5th gen 4WS rear end vibration noise when turning

[Anzezaf]

Hey, owner of a 5th gen w/ 4WS here

So I've been wrapping my head around this one for a while now.

I have this vibration-like noise that comes from the rear end of the car, right near the bottom of the trunk where the 4WS actuator sits (not from the rear struts, or around the upper control arm areas. I was lying down in the trunk and listening, so I know where the sound comes from.)

It happens with a 99% certainty when I turn left at city driving speeds (when the rear wheels turn to the right). This usually means when going around roundabouts or when turning at crossroads when I turn the steering wheel enough.
It does not happen when parking the car, due to the too low speed.
When going straight, this almost never happens. My previous 4WS motor also did this, that was one of the reasons I made a swap to another one. (Although, with the previous 4WS motor it did also happen on straights, but that motor was in a rough shape, the innards had some free play and this probably made the noise worse)

So you might think that yeah, the 4WS motor must have some loose ball joint or a thing like that. Except it doesn't - I installed this motor 3 weeks ago and I checked everything thorougly, it's as good as new, even the innards.

Anyways, here's the video of the noise. I was lying down in the trunk so you probably cant see anything on the video, but the noise is definitely there. Starts around 0:06 and this is when the car went into a roundabout.

[Anzezaf]

I'm lost.. One thing that comes to mind when I'm writing this is that the 4WS control computer could be having some sort of seizure and sending some mixed signals the motor itself.
So if the motor were to receive input to change direction 10 times a second, this could produce such a sound..

Fellas imma be honest, I had such a jobby experience with my prelude through my 3 years of ownership now. I am never buying a honda again in my life. Shittiest reliability
I fix one thing, and two others start acting up, and frankly I'm tired of always having something to go wrong and trying to fix

[Sailor]

It sounds like dry bearing or a slipping rack. Might it be worth checking alignment again?

[Scott560]

I think I had this on my old 5th gen. It would only happen intermittently, but normally when turning right at lowish speeds. It never happened often enough to investigate further and it never threw the 4ws light. Doesn't happen on my new one. the old 5th gen would occasionally throw a 4ws check light when I stalled it whilst turning - the voltage would drop and the rack wouldn't have enough power to move. I'm sure you have, but worth checking the main power feeds from the fuse box incase the connection is poor and the power is dropping when trying to turn?

Like you say - it sounds like an unintended action from the ECU to move the actuator. The actuator must have some feedback to the ECU to report its position? Perhaps it does not believe its 'home'? I'm not sure what to suggest as you have worked on the 4ws a lot more than I.

Don't give up - the rest of the car should be very reliable! in the last 8 years across 2 preludes, I've only ever had to do the odd reset....

[Anzezaf]

It sounds like dry bearing or a slipping rack. Might it be worth checking alignment again?

Bearing would act up with higher speed, and the pitch/frequency of the sounds would change, so I don't think the bearing can be at fault here.
Rack can't slip in this 4WS unit, unless something was horribly broken. And in that case the car would be undriveable since the wheels wouldnt be held in place

I'm sure you have, but worth checking the main power feeds from the fuse box incase the connection is poor and the power is dropping when trying to turn?

Like you say - it sounds like an unintended action from the ECU to move the actuator. The actuator must have some feedback to the ECU to report its position? Perhaps it does not believe its 'home'? I'm not sure what to suggest as you have worked on the 4ws a lot more than I.

Don't give up - the rest of the car should be very reliable! in the last 8 years across 2 preludes, I've only ever had to do the odd reset....

Good idea with the power cutting off, but I feel like that would indeed throw an error at least.

I'm rather going to try and change the 4WS control unit and hopefully it will work. I have a spare one but it kept throwing an error at me when everything else was in order.

The rest of the car is only slightly better off in terms of reliability, let me quickly list out the things I had to sort out in my 3 years of ownership:

- Change conrod and main bearings
- Change clutch and timing belt service (expected)
- Change both driveshafts in the span of 6 months
- Change all sway bar links on the car (intermittent failures on all of them)
- Change rear sway bar rubber mounts due to creaking
- Change headlights due to burnt lenses on one side
- Change front steering rack, tie rods and front subframe
- Change front and rear engine mounts (front squeaking again after a year)
- Rework the wiring harness on drivers door due to torn cables
- Rewire the sensors for door closing on both sides, due to the multiplexer unit failure
- Replaced front main sensor for the 4WS system
- Replaced 2 or 3 4WS control units
- Refurbish and replace the rear 4WS actuator
- Replace rear upper control arm
- Replace 1x front and 1x rear lower ball joints
- Refurbish all of the brake calipers
- Replace clutch slave cylinder
- Replace master slave cylinder (failed 6 months after slave replacement)
- Make a makeshift cabin air filter since honda in their genius haven't fitted one to a premium car in 1997

There's at least just as many things I cant remember off the top of my head, but yeah.. Reliablity and honda prelude is 100% a paradox if you ask me
Oh and wrenching on the car wouldn't really bother me that much if half the needed parts weren't end of life, and aftermarket quality parts are near impossible to find. So if anything too specific fails, youre pretty much drokked

[K30DPC]

That's the beauty of driving 20+ years old cars. With 4gens is even harder now. But I'm sure I don't wanna swap it for anything relatively new.

[Max]

The Prelude curse is real

[tom023]

Hey, owner of a 5th gen w/ 4WS here

So I've been wrapping my head around this one for a while now.

I have this vibration-like noise that comes from the rear end of the car, right near the bottom of the trunk where the 4WS actuator sits (not from the rear struts, or around the upper control arm areas. I was lying down in the trunk and listening, so I know where the sound comes from.)

It happens with a 99% certainty when I turn left at city driving speeds (when the rear wheels turn to the right). This usually means when going around roundabouts or when turning at crossroads when I turn the steering wheel enough.
It does not happen when parking the car, due to the too low speed.
When going straight, this almost never happens. My previous 4WS motor also did this, that was one of the reasons I made a swap to another one. (Although, with the previous 4WS motor it did also happen on straights, but that motor was in a rough shape, the innards had some free play and this probably made the noise worse)

So you might think that yeah, the 4WS motor must have some loose ball joint or a thing like that. Except it doesn't - I installed this motor 3 weeks ago and I checked everything thorougly, it's as good as new, even the innards.

Anyways, here's the video of the noise. I was lying down in the trunk so you probably cant see anything on the video, but the noise is definitely there. Starts around 0:06 and this is when the car went into a roundabout.

I had the exact same problem but turning to the right slightly at cruising speeds. 80km/h and a gentle curve was always a problem. As soon as I straightened the wheel the noise disappeared.
I was lucky enough to pick up a second 4ws mech and replaced the whole thing.

I investigated a lot in forums... Etc at the time but surprisingly came up empty.