Q: I have a 2020 Nissan Rogue. The first time I brought it in for an oil change, the service department told me I needed to replace the brake fluid. I am older generation and remember to only replace fluid if you replaced a brake part and needed to add fluid.
Do new cars really need to replace brake fluid every 5,000 miles?
A: Clean brake fluid is crucial for a modern ABS braking system. Nissan, Subaru and some other manufacturers recommend replacing brake fluid every 30,000 miles.
At AAA, our engineering group has performed testing and recommends a 30,000 mile replacement due to moisture contamination.
If you change your Nissan’s oil every 5,000 miles, it would make sense to replace the brake fluid at the sixth oil change.
Q: My 1998 GMC Sierra defroster is not blowing hot enough to defrost the windshield. The engine was replaced with a new crate engine. I had three new heater cores installed (one is the factory part). I also checked the ventilation system for proper operation and obstructions twice. The incoming temperature to the heater core is within the correct specification.
When the truck was new, it was blowing a storm of hot air. Of course, these observations are taken from what I’ve been told by “certified” mechanics, and I’ve had it in more than one shop. Thoughts?
A: In the case of this truck, the system is quite simple. I would start at the beginning. The thermostat should open at 205 degrees and close at 185 degrees, so the temperature of the coolant entering the heater core should be around this temperature.
The temperatures of the inlet and outlet pipes of the heating radiator should be between 10 and 20 degrees from each other. This should translate to air duct temperatures of around 150 degrees, which is more than enough to defrost the windshield. I would also look for places where cool air could enter which would dilute the heat.
Q: My old Dodge truck dies from time to time for no reason. It won’t start and the gauges don’t work.
If I leave the key on and wait about 10 minutes the gauges start working and the engine starts and runs for an unknown amount of time. It is never the same duration; maybe five minutes, or it could be four or five days.
I replaced the crankshaft position sensor and the engine relay. Each helped for a while, but they still die at random times.
Do you have any idea what could be causing this? Some say it’s the ECM (computer) or maybe the instrument cluster.
A: I would start by locating, checking and clearing all electrical grounds. Performing a simple voltage drop test can help locate the problem.
The other possibility is a faulty ignition switch.
As for the vehicle’s computer, you can try warming it up with a heat gun as well as tapping and shaking it. If you notice a change in engine operation, replace the ECM.
Q: I have a 2012 Toyota Prius with over 100,000 miles. My mechanic uses synthetic oil for my oil changes, claiming the Prius engine runs hotter. Is it correct?
Second, I’ve noticed in satisfaction surveys conducted by Consumer Reports that Honda and Toyota are down from previous years. An explanation for this?
A: Looking at engine temperature alone, the Prius runs the same temperature as most internal combustion vehicles. The oil will begin to break down at temperatures above 250 degrees.
Synthetic oil flows faster, lubricates better and is more resistant to chemical breakdown.
Considering Toyota recommends oil changes once a year, or every 10,000 miles, paying the extra cost for the benefits of synthetic oil is well worth it.
As for the quality of Honda and Toyota products slipping, I think it’s more of a case where other manufacturers have improved.
Honda and Toyota are constantly innovating and with innovation there can sometimes be quality issues.
I recently had Mike Quincy of Consumer Reports on my radio show to discuss “top picks.” You can find the interview on johnfpaul.podbean.com.
John Paul is the AAA Northeast Automotive Physician. He has over 40 years of experience in the automotive industry and is an ASE Certified Master Technician. Write to John Paul, The Car Doctor, at 110 Royal Little Drive, Providence, RI 02904. Or email [email protected] and put “Car Doctor” in the subject field. Follow him on Twitter @johnfpaul or on Facebook.