LUVTruck.com

Hi all I have a 1980 luv with a moderetly built 350 pushing 455 hp. The motor is carbed btw. Anyways the issue I'm having is really strange with the brakes. It has the factory brake system in it still and has been working great till just recently. I have noticed that at a low running temp the brakes are very responsive like they are supposed to be. But once the truck heats up at around 180 degrees and is ran hard or jumped on real hard the brake pedal gets super soft then drops to the floor and the light comes on,,,, also does this during city driving and in traffic on the freeway but once I'm moving steady and the engine cools back down my brake pressure comes back again. I'm totally stumped I've never seen this before on any cars or trucks. I have checked for vac leaks to the booster andbled out the lines and everything just to ensure there wasn't any air anywere and everything is in perfect order so if anyone knows what could be causing this to happen please feel free to let me know. Thanks!

Changed mufflers or headers recently? Sounds like a heat soak issue...

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If you think no one cares, try missing a couple of payments...



FIAA!

SFPP!

When I did the v8 swap I had side pipes that spout just under the drivers and passenger side doors but the pedal pressure loss at high temp seems to be a recent thing that just came up and I noticed its becoming more frequent once the motor hits around 180+ on the water temp. ,,,,, just curious u said heat soak like the boosters getting to hot or the brake lines might be getting to hot from the exhaust? If that's what u mean how can I prevent this from happening? Any other ideas would be greatly appreciated to what might be causing this. Thanks!

See where the lines are running close to the exhaust. It does sound like a heat soak issue to me...

_________________
If you think no one cares, try missing a couple of payments...



FIAA!

SFPP!

I agree probably something like the bundle of brake lines theat leave the booster on the driverside come close to the header by the frame rail . Might try to sheild the lines or wrap the header when you find the "hot spot" . Also might try a fliud swap . I believe Vavoline has a dot 3-4 synthetic that is compatible with the old DOT 3 that has a raised boiling point . Changing the old fluid with new and a higher boil point ( which probably needs to be done anyway ) and some time with a cheap harborfreight temp gun would be a start .

This may help

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1978 pro street step/side 455Buick, 4sp,4.11s, 31/18.5s

Thanks guys for all the ideas so far. Ill definetly be giving the fluid change and try wraping the headers and make a heat deflector plate for the booster and master cylinder. Hopefully this cures the issues I'm having. If it doesn't I sure as hell hope its not the booster going bad or anything more serious along those lines cause parts for luvs r really limited in this part of my state. Ill definitly keep everyone posted if these help. Thank!

You really don't need a booster mine worked just fine with the 94 Jeep Cherokee Master cyl. pictured.

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1978 pro street step/side 455Buick, 4sp,4.11s, 31/18.5s

Well I've discovered the issues with the brakes,,,,I feel so stupid but this happens to the best of us at times hahaha the master cylinder was sticking partially open and the brake booster push pin needed to be greased,,, new master cyl. And grease job and my brakes work perfect again! But to make this whole job worth while I heat wrapped all the brake lines even sheilded the booster and master cyl. With a heat deflector sheild and sprayed every brake line that wasn't wrappable with 2500 degree heat and flame deflectant AND stepped up the fluids to dot 4 high temp fluids...... I know some might be shaking ur heads and thinkin damn man u went the whole 9 yards "over doing it" but my brakes r awesome and at least ill never have a heat soak issue and it looks very nice and proffesional since I have a custom conversion a little more customized look wouldn't hurt lol thanks all for the advice it really helped and was definetly worth the improvements! THANKS!

Pics or it didn't happen , JK .