callahan73

Hi there CL! I just want to start off by saying this forum has been so, so invaluable for me in my foray into owning my first SC, a one-owner 1993 SC400 with 105k original miles. I've done so many little things and saved so much money, from trunk struts to power tilt washers to power steering flushes, and it's all thanks to you! With that said, I'm having another problem that I can't seem to diagnose myself with extensive searches on the forums and so I wanted to know if any of you have ever run into this before. I'm going to provide you with as many details as I can, as well as a sound clip that (albeit quietly) illustrates the problem.

Virtually the whole time I've owned the car, it has made a clicking sound at approximately 300-360 beats per minute under the hood at times while driving. Initially, it really only seemed to happen when the air conditioning was engaged (and at that time, it almost sounded like it was coming from the driver's side under the engine bay when standing outside the car). The dealership noted when I had it looked over "noisy air compressor" as the possible culprit. However, I know from service records that the car was converted to R32 in 2012 and lightly used after that. Furthering my doubts, the car has now started to do it with the AC completely off and sometimes doesn't make the noise with the AC on.

It seems to be somewhat RPM-dependent, but not linearly - it's almost as though there is a band of RPM between say 1800 and 2500 when it's at its worst. It is much worse when the car is first started, independent of temperature (I live in South Carolina and have been below freezing and above 70 in the last 2 weeks and it was virtually the same), and fades somewhat as the car warms up, but will continue to happen almost exclusively at lower speeds. When it is happening and I brake for a stoplight, it will completely stop when I fall below a certain speed, although this speed is not consistent from time to time.

My theory is that it may be a pulley bearing somewhere and just seemed to be the AC at first because the AC added load to the engine and made the serpentine belt spin faster, but as it has continued to wear it's started happening under different loads. I just don't get the unpredictability of it. For reference, I cannot verify that the car has had the timing belt/water pump done (I know this is a big priority and will be doing it soon), I just changed the serpentine belt about 5k miles ago, oil change is good, check engine light is because of the driver's side O2 sensor, the engine shield underneath is still present but missing a few bolts. If there are any other questions I can answer feel free to ask, and thanks in advance for all of your help and expertise!

Note about the video clip: you can faintly hear the noise RIGHT as the video starts and it fades out as I turn, not coming back. Sorry I don't have anything better quality, but this is the best my phone can pick up and it rarely if ever happens with the car stopped anymore.

Ali SC3

iTrader: (10)

Couldn't hear it in the video but my best guess would be the serpentine belt tensioner. it clicks when its going bad. on the side of the tensioner there will be 2 marks and an arrow, if the arrow is within the 2 marks its still good technically, but over time as the spring wears out the arrow will be outside of the marks, and that is when it will start clicking alot when the spring has gone weak. a new belt can help for a while but it will just return in due time. Turning the a/c on and off can affect the load on it and thus where the spring rests, same with rpm so when it starts happening its usually only at certain loads, eventually it will click all the time if that is it.

in the video sounds like a loud clicking sound inside the car when you turn... you might have a bad clockspring (the thing that rotates behind the steering wheel).

callahan73

Thanks for the response! Makes sense to me that that could be it. I'm not entirely positive what the marks are supposed to look like, so I've included here an image of what I think you're referencing. If not, let me know and I'll try to find it!

Edit: I can for some reason hear the loud clicking inside the car that you attributed to the clockspring much more prominently on the video than I can while driving it, but I'll definitely look into that because wow, it's prominent on that video haha. The noise is very, very low on the video and it's RIGHT as the video starts. I'll try to get a better clip of it soon.

Ali SC3

iTrader: (10)

Yeah those are the marks that I was talking about. if you have it idling while its making the sound go and look at the tensioner, you might even be able to see it moving in rythym with the sound.

callahan73

And it's supposed to be in between the three hashes to the left, right? I'm assuming those represent top end, low end, and sort of Goldilocks in the middle?

Ali SC3

iTrader: (10)

Yes, that is pretty much it, somewhere in the 3 marks.
If its within any of the 3 marks it is acceptable for an old belt.
If it is a new belt it needs to be within the last 2 marks (new belt is generally tighter).

The picture you posted above, not sure if that is your engine, but its showing outside all 3 marks meaning its worn beyond spec and is time to replace, especially if its a new belt.

This is from a 2jzge but it gives you an idea.

callahan73

That is a picture of mine and the belt is about 2k miles old so I'm sure that's the problem. It also seems to be shaking side to side way too much so I'm sure that's it, thank you SO MUCH! One last question - I'd really rather just shell out for the OEM tensioner since I don't want to have to notch my timing belt cover. Any recommendations on places to find one? Usually I'm pretty resourceful with this kind of thing but I seem to be striking out right now. Thanks again!

Ali SC3

iTrader: (10)

you can find the part number and check online or try the part number at toyota even. sometimes rock auto will have good deals on aftermarket replacements
I usually just get the oem parts from toyota or the parts stores online.