So I have replaced 3 frozen calipers with used ones from another car. After bleeding the system I went to throughly test them out. I did 4 rubber burning stops from 75mph and some fairly serious braking from ~35mph. Finally on th way home the pedal went ALMOST to the floor. There was still some braking left (perhaps the booster was failing?). When I got home I checked the brake fluid and it had boiled over. I have heard that the brakes and vacuum system are linked but I do not know how. Following this I have had some vacuum system issues. The fuel shutoff is not doing its job and the drivers door doesnt close properly. It was fairly damp last night and perhaps that caused the fuel shutoff/door issues? Is the boilover normal followed by loss of some braking? I know I should have replaced the calipers in pairs with 4 new (reman oem whatever) ones but money is tight. I purposely tried to get the brakes to overheat and braking was excellent until the loss.

I'm not sure what you meant by "boiled over". Do you know precisely the point or points where the brake fluid was lost? Was there sufficient fluid left in the reservoir(s) so that the M/C piston(s) were not trying to pump air?

I mean literally that brake fluid came out through the top. I assumed this was due to the heavy breaking causing the fluid to expand back from the calipers up to the resevoir. Part of the reason that I think it might be the power booster is that as soon as I turned the car off, the brakes firmed up considerably.

With three very heavy stops all in a row, without any cooling time between the stops, it's entirely possible that the fluid vaporized, especially if it's old fluid with some absorbed water.

The return of the system to proper function had nothing to do with the vacuum system. The time to allow the system to cool and the fluid to condense was the issue that allowed proper function again.

Drive the vehicle now that it's returned to a normal temperature. I'll bet the vacuum system functions as designed.

The vaccum issues started AFTER the brakes had cooled. Vehicle failed shutoff the morning after. Like I said it may have been related to the cool rainy night last night.

I did alot of extra bleeding on the brakes in order to attempt to flush the system. The fluid that was in the resoiver now looks black. Should I take the car somewhere to have it pressure flushed or is this something I can do myself?

What model do you drive?
How many miles do you have?
Where are you?
Can you go to the USER CP and put this info in.

The brake booster used vacuum to work. Without vacuum your brakes will still work but the pedal will be hard.

Your Engine shutting off is independent of your brake issues. You more than likely broke or accidentally disconnected a brake line while working under the hood.
You need to test your whole vacuum system.

You door not closing is a totally different problem also.

Danny

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Added car info in cp, located in Atlanta.

How to test vacuum system? I didnt see anything in Clymers...

I think the door closing and engine shutoff are humidity related as both act up when it gets wet. The outside door handle gets stuck and causes the latch to miss (or so Im guessing) I will load it up with some wd40 tonight.

I am fairly certain the vaporized brake fluid is the most likely culprit, I dont even think my Honda would have done nearly as well.

See?......The vehicle year makes a difference. The earlier 123's use engine vacuum for the doors and the later models have a seperate vac unit in the trunk. At least I think. Someone familar with the 123 may chime in here.

Anyway you need to test the vac system. You will need a mity-vac. www.harborfreight.com has them. So does Sears. You can rent one for free from AutoZone.
Look here for vacuum diagrams:
Vacuum Diagrams

Start at the pump and work your way out. It's real simple once you get started.

Danny

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1984 300SD Turbo Diesel 150,000 miles

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Since the boilover the brakes have been rockhard. I will check the vacuum system as soon as i get a chance.

Glad to see another Atlantan here on the forums!

Have you checked the pictorial on how to do some quick checks?

http://dieselgiant.com/mercedesvacuumtroubleshooting.htm

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1981 300D 147k
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1979 300D 234k (sold)
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