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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 41 YEAR 2000
by Bob Hagin
Q. Recently, we took my son's 1990 5.8-liter Ford Bronco in for service. He is a freshman in college and needed to get the work done before leaving for school. The service dealer said oil was leaking from the front timing cover, intake gasket and valve cover gaskets and it needed a complete tune-up. The original estimate was for $1500, but with the replacement of the timing chain, harmonic balancer, etc, the bill was $1838. The installer said the vehicle was now road tested and in good condition. That same day my son left for school. He reported that the oil pressure gauge was indicating low pressure at idle and the red dash light would illuminate. The oil level was OK. This hadn't been a problem before. He returned the next weekend for the original installer to check. The installer recommended replacing the oil pump and its screen to repair the low pressure (at idle 8 to 10 psi at normal operating temperature). It was done at a cost of $683. This did not change the oil pressure more than a few psi. He then changed the oil to 20w/50 and that didn't have any effect. The installer said it had a worn engine and would have to be torn down. I declined. Is it possible that this could have been caused by the original repair work?
A. I assume the oil pressure sending unit is reading correctly. When the various parts were removed and replaced, it's possible that a pressurized oil passage or restrictor was allowed to leak, especially in the timing chain area. When the oil pump was replaced, it would have been a good idea to use a static oil pressure leak detector which pumps up the system and lets the mechanic see what's happening. Oil pressure at idle isn't as important as what it reads at normal road speeds.
Q. I have a 1994 Ford Thunderbird with a 4.6-liter V8. It has 27,000 miles and one problem has been bothering me. When the car sits for a long time, maybe three days or more between starts, it has a knock in the engine when it is first started. As soon as the oil pressure comes up, the noise stops and there is no noise from then on. I talked to the dealer and they told me it was piston slap and not to worry about it since all the 4.6-liter V8s do it. It sounds a lot like the lower end is knocking. Can you tell me if this engine has a history of lower end trouble or is this problem only pistons as the dealer says? If so, what should I do to keep the engine from giving me trouble in the future?
A. If the engine noise stops the instant the oil pressure comes up, the problem is a drain-down of the lubrication system. It may be that the oil filter isn't holding its "prime," so try changing it to a different brand. It's also possible, but not probable, that the oil pressure relief valve in the oil pump is sticking.
Q. I have a 1995 Toyota Camry. This car has an automatic transmission with a four-cylinder engine and an overdrive. It had 30,000 miles on it when I purchased it and it now has 68,000. The car performs well with great economy. My problem is as follows: between 62 and 69 MPH, there is a whistling sound from the engine area. It stays constant when holding this speed or accelerating in this speed range. If I let off on the gas pedal, the sound will stop and start again if I accelerate. I was told that turning on the radio may take care of the problem.
A. Have your mechanic check for cracked or split vacuum/pressure hoses that trigger all the engine management systems under the hood. A leak under acceleration or during engine load may be the culprit, since the hoses often go bad. If you turn up the radio loud enough it will mask almost any engine noise.
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