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Hello,
I may need some help here. I have been topping off the left brake fluid reservoir a few times now as it shows empty after parking the TGB11 for a few weeks in the garage, not even driving it. There is no leak visible anywhere. Today, I topped it off again, and pumped the brake pedal it showed some resistance, but I was able to push it all the way down, while watching my reservoir slowly emptying again. I then turned it on, and after pumping the pedal a few more times, the exhaust fumes turned from normal to blue and A LOT, but didn't smell like oil. It appears that the brake fluid got mixed in somehow with the engine. Any ideas what could leak? Master cylinder, brake servo, etc?
Thank you for any advice you can give me!
Marcus

Hi Marcus,

Check the brakeservos.

Some more Infos on C303.de:

https://www.c303.de/c303-forum/index.ph ... _next=next
https://www.c303.de/c303-forum/index.ph ... 59;start=0

Viel Erfolg
Uli

Thank you! I thought the same thing, but then a local TGB guy told me he is sure it is the master cylinder. The interesting thing is that only the left reservoir is empty. Does that mean only one brake servo is damaged? What am I looking for when taking the servo out? Where could it cross contaminate into the engine? Will there be any damage, or should I be OK fixing or replacing the servo, and then just have the engine blow out the remaining brake fluid until it is no longer smoking?

Best,

Marcus

Marcus,
Rebuilding the brake boosters is not difficult...just a bit tedious getting them out of the truck. Tatanka Parts ( https://www.tatanka.nu/en/category/brakes ) has both a small gasket and seal set and a full rebuild set. My suggestion is that, if your are going to rebuild one, you might as well rebuild both at the same time. One less thing to worry about down the road.
Take care.

Jim Molloy

Thank you!

Ok, I removed the upper brake booster, and it was full of brake fluid. Is it safe to assume that, given only one brake reservoir is drained empty, the other brake booster should be fine?
Also, the vacuum membrane looks good, but obviously there's fluid all over, so the shaft, or piston that is filled with brake fluid must be leaking into the vacuum chamber. Hope that the repair kit will have the required parts. Next question is how do I take the darn thing apart without using a sledge hammer (kidding)? Is there a trick? The hard round black disk that is holding up the membrane is firm against the membrane, and both are just spinning, so unscrewing isn't going to work.

Thank you as always for being helpful.

Happy Holidays!!!
Marcus

You have to pull off the main membrane, then a metal pin approx. 15mm wide will appear in the groove. Lay the brake booster on its side, the cotter pin points downwards, press the siphon lid in very lightly ... lift the whole thing up once and let it fall onto the table with a jerk, then the cotter pin falls out and the lid goes down. It's very easy!

...and make sure that you also change the small o-ring (number 3 in the picture).

Hallo,

Vielen dank fuer alle Ratschlaege!!!
Aber jetzt auf Englisch weiter, ...
I was able to repair the upper brake servo with the repair kit from Tatanka. I did not touch the lower servo, as it was still doing OK. Bled the brakes, and it was all running fine. The left reservoir is connected to the upper servo, so I assume the right is connected to the lower servo. After having parked the truck in the garage for another two weeks, the right reservoir is now empty, and there is no visible leak. The brake pedal goes all the way to the floor, and there is no braking, but there is also no white smoke coming out of the exhaust, compared to last time. Maybe because the lower servo does not go directly to the engine intake? Could it be that the lower servo now went bad? Why would both servos go bad almost at the same time?

Schoenes Wochenende!

Marcus

Hello Marcus,
did you reset the warning valve? If not, this could be the cause of the problem or the defect in the other brake servo. Just open it up and see if there's brake fluid in it, then you'll know.
Regards
Uli

https://www.c303.de/c303-pdf/service/se ... rakes3.pdf

Hi Uli,

I reset thee warning valve after I fixed the first servo and before I bled the brakes. I must assume the second servo is kaputt.

Danke!