HOW TO DO AN ADVANCED SEARCH.

Mon Jul 08, 2013 3:56 pm by Admin


For the benefit of 944Hybrids users there are two search functions available for you to use.
The purpose of this sticky is to explain the "Advanced Search" function because it is much more powerful and is the best choice when researching information.

When you log on to the site a list of options is shown in a line at the top of the page. One option is labelled "Search", use this option (NOT the search box lower down on the right).

After you click on the upper search option, a drop down box appears. At the bottom of this box is a radio button marked "Advanced …

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Brakes locked up

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Brakes locked up

Post  jpkinerk on Fri Nov 27, 2015 8:38 pm

Hi guys, 

So I was out driving the 944 after my first track session (went well minus a slipping clutch), and the brakes just started locking up at anything under 45 mph if I even looked at the brake pedal. By the time I was able to pull over it was locking up by itself at slow speeds without even touching the brakes. Had it towed home and here I am. 

I'm running the BMW hydroboost system, with a new 944 master, new "bomb", reman'd booster, and used regulator. My gut is telling me to swap out the regulator, just thought I'd run this past everyone here in case I've overlooked something. Those damn regulators are hard to find, and pricey. 

Thanks,

JP
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Re: Brakes locked up

Post  Arthropraxis on Fri Nov 27, 2015 9:13 pm

Maybe, a sticking caliper?
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Re: Brakes locked up

Post  Techno Duck on Fri Nov 27, 2015 9:25 pm

Are you running a power steering cooler? I seem to remember someone had an issue like this and it was overheated fluid.

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Re: Brakes locked up

Post  spence on Sat Nov 28, 2015 4:45 am

Push rod too long? You could try adding a shim to the master cylinder and see what happens....
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Re: Brakes locked up

Post  Lemming on Sat Nov 28, 2015 8:39 am

Spence is on the right track, I would bet that the MC is not able to retract completely. Seen it a few times at the track after someone adjusts their pushrod.
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Re: Brakes locked up

Post  jpkinerk on Sat Nov 28, 2015 7:28 pm

Thanks guys, I tried swapping out the regulator (before I saw these replies) and it didn't like that. Turn One pump started howling even when full of fluid. I had drained the resevoir and released the pressure from the "bomb" before removing the pressure and return lines to the regulator. Once all back together, it started to cycle like usual and I began topping it off, except the groaning didn't go away. Once I turned off the car, the resevoir started overflowing like mad! It was all airrated and bubbling over for about 10 seconds. Horrible mess. 

Anyway, I am running a cooler and the car rolls freely when the engine isn't on, so I guess that mean it's time to look at the pushrod, as suggested. My only question is, I just had this car on the track with no issues a few weeks ago. Could a pushrob problem like this present itself after working properly to begin with?
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Re: Brakes locked up

Post  spence on Sun Nov 29, 2015 5:12 am

With the fluid cold and with the engine and key off, pump the brake pedal at least 20 times. Then check the fluid level in the hydraulic reservoir. When you pump the brake you bleed out all the pressure thats stored in the pressure accumulator and the fluid level will rise. So you fill it when all the pressure is bled out and then you start the car. The fluid level will go down quite a bit but you don't add any more to it.

If it's overfilled the brakes won't release till you get off the pedal and the pump sucks the fluid down cause the fluid has no where to go. The air bubbles sound like cavitation/aeration ... So make sure all the lines are tight.

Did you add any fluid when the brakes started to lock up at the track?
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Re: Brakes locked up

Post  jpkinerk on Sun Nov 29, 2015 6:03 pm

Thanks for the help, guys. But we can chalk this one up to good 'ol fashioned idiocy and bad luck. 

The pump was overflowing because I had the hydroboost and pump lines switched. Embarassed

As for the locking of the brakes, it wasn't the regulator to begin with. Turns out one of my front calipers was missing a bolt into the spindle. The symptom didn't appear at the track because the bolt must have not backed out/failed until just the other day. First thing I did when the tow truck dropped it off was check for a sticking caliper, but the pads came out fine with no movement in the calipers. However, today when I just so happened to get up off the ground, I grabbed the caliper and it almost spun around the rotor. Shocked

Anyway, everything is back together and working properly now. Sheesh, I sweat this car is trying to kill me.
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Also, for future reference

Post  948 on Thu Dec 03, 2015 8:17 am

If there are excessive restrictions in the Hydroboost fluid return line, back pressure will cause the unit to apply the brakes a little. I had this issue. My return line was tee'd right into the return from the rack which was before the cooler. Moving the return line downstream of the cooler, so that it dumped directly into the reservoir, solved my issue.
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Re: Brakes locked up

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