Click and Clack talk cars
BY TOM and RAY MAGLIOZZI
Tuesday, August 30, 2011
Dear Tom and Ray:
I’m an idiot. I just poured synthetic
motor oil into my master cylinder. Am I
destined to crash? – Lisa
RAY: Well, not unless you drive the car,
Lisa. If you leave it parked, you should be
fine.
TOM: It’s a tricky problem, Lisa. We
checked with the brake engineers at Bosch,
and they said that the Ethylene Propylene
Diene Monomer seals in the brake
components are compatible only with glycol-based
fluids.
RAY: In other words, you’re gonna crash.
TOM: Motor oils, including synthetic
ones, are based on mineral oils. The problem
is that mineral oils and rubber don’t mix well.
The oils can cause rubber to swell or deform,
and because there are lots of rubber seals in
your brake system, that eventually can make
your brakes stick, leak or even fail completely.
RAY: So the safest thing to do would be
to replace every part of your brake system
that uses rubber seals. That’s pretty much
everything except the steel brake lines! So
that’s going to run into big money.
TOM: A less-drastic measure (assuming
you haven’t driven the car and mixed the
synthetic oil with the brake fluid) would
be to siphon as much as you can out of the
brake-fluid reservoir. Hopefully, you’d get the
vast majority of it out that way.
RAY: Then you could remove the brake
lines from where they connect to the master
cylinder and flush out the cylinder – without
sending any of that potentially contaminated
brake fluid down the brake lines.
TOM: Or you could just replace the master
cylinder entirely, since that’s the component
whose seals are most likely to be affected by
the oil.
RAY: In either case, once you have a clean
master cylinder, you could then reconnect
the brake lines and flush the rest of the system
by bleeding the brakes at all four wheels.
TOM: But remember, you’d be taking a
shortcut with your brakes! So have the car
towed to a mechanic you really trust, and
ask him to try to figure out how much oil has
gotten into the brake fluid and how far it’s
gone. Then you can get his best advice before
deciding on a course of action.
RAY: If it were my brother’s car, I’d
probably take my chances. But if it were a
real car, I’d probably go the replacement-part
route.
TOM: And if you think you’re an idiot
now, Lisa, wait ‘til you see what phrases come
to mind once you see the bill for that job.
Good luck!
***Wait! Don’t buy another car without
the mechanic’s checklist that’s included
in Tom and Ray’s pamphlet “How to Buy
a Great Used Car: Secrets Only Your
Mechanic Knows.” It will help you get a
good used car and avoid the clunkers. Send
$4.75 (check or money order) to Used Car,
P.O. Box 536475, Orlando, FL 32853-6475.
Get more Click and Clack in their new
book, “Ask Click and Clack: Answers from
Car Talk.” Got a question about cars? Write
to Click and Clack in care of this newspaper,
or email them by visiting the Car Talk
website at www.cartalk.com.
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