power brake master cylinder problem?

[Timebender]

Yeah I saw the big panel that you can get to the master cylinder - interestingly my master has a sensor on the cap of the reservoir, which I've never seen on other DeLoreans. That's the one?

[Timebender]

Remove the access panel under the hood with the rubber plug to access the master/booster. Vacuum taken off right plenum of intake IIRC.

Brake master won't leak into cabin, but the clutch will if you have a 5spd.

I had mentioned the moisture as someone on another thread said if the booster was bad, brake fluid would end up in the driver footwell.

[sdg3205]

All deloreans have that switch. It's the low fluid switch. It operates via float.

Yup, that's what you're looking for.

If you suddenly have a soft pedal, check your fluids first. Perhaps you're low and your brake light is burnt out? Or perhaps the harness wasn't in place on the resovoire cap?

Edit - technically they are correct. The clutch uses the same "brake fluid." Aka dot 4. But the brake doesn't leak into the car as far as I know. Only a failing clutch master will.

[Timebender]

All deloreans have that switch. It's the low fluid switch. It operates via float.

Yup, that's what you're looking for.

If you suddenly have a soft pedal, check your fluids first. Perhaps you're low and your brake light is burnt out? Or perhaps the harness wasn't in place on the resovoire cap?

Edit - technically they are correct. The clutch uses the same "brake fluid." Aka dot 4. But the brake doesn't leak into the car as far as I know. Only a failing clutch master will.

So as I thought, due to a higher than loud whooshing sound in my engine compartment along with a rough idle (and acceleration problems like the engine has the choke on), there's a hose going from the intake manifold now to nowhere... there's a hard line on the passenger side of the engine bay, and one on the driver side - I'm guessing one is for the brake booster and the other for the hvac control knob/valve in the cabin, as turing that gets no external air (vent mode) into the car.

The hose coming off the engine is larger, and it can almost reach the hard line on the passenger side, but even if it's close it's too large of an opening. Could be there was a connector between it and the pipe. I'm assuming since it looks like a brake line, it could be the one to the booster (though odd it's on the right).

Or it could be the other, but I know it's best to take the vacuum from the intake vs. off the carb manifold for the brakes.

If I plug it the engine runs smooth as silk (surprise..).

Which pipe does what? I can hook up another smaller vacuum T'd off something for the one on the driver side. Or run the big line to it with an adapter/stepdown.

Greg

[sdg3205]

So as I thought, due to a higher than loud whooshing sound in my engine compartment along with a rough idle (and acceleration problems like the engine has the choke on), there's a hose going from the intake manifold now to nowhere... there's a hard line on the passenger side of the engine bay, and one on the driver side - I'm guessing one is for the brake booster and the other for the hvac control knob/valve in the cabin, as turing that gets no external air (vent mode) into the car.

The hose coming off the engine is larger, and it can almost reach the hard line on the passenger side, but even if it's close it's too large of an opening. Could be there was a connector between it and the pipe. I'm assuming since it looks like a brake line, it could be the one to the booster (though odd it's on the right).

Or it could be the other, but I know it's best to take the vacuum from the intake vs. off the carb manifold for the brakes.

If I plug it the engine runs smooth as silk (surprise..).

Which pipe does what? I can hook up another smaller vacuum T'd off something for the one on the driver side. Or run the big line to it with an adapter/stepdown.

Greg

I'd have to double check but I think the vacuum line off the right intake plenum joins a T-junction.

[Ron]

Greg, check out #50 thru #54 here- http://store.delorean.com/c-365-7-3-...-controls.aspx

[PJ Grady Inc.]

I can only speak to what I did on my car and that was to replace the master cylinder with a new one (NOS). The one I bought is shown here on the Houston webstore:

http://store.delorean.com/p-7478-mas...der-brake.aspx

I understand the brake boosters are considerably less likely to fail, but was surprised/relieved to see on the same brakes page (6-3-0) of the parts store that you can buy replacements.

I am betting it is your master cylinder that is the problem, but like David said, look at the other areas as well. Flush the fluid and then ensure it is properly bled of any air. Puddles under the car or in the drivers footwell are obvious signs.

If you do go ahead and replace various aspects of the braking system like the hoses, master cylinder, rebuild the calipers, etc., you might want to check out the kits available on most vendors websites. Josh has some great looking performance kits for sale and there was a thread on the forum here recently talking about a brake upgrade to some degree, although I'm not sure of the status of that kit.

It is often pointless to rebuild the brake master unless you have the cylinder sleeved first. The cast iron bore usually is pitted so it must be sleeved to achieve a smooth sealing area. We have brass sleeved units that will last longer than new ones. Brass is self-lubricating which means there is much less chance of the seal sticking to the bore surface causing a torn seal on cars that sit for extended periods. Brass is not susceptible to pitting the way iron is. We also offer it with a cleaned reseviour as these tend to hold debris and are also hard to find nowadays. We do all our rebuiling inhouse to assure the quality of these and other safety critical parts.
Rob