Brake Lock Up - Impala Tech
Brakes & Suspension Conversion Questions & more

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post #1 of 9 (permalink) Old 10-05-2019, 07:12 AM Thread Starter
Join Date: Jan 2012
Location: Kitts Hill, OH
Posts: 9
Brake Lock Up

I have a 1962 Impala with a 409 engine and drum brakes and new stainless lines throughout. The engine runs hot. If I drive the car more than a few miles (maybe 25), the brake pedal is at the top and I cannot push it down at all until the engine cools down. During this the brakes are somewhat locked up. Someone told me the brake fluid is boiling. Is this possible or is something else going on.
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post #2 of 9 (permalink) Old 10-05-2019, 10:54 AM
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It is possible but not likely as even DOT 2 brake fluid boils at 374 degrees. If you routed the brake lines in the original location and are NOT using tubular headers.

As to your cooling issues if you are cruising (above 35 mph) and the motor over heats your problem lies with your radiator (clogged or under sized). If on the underhand the motor cools off while cruising but over heats at idle you have a fan that is not moving enough air (an aftermarket flex fan, or original fixed blade four bladed fan off a six or small V8), or it is missing the ducting from the fan shroud.

A 409 is a big lock Chevy (Mark I) and produces as much heat as the 396 BBC (Mark IV) engine. As such it will require a four row copper/brass or a two row one inch tube aluminum radiator. If some previous owner dropped in a 409 and retained the small V8 or six cylinder radiator it will always over heat because the radiator is inadequate to do the job.

Further the water pump on the 409 is an open design (think paddle wheel), compared to more efficient enclosed scroll impellers used in high performance water pumps like those made by Stewart. A Stewart Phase III SBC water pump moves twice the volume of water as a stock water pump, but takes only half the power that a stock water pump draws because of the scroll impeller and a smoother high capacity casting. I just don't think it will be an option for you so the best you could do is an Edlebrock water pump which uses an enclosed straight blade.

The condition of the hoses affects cooling because as the rubber ages it gets soft and the bottom hose will collapse under suction (or balloon out on the top). Hoses and belts should be replaced as routine maintenance (something most car owners ignore until they are stranded on the side of the road).

Finally ignition timing will affect how hot the motor runs. Get it too far advanced and you can actually destroy the piston ring lands from excessive heat as the fuel charge is burnt before the piston ever gets to top dead center.

Big Dave
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post #3 of 9 (permalink) Old 10-06-2019, 10:07 PM Thread Starter
Join Date: Jan 2012
Location: Kitts Hill, OH
Posts: 9
The engine has been balanced and blueprinted. It has about 600 miles on it. The radiator is a new four core reproduction It has a 409 specific fan shroud. I am running a five blade flex fan. The water pump is an Edelbrock chrome again specific to the 409. Timing is +2 degrees. Hoses are new. This is a frame off restoration. Everything is new. This is not my first 409. They have all run hot. My question is what could be causing my brake pedal to be at the top and cannot be depressed, even a little after being driven a bit. I have a single master cylinder and all new everything for the brakes. The engine is not overheating when driving, just runs hotter than other engines I’ve had. The brake pedal is the issue. Thanks for your reply to my post.
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post #4 of 9 (permalink) Old 10-06-2019, 10:09 PM Thread Starter
Join Date: Jan 2012
Location: Kitts Hill, OH
Posts: 9
I’m giving a picture. Maybe you can see something I’m missing.
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post #5 of 9 (permalink) Old 10-07-2019, 08:41 AM
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If you haven't already, also stop by the 348-409 Forum. They would love to see your car over there: Info Exchange Forum

-Parting Out over 75 '58 to '73 Full Size Chevy Cars-


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post #6 of 9 (permalink) Old 10-08-2019, 01:04 PM
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Location: Coopersville, MI
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Could your brake fluid have gotten contaminated by something that boils or expands quicker than brake fluid?

I believe the rear brakes have a check valve and maybe it was accidentally installed incorrectly?

The only places your lines could come close to the exhaust is as it travels across your front cross member and where the rear line runs down to go through the X tunnel of the frame. I would look at all places it runs close to the exhaust and look for discoloration. you could have a small exhaust leak blowing right on a brake line.

Last thing I could think of is maybe one of your auto drum brake adjusters are installed wrong and instead of doing the adjusting while backing up it does it while going forward. (This assumes you have upgraded to auto adjusters and not still using the manual ones. Also this wouldn't make much sense if the pedal returns to normal.
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post #7 of 9 (permalink) Old 06-21-2020, 09:32 PM Thread Starter
Join Date: Jan 2012
Location: Kitts Hill, OH
Posts: 9
So I’ve checked the exhaust, no leaks. No discolored brake lines. Someone told me it’s probably a bad brake hose even though they are all new. Any new suggestions?
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post #8 of 9 (permalink) Old 06-22-2020, 07:38 AM
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Since it looks like you don't have a power brake booster you really have no connection between the engine and the brake system. No vacuum or anything like that. I would be interested to see if you could reproduce it at a stand still. How long into a drive does it get hard to push? I might try to sit and the car and pump the brakes on and off for a similar amount of time and see if it does it with the engine off and at a stand still. If it does then you have something plumbed wrong. If that doesn't work wait for a while then start the engine and let it sit and idle up to temp and sit there for a while to see if the brake problem develops. Might want to set up some box fans to help keep air moving through the radiator. If it happens in this scenario, since you have no hard connection to the motor, you have to look for proximity connections. If you don't get it in either of these conditions than probably a problem in one of the wheels where the wheel cylinders don't want to move as the brake pads get hot.

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post #9 of 9 (permalink) Old 06-22-2020, 08:03 AM
Join Date: Jun 2020
Location: Lake Camanche, CA
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Use a Temp gun to check your brake line that crosses your engine. May not have discoloration but it may still heat the line which affects the fluid.

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