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Hi all,
I thought I would share this brake failure story with you all. It's kind of scary.
Anyhow, my '85 740 Turbo is still running well thanks in part to the great info on the brickboard. I had changed most of the rubber parts in the engine that I could, and the reliability has been good. One part which I missed is the little rubber hose which controls the turbo wastegate. I actually thought it was a hard line because the rubber was so hard (mistake #1).
One day I noticed the car accelerated like it was a race car. Wow, what was that, I thought ? The next time it happened I saw the turbo gauge was way into the red. I figured it would not hurt if I take my foot off the gas quickly (mistake #2). I stepped on the gas to pass a car on the highway in heavy traffic. The car made a pop sound and a puff of black smoke came out the back, but it was still running OK. I was going to stop as soon as I could. As I exited the highway I soon discovered NO BRAKES, YIKES. Luckly it was a gentle curve, and I was not going that fast. I had to use my emergency brake to stop. Believe me it is a sick feeling to have no brakes while moving about 45 mph.
The wastegate hose had come apart on the turbo and over boosted the manifold. That pressure blew the check valve apart on the brake booster. It was easy to find since I heard the sucking sound with the hood open.
Lucky for me I did not have to stop for a train. Also lucky for me, my dealer did not have the check valve in stock so the parts guys pulled a used one from a dead 240 on their lot to get me going until the new one came in. Talk about good service.
There is supposed to be a switch that would cut the engine during an overboost condition, but apparently it did not work. Maybe it's not on the '85. The bottom line, it is a good idea to change that little turbo wastegate hose and maybe the check valve too. My check valve appeared brittle, at least what was left of it. Kaboom.
Cheers,
Randy
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