Squealing noise at idle
Discussion
For a while now there is this intermittent squeal that happens at idle. It is most prominent when I am doing a base idle set and the rpm is below 800 and sounds like a whining dog. It's quite loud so you don't need to get up close to the engine to hear it.
When the rpm is raised slightly it goes away and also mostly goes while out on the road.
It's not an alternator whine or a fan belt squeal and sounds like it is coming from the front of the engine so I suspect it could be the water pump. The fan belt tensioner was changed a couple of years ago BTW.
For 80% of the time the sound is not there but occasionally it happens for a few minutes and then goes away.
If it is the water pump then do these spectacularly fail and strand you by the roadside or is it something you can diagnose and replace in time?
When the rpm is raised slightly it goes away and also mostly goes while out on the road.
It's not an alternator whine or a fan belt squeal and sounds like it is coming from the front of the engine so I suspect it could be the water pump. The fan belt tensioner was changed a couple of years ago BTW.
For 80% of the time the sound is not there but occasionally it happens for a few minutes and then goes away.
If it is the water pump then do these spectacularly fail and strand you by the roadside or is it something you can diagnose and replace in time?
ric355 said:
Your description sounds like it is air flow resonating in the inlet. I have had this myself and it's like the noise is coming from the front of the engine when in fact it is not. The position of the idle screw can affect this significantly and if I'm right you may find a sweet spot for the screw where it doesn't do it. Several mentions of this in the archives.
When I did my ECU conversion the AFM went and was replaced with a bigger bore pipe and this caused it to howl until I tweaked the screw to find that sweet spot after much scratching of my head. Any change that alters the dynamics of the inlet can cause it.
That's interesting.When I did my ECU conversion the AFM went and was replaced with a bigger bore pipe and this caused it to howl until I tweaked the screw to find that sweet spot after much scratching of my head. Any change that alters the dynamics of the inlet can cause it.
Would it be dependant on slower than 950 rpm? When I am doing a base idle set, and I get the idle down to 600 rpm, it squeals like that, like someone is playing the violin in the engine bay. If I blip the throttle or take off the clamp to the stepper motor hose, it goes.
By playing with the idle screw, are you talking about a very small amount ie, to not upset the base idle setting and would bunging the screw hole with some putty, or rubber or something make a difference?
Power steering is electric
I had a whine from the alternator, a squeal from the fan belt and hum from the tensioner in the past. All changed and the noises gone.
This is more like a screeching violin and it is constant, not on-off. But then after increasing the rpm to say 1100, it goes.
Usually, I do not hear it when I am out on the road and am at lights or something, but yesterday as I pulled into the drive I could hear it. So I drove down the road, about 10 minutes away to a garage for an opinion and by the time I got there, the noise had gone again.
This is more like a screeching violin and it is constant, not on-off. But then after increasing the rpm to say 1100, it goes.
Usually, I do not hear it when I am out on the road and am at lights or something, but yesterday as I pulled into the drive I could hear it. So I drove down the road, about 10 minutes away to a garage for an opinion and by the time I got there, the noise had gone again.
Classic Chim said:
How many turns outward so anti clockwise from the stop is your idle screw. Very weird ?
I can’t quite remember but think it’s only something like 1-1/2 turns. Screw should feel tight. Could be a leak there or just set to far out somehow.
Within the 1 or 2 turns off completely closed if recall correctly.I can’t quite remember but think it’s only something like 1-1/2 turns. Screw should feel tight. Could be a leak there or just set to far out somehow.
Just a bit of additional info.
Turning it off today after a run (where btw it did not make that noise during the drive) as the engine turned off, it made the squeaking noise for a split second just as the engine stopped turning.
I then remembered that often the engine makes that same squeak as the engine stops, and it is that noise that I am referring to that it intermittently makes at idle at low revs.
Perhaps some of you also hear that same squeak when you turn the car off.
Turning it off today after a run (where btw it did not make that noise during the drive) as the engine turned off, it made the squeaking noise for a split second just as the engine stopped turning.
I then remembered that often the engine makes that same squeak as the engine stops, and it is that noise that I am referring to that it intermittently makes at idle at low revs.
Perhaps some of you also hear that same squeak when you turn the car off.
The car is out of hibernation now and it's back on the road.
The squealing violin is back, and this time it is more or less constant at idle speeds once the engine is warm. All the time. If I raise the idle speed with the throttle, by even 200 rpm, it goes completely. It does not come back again at higher engine speeds until it slows down to idle again.
Last year, each time I tried checking the idle screw and got my tools out to check it, sod's law, the noise had gone, but now it's back more or less constantly, I would like to have a look at it again.
My question is, how critical will the final position of the idle screw be as far as the stepper motors performance is concerned? I mean, if I have set it with everything clamped to 650 rpm, which in the past was when it squealed the loudest, if I then add another turn to it to stop the noise with the hose unclamped, what would the effect be to the rest of the running? Will the stepper start acting up?
The squealing violin is back, and this time it is more or less constant at idle speeds once the engine is warm. All the time. If I raise the idle speed with the throttle, by even 200 rpm, it goes completely. It does not come back again at higher engine speeds until it slows down to idle again.
Last year, each time I tried checking the idle screw and got my tools out to check it, sod's law, the noise had gone, but now it's back more or less constantly, I would like to have a look at it again.
My question is, how critical will the final position of the idle screw be as far as the stepper motors performance is concerned? I mean, if I have set it with everything clamped to 650 rpm, which in the past was when it squealed the loudest, if I then add another turn to it to stop the noise with the hose unclamped, what would the effect be to the rest of the running? Will the stepper start acting up?
Belle427 said:
Just wondered how you got on with this, strangely I started my car yesterday to warm it up and I had the howling which comes and goes.
I confirmed it is the stepper circuit as I’m able to remove my inlet hose due to being on megasquirt.
I’d be interested to know how far out other peoples bypass screws are too just as a baseline to work from.
Well, my car did me a favour in the end as I had checked everything and just couldn't find where it was coming from. I saw a small pool of water under it as I backed out of the drive and saw the drip was coming from behind the water pump pulley where I understand there is a weep hole. So I ordered a new pump, fitted it and after just having driven it for about 10 odd miles, it seems the noise has gone. I confirmed it is the stepper circuit as I’m able to remove my inlet hose due to being on megasquirt.
I’d be interested to know how far out other peoples bypass screws are too just as a baseline to work from.
So it points towards the water pump, although it does not explain why even with only 200 rpm more, the noise went away rather than got louder.
I will see how it goes after I have had a chance to drive it some more.
Belle427 said:
I changed my pump as when I had the noise I removed the serp belt and it went away but sadly it wasn’t this.
It was hard to pin down but I eventually heard it through the air filter, so then took the inlet pipe work off with engine running to confirm it’s howling through the stepper circuit.
I'm hoping mine has gone but won't know for sure until I've driven it for a few daysIt was hard to pin down but I eventually heard it through the air filter, so then took the inlet pipe work off with engine running to confirm it’s howling through the stepper circuit.
😊
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