Sometimes the symptoms don’t fit the problem. Sometimes the symptoms don’t even make common sense.
The last few winters brought us just such a problem. The solution was not a repair so to speak. It was an explanation. I have never got down to the science of the problem.
A customer complained that his brakes smelled like they were burning when he got to Rossland from Trail. Now burning brakes is not something to take lightly as overheated brakes will fade (loose stopping power).
Everyone knows the smell of burning brakes. So definitely the questions that follow are brake questions.
How do the brakes feel? Does the pedal feel solid? Yes. Does the vehicle stop well? Yes.
Well, let them cool off and check them again. If they function well, still bring the vehicle down (carefully) and we will inspect them.
A complete inspection of the brakes shows no apparent problems. A road test reveals normal temperatures and performance. So what is up?
Yes. So what is up? We don’t know.
Another customer complains. Same complaint. Burning brakes in Rossland. Are they burning when you get to Trail. No, no problem there. Okay. This is weird.
Another similar complaint. Okay time for a more serious investigation. Road test to Rossland. Hey, smells like burning brakes especially around the back of the vehicle. Touch the wheels. They are cold like they should be. Where is that smell coming from?
Believe it or not the exhaust smells like burning brakes maybe burning rubber. Not exactly but very close to it.
The complaints have continued. Only in the winter. Only after driving up hill.
Our conclusion; it is something in the fuel.
In case you did not know it, gasoline is blended differently for winter than summer. Winter fuel must be more volatile. In order to ignite the air fuel mixture in an engine cylinder the fuel must turn to a vapor from liquid. Cold temperatures require a lighter fuel that vaporizes at lower temperature.
We have assumed that winter fuel has a certain additive that produces this smell. Driving uphill requires a richer mixture.
This increases the exhaust temperature, particularly the catalytic converter. We assume there is a reaction in the converter with the additive that produces the smell.
Do we have proof? No. Just a lot of complaints.
Are we right about this? I have decided to do some investigation.
My early investigation results are in.
There are many suggestions that the smell is more towards burning rubber and it is the result of winter road salt burning off the exhaust system.
Maybe it is the result of the new salt brines that are sprayed on the road. This salt solution then sprays up under the vehicle onto the hot exhaust and burns off.
Is this a better explanation? I am not sure. If you know the answer drop me an email.
Trail’s Ron Nutini is a licensed automotive technician and graduate of mechanical engineering from UBC. E-mail: firstname.lastname@example.org