Brake bleeding sequence & tricks 250 Gte

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chris
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Brake bleeding sequence & tricks 250 Gte

Post by chris » Thu Dec 19, 2019 2:54 am

Dear Al,

I will fill the brake system on my 250 Gte S3 (see photos) soon and have some questions:
1. What fluid do you recommend? Silicon or normal Dot4?
2. What is the best sequence for bleeding 250 brakes?
3. Are there any tricks which make it easier?

I do have a hand pressurised bleeder which connects to the reservoir.

Thanks
Christopher
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DWR46
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Re: Brake bleeding sequence & tricks 250 Gte

Post by DWR46 » Thu Dec 19, 2019 1:41 pm

I have answered your questions on Ferrari Chat.

chris
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Re: Brake bleeding sequence & tricks 250 Gte

Post by chris » Thu Dec 19, 2019 4:17 pm

Thanks! :roll:

Menlodon
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Re: Brake bleeding sequence & tricks 250 Gte

Post by Menlodon » Fri Dec 20, 2019 7:47 pm

I have had trouble with DOT 5 causing swelling with my GTE. Check with the supplier of your parts. The one I used (second time around) said DOT-5 would not work.
I used a pressure bleeder on the reservoir - worked perfectly

chris
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Re: Brake bleeding sequence & tricks 250 Gte

Post by chris » Sat Dec 21, 2019 3:59 am

Will check. Thanks for the advice!

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tyang
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Re: Brake bleeding sequence & tricks 250 Gte

Post by tyang » Sat Dec 21, 2019 9:41 am

Hi Christopher,

There are a ton of places for air to get trapped in the 250 system when you're starting with an empty system. I rarely see a system like this bleed correctly with just pumping on the brake pedal. With lines heading down to the brake M/C, then coming back up to the booster, and then back down to the a "Y" fitting, you can imagine where air can get trapped. One push of the brake pedal is sometimes not enough to move a large air bubble far enough to expel out of a bleeder. I use a reverse bleed system to force fluid back through the bleeders, but a pressure bleeder working from the reservoir end will work in a similar fashion. Start with the booster. If you're working with a pressure bleeder, open the top bleeders at the booster one at a time, and push fluid through the bleeders until there is no more air. Air can also get trapped at the equalizer, and sometimes cracking open the output fitting will make sure all the trapped air is expelled.

I have often found a combination of a few techniques will get a air-free system. Good luck.

Tom
'63 330 America #5053

chris
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Re: Brake bleeding sequence & tricks 250 Gte

Post by chris » Sat Dec 21, 2019 10:31 am

Hi Tom,

thanks a lot for your advice. I will do as you recommend.

Thans
Christopher

Jumprun
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Re: Brake bleeding sequence & tricks 250 Gte

Post by Jumprun » Mon Dec 23, 2019 1:55 pm

I've had pretty good luck with the GTC by assembling everything then closing all the bleed screws. I then fill the resevoirs and attach a clear hose to the farthest bleed screw and open it up. Take a break while keeping an eye out to let gravity take over till you get a little flow. Do all the corners, one at a time ending with the closest bleeder screw.
Of course watch the resevoirs, dont let them go dry. I finish it off with a vacuum pump at each corner in the same sequence. It usually takes a few rounds to get it all.

I understand the 250 system is more complex than my car, which has no equalizer, but starting with gravity has also worked for me on different cars.

One thing I learned through the years is no two cars ever bleed the same. Sometimes it takes pressure and sometimes vacuum at the screws.
I gave up the pedal pump method years ago. I use a Mity Vac brand pump.

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tyang
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Re: Brake bleeding sequence & tricks 250 Gte

Post by tyang » Tue Dec 24, 2019 12:20 pm

Jumprun, you're absolutely right that no two cars bleed exactly the same way, even it they have identical systems! The problem with the 250 system is there is too long of a brake line that travels up and down between the booster, the M/C, and the reservoir to allow the head pressure from the reservoir to push fluid to the calipers if there is air trapped in one of those lines. This system will gravity bleed once all the air is removed because there a siphoning effect in the lines when there is no air. You also have to remove the little check ball inside the caliper under the bleeder (if it hasn't been replaced by a different bleeder screw!) to allow fluid to flow freely when gravity bleeding.

The later, SII 330s and GTCs have a much better brake system, and bleeds out like a modern car.

Another tip is to use teflon tape on the bleeder screws if you're using a vacuum system from the calipers. An air tight seal at the bleeder screw will keep you from being misled with air bubbles in the line when it's actually being sucked in past the threads of the bleed screws.

Tom
'63 330 America #5053

Jumprun
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Re: Brake bleeding sequence & tricks 250 Gte

Post by Jumprun » Tue Dec 24, 2019 1:24 pm

Good tip about using teflon tape to prevent false bubbles. This GTC has proven to be one of the easier cars to bleed, except the clutch! It gave me more trouble than you would think.

Merry Christmas and wishing everyone Blue Skies and Soft Landings for 2020.
Tom Martinez in Southern California.

DWR46
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Re: Brake bleeding sequence & tricks 250 Gte

Post by DWR46 » Tue Dec 24, 2019 4:03 pm

Tom: The problem with the GTC clutch is the outlet line from the master goes up and then down in the shape of a "U". This allows air to be trapped at the top of the curve and fluid will just flow underneath the air and not move it. Reverse bleeding from the slave will usually push the air back to the reservoir, or High vacuum or pressure will also move the air across the top of the "U" and get the job done.

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