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AUTO Q AND A: Brakes lose vacuum assist in subzero cold

Question: I have a 2001 Ford Escape with the V6 engine. When it gets below zero I lose hydraulic assist on the brakes. The brake pedal becomes hard to push, as if you had turned the engine off. If you pump the brakes a number of times, the brakes...

Question: I have a 2001 Ford Escape with the V6 engine. When it gets below zero I lose hydraulic assist on the brakes. The brake pedal becomes hard to push, as if you had turned the engine off. If you pump the brakes a number of times, the brakes return to normal. If the car is sitting out in the subzero cold, this happens right away. If it is parked in our garage overnight, the problem doesn't happen until traveling on the freeway for 10 to 15 minutes; the engine compartment must cool off from the passing air.

Answer: First, an important clarification. When you have this problem, your vehicle's brakes still work. You haven't lost the hydraulic assist on the brakes, you've lost the vacuum assist that helps you apply the brakes -- that's why the pedal feels so hard. But remember, even without power assist, the hydraulic brake system will still stop the vehicle -- you just have to push the pedal much, much harder.

The most likely culprit in the loss of vacuum assist in subfreezing temperatures is the one-way vacuum check valve in the vacuum hose between the engine's intake manifold and the power brake booster housing. The valve is designed to open when engine vacuum is applied, allowing vacuum to the booster housing. When vacuum drops, such as during hard acceleration, the valve closes, preventing vacuum from bleeding out of the housing. Moisture or debris is likely freezing or sticking this small valve closed so that no vacuum reaches the booster diaphragm to generate the boost to help you apply the brakes. Once that moisture thaws, the valve opens and vacuum reaches the booster.

Check, clean and dry the vacuum fittings, hoses, check valve and check the booster housing for vacuum leaks. A new check valve will likely solve the problem.

Q: I have a 2002 Town & Country minivan. The engine started to vibrate at idle, so I took it to the dealer. They said it was sagging motor mounts, with a $750 repair bill, but it doesn't need immediate attention. Is this something an independent repair shop could handle?

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A: Did the dealer check the aluminum casting on the right-side engine mount? My Alldata automotive database pulled up service bulletin 09-003-02 that describes the symptoms from this failure, which include vibrations. A full-service independent shop should be able to replace engine and transaxle mounts. And as long as the casting isn't broken or one of the mounts completely separated, the dealer is correct -- this isn't an issue requiring immediate attention.

Q: Our son recently purchased a 1995 Nissan Altima from a local used-car dealer. He took the car to a service station to price out a new muffler/exhaust system, and they told him there was no catalytic converter installed. The dealer sold him the car without a catalytic converter in it. Is it illegal in Minnesota to sell a car without a catalytic converter?

A: Minnesota statute 325E.0951 "requires that anyone selling a vehicle in the state must certify, in writing, that the vehicle has all its proper pollution control equipment. The law parallels Minnesota Rule 7023.0120 that prohibits the transfer of a vehicle title unless the emission controls are in place and working properly." Ask the dealer to restore the emissions system or refund your money.

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