Sound heard at fixed speed

**mirrage** · 10-05-2016, 04:03 AM

I bought mitsubishi mirage 2014 in April [imported from Japan; its Thailand made]. Recently I heard very minor noise and a small jerk on accelerator when car is driven from cold state. Its always heard at fixed speed of 40 kmph and just once; till the car is parked again. Even if I keep driving it for one hour and car stops in between accelerates from speed zero many times then neither I hear any sound nor I observed any jerk on accelerator. When I park car for 10 minutes and run again then same noise is heard and impact on accelerator.

Once while using reverse gear I felt minor grinding impact on accelerator in inclined drive. Any suggestions? What can it be. And what is making noise heard only at fix speed. Is it cvt or throttle. Cvt fluid is as clean as it can be. Car is just 26k driven. I usually don't drive more than 80 kmph speed.

**daleWV** · 10-05-2016, 04:06 AM

Probably the anti-lock brakes testing themselves. They only do it once after the car is started up and you first start driving.

**mirrage** · 10-05-2016, 04:13 AM

How to check it or get it normal? If I keep car warming for 5 minute then the sound diminished or intensity is reduced? Can it be the same thing?

**daleWV** · 10-05-2016, 04:23 AM

If it is the anti-lock brakes testing themselves, it is completely normal and there is nothing to do unless a warning light comes on your dash after it completes it's test. I believe it is more noticeable when the engine is cold. I usually only notice it on cold mornings.

**mirrage** · 10-05-2016, 04:37 AM

I hear it daily even in warm temperature of 40-45 Deg C. Buts its for cold state start only or when car is parked for 10-15 minutes.

**daleWV** · 10-05-2016, 05:28 AM

I found this section in the service manual concerning louder than normal noise when the anti-lock brake hydraulic unit performs it's self check. It does agree with your statement that the noise will occur at 40kmph. It seems to imply that possibly adjusting the positioning of the brake lines slightly or the mounting of the hydraulic unit could help reduce the noise.

Inspection Procedure 15: The initial check sound of hydraulic unit is loud.
CAUTION
When installing brake tube, match the axial center of flare nut and brake tube with the center of hole at the hydraulic unit side, and check that the fluid does not leak.
.
COMMENT ON TROUBLE SYMPTOM
The operation sound may be decreased by reducing the load at the rubber mount portion of the brake tube and hydraulic unit.
.
PROBABLE CAUSES
Improper installation of the hydraulic unit
Improper installation of the brake tube
DIAGNOSIS
DRIVING CHECK
(1)Turn the ignition switch from the "LOCK" (OFF) position to the ON position.
(2)Drive the vehicle until the vehicle speed reaches 40 km/h (24.9 mph), check the operating sound volume and compare it with that of the same model.
OK: The operating sound is the same volume or less by comparing with that of the same model.
Q:Is the check result normal?
YES :
This diagnosis is complete.
NO :
Carry out adjustment for hydraulic unit installation (Refer to P.35C-131).