‘67 imperial discs heat up

[Rdtreur]

on my ‘67 imperial I found out that de front discs heat up while driving. I can turn the front wheels by hand but I do feel resistance. Rear drums don’t heat up.
I looked in the shop manual and the say the “residual pressure valve” might be the problem and needs to be removed from the mc.
-So what are your idea’s About this?
-what is this valve doing?
-do aftermarket mc have a residual valve?
-how can i check if it really is this valve?
-any other idea’s?
Thanks for your help guys
Ramon

 

[Rdtreur]

Photo of the shop manual

 

[67Monaco]

Is the car new to you? If so it would be worth pursuing. If not did you replace the master recently? If so then I would see it being a worthwhile endevor as well. If you've owned it for some time and no changes, I'd say check for sticking pistions in the calipers.

 

[FURYGT]

I would check to see if the caliper pistons are retracting enough after you apply the brakes. The FSM should tell you how to do this and how to measure. The caliper pistons could be sticking. I would also check the wheel bearings if the calipers are properly retracting the brake pads from the rotor.

 

[detmatt]

So you’re sayin that with the front wheels off the ground you can spin them freely but do they continue to spin on their own at all? With the Budd’s the pads do actually ride on the disc at all times. How hot do they get? Can you touch the wheel after you drive it?

 

[Rdtreur]

So you’re sayin that with the front wheels off the ground you can spin them freely but do they continue to spin on their own at all? With the Budd’s the pads do actually ride on the disc at all times. How hot do they get? Can you touch the wheel after you drive it?

I can turn the wheels by hand but do not continue to turn freely. The get pretty hot . I can not my hand on the rotor for a few second .

 

[Rdtreur]

I do can touch the wheel, the wheels are just warm.

 

[67Monaco]

I can turn the wheels by hand but do not continue to turn freely. The get pretty hot . I can not my hand on the rotor for a few second .

Yeah you shouldn't be able to touch the rotor at all. Well depending on how long you drove. But, even a very short d I've with limited braking would put you in the 150f range easily. Under normal driving 3-400 degrees wouldn't be outside the norm. Maniac driving, hard braking like I do 6-700 degrees and the pads really start to bite. Racing temps on racing cars somewhere north of 1200f degrees.

Get a infrared thermometer and take a reading, that will tell you for sure how hot things are getting.

Outside of that, if you haven't flushed fluid recently, 3+ years, I'd say it's time. And if it's still a concern pull the calipers and ensure all 8 pistons move freely.

 

[detmatt]

The one thing I’ve noticed about the Budds is that if one side is working at all differently than the other you really feel it in the steering wheel so if something isn’t working properly it would make sense that it was further upstream.

 

[Rdtreur]

Thanks for the input guys! It stops straight and both wheels seems to turn the same. I think it’s just how it should be with those budd brakes. I unbolted the mc from the booster just to check if that releases the rotor but it is not making any diffirance. So for now i’m good (I think;-))

 

[detmatt]

You will want to be sure though because the pads and the rotors are a bit pricey.

 

[67Monaco]

A bit? slightly understated don't ya think?

 

[CBODY67]

Until fuel economy became such a big deal in the earlier 1980s, ALL disc brake pads "touched" the brake rotors in operation. This is why, after replacing the brake pads and then reinstalling the caliper, you're supposed to STOMP on the brake pedal to get everything "to spec" again . . . otherwise, that first brake application might not go so well! Just a very mild bit, but still touches the rotors. This was normal. In the '80s, new designs of master cylinders and such got a bit more retractions of the pads for less drag and more mpg. This was a coordinated component situation where both the calipers and mater cylinder would need to be set up for this to happen.

I believe there are residual pressure valves of different calibrations. One for drum brakes and one for disc brakes. They keep the system "charged" past the master cylinder for quicker braking response. This works for the drum brakes as they are adjusted with no lining "touch" of the brake drums.

The question would be just how hot the front brake components are getting? IF they are "dragging", then it's just like driving with one foot lightly on the brake pedal (i.e., partial engagement). Remember that disc brakes dissipate heat better than drum brakes, so any possible heat buildup is quickly dissipated.

The OTHER consideration is the front wheel bearing adjustment. It could be "too tight", which could cause additional drag on the wheel. OR it might need some new grease in them.

I would say that if you can still turn the wheel reasonably easy, then all is fine. DO check that front wheel bearing adjustment, though, even getting them repacked, for good measure. The front wheels should spin a bit, just not as easily as would be the case with drum brakes properly adjusted.

CBODY67