Guest Blogger: Tim Paske, Retired Automotive and Technology Education Teacher for 38 years at Osseo High School in Minnesota
Problem: Well, I finally finished my 15 year street rod project, a 1934 Plymouth, four door sedan, model PF. This is the short wheel base model for those of you who know old Mopars. I put in a new ZZ3 (ZZ383) crate motor with a GM 350 turbo transmission, a Ford 9 inch differential, with “coil overs”, a Mustang II front end, with disc in front and drum in back. A photo of the car is shown below.
After showing the car at Back to the 50’s, and on our way back to my place in Osseo, (about 10 miles) my brother was behind me in his1962 Corvette. He said he smelled burning brakes or clutch. When we got home to Osseo, we originally thought the smell was coming from my brothers Vette. I was fairly certain that the smell wasn’t coming from my car. WRONG!!!
As we were wiping down the cars for the day, I almost burned my hands when I touched the rear wire wheels on my car. The wheel rims were very, very hot. My first thought was a stuck brake. So I jacked up the car, pulled the wheels and rims off, (while wearing gloves off course), and low and behold, everything looked fine.
I then checked the differential lube and it was full. It was getting late so I put things back together and got ready to show the car the second day at Back to the 50’s.
Solution: While at the show, I talked with a few people to pick their brains about the problem I’m having with the rear rims getting so hot. I got lots of good, reasonable suggestions: 1) the brake lines are too close to the exhaust, 2) wrap the exhaust so the brake fluid doesn't expand and hold the brakes on, 3) make sure the emergency cable is releasing, 4) make sure that Silicon brake fluid is being used, 5) check to see if the master cylinder is too close to the exhaust. When we got home from the show, the wheels and rims were again, very, very hot.
The next week, after showing at Back to the 50’s, I decided to wrap the exhaust where it was close to the brake lines. I did this just in case there was too much heat being radiated into the brake lines. I then took the car out for a test drive. When I
returned, again the rear wheels were so hot I couldn’t touch them. However, the front wheel rims were cool as cucumbers. This is maddening.
Now I'm thinking, it's has to be the rear end or the wheel bearings. Well the differential was professionally rebuilt, and the rear wheel bearings are all brand new. So most likely these are not associated with the problem.
Now it's time to do what I always encouraged my past automotive students to do, which is to use your resources. I called one of the companies I previously used from the Street Rodder magazine, and talked to their technical support people. I conveyed the problem as best as I could, and after a few questions he asks me a very important question. “Are you using a brake proportioning valve?" Of course, I answered yes. He then asked me “How did you adjust it?” I told him that I followed the installation instructions that came with the valve. However, after thinking about it, I overlooked one important component. Sure the brakes stopped the car, but how much braking was being done by the front brakes in relationship to the rear brakes. The proportioning valve is used to adjust the amount of braking between the front and rear brakes of the vehicle. The photo below shows the proportioning valve with the adjustment knob facing down. In this position it can be adjusted easily. The hydraulic brake lines are also shown.
For more information on the proportioning valve in this website, click on