Chimaera - brakes go hard-lost my boost

[twobone]

Hi.

I just purchased. Used chimera here is Canada. Drive home was fine until stop and go traffic in high heat. Brake warning light goes on and pedal is rock hard.

Brake fluid level is fine. How is the warning light triggered?

Previous owner did a LHD conversion and put an access panel in the wheel well to get access to the brake booster. He also put a separate brake fluid reservoir in the wing with a hose down to the master cylinder.

He said he had tested the booster for pressure last year. It seems weird that the booster would loose power mid drive, but it was a super hot day.

Any thoughts? Could brake fluid boil cause the problem of rock hard brakes if the brake lines run too close to the headers in his reroute?

Is this DIY or do I need to tow to a mechanic? Do I need a TVR specialist (they are far away). Or can a good British classic car mechanic figure it out?

[ClassiChimi]

Any good mechanic that's worked on Brit motors should solve this.
I'm not expert enough to offer an opinion but boiling brake fluid normally results in a long pedal.
Hopefully someone will be along shortly who can answer your question.

[sparkythecat]

The first thing I would check is the vacuum hose that runs from the brake booster to the inlet manifold. If the hose is split or leaking or has collapsed the brakes will display the symptoms you've described.

[QBee]

It's a totally standard servo assisted brake system. Any good classic car mechanic should know immediately what is wrong.
Try it again locally before taking it to a garage.
As Classichimi says, boiling the brake fluid results in a long pedal, leading to no pedal, but no way would a drive home in hot weather cause the fluid to boil. Mine boiled with brand new sintered race pads, old fluid, and race track use - lost the pedal at 120mph.

[twobone]

I'm wondering if he failed to install a non-return valve. Would I find it as an in-line item sliced somewhere in the vacuum line?

[sparkythecat]

This animation with voice-over explains how the system works.
The valves are inside the power booster and not in the vacuum hose.
Have you checked the vacuum hoses condition yet?

https://m.youtube.com/watch?v=0sj5d48mcss

[ClassiChimi]

^^^^^ Great explanation that.

[twobone]

Yes, no obvious loose or cracked hoses. I guess the shop will need to do a full pressure check and work thru to see where the leak is.

Is it true that Brake boosters are very hard to find or is there a common replacement part?

My shop is not a TVR expert.

[Steve_D]

twobone said:

...Is it true that Brake boosters are very hard to find or is there a common replacement part?
My shop is not a TVR expert.

You could get one from the UK but remember you are asking for a Brake Servo not a booster.
http://tvr-parts.com/tvr-parts/part-details/tvr-j0...


Another test for you.
Sit in the car and pump the brakes several times with the engine off.
Press on the pedal and hold that pressure whilst you start the engine. If the servo is working the pedal will go down a little further.

Steve