more water to accumulate in the system anyway. I'm not sure if it's really practical to warm up brake fluid in any other way.Do you have any other suggestions on how to remove this stuff from the system? Are there other liquids that may work as a solvent to dissolve this stuff - some type of mineral-based detergent mix - or is using DOT-4 better than DOT-3 for this type of solvent action?Thanks for your advice.

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