Restrictor reduces coolant-flow noise

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By Junior Damato MOTOR MATTERS

Dear Doctor:

After reading your column for quite some time, I find myself with a question and need your expertise. I own a 2004 Chevy Impala with the 3.4-liter V-6 with 95,000 miles. There is a waterfall-like noise running from under dash that becomes more noticeable on acceleration. It does not appear to be motion-linked (e.g., turns or stopping). There is no leakage, no smell, no window fogging, the heater works fine and the coolant level is stable. I recently had the cooling system drained/flushed and replaced the radiator cap. What is your advice? - Chris

Dear Chris: The noise you hear is coolant flowing in and out of the heater core. If the system is full and there is no air in the system, then I would suggest the installation of a small restrictor in the heater hose to slow the circulation down if the noise bothers you.

Dear Doctor: I own a 2002 Toyota Sienna minivan. I recently had a problem with one of the front brakes sticking. I feel it at 60 mph when the steering wheel begins to shake. When I step on the brakes, the car responds with a lot of front-wheel shaking. I also notice that if I bang the brake pedal hard when this happens it will release. I asked my mechanic if there were any computer fault codes he could check. He said there were no fault codes for this problem. Can you please help? - Frank

Dear Frank: You may end up at the dealer or finding a qualified ASE-certified shop. Indeed, the first step is to check the brake system for trouble fault codes. Second, a simple test is to open the bleeder screw to see if the wheel loosens at all. I have seen sticking caliper slides and partly collapsed rubber flex hoses that can cause this problem once they get hot, such as driving at highway speeds.

Dear Doctor: I have 1991 Plymouth Voyager with 135,000 miles. The problem that I have is engine shudder under light throttle conditions. I have changed plugs, wires and added a new air filter. I also have a 2001 Nissan Quest with a similar problem that happens only under load condition, such as when climbing a hill. On the Quest, I have installed new plugs, wires, distributor cap and rotor. It now seems to run fine under no load. What am I missing? - Howard

Dear Howard: First, we need to make sure the sensation you describe is engine-related. Under part throttle and light loads, the engine runs very lean. Any breakdown will be noticed under these conditions. A secondary ignition breakdown can add to the problem. A full engine performance test may be required to locate the source of the breakdown. Fuel pressure and dirty fuel injectors can also be the culprit.

Dear Doctor: I own a 2002 Toyota 4Runner 4x4 with 67,000 miles. This past winter, I did not get the oil changed and had driven 7,000 miles. The technician said the oil that drained out was very dirty and that I should have an engine crankcase flush performed. What do you think? - Diane

Dear Diane: I suggest you get a second opinion. You can buy a can of engine oil flush from any auto parts store for around $5. This flush chemical is put in the engine crankcase a few minutes prior to the oil change. (Note: Engine oil should always be warm when drained - never cold). I do not recommend flushing the crankcase with any type of engine flush machine. I would recommend having the oil and filter changed twice within 90 days. This will help clean any old sludge out of the engine.

Dear Doctor: I heard that BMW makes a new diesel 3 Series. I've heard the diesel engine is rather loud and lacks power. What is your opinion? - Raymond

Dear Raymond: I recently drove the 2009 BMW 335d. The "d" stands for diesel and is rated at 245 horsepower. Let's start with the premise that diesel engines are loud, blow black smoke and lack power. This is true of yesteryear diesels. My average mileage on the road was 35 miles per gallon. As for the black smoke and diesel smell out the exhaust, there is neither.

c Junior Damato is an ASE-certified Master Technician. E-mail questions to info@motormatters.biz.