Niagara Gazette

August 29, 2013

TOM'S CORNER: Possible causes of decrease in engine temp

By Tom Torbjornsen
Niagara Gazette

Niagara Gazette — A few questions and answers this week:

JOHN FROM NIAGARA FALLS: Help! When my car is parked, the engine temperature increases to a normal temperature. When the car starts moving, the temperature drops. What’s happening and what can I do about it?

TOM: It’s important to give me the year, make and model of your car when seeking information. That said, check the coolant level. It is probably low and that’s the reason for loss of heat when driving. When an air bubble gets into the system, it travels throughout the system while the engine is in operation causing loss of heat and, in worse case scenarios, overheating. Another possible cause of this problem is a bad thermostat that is stuck in the wide-open position, offering no resistance in the system. Consequently, there is no time for the coolant to absorb heat from the cylinders and carry it to the heater core where the heat is transferred into the vehicle cabin.

•••

JOHN FROM ACKWORTH, IOWA: I own a ‘99 Buick Park Ave with110, 000 miles (automatic transmission). There is a buzzing sound up front when driving. This sound persists when I select neutral and speed up the engine with no change in sound frequency. When I steer left it stops; going to the right it continues. Is this a wheel-bearing problem?

TOM: Based on your description of the problem, I would say that yes, you have a bad wheel bearing on the right front side. What is happening when you turn left: You relieve pressure on the bearing by shifting the vehicle’s weight up and off the bad bearing. When you turn right, you intensify the noise by shifting vehicle weight downward onto the bad bearing causing it to growl (or buzz, as you call it). A good tech can put the car on a lift and pinpoint which bearing is bad with an electronic listening device.

•••

PAUL FROM SPRINGFIELD, Mass: I own a 2006 Silverado crew cab Z71. The reverse lights, the dome lights and door chimes don’t work. I have checked all the fuses and can’t find the source of the problem. Any suggestions?

TOM: The reverse light circuit is not related to the courtesy lights or door chime. The door chime and courtesy lights may be related. I checked the wiring diagrams and found that the reverse lights operate through the run/start circuit and are routed through the ECM (Engine Control Module). The dome light is routed through the BCM (Body Control Module) and the door chime is routed through the run/start circuit and BCM as well. These circuits will have to be traced out to determine the location of the problem. They may share a common ground connection, and it it’s loose, this could affect all three at the same time. Only an in-depth diagnostic and tracing of each individual circuit will reveal the culprit. I saw no TSBs concerning this problem. Success to you.

•••

WILEY FROM COLORADO: My ‘89 Honda Prelude 2.0 4cyl, 5 speed sat undriven for an entire year. I replaced the fuel filters, distributor, plugs, oil, etc. The car starts fine. However, once it is hot and I restart it, the car idles and stalls. I don’t think the problem is with the fuel pump, but I don’t know what it could be. Any ideas?

TOM: The best place to start is to determine what’s missing when the car doesn’t start. A vehicle has to have fuel, spark, and air (compression) in order to start. Diagnosis your problem might require that you do the following: (1) Install a fuel pressure gage on the fuel system to determine the fuel pressure (2) Use a spark measurement tool to determine how hot a spark you have (3) Do a compression test to “see” the internal condition of the engine. Only after running these tests can you proceed with a repair intelligently. Any other approach is employing the Wiley E Coyote philosophy of car repair which is: Ready – Shoot – Aim!

•••

GENE FROM LUBBOCK, TEXAS: I own a 2003 Chevy S-10 pickup. The SERVICE ENGINE LIGHT is on and it is showing a P0128 code. What do I need to do?

TOM: This code is related to the coolant temperature sensor circuit. Typically, when you see this code, the sensor is bad. However, before replacing the sensor it is a good idea to confirm that it is indeed a bad sensor. You can do this with a few pinpoint tests measuring voltage values. What happens when this sensor goes bad is that it incorrectly senses coolant temperature and thus sends incorrect data to the ECM (Engine Control Module). The ECM then commands the fuel delivery system to either richen or lean-out the fuel mixture according to what the temp sensor read. This response can result in dramatically decreased fuel economy or diminished power.

•••

JOYCE FROM LANSDALE, PA.: My ‘05 Subaru Forester shifts into gear with a jolt bad enough for my daughter to think we had been hit from behind. This only happens when it is 40 degrees or colder and only for the first couple of miles. What might be causing this problem?

TOM: Subaru issued a TSB (Technical Service Bulletin) for this very condition. It is TSB NUMBER16-69-07. Apparently there is a drivetrain control module software update that solves the problem. Call your local Subaru dealer with your VIN (Vehicle ID Number) and this information. They should be able to solve your harsh shift problem at no charge.

•••

JOHN FROM BURLINGTON, VT.: I am looking at a 2007 Suburban with really high mileage. However, the car is out of state. It appears to be in very good condition (paint, seats, interior, etc), but I’m not so sure of the mechanics. Can you offer any advice? Do you have anyone I could discuss this with over the phone?

TOM: The best thing you could do is to hire a tech to do a pre-purchase inspection before purchasing the vehicle. Contact the local AAA Club in the area where the vehicle is located and ask them for the best AAA Approved shop in the area. It will probably cost you about $100 but the shop will turn up any problems prior to your handing over the $$ and taking possession of the vehicle. Don’t be penny wise and pound-foolish.

‘Til next time ... Keep Rollin’

“America’s Car Show” with Tom Torbjornsen airs 7:30 p.m. Wednesday, 9 a.m. Thursday and 11 a.m. Saturday on WBBZ-TV.

"America's Car Show" with Tom Torbjornsen airs 7:30 p.m. Wednesday, 9 a.m. Thursday and 11 a.m. Saturday on WBBZ-TV.